Feline lower urinary tract disease (FLUTD)

Signs of lower urinary tract diseases in the cat have been described in the veterinary literature for more than 80 years (Kirk, 1925). The term feline urological syndrome (FUS) was coined in the 1970s (Osbaldiston and Taussig, 1970) and replaced in the 1980s (Osborne et al., 1984) by  feline lower urinary tract disease (FLUTD) to indicate the clinical pictures characterized by the variable presence of strangury, pollakiuria and periuria (micturition in inappropriate places) in the cat. These signs are common to a number of conditions that can affect the bladder or urethra of cats but, unfortunately, are rarely indicative of a specific aetiology.

Despite a full diagnostic work-up, it is not possible to make an aetiological diagnosis in about two-thirds of cats with signs of FLUTD and in these cases, the term feline idiopathic cystitis (FIC) is applied (Buffington et al., 1999). The remaining cases are divided between urolithiasis, bacterial infections, anatomical malformations, neoplasms and neurological problems (e.g. reflex dyssynergia) (Hostutler et al., 2005).

PATHOPHYSIOLOGY

As said above, FLUTD comprises a variety of diseases; for greater clarity, these will be dealt with separately. Furthermore, it should be appreciated that in recent times our understanding of the pathophysiology of many of the causes of FLUTD has improved and the focus of attention has shifted from stones and crystalluria to other disorders such as FIC, which has been found to be the most frequent cause of FLUTD (Gunn-Moore, 2007).

FELINE IDIOPATHIC CYSTITIS
The cause of this disease remains unknown; however, from studies carried out in the last decade, it appears to be related to complex abnormalities of the nervous and endocrine systems, thereby going beyond simple bladder alterations. All this seems to be further accentuated by a change in the layer of glycosaminoglycans (GAG) which normally covers the wall of the bladder, inhibits bacterial adhesion and protects the urothelium from the harmful constituents of the urine itself (Fig. 1). If the layer of GAG or endothelium is altered, the permeability of the bladder is increased and this would allow noxious substances within the urine to cross the urothelium and cause neurogenic inflammation. Furthermore, it has been seen that the bladder wall of affected cats typically contains a notable increase in C fibres (non-myelinated pain fibres localised in the submucosa of the bladder), and in the related receptors (substance P receptors) and mast cells (Fig. 2). Stimulation of the C fibres by central triggering factors (such as stress) or by particular properties of the urine (acid pH, concentrations of potassium, magnesium and calcium ions) can cause the release of neuropeptides (such as substance P); in their turn these can cause pain, vasodilatation in the bladder wall, increased permeability of the vasculature and of the bladder wall itself, submucosal oedema, smooth muscle contractions and degranulation of mast cells. This last effect induces the release of inflammatory mediators (e.g., histamine, heparin, serotonin, cytokines and prostaglandins) which can further exacerbate the effects of the C fibres; this triggers a vicious cycle with the recruitment of further C fibres and worsening of the pathological condition (Hostutler et al., 2005; Buffington and Chew, 2007; Gunn-Moore, 2007).

It is thought that stress plays an important role in triggering and/or aggravating FIC. Indeed, it has been seen that cats with this disease respond in a rather particular way to stressful events. Under physiological conditions stress leads to activation of the hypothalamus-pituitary-adrenal axis with increased activity of the locus caeruleus  (an area of the brain dedicated to vigilance and autonomic activity), increased plasma concentrations of catecholamines, heightened adrenal gland sensitivity to adrenocorticotropic hormone (ACTH), increased secretion of glucocorticoids by the adrenal cortex and raised levels of cortisol in the urine. Glucocorticoids and other agonists of a₂adrenergic receptors ensure a negative feedback to control the response to stress by inhibiting further transmission of nociceptive signals to the brain. In the case of stress, cats with this physiological response manifest fear, aggression, a tendency to hide and anorexia. In contrast,  cats with FIC which are subjected to stress increase their consumption of food and drink, grooming and micturition. It is interesting to note that while these cats show increased activity of the locus caeruleus, with increased sympathetic activity, they do not have increased plasma concentrations of ACTH and cortisol: this uncoupling of the hypothalamus-pituitary-adrenal axis is also seen in some chronic pain syndromes in humans and is thought to derive from desensitisation or under-regulation of agonists of a₂-adrenergic receptors secondary to chronic stimulation. It has been hypothesized that stressful factors include living with other cats (particularly if there are conflicts between the animals), a change of home, poor management habits and environments lacking suitable stimuli (Buffington and Chew, 2007; Gunn–Moore, 2007).

UROLITHIASIS
Urolithiasis is the formation of stones within the urinary system. Stones differ by their mineral composition; the types most frequently seen in cats are struvite and calcium oxalate. In recent years the consumption of diets specifically designed (with a reduced supply of magnesium and acidifying) to dissolve struvite stones has coincided with a notable increase in the proportion of calcium oxalate stones (Houston, 2007).

A small proportion of cats have stones made of urates, calcium phosphates, cysteine, silica, xanthine and potassium and magnesium pyrophosphates. Furthermore, there are compound uroliths, made of a nidus of one type of mineral and a concretion, or shell, of another type (Houston, 2007). Finally, stones formed of dried, solidified blood have been described (Westropp et al., 2006).

URETHRAL PLUGS
The incidence of urethral plugs is about the same as that of uroliths and the plugs are often associated with urinary obstruction. They are formed of a protein-colloidal matrix (mucoproteins, albumin, globulins, cells) and, in some cases, by crystalloid material (typically struvite). It is thought that the colloidal matrix derives from inflammation of the bladder wall of a neurogenic, idiopathic nature or secondary to infections, neoplasms or urinary stones (Gunn-Moore, 2007).

Crystalluria, if very severe, can cause urethral obstruction, but in most cases, in the absence of a colloidal matrix, it is asymptomatic. Most cats fed a dry diet will develop crystalluria (Gunn-Moore, 2007).

BACTERIAL CYSTITIS
Bacterial infection is an uncommon cause of FLUTD, except in elderly cats and in animals with concomitant disorders or conditions that lower the specific gravity of the urine (chronic renal failure, diabetes mellitus, hyperthyroidism, administration of corticosteroids, etc.); cats with  a normal urine concentration very rarely develop infections of the urinary tract. Other predisposing conditions predisposing to bacterial cystitis are the presence of stones or anatomical defects of the urinary tract. These infections may also be iatrogenic (e.g. following catheterisation). Independently of the underlying cause, affected cats are predisposed to recurrent infections (Gunn-Moore, 2007).

