Female pet rabbits in Singapore are commonly affected by a condition known as uterine adenocarcinoma. Simply put– it is the presence of a tumour that develops into cancer in the uterus. It may be difficult to spot the early signs as rabbits are known to “hide” their symptoms– a primitive behaviour developed as a prey animal to avoid becoming a bigger target to predators. Some telling signs that your rabbit may be affected by uterine adenocarcinoma are;
Blood in the urine or bloody vaginal discharge– indicative of urinary tract infections.
In breeding rabbits, stillborn kits or abortion are possible signs.
Reduced appetite
Lethargy
Reduced fecal production
Chronic weight loss.
A sudden behaviour change such as lethargy and disinterest in play is often indicative of sickness.
Other signs will depend on where the cancer cells have spread. If the cancer has spread to the lungs, breathing difficulties or increased breathing rate will be seen. Acute fractures of the limbs or spine may happen if there is cancer spread to the bones.
Suspect your pet rabbit may be affected by uterine adenocarcinoma? Read further as we take a deep dive into the condition and how it may impact your furry friend.
What is uterine adenocarcinoma?
Uterine adenocarcinoma is the most common uterine tumour in female rabbits. The estimated incidence of uterine adenocarcinoma is 4% in rabbits less than 3 years and increases to 80% by 6 years of age.
Cystic endometrial hyperplasia (CEH) is a non-cancerous uterine condition that commonly occurs in female rabbits which are less than 3 years old. It is often found together with uterine adenocarcinoma, which suggests that it may be a pre-cancerous state. However, CEH is not found in all cases of adenocarcinoma.
Spreading (metastasis) of cancer cells from the uterus can occur to the surrounding abdominal organs through direct spread or via the blood and lymphatics to distant sites. The common metastatic areas are the lungs, liver, spleen, kidney, lymph nodes, gastrointestinal tract and central nervous system. The possibility of metastasis ranges from 20-80%.
Rabbit with confirmed uterine adenocarcinoma without lung metastasis.Rabbit with confirmed uterine adenocarcinoma with lung metastasis.
Case Study: Tale of 2 Rabbit Patients with Uterine Adenocarcinoma
Case 1: Timely Detection
A 5 year-old, female, unsterilised rabbit was presented for reduced fecal size and soiling of its bum and feet. It was usually a very clean rabbit according to the owner. An ultrasound was done which showed that the uterus was thickened and lumpy. Radiographs of the lungs did not reveal any metastasis. The rabbit underwent an ovariohysterectomy and the uterus was sent off for a biopsy. It was confirmed to be a uterine adenocarcinoma. The rabbit recovered well after the surgery and on its two months follow up radiographs, there was still no signs of lung metastasis.
Case 2: Delayed Intervention
A 6 year old, female, unsterilised rabbit was presented to Dr Paws Vet Care for reduced appetite and defecation for three days. The owner also noticed that the bunny was breathing harder than usual with her head bobbing for two days.
A mass was palpated in the abdomen and confirmed to be arising from the uterus after doing an ultrasound. Uterine cancer was suspected.Unfortunately, radiographs of the thorax revealed that there was possibly already metastasis to the lungs. The rabbit was sent home with palliative care and passed away three days later.
How is uterine adenocarcinoma diagnosed?
Any unsterilised, middle-aged to older rabbit will raise the suspicion of uterine adenocarcinoma if they are unwell as the clinical signs can be very vague and unspecific as mentioned above. A veterinarian should be able to palpate an enlarged and painful mass in the abdomen and call for an abdominal ultrasound to investigate the mass.
On an abdominal ultrasound, an enlarged uterus with thickened and irregular walls is highly suspicious of cancer. However, in some cases, CEH may have a similar appearance. The other abdominal organs can also be examined during the ultrasound to check for any metastatic growth.
A definitive diagnosis can only be obtained by doing a biopsy of the uterus. Radiographs may be able to see an enlarged uterus but an abdominal ultrasound is more sensitive. If the abdominal mass is confirmed to be arising from the uterus after an abdominal ultrasound, radiographs to check on whether there has been metastasis to the lungs will be advisable.
What are the treatment options for rabbit uterine adenocarcinoma?
A surgery called ovariohysterectomy (also known as a spay) to remove the ovaries and the entire uterus is the best treatment. A biopsy is highly recommended as a visual inspection of the affected organ is not an accurate way to diagnose cancer.
Unfortunately, if the cancer is found to have spread to other parts of the body, chemotherapy is currently not an option for rabbits. These rabbits can only be treated with palliative care until the end of life.
What is the aftercare for rabbit uterine adenocarcinoma?
If your rabbit was unwell before the surgery, hospitalisation for intravenous fluids, pain relief and force-feeding may be required after the surgery for a few days until she looks more comfortable.
For the fortunate rabbits who have surgery done before any noticeable spread of cancer, regular checkups with radiographs (X-rays) of the thorax and abdomen are required every 3-6 months to monitor for metastasis.
What is the prognosis (potential outcome) for rabbit uterine adenocarcinoma?
Prognosis is good for rabbits which undergo surgery before any metastasis is detected.
Neutering or spaying your female rabbit when she is at least 6 months old is the best way of protecting your rabbit. Spaying also helps to prevent mammary cancers, pyometra (infected uterus) and unwanted pregnancies.
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