Gastrointestinal (GI) stasis is among the most frequent reasons for which rabbits are taken to the Veterinarian. GI stasis is characterized by the presence of an adynamic ileus of the gastrointestinal tract, without obstruction. The conditions responsible for this disorder are many. In the rabbit, intestinal motility is regulated by the presence of dietary fibre; any condition that induces pain, causing dysorexia or anorexia, reduces or prevents the introduction of fibre into the digestive tract, thus leading to stasis.
The more common causes of GI stasis include: symptomatic dental malocclusion, urinary tract disorders (urolithiasis, hypercalciuria) and postoperative pain. Non-painful conditions such as malocclusion of the incisors, that physically prevent the animal from taking food, and all the major causes of respiratory distress, which make feeding difficult, are also a possibility. A major cause of GI stasis is the administration of a diet poor in fibre content, such as when using commercial diets based on seeds, grains and flaked cereals. Rabbits fed in this way are more likely to develop GI stasis compared to those fed with an appropriate diet.
Stress and fear may be a direct cause of the condition, as the catecholamines being released have an inhibiting action on intestinal motility.
Once present, GI stasis self-perpetuates itself, as it induces pain and discomfort, which in turn inhibit the intake of food and hence of fibre, further reducing intestinal motility. A vicious cycle is thus activated, leading to a progressive deterioration of the health status of the animal, until death.
Some rabbits are subject to recurrent episodes of GI stasis for no apparent reason, notwithstanding an optimal diet and management. In such cases a primary intestinal motility disorder may be present. Stagnant food in the digestive tract gradually becomes dehydrated (Fig. 1), it may undergo abnormal fermentation and cause meteorism. Pathogenic bacteria may then develop, with the production of toxins, shock and death.
Initially, although uninterested in food, rabbits with GI stasis often appear energetic. The condition then progressively worsens, because of the pain and dehydration. The clinical history is particularly useful as it allows to verify if the diet is adequate and if underlying triggering factors or pathological conditions are present. The physical examination must be thorough and exhaustive, in order to detect any problems that may have induced GI stasis. Special attention must be paid to the examination of dentition, molar teeth included.
Blood work is useful for evaluating the functionality of the internal organs or to detect eventual signs of infection. Radiographs are the most useful diagnostic test (Figs. 2-4), as they allow to observe the degree of ileus and of meteorism present and to detect predisposing factors such as stones or hypercalciuria. Typical radiographic findings include stomach dilation, because of the food content, and a variable degree of gastrointestinal meteorism, which may at times be dramatic. In addition, radiographic examinations are also useful for the differential diagnosis of bowel obstruction.
Aim of the treatment is primarily to rehydrate the intestinal content, introduce fibre and calories and fight pain. Warm fluids should be administered (e.g., Ringer lactate) for rehydration, 100-150 ml/kg per day. The subcutaneous route is the most used as it is well tolerated and allows rapid fluid resorption. In more severe patients the IV route is used, via an intravenous catheter in the cephalic vein of the forelimb. Assisted feeding is essential to restore intestinal motility, using a specific fibre-rich diet. Several fractionated meals are administered throughout the day, as the stomach may be replete. If the condition is severe and the patient refuses to take food, a nasogastric tube is inserted in order to provide liquid concentrated food to rehydrate the gastric content and to provide calories to prevent hepatic lipidosis. Within 2-3 days the rabbit should return to accept food orally.
Analgesics are necessary, as pain prevents the recovery of motility. In the presence of normal renal function and of normovolaemia once the dehydration has been corrected NSAIDs may be used, such as meloxicam. Buprenorphine is another possibility, as its sedative effect is minimal. Prokinetics are widely used, although no studies are available showing their clinical utility; clebopride or metoclopramide can be used. Ranitidine is useful both as a prokinetic agent as well as for the prevention of gastric ulcers, which are a possibility in the presence of stasis. Simethicone (an anti-foaming agent) is only useful in the presence of foamy meteorism. Should the rabbit be hypothermic, before starting with the administration of food or drugs normothermia should first be restored.
With appropriate therapy the prognosis is in most cases good. Treatment should be continued until the resumption of spontaneous feeding. Any concomitant disease or dietary errors must be corrected to prevent recurrence of the condition. Useless therapies include the administration of Vaseline oil, papaya proteolytic enzymes, pineapple juice, intestinal ferments and enemas.