ANATOMICAL MALFORMATIONS
Anomalies of the urachus are among the most common anatomical malformations of the bladder that predispose to both urinary stones and bacterial infections. The urachus is the canal that, during foetal life, enables exchange of urine between the developing bladder and the placenta. Normally this canal has completely atrophied and is no longer functional by the time of delivery, but if the atrophic process has not been completed, vestigial remnants give rise to persistent urachus, urachal cysts or urachal diverticula. A persistent (or patent) urachus is the situation in which the connection between the bladder and umbilicus remains functional, leading to loss of urine from the umbilicus. In contrast, urachal cysts form when the epithelium of a persistent tract of the urachus continues to secrete fluids into an isolated segment. A vesico-urachal diverticulum occurs when a part of the urachus located at the top of the bladder gives rise to a blind-ended diverticulum that protrudes from the apex of the bladder. A vesico-urachal diverticulum may be microscopic; in this case it is usually asymptomatic, but can become larger during acquired diseases of the bladder or urethra (infections, stones, FIC, etc.) because of inflammation or increased intravesical pressure (Bartages and Kruger, 2011).

Rarely the urinary bladder may communicate with the colon (colo-vesical fistula) or with the uterus (vesico-uterine fistula); these abnormalities can also predispose to urinary tract infections or provoke urinary incontinence and signs of FLUTD (Bartages and Kruger, 2011).

NEOPLASMS
Bladder tumours are rare in dogs and cats. In dogs these tumours are located mainly in the trigone, whereas in cats the apex of the bladder is often involved. Malignant spread occurs through contiguity or the lymph-haematogenous system (Marconato, 2005).

The most common bladder neoplasm in cats is transitional cell carcinoma, which is more frequent in males. Metastases are rare and usually involve the lungs, regional and other lymph nodes, omentum, spleen, small bowel, diaphragm, skeletal muscles and liver.

Other bladder neoplasms include squamous cell carcinoma, adenocarcinoma, rhabdomyosarcoma,  fibroma, haemangiosarcoma, leiomyoma, leiomyosarcoma and epitheliotropic T-cell lymphoma (Marconato, 2005).

NEUROLOGICAL DISORDERS
A complete description of the neurological disorders of micturition goes beyond the aims of this article, which is limited to a consideration of the most common neurological pathologies that, by causing a defect in bladder emptying, can produces signs of FLUTD, as well as complications such as infections of the lower urinary tract. For a more detailed treatment of this subject, the reader is referred to specific textbooks. The innervation of the bladder is illustrated in Figs. 3, 4 and 5.

Neurological disorders of bladder emptying can derive from inadequate urethral relaxation, reduced contraction of the detrusor or both.

Inadequate detrusor contraction
The causes of inadequate detrusor contraction include lower motor neurone diseases, such as cauda equine syndrome, sacro-iliac subluxation, intervertebral disc pathology caudal to L5, bilateral damage to the pelvic nerve or pelvic plexus, sacro-coccygeal fractures or separation (the so-called “tail-pull” injury), congenital malformations (reported, for example, in the Manx cat) and neoplasms (Bartages and Kruger, 2011).

Dysautonomia should also be remembered. This rare, idiopathic neurogenerative disease affects the autonomic nervous system (sympathetic and parasympathetic) and is manifested by chromatolytic degeneration of the neurones of autonomic nervous system ganglia.

Prolonged over-distension of the bladder, of any cause, can provoke over-distension (myogenic) detrusor atony. In fact, the smooth muscle fibres of the detrusor are coordinated through the so-called tight junctions which, if stretched excessively for prolonged periods, can separate, leading to an interruption in neuromuscular transmission and giving rise to weak, uncoordinated contractions or the loss of bladder contractions (Bartages and Kruger, 2011).

Increased urethral resistance
An upper motor neurone disease can be the result of lesions in the spinal cord in the tract between the sacral segments and the pontine micturition centre and causes lack of inhibition of contraction of the urethral sphincter even in the presence of contraction of the detrusor.

Reflex dyssynergia or detrusor-urethral dyssynergia is said to be present when the start of the contraction of the detrusor is accompanied by a contraction of urethral muscle (smooth and/or striated) which creates a very high urethral pressure that prevents micturition. This pathology can be the consequence of upper motor neurone diseases, secondary to partial lesions of the reticulospinal tract or to lesions cranial to the caudal mesenteric ganglion, but may also be idiopathic (Bartages and Kruger, 2011).

The term functional (or myogenic) urinary obstruction describes a condition in which heightened sympathetic stimulation increases the tone of the urethral sphincter, preventing urinary voiding. Sometimes this has a neurological cause, but in other cases it is due to irritation of the urethra (e.g. because of repeated catheterisation). The anxiety generated by unsuccessful attempts to urinate further increases the sympathetic stimulus creating a vicious circle.

CLINICAL SIGNS

The clinical signs include a variable combination of pollakiuria, dysuria, periuria (micturition in inappropriate places), haematuria, urinary incontinence, agitation or vocalisations during micturition. Often the owner does not notice the urinary problem, but reports a change in behaviour: the cat no longer uses its litter tray or is aggressive. In other cases, the owner may confuse the strangury with constipation or erroneously interpret behavioural problems as symptoms of FLUTD. Some cats exhibit excessive grooming and develop areas of alopecia on the ventral surface of the abdomen or the perineal region, presumably in response to a local painful stimulus. In the case of urinary obstruction, the owner may report anuria. The severity of the clinical signs depends on the duration of the obstruction.

DIAGNOSIS

The diagnostic plan is aimed at identifying the specific causes of the FLUTD. The diagnosis of FIC is made when, despite a full diagnostic work-up including urinalysis, urine culture, plain X-rays, X-rays with contrast media and abdominal ultrasound, no underlying cause can be found. If characteristic submucosal petechial haemorrhages (glomerulations) are found during cystoscopy, the condition can be called interstitial cystitis (Buffington et al., 1999), a term chosen for the numerous similarities of this condition with human interstitial cystitis, which is a syndrome of chronic pelvic pain characterized by difficult, painful and frequent micturition in the absence of a diagnosable cause  (Buffington et al., 1997).

SIGNALMENT AND HISTORY

The first step is to determine the age, sex and breed of the patient; although FLUTD can affects cats of any age, sex or breed, signalment is very useful in formulating a differential diagnosis. For example, cats under 1 year old usually have bacterial infections or stones associated with anatomical or functional defects (Osborne et al., 2000); in young and adult patients most cases of FLUTD are due to FIC, whereas in elderly cats, stones, bacterial infections and neoplasms are more common (Gunn-Moore, 2007). Furthermore, males have a higher probability of developing urinary obstruction (Gunn-Moore, 2007).

The history can also be very useful. Although FIC can cause clinical signs throughout the year, this condition is seen more frequently in the autumn and winter, or after a stressful event such as moving house or hospitalisation. Furthermore, it is observed more frequently in cats that live in households with several cats and in those fed a diet of dry food (Gunn-Moore, 2007). For this reason it can be useful to ask the patient’s owner to fill in a questionnaire on the cat’s signalment, lifestyle and habits, environment in which it lives, concomitant disorders, etc. (Westropp and Buffington, 2004).

