Uterine adenocarcinoma (Figs. 1 and 2) is the most common type of cancer found in the female rabbit; in subjects over 3 years of age the incidence can be of 50-80%, depending on the breed, while under 3 years of age it is instead uncommon. The condition is entirely preventable with sterilization, preferably performed at 6-12 months of age.
The breeding history of the animal does not influence the incidence of uterine adenocarcinoma; there is no difference between nulliparous rabbits and does which have already given birth. Some breeds are more predisposed, such as the Netherland, Californian, New Zealand and dwarf breeds, but all breeds can be affected, including mixed breed rabbits. The tumour is multi-centric, and eventually involves both uterine horns. The evolution is slow and progressive, with initial invasion of the myometrium and subsequently of the peritoneal cavity; within 1-2 years haematogenous spread is present with metastases to the lungs, bones and liver.
The severity of symptoms varies greatly from subject to subject and depending on the stage of the tumour. The symptoms are sometimes completely silent and the tumour is either suspected in view of the detection, during a regular physical examination, of an increased uterine volume on palpation of the abdomen (always an abnormal finding), or found in the course of a routine ovariohysterectomy (Figs. 3 and 4). The reason for the visit is at times the presence of respiratory distress secondary to pulmonary metastases, without there being any signs related to the underlying primary tumour. In some subjects blood may be noticed at the end of urination; in chronic cases pallor and weakness may be present due to anaemia. The tumour may be accompanied by hormonal changes that may result in mammary cystic formations or in behavioural disorders such as aggressiveness. Uterine adenocarcinoma may be the cause of abdominal pain and of anorexia. In advanced stages, with metastases, dyspnoea, ascites, weight loss, depression and anaemia may be present.
The presence of an easily palpable, irregular uterus should always be considered as an abnormal finding. A radiographic examination may detect the presence of soft tissue in the caudal abdomen (the enlarged uterus), sometimes accompanied by calcifications. Ultrasonography reveals increased uterine volume, eventually with fluid content.
In all cases of suspected uterine carcinoma a chest X-ray is necessary in order to rule out the presence of lung metastases (Figs. 5-9). Lung metastases appear as rounded, radiopaque areas scattered in the lung fields.
Surgical treatment must be preceded by a thorough examination of the health status of the rabbit, with blood work, X-rays and possibly abdominal ultrasonography. If metastases are present the prognosis is poor; in the presence of respiratory distress, euthanasia is advisable.
In the absence of metastases, and should the conditions of the animal allow it, ovariohysterectomy is curative. Care must be taken to transect the uterus caudal to the cervices, in order to ensure the removal of the entire uterine tissue (Fig. 3). Radiographic control of the chest is then performed at 6 and 12 months. Should lung metastases not be observed during this time interval, it is unlikely that they may occur later.