The description of the micturition may be illuminating; in fact, cats with behavioural problems usually urinate in one or two inappropriate places, whereas those with a urinary tract pathology urinate more indiscriminately. It should, however, be remembered that a physical disorder can trigger behavioural problems, so the distinction between the two is not always clear-cut (Gunn–Moore, 2007).

CLINICAL EXAMINATION

The first thing to evaluate during the clinical examination is the size of the bladder; in the case of a very distended bladder, there may be obstruction of the urethra. If the history is suggestive of obstruction, but the bladder is not palpable, the possibility that the bladder has ruptured must be taken into consideration. The caudal part of the abdomen is often tender and, in male cats, the prepuce and/or penis may be swollen. The physical examination also enables the detection of concomitant disorders such as cardiac arrhythmias and bradycardia, which may indicate severe hyperkalaemia secondary to obstruction. It is also important to evaluate the animal’s nutritional status, since it has been demonstrated that FIC occurs more frequently in overweight cats (Gunn-Moore, 2007).

The electrocardiogram may show alterations due to hyperkalaemia: bradycardia, absent P waves or P waves with a reduced amplitude, increase in the duration of QRS complexes and high, spiked T waves (Walker, 2009).

URINALYSIS

It essential that the urine of all patients with FLUTD is examined. The urinalysis should include a physicochemical evaluation, assessment of the sediment, culture tests and an antibiogram and should be performed before starting any treatment because otherwise the results could be unreliable. The specific gravity of the urine must be determined by a refractometer and the leukocytes interpreted in the light of the sediment findings, since a dipstick often gives false positive results in the cat. Cats with FLUTD often have very concentrated, acid urine, although the pH may become alkaline in response to diet or during infection with urease-producing bacteria (Staphylococcus and Proteus spp.); it should not, however, be forgotten that the pH may be falsely increased by prolonged storage and by contamination by detergents containing quaternary ammonium salts. Haematuria is common. Proteinuria may be present and is often secondary to inflammation of the bladder wall (Gunn-Moore, 2007; Wamsley and Alleman, 2007). In FIC the number of leukocytes is usually limited, while haematuria and proteinuria are frequent (Hostutler et al., 2005).

The urinary sediment is examined with a view to determining whether crystals, red blood cells, white blood cells and casts are present; it should, however, be remembered that some types of crystals (struvite and calcium oxalate dihydrate) can also be found in the urine of healthy cats and so this finding should not be given excessive importance, especially if there are few crystals and no stones or secondary infection. It is not uncommon to find lipid droplets of various sizes (Gunn-Moore, 2007; Wamsley and Alleman, 2007).

In the case of inflammation, besides the typical inflammatory findings, there may be dysplastic type changes in transitional cells, which may be confused with neoplastic cells and give rise to problems of interpretation. In the case of suspected neoplasia, the urine should be collected by spontaneous micturition or catheterisation; cystocentesis should not be performed because of the risk of iatrogenic seeding of malignant cells along the needle track and in the abdominal wall (Marconato, 2005).

Urine cultures should be made from samples taken by cystocentesis, kept refrigerated and sent to the laboratory for analysis as quickly as possible. E. coli is the pathogen most frequently isolated from the urine of cats (Gunn-Moore, 2007; Wamsley and Alleman, 2007).

BLOOD TESTS

The blood tests of a cat with FLUTD are usually within the norm unless the animal has a concomitant disease. Nevertheless, it is important that these tests are carried out in all cats with FLUTD, in particular those with urinary retention, which could have metabolic alterations, and in elderly ones, which could have an underlying systemic pathology. Some patients with severe, chronic haematuria may develop anaemia as a result of the blood loss (Gunn-Moore, 2007).

DIAGNOSTIC IMAGING

Abdominal ultrasound
Ultrasonography can show sediment within the bladder, stones (even small ones) and bladder wall thickening, neoplasms, polyps and defects (Fig. 6a); in contrast, the full length of the urethra cannot be visualised in ultrasound studies. Possible findings in FIC include hyperechoic foci, clots and irregularities or thickening of the bladder wall (Gunn-Moore, 2007).

Plain X-rays
Plain X-rays, including those of the pelvic and penile urethra, may be sufficient to identify the presence of radio-opaque stones (struvite and oxalates) larger than 3 mm in diameter; however, other stones, such as urate ones, are radiolucent (Hostutler et al., 2005).

Radiography with contrast media
Radiography with contrast media (cystography, urethrography and urethrocystography) can show radiolucent stones, bladder diverticula, urethral stenosis, anatomical defects (Figs. 6b and c), neoplasms and inflammatory polyps. These imaging techniques are usually reserved to patients with recurrent signs; in these cases, the recommended investigations are usually double contrast cystography and positive contrast urethrography (Hostutler et al., 2005).

These studies are often within the norm in cats with FIC although, in some cases, small stones may be seen or thickening of the bladder wall, in particular in the apical area, irregularity of the mucosa, urethral stenosis and, in the more severe cases, filtration of the contrast agent through the planes of the bladder wall (Scrivani et al., 1997; Scrivani et al., 1998).

Uroendoscopy
This examination includes cystoscopy and urethroscopy. This investigation, too, is reserved only for patients with recurrent or persistent signs despite adequate treatment. It can be used to inspect the mucosa of the urethra and bladder, evaluate anatomical malformations and masses directly and to take samples. In animals with FIC it can reveal the characteristic glomerulations (focal areas of submucosal haemorrhages), increased vascularisation and ulceration of the urothelium. These abnormalities are not, however, pathognomonic of FIC (Hostutler et al., 2005; Gunn-Moore, 2007).

CYTOLOGY AND HISTOLOGY

Bladder neoplasms do not often exfoliate so the urinary sediment is rarely diagnostic. The simplest method for sampling cells from the bladder wall is to take a biopsy via a catheter. Once the bladder has been voided, a catheter with a lateral hole, connected to a syringe containing physiological saline, is advanced to the site of interest. The contents of the syringe, except for 1 ml, are introduced into the bladder and then, by pulling back the plunger, a negative pressure is produced: a small part of the mucosa is aspirated into the aperture in the catheter and, with the plunger still retracted, the catheter is moved small distances cranially and caudally. At this point the negative pressure is gradually released and the catheter is withdrawn. Finally, the biopsy sample is removed from the catheter by injecting the remaining quantity of isotonic solution and collecting it in a test-tube (Osborne and Lulich, 1999). Alternatively, a biopsy can be taken during cystoscopy (Marconato, 2005).

There are typical, albeit not pathognomonic, alterations in FIC, such as oedema, haemorrhages and dilatation of submucosal blood vessels; in some cases there is an increase in mast cells (Buffington et al., 1997). Electron microscopy may reveal areas without urothelium and changes in the gap junctions (Lavelle et al., 2000).

QUANTITATIVE ANALYSIS OF URINARY STONES

A precise identification of the type or types of mineral present in uroliths is the key element in selecting the correct therapeutic and preventive management. Thus, when urinary stones are expelled or removed, they should be sent to the laboratory for a quantitative analysis of their composition. This involves identification and analysis of all the layers making up the stone. The most important part is, however, the central core (called the nidus) because the treatment essentially depends on its composition (Moore, 2007).

There are various different techniques available for the quantitative analysis of urinary stones: optical crystallography enables identification and quantification of most of the common constituents, although if unusual minerals or pharmacological metabolites are present or if the nidus is very small, other techniques are better. Electron microscopy enables the analysis of very small samples and can provide the elemental composition of all materials examined; it is, however, more effective when used to analyse inorganic materials such as minerals and less effective when used on organic materials such as xanthine and uric acid and does not distinguish similar compounds such as brushite and apatite. In this case infrared spectroscopy is necessary. This technique, besides identifying a wide range of organic materials, including numerous components commonly found in urinary stones, is irreplaceable for distinguishing various types of urate, for differentiating calcium oxalate dehydrate from the monohydrate and for identifying the various types of phosphate such as brushite, apatite and tricalcium phosphate. This technique can also be used to analyse microscopic quantities of material, very small nidi, single crystals and very unusual stones (Moore, 2007).

Qualitative analyses using commercially available kits based on rapid chemical tests are rather unreliable, giving both false negative and false positive results (Moore, 2007).

NEUROLOGICAL EXAMINATION

In some cases a neurological examination may reveal neurological damage that could be the cause of poor bladder voiding. For this purpose, the neurological examination must include an evaluation of the degree of bladder distension, the facility or otherwise with which the bladder is emptied manually and observation of the process of urination (quality of the urinary stream, brusque interruption of the stream, whether the urination is voluntary).

Various degrees of atony of the detrusor muscle and hyporeflexia of the external urethral sphincter can occur in lower motor neurone diseases; the bladder is, therefore, distended but empties easily and an affected animal is usually incontinent from overdistension when the bladder is full. The tone of the internal urethral sphincter is usually preserved since this is innervated by the hypogastric nerve. Other common findings are a decreased or absent peritoneal reflex, an atonic anus and paresis or paralysis of the tail.

In contrast, in patients with upper motor neurone diseases, the bladder is usually tense and difficult, if not impossible, to empty manually. Often the neurological examination also detects paresis or paralysis of the hindquarters and ataxia.

Dysautonomiacauses bladder atony and loss of urethral sphincter reflexes, with overflow incontinence; there can also be other signs of autonomic nervous system dysfunction, such as dilated, non-responsive pupils, dry mouth, prolapse of the third eyelid, absent anal sphincter tone, regurgitation and/or vomiting.

In the case of myogenic detrusor atony,contraction of the detrusor is decreased or absent and the bladder is, therefore, distended and flaccid even following attempted micturition, which is, therefore, only partial or weak. The perineal reflex is not altered.

The diagnosis of reflex dyssynergia is more complex in that the neurological and clinical evaluations require urodynamic and electromyographic studies, which are not often performed in veterinary practice. The diagnosis is, therefore, made after having excluded a mechanical obstruction, on the basis of signalment, the physical examination and in the light of the characteristics of the micturition. Patients with this pathology often start to urinate, but stop before they have voided the bladder and repeat this process several times before giving up (Bartages and Kruger, 2011).

TREATMENT

RELIEVING OBSTRUCTION IN AN OBSTRUCTED PATIENT

Stabilisation of the patient
In cases of urethral obstruction of any cause, it is essential to intervene promptly to stabilise the patient and relieve the obstruction because the metabolic and renal consequences of obstruction can rapidly lead to the patient’s death. Cats with obstruction lasting for more than 48 hours are probably in a critical state and require intensive care. Before sedating the patient to relieve the obstruction, it is fundamental to look for and correct any metabolic alterations, such as hypothermia, uraemia, metabolic acidosis, hyperkalaemia and hypocalcaemia (Table 1) (Walker, 2009).

Table 1. Correction of the metabolic alterations secondary to urethral obstruction (modified from: Lulich and Osborne,_¹ 2001)

Relieving the obstruction
Unless the cat has severe sensorial depression, sedation or anaesthesia is usually necessary, together with analgesic treatment. The animal can be sedated with a combination of ketamine (2-4 mg/kg i.v.) and midazolam (0.1-0.2 mg/kg i.v.) or diazepam (0.2-0.3 mg/kg i.v.). Acepromazine (0.05 mg/kg i.v.), which reduces anxiety and helps to resolve urethral spasm, can be used in cats with an adequate blood pressure (Lulich and Osborne,_¹ 2010). In some cases sedation is not sufficient and general anaesthesia is necessary: induction with propofol, intubation and maintenance with inhaled anaesthetics (Walker, 2009).   

The choice of technique used to relieve the urethral obstruction depends on the cause of the urinary retention and the severity of the clinical picture.    

Urethral massage. Urethral plugs or small stones often lodge near the external urethral sphincter; in these cases an attempt to dislodge and expel the plugs can be made by external flexion and delicate massage of the penis; in some cases this is sufficient to resolve the obstruction (Walker, 2009).

Urethral catheterisation and retrograde flushing. In most cases, however, urethral catheterisation with retrograde flushing is necessary. Before proceeding to catheterisation with a specifically designed urinary catheter, an attempt can be made to ‘drill’ through the material present in the urethral lumen using a venous catheter. This is particular useful in the case of urethral plugs since the procedure can make the plugs less compact and thus facilitate the subsequent catheterisation (Video 1).

In order to catheterise a cat, the penis should be extended caudally and dorsally so that it is parallel to the vertebral column: this eliminates the flexure of the distal urethra and reduces the risk of trauma. The catheter, lubricated with sterile anaesthetic gel, is then advanced up the urethra until it reaches the site of the obstruction. The urethra is flushed with warm, sterile physiological saline contained in a small 5-10 ml syringe attached to the catheter byan extension tube for a fluid infusion set (Fig. 7). The fingers are used to occlude the urethra around the catheter at the tip of the penis to prevent backflow of the fluid out of the external urethral orifice. This means that the urethra dilates, which helps the stones or urethral plug to move up into the bladder. A damp gauze can be used to help to minimise trauma to the external urethral meatus (Lulich and Osborne,¹ 2010).

If the catheter fails to advance easily, it should not be forced since this could cause trauma to the urethral wall; in this case it is better to withdraw the catheter slightly and repeat the flushing. If the catheter reaches the bladder a sample of urine should be taken for a full examination and to set up urine cultures. At this point the bladder should be emptied and then bladder lavage should be performed repeatedly with warm, sterile physiological saline until the fluid draining from the bladder is completely clear (Gunn-Moore, 2007; Walker, 2009).

If the bladder is very distended, the urine exerts a considerable pressure on the terminal part of the urethra, making the catheterisation more difficult; in this case, before trying to relieve the obstruction, it may be useful to attempt immediate decompression of the bladder by cystocentesis. Using a 23 or 22 G needle, attached to a syringe by an extension tube with a three-way tap (Fig. 8), as much urine as possible is removed. There may be a small trickle of urine from the abdomen, but the risk of this is greatly reduced if the bladder is emptied completely; a leak of urine is a greater problem in the presence of infection. Another possible complication is rupture of the bladder wall; this, however, usually occurs only when the wall is particularly compromised (Hostutler et al., 2005; Walker, 2009).

In some situations it may be necessary to leave the catheter in situ, usually for 24-72 hours (Walker, 2009); in these cases it is preferable to use only soft, non-irritant catheters such as those in silicone or teflon or use a nasogastric feeding tube (see Video 1), which can be fixed to the tail (Fig. 9). Catheters made of polypropylene (the classical tom-cat catheters) can cause irritation if left in contact with the urethral mucosa (Bartages and Kruger, 2011).

The catheter may be connected to a closed collecting system to avoid ascending infections from becoming established. Alternatively the catheter can be closed with a perforable cap and emptied frequently during the day. An Elyzabethan collar must be applied to most cats to prevent them pulling the catheter out. Preventive antibiotic therapy should not be started while the catheter is still in situ in order to avoid the development of multiresistant infections. Once the catheter has been removed, antibiotic therapy is recommended, preferably with an antibiotic chosen on the basis of the results of cultures of the urine and/or catheter tip; penicillins (amoxycillin, ampicillin, amoxycillin +  clavulanic acid) and cephalosporins (cephalexin) are rational choices for empirical use (Walker, 2009).

It is not, however, advisable to leave a permanent, indwelling catheter unless strictly necessary. The decision is based on various factors, such as the duration of obstruction, difficulty in removing the obstruction, diameter of the urinary stream after removal of the obstruction, bladder tone and levels of urea in the blood (Lulich and Osborne,_¹ 2010).

Anterograde expulsion through bladder compression. When it is not desirable or not possible to catheterise the patient, an attempt at anterograde expulsion, by compressing the bladder, can be made. This technique is undoubtedly cheap and avoids trauma from a catheter, but it is not always effective; furthermore, excessive pressure on the bladder can cause trauma, rupture of the bladder wall and backflow of potentially infected urine into the ureters. This technique is performed by exerting firm, but not excessive, pressure on the bladder wall, after having massaged the urethra and, if necessary, sedated the patient (Cooper et al., 2008).

Anterograde expulsion through pharmacological relaxation of the urethra. Another technique experimented with a certain success involves pharmacological relaxation of the urethra through administration of acepromazine (0.25 mg i.m. or 2.5 mg p.o./cat) and buprenorphine (0.075 mg/cat) three times a day. If the cat does not start urinating within 24 hours, medetomidine (0.1 mg i.m./cat) can be added; leaving the patient in a dim, peaceful room can minimise stress. With this strategy, cats usually start to urinate again within 3 days. In the meantime, the bladder should be emptied frequently (e.g. with decompression cystocentesis, usually 3 times a day) and kept small. Nevertheless, even with this technique, there is the risk of trauma and rupture of the bladder wall; furthermore, it is not always effective (Cooper et al., 2008; Lulich and Osborne,_¹ 2010).

Post-obstruction diuresis
If the obstruction persists for several days and in cases of severe uraemia, once the obstruction is relieved, there may be post-obstruction diuresis, which is usually proportional to the degree of uraemia. It is, therefore, important to measure urinary output to avoid underestimating the amount of fluids to administer. A balanced crystalloid, such as Ringer’s lactate, can be sufficient to stabilise the patient; the diuresis may, however, cause hypokalaemia. In this case, the fluids should be supplemented with KCl (Table 2), remembering that potassium supplementation should not exceed 0.5 mEq/kg/hour. Once the uraemia and the post-obstruction diuresis have been resolved, the fluids are usually gradually withdrawn; the uraemia generally resolves within 24 hours. The haematocrit, total solids, urea, creatinine and potassium must be monitored daily in the first 48-72 hours. Following removal of the catheter, the patient must remain in hospital until it has passed a good stream of urine. If, after removal of the catheter, the patient does not urinate, it should be sedated and re-evaluated: if the catheter passes easily, urethral spasm should be suspected (Hostutler et al., 2005; Walker, 2009). In most cases,  catheterisation followed by targeted medical treatment is sufficient to resolve the obstruction, but if it is not, surgical management, by cystotomy with a drainage tube or urethrostomy, is necessary (Gunn-Moore, 2007).

Table 2. Guidelines for intravenous potassium supplementation in dogs and cats (DiBartola and de Morais, 2006).

Cystostomy with a drainage tube
This is a technique that involves placing a drainage tube directly in the lumen of the bladder through an incision along the ventral or ventro-lateral surface of the abdomen, towards the apex of the bladder; this diverts the urine in all those patients with obstruction or dysfunction that prevents the bladder from being emptied. The tube can be left as long as necessary to stabilise the patient, even in the prospect of more invasive surgery. A Foley’s catheter or a modified gastric tube can be used. The tube is then fixed to the body wall and connected to a closed circuit drainage system; alternatively, it can be capped and emptied at least three or four times a day (Beck et al., 2007). The system can be left uncovered or bandaged and an Elyzabethan collar can be applied to the animal’s neck to avoid the cat damaging the catheter. In a retrospective study (Beck et al., 2007) complications were recorded in about half of the patients. The most common complications included involuntary removal of the tube, inflammation, irritation or oozing of urine around the tube entry site; other possible complications are haematuria, obstruction of the tube, breakage of the tube during its removal, and the formation of fistulae following removal of the tube. Persistent or recurrent infections of the urinary tract are common, probably in relation to the residual urine in the bladder or to the formation of a biofilm on the luminal surface of the tube. Nevertheless, the use of prophylactic antibiotics is not recommended because they do not prevent these infections but increase the risk of resistance to antibiotics. Complications are more common if the tube is left in situ for a long time (> 7days) (Beck et al., 2007).

Urinary diversion using a Cystofix® or Easy Cyst® system deserves separate mention. These diversion sets consist of a needle-guide that facilitates entry into the bladder, a peel-away introducer and tube with a pig-tail extremity. The advantage of this technique is that it does not require surgery: the tube is introduced directly into the bladder through the abdominal wall with the aid of the needle-guide (Fig. 10a and b). This device has been used for several years in human medicine for suprapubic urinary diversion, as an alternative to transurethral catheterisation (Müller and Sulmoni, 1992). Although there are currently no publications on the use of the technique in cats, it has also been employed for urinary diversion in this species (Video 2).

Urethrostomy
Perineal urethrostomy is a surgical procedure used in male cats to create a permanent opening  between the pelvic urethra and the skin of the perineal region. In the case that an emergency, irreparable damage to the membranous urethra or stenosis of the urethra makes a perineal urethrostomy impossible, an antepubic urethrostomy, that is, a urethral stoma in the ventral region of the abdominal wall, can be performed (Hosgood, 2007). There is also a description of a modification of the procedure which creates a transpelvic stoma (Bernarde and Viguier, 2004).

Urethrostomy should not be considered an emergency procedure: if it is not possible to relieve a urinary obstruction, cystotomy with placement of a drainage tube is indicated rather than urethrostomy. Once the patient has been stabilised, further attempts can be made to relieve the obstruction (Hosgood, 2007). Urethrostomy should be reserved for those patients with recurrent obstruction, patients in which conservative techniques fail to relieve the obstruction, and patients with strictures, irreversible urethral trauma or neoplasms. Furthermore, before carrying out this procedure the owner should be informed about the possible post-operative complications. The most frequent post-operative complications include cystitis of ascending infections of the urinary tract and urethral stricture; bleeding of erectile tissue, wound dehiscence, urinary and faecal incontinence, perineal hernia and retro-urethral fistulae have also been reported (Smith, 2002).

Treatment of urethral spasm
Independently of the specific cause of FLUTD, cats with this condition often also have urethral spasm which can be triggered by pain or local inflammation and may involve both the smooth and striated muscle of the urethra.

In some cases the spasm is simply due to local inflammation and treatment with non-steroidal anti-inflammatory drugs, such as meloxicam (0.1 mg/kg p.o. the first day and then 0.05 mg/kg/die on the subsequent days) can, therefore, be useful. Some authors (Forrester and Roudebush, 2007) advise maintaining the dose of meloxicam at 0.1 mg/kg s.i.d. to treat pain and inflammation in the acute phase of FIC. It may be necessary to combine this treatment with analgesic therapy to relieve pain: buprenorphine at a dose of 5-20 µg/kg every 8-12 hours or butorphanol (0.2-0.4 mg/kg every 6-8 hours) can be used for this purpose.

In cases in which this is not sufficient, a myorelaxant may be indicated. Among the drugs that act on the smooth muscle, it is worth remembering prazosin (0.5-1 mg/cat p.o. every 8-12 hours), phenoxybenzamine (0.5-1 mg/kg p.o. every 12 hours) and acepromazine (0.05-0.2 mg/kg i.v., i.m., s.c. or 1-3 mg/kg p.o.). The drug that is active on striated muscle is dantrolene (0.5-2 mg/kg p.o. every 12 hours) (Gunn-Moore, 2007).

A limited number of studies have been published on the use of these drugs in the treatment of urethral spasm in the cat; it should be remembered that all drugs that act on smooth muscles can cause hypotension and that dantrolene may provoke hepatic toxicity (Gunn–Moore, 2007).

CAUSE-SPECIFIC TREATMENT

It is important to remember that FLUTD is very rarely of bacterial origin so there are no indications for starting empirical antibiotic therapy without first having confirmed the need by culturing a sample of urine.

TREATMENT OF FELINE IDIOPATHIC CYSTITIS
FIC tends to resolve spontaneously within 5-10 days even without the patient having been treated; despite this, it is important to establish treatment promptly since this is a very painful and stressful pathology for the patient. Furthermore, there is a high rate of relapse and affected animals may develop bacterial infections or obstructive conditions secondary to the persistent vesico-ureteral inflammation and chronic spasms of the urethral muscles. Vesical  or urethral diverticula may also develop (Zatelli, 2006).

The treatment of FIC is essentially based on strategies aimed at reducing stress because it has been demonstrated that this is the most effective approach for reducing the severity of the signs (Buffington et al., 2006). The role of the behavioural therapist is fundamental in evaluating behavioural and environmental factors.

Multimodal Environmental Modification (MEMO)
Multimodal Environmental Modification (MEMO) includes a series of changes to make to the environment in which the cat lives in an attempt to reduce the severity of the FIC by lowering the possibility of activation of the stress response system (Buffington et al., 2006). These changes include educating the owner, diet, the animal’s inanimate surroundings and its interactions with other cats, animals or human beings. The Indoor Cat Initiative considers the amount and type of interactions between the owner and the cat, the adequacy of resources (according to the 1 + 1 rule applied to the litter tray and bowls for food and water - that is, one for each cat and one extra),  the position and cleanliness of the litter tray, the arrangement of the bowls (the cats must be able to eat in a peaceful, quiet place away from other animals), measures to reduce conflicts between cats (raised floors, areas in which to hide, be isolated and rest undisturbed, avoidance of competition for resources, gradual introduction of any new animals), predatory behaviours and play; if feasible the cat should have the possibility of going outside (Westroppe  and Buffington, 2004). These measures help to reduce stress. Some owners manage to identify events that are stressful for their cat or even a particular event that triggered an episode of FLUTD, in which case similar situations should be avoided if possible.

Increased water intake
An increase in water intake promotes an increase in the volume of urine and also dilutes the urine, lowering the concentrations of toxins, irritant substances and mediators of inflammation in it. In order to achieve this increased water intake, it may be sufficient to give moist food or, if the cat does not like such food, to add water to dry food. If the cat prefers running water, fountains can be used. The addition of flavouring or the use of several bowls of water placed in different parts of the house may also help. Some diets may promote the intake of water through the addition of a controlled amount of salt to the food. Given the absence of studies on the effects of such supplementation in cats with renal disease or hypertension, these diets should not be used in cats with these conditions (Forrester and Roudebush, 2007).

Pheromones
There is a commercially available, synthetic analogue of feline facial pheromone, developed to reduced anxiety-related behaviours in cats. The product is available in a spray form or for diffusion in the environment. One study carried out in cats with FIC (Gunn-Moore and Cameron, 2004) did not find sufficient evidence of efficacy to recommend the routine use of this pheromone in this pathology, but did demonstrate its efficacy in reducing anxiety in cats facing unfamiliar situations and is, therefore, considered an auxiliary aid in the treatment of FIC (Westroppe and Buffington, 2004). However, a recent systematic review of the literature on this subject concluded that the scientific evidence on the efficacy of this drug is still scarce (Frank et al., 2010).

Glycosaminoglycans
As already mentioned, GAGs line the bladder wall protecting it from irritant substances present in the urine and inhibiting adhesion of bacteria. This lining is altered in FIC. GAGs have been used with some benefit in human medicine. In veterinary medicine the only study on their use in FIC did not demonstrate that they were particularly effective (Gunn-Moore and Shenoy, 2004); nevertheless, they can be considered an aid in addition to other drugs.

Pharmacological treatment
Animals refractory to the treatments described above may need auxiliary drug therapy. Long-term treatment is reserved to the most severe cases, with persistent signs or multiple recurrences. In the case of acute signs, a short cycle of analgesics, such as non-steroidal anti-inflammatory drugs, butorphanol, buprenorphine and fentanyl, can give some benefit, even though scientific evidence supporting their routine use in the case of FIC is lacking (Hostutler, 2005).

Amitriptyline, a tricyclic antidepressant, seems to have some efficacy in the treatment of chronic forms of FIC (Chew et al., 1998), due, in part, to an analgesic effect (Hostutler, 2005); its efficacy as short-term therapy has not been demonstrated (Kruger et al., 2003). The initial dose of 5 mg/day is effective in most cats; if it is not, the dose can be increased gradually to a maximum of 12.5 mg. If positive results are not seen within 4 months, the dose of the drug should be gradually tapered down until the treatment is suspended (Hostutler, 2005).

Other drugs used in the treatment of FIC include clomipramine, fluoxetine and buspirone. Diazepam is not recommended because of its potential toxic effects on the liver (Center et al., 1996). Glucocorticoids have not been found to be effective in reducing the clinical signs or accelerating the healing of cats with FIC (Hostutler, 2005).

TREATMENT OF URINARY STONES
Medical treatment can be used to dissolve struvite and urate stones, but not uroliths of calcium oxalate. It is important to remember that crystals do not damage the urethra and/or bladder wall directly, so the presence of crystals in the urine does not in itself require dietary therapy.

Struvite
There are well-known diets formulated to dissolve this type of stone: these diets are acidifying, poor in magnesium and supplemented with salt. Their aim is to obtain urine with a specific gravity below 1030 and a pH lower than 6.3 (Hostutler, 2005). Moist diets are preferable to dry ones because the former are associated with more rapid dissolution of stones (Lulich and Osborne, 2010). It is also very important to increase the animal’s water intake in order the dilute the stone-promoting minerals in the urine (Hostutler, 2005). When there is a concomitant bacterial infection, antibiotic treatment, chosen on the basis of the results of urine culture, should be administered and continued for at least 2 weeks after complete dissolution of the stones. Indeed, bacteria remain alive within the matrix of the urolith during therapy (Hostutler, 2005; Lulich and Osborne, 2010). In order to evaluate the efficacy of dietary therapy and the owner’s compliance, it can be useful to assess the patient by X-ray studies and urinalysis every 2 or 3 weeks: treatment is considered effective if struvite crystals are not found in the urine and there is radiological evidence of a decrease in the size of the stones (Lulich and Osborne, 2010). Most sterile struvite calculi dissolve within 2 to 4 weeks while infected ones usually take longer. Stones in the urethra respond less well to dietary-induced dissolution because they are not continuously surrounded by “medicated” urine and so, even if they are not causing an obstruction, they should be monitored periodically and propelled into the bladder (Lulich and Osborne, 2010).

The diet should be continued in the 4 weeks following radiological demonstration of the absence of stones and then a maintenance diet introduced. A maintenance diet helps to prevent recurrences, reduces the relative supersaturation of minerals and decreases the precipitation of struvite crystals (Forrester and Roudebush, 2007). This diet should be continued until the animal is at least 7 years old, an age at which the risk of recurrences decreases. It should be remembered that acidifying treatment given with the purpose of preventing the formation of struvite stones can promote the formation of calcium oxalate stones. Furthermore, it is essential to diagnose and treat promptly all urinary tract infections to prevent the formation of infection-induced struvite stones (Lulich and Osborne, 2010).

The only candidates for surgery are patients with persistent or recurrent urethral obstruction and those which, despite medical therapy, are found to have stable-sized or enlarging stones during monitoring. Surgery may also be used when the compliance of the owner is poor or in the case that the patient has persistent pain despite appropriate analgesia (Lulich and Osborne, 2010).

Calcium oxalate
As stated earlier, this type of stone cannot be dissolved. For stones up to 5 mm in females and 1-2 mm in males, a technique of micturition urinary flushing may be attempted. The bladder is distended moderately by introducing sterile physiological saline through a urethral catheter (in principle about 4-6 ml/kg of fluids are necessary to distend an empty bladder). The catheter is then removed and the patient is constrained in such a way that its vertebral column is vertical. The bladder is agitated to facilitate the movement, under the effect of gravity, of the stones towards the neck of the bladder and then micturition is induced by constant digital pressure on the bladder wall, which causes emission of urine and the stones. The stones should be collected into a container and if the number of stones collected is lower than the number seen on the X-rays, the procedure can be repeated (Osborne et al., 1999). In some cases this procedure can be performed in the absence of anaesthesia but, even if anaesthesia is used, it is required for a shorter time than when needed for a cystotomy; furthermore, since no incision is needed, the recovery times are much shorter (Osborne et al., 1999). Before the procedure is concluded, a double contrast cystography should be performed to ensure that all the stones have been removed (Osborne et al., 1999).

Great care should be taken not to underestimate the size of the stones when using this technique, because it could cause urethral obstruction, particularly in males. Furthermore, it should not be performed in any case in which compression of the bladder could cause extravasation of the urine into the peritoneum, as, for example, in the period of healing after bladder surgery. Finally, bacterial infections should be excluded in order that the bladder compression does not cause vesico-ureteral reflux of infected urine (Osborne et al., 1999). If this flushing technique is not successful, surgical removalof the stones is necessary.

After surgical removal of stones, a specific diet should be started to reduce the risk of recurrence by decreasing the supersaturation of calcium oxalates, increasing the concentration or activity of their inhibitors and promoting the dilution of urine (Forrester and Roudebush, 2007). Furthermore, it has been seen that cats eating a diet with a high water content have a lower risk of developing this type of stone, so it is advised that these animals are fed a moist diet and, very importantly, that they are encouraged to drink water (Forrester and Roudebush, 2007). It is also important to detect and treat hypercalcaemia, if present, in order to prevent recurrences. It has been seen that the presence of suture material is a risk factor for the precipitation of calcium oxalates, and for this reason stiches should not be made in the internal surface of the bladder (Lulich, 2010).

Supplemental potassium citrate, an alkalinising agent, can be considered for all those patients which have frequent recurrences, despite an appropriate diet; the recommended dose is 50-75 mg/kg b.i.d. (Forrester and Roudebush, 2007).

Vitamin B₆ (2-4 mg/24-48 hours) supplements can also be given to all patients fed a homemade diet or a diet deficient in this vitamin (Lulich, 2010) because this vitamin can decrease the formation of oxalates (Forrester and Roudebush, 2007).

Thiazide diuretics have been recommended in human medicine to reduce the recurrence of calcium oxalate stones, given their capacity to decrease the urinary excretion of calcium. However, although hydrochlorothiazide administered to healthy cats at a dose of 1 mg/kg p.o. b.i.d. has been demonstrated to decrease the relative supersaturation of calcium oxalate, the reduction of urinary excretion of calcium was found to be minimal. Furthermore, these diuretics are contraindicated in hypercalcaemic patients because they promote the retention of calcium. Their efficacy in cats with calcium oxalate stones has not yet been determined, but they could be considered at a dose of 1-2 mg/kg p.o. b.i.d. for patients with very frequent recurrences which are not hypercalcaemic (Lulich, 2010).

In human medicine it has been hypothesized that prolonged antibiotic treatment could reduce intestinal levels of Oxalobacter, a bacterium that breaks down oxalates. This would have the effect of reducing the absorption of oxalates, thus increasing their excretion in the urine. This is another reason for avoiding the indiscriminate use of antibiotics (Lulich, 2010).

All animals should be monitored for possible recurrences by examination of the urine every 3 months and X-rays or ultrasonography every 6 months (Forrester and Roudebush, 2007).

Urates
In order to dissolve or prevent recurrences of this type of stone, the animal should be given a purine-poor diet in association with allopurinol (which inhibits xanthine oxidase, the enzyme necessary for the production of uric acid) at a dose of 9 mg/kg/die (Hostutler, 2005).

TREATMENT OF URETHRAL PLUGS
The treatment of urethral plugs is aimed at reducing the protein matrix (see treatment of FIC), crystals (by changing to moist foods, perhaps of a specific type) and urethral spasm (see treatment of urethral spasm).

TREATMENT OF BACTERIAL CYSTITIS
The antibiotic should be chosen on the basis of the results of urine culture and an antibiogram, giving preference to antibiotics that reach a good concentration in the urine. Treatment should be continued for 2-3 weeks or for 4-6 weeks if renal involvement is suspected (Hostutler, 2005).

Penicillins (amoxycillin, ampicillin, amoxycillin + clavulanic acid) and cephalosporins (cephalexin) are reasonable choices if empirical therapy must be undertaken; the use of fluoroquinolones or third-generation cephalosporins is discouraged unless specifically indicated by the result of the antibiogram (Walker, 2009).

In the case of recurrent cystitis the urine culture should be repeated during treatment (7-10 days after starting the therapy) to check the in vivo efficacy of the antibiotic; if the culture is negative the antibiotic should be continued for a total of 4-6 weeks, depending on the site and type of the infection. If the kidneys or prostate are involved, the treatment should be continued for 6-8 weeks. The urine culture is then repeated 1 week and 1 month later after suspension of the treatment. If the recurrent cystitis is secondary to the presence of infected stones, removal of the calculi is usually necessary in order to resolve the cystitis (Westropp and Adams, 2008).

TREATMENT OF ANATOMICAL MALFORMATIONS
Anatomical malformations usually require surgical correction. The only exceptions are microscopic bladder or urachal diverticula which, as mentioned previously, usually only cause problems when, secondary to acquired pathologies of the bladder or urethra, they become macroscopic. In this case the enlarged diverticula usually regress spontaneously within 2 or 3 weeks of resolution of the acquired pathology. In the case of urachal anomalies it is, therefore, important to re-assess the patient during treatment to determine whether there has been any improvement; if the anomaly does not resolve or recurs, a diverticulectomy is indicated (Bartages and Kruger, 2011).

TREATMENT OF BLADDER NEOPLASMS 

TREATMENT OF NEUROLOGICAL DISORDERS
Treatment of complete atony of the detrusor muscle and areflexia of the external urethral sphincter in lower motor neurone disease is usually unsuccessful unless the triggering cause is reversible. When the denervation is partial, the detrusor contractions can be increased by parasympathomimetic drugs, such as bethanecol (at a dose of 1.25 – 5 mg/cat p.o. s.i.d.); this drug is, however, ineffective and contraindicated in cases of complete damage to the pelvic nerve and obstruction or marked resistance of the urethra since it could cause bladder rupture. The patients should be managed at home with manual bladder voiding at least three or four times a day and frequent washing of the perineal region to avoid urine-induced dermatitis. The animals should be monitored regularly and the urinary infections to which they are prone should be treated.

In the case of dysautonomia if the pathology affects only the urinary system, a parasympathomimetic agent together with manual emptying of the bladder can give good results. Treatment is not usually successful when other systems are involved (such as in the case of ileus or mega-oesophagus).

In acute forms of myogenic detrusor atony it may be sufficient to leave an indwelling catheter, connected to a closed urine collection system, for a period lasting from 72 hours to about 2 weeks. This usually enables recovery of the tight junctions and detrusor function. Parasympathomimetic agents may help detrusor contractility, but should not be administered before having restored a low urethral resistance (by catheterisation, removal of any physical or anatomical obstruction present, through the use of drugs). The prognosis depends on the reversibility of the underlying cause; however, if the condition becomes chronic the possibility of functional recovery decreases.

In the case of functional obstruction drugs are needed to reduce the resistance of the internal and/or external urethral sphincter (see treatment of urethral spasm). An anxiolytic such as acepromazine (at a dose of 0.02-0.05 mg/kg s.i.d. or b.i.d. i.v. or 1.1-2.2 mg/kg p.o. s.i.d. or b.i.d.) or alprazolam (0.125-0.25 mg/cat b.i.d. p.o.) may be useful to reduce the stress and, consequently, the sympathetic stimulation; in some cases catheterisation may be necessary while waiting for the drugs to take effect. Only soft, minimally irritant catheters should be used to reduce urethral spasm. It may be appropriate to use urethral relaxants both during and after the period of catheterisation or, if the patient is not uraemic, a single dose of a non-steroidal anti-inflammatory drug at the moment of catheterisation.

Caution is required in attempting manual emptying of the bladder in the case of acute upper motor neurone disease both because the manoeuvre can lead to rupture of the organ and because repeated manual compression can interfere with the healing of the detrusor. Catheterisation or drugs to reduce internal and external urethral sphincter tone are often needed to empty the bladder in this stage. Within a few days or a week, some capacity to urinate can be recovered thanks to a local spinal reflex which provokes involuntary bladder voiding when the threshold capacity is reached: this phenomenon is called automatic or reflex bladder. Manual emptying of the bladder is usually possible in this phase.

The treatment of reflex dyssynergia is based on decreasing the resistance of the internal and external urethral sphincters and if, necessary, recovering detrusor function (Bartages and Kruger, 2011).

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