Gastrointestinal Problems in Rabbits

Key Points

  • Gastrointestinal problems are common in rabbits.
  • True diarrhea is most often seen in young rabbits and may be the result of parasitic enteritis, usually secondary to Eimeria spp.
  • Bacterial enteritis may manifest as mucoid enteropathy in rabbits housed in commercial or laboratory settings.
  • Cecal dysbiosis can occur in rabbits fed carbohydrate-rich diets. Affected rabbits intermittently pass thick, pasty stool with a pungent odor.
  • Gastrointestinal stasis is often caused by multiple factors including low dietary fiber, inappropriate diet, stress, and/or dehydration.
  • Aggressive supportive care is often necessary to nurse a rabbit through a bout of gastrointestinal stasis or ileus. Treatment often relies upon analgesia, fluid therapy, enteral feedings, gastrointestinal motility agents, encouraging exercise, and/or abdominal massage.
  • Obstruction of gastric outflow is often caused by a small mass of dehydrated ingesta. The resultant gastric distension or bloat can very quickly become life threatening if left untreated. Patients often respond to intravenous fluid therapy, prudent use of metoclopromide, and gastric decompression although surgical intervention is sometimes necessary.
  • Rabbits with intestinal obstruction are occasionally presented and create a diagnostic and therapeutic dilemma. Cases are most commonly the result of a small trichobezoar or hair-filled cecotroph. The duodenum and ileocecal junction are the most common sites of obstruction.
  • Abdominal radiographs may help to distinguish between gastrointestinal obstruction and ileus, with the later the gas pattern tends to extend into the colon.

Introduction

Gastrointestinal problems are common in the pet rabbit (Oryctolagus cuniculi) . A thorough history, including a detailed dietary history, can provide invaluable clues to the problem at hand. Signs of gastrointestinal discomfort in the rabbit may include bruxism, reluctance to move, and anorexia. If there is a history of anorexia, it is imperative to differentiate whether the rabbit is not eating because it has no interest in food, or if it is showing an interest in food but unable to eat. A complete lack of appetite is most commonly seen with physiological problems such as renal failure, whereas a reluctance to eat is a classic presentation in rabbits with dental disease.

 

Dental disease

Dental disease is an important cause of anorexia in the rabbit. The most common problems being being elongation of the roots and deterioration of underlying tooth structure, along with misalignment and overgrowth of the crowns of the cheek teeth. With progression of acquired dental disease curvature of the cheek teeth and subsequent development of sharp enamel spurs ensues. These painful dental spurs often result in eating and grooming difficulties, excessive salivation and weight loss over time. Over 90% of the time, dysfunction of the upper arcades creates spurs that grow into buccal mucosa while spurs of the lower arcades generally impinge on the tongue. An oral examination of the conscious patient may reveal the offending spurs, however, a more thorough exam under sedation is often necessary. Incisor malocclusion leading to tooth overgrowth can also prevent a rabbit from eating properly. Whenever dental disease of any form is present, it is imperative ideal to take skull radiographs to fully evaluate the extent of the disease process. Skull radiographs, preferably 6 views that evaluate lateral, ventrodorsal, dorsoventral, rostrocaudal, and right and left lateral oblique projections, are an invaluable aid in assessing rabbit dental health.

 

Diarrhea

True diarrhea is most often seen in young rabbits. In pet rabbits diarrhea is usually secondary to coccidiosis caused by Eimeria species. Overcrowding and damp, dirty conditions can contribute to the spread of coccidiosis. Manage affected rabbits with fastidious cleaning of the environment, fluid therapy as needed to control dehydration, nutritional support, and trimethoprim/sulfamethoxazole (30-40mg/kg PO q 12 hrs for 7-10 days) and supportive care as needed.

Young rabbits in commercial or laboratory settings may develop diarrhea secondary to mucoid enteropathy. Rabbits on low fiber (<12%), high-energy diets are predisposed to bacterial imbalances resulting in overgrowth of E. coli and toxin producing Clostridium spp., as well as parasitism caused by Eimeria spp. and Cryptosporidium. Clinical signs include depression, hypothermia, and abdominal swelling secondary to distension of the stomach and jejunum with fluid and gas, along with distension of the colon with clear, gelatinous mucus. Diarrhea may be seen in early stages of disease, while later in the disease process the rabbit may pass mucus alone or mucus mixed with fecal material. The mortality rate can be high.

 

Cecal dysbiosis

Instead of completely fermenting all ingested plant fiber, rabbits utilize a mechanism to sort out indigestible fiber and expel it from the body. This sorting mechanism occurs as end products of digestion enter the colon where muscular contractions facilitate the separation of larger particles of indigestible fiber from smaller particles of complex carbohydrates. These different breakdown products of digesta simultaneously move in opposite directions with the indigestible component moving down the colon to be voided as hard fecal pellets. The small particle fraction enters the cecum where fermentation by bacteria and protozoa results in the production of amino acids, water soluble vitamins and volatile fatty acids, an energy source for the rabbit. Some nutrients produced by the cecal microflora are absorbed across the cecal wall, with the remaining contents being formed into soft, fecal pellets called cecotropes or ‘night’ feces, which are voided from the body and ingested by the rabbit directly from the anus. This practice of consuming cecotropes is called copraphagy or cecotrophy, and is an integral part of the rabbit’s digestion process.

Cecal dysbiosis occurs when the rabbit consumes a diet rich in sugars and other simple carbohydrates such as whole or cracked corn, fruits, seeds, crackers, cereals, or “yogurt” treats. This carbohydrate overload is thought to be a predisposing factor in the development of yeast overgrowth and an imbalance of the bacterial flora.

Owners frequently complain of diarrhea that is actually abnormal cecotrope production due to cecal dysbiosis. Affected rabbits typically continue to produce normal hard fecal pellets, but they also pass loose, thick, pasty excrement that has a very pungent odor. Large numbers of S. guttulatus are frequently seen on microscopic examination of malformed cecotropes.

Dysbiosis is best addressed with supportive care as indicated by the patient’s clinical status, along with strict diet changes. Eliminate all simple carbohydrates and encourage the rabbit to consume coarse fiber primarily in the form of hay along with some leafy greens. Eliminate all concentrates such as pellets until the rabbit improves. Transfaunation or enteral feeding of cecotropes gathered from a healthy bunny as well as supplementation with probiotics, are effective adjunct therapies.

 

Ileus or gastrointestinal stasis

Due to their fastidious grooming habits, rabbits always have some hair present in their gastrointestinal tract (GIT). If they are taking in adequate amounts of coarse fiber and water, this hair is passed regularly in the fecal pellets. Although true trichobezoars can occur in rabbits, most often a decrease in or lack of production of fecal pellets is due to ileus or gastrointestinal stasis.

Multiple factors are usually involved in the development of gastrointestinal stasis including inadequate dietary fiber, stress, pain, and/or dehydration secondary to underlying conditions like dental disease. When the rabbit becomes dehydrated, water is pulled from the GIT to keep the rest of the body hydrated. This results in compacted, dry or doughy gastric and cecal contents.

Rabbits with gastrointestinal stasis frequently present for lethargy and partial or complete anorexia. Stool production may be scant or entirely absent. Physical examination findings often include depression, hypothermia, a doughy stomach and cecum on palpation, and gas filled intestinal loops. Auscultation of the GIT may reveal normal or hyperactive gut sounds early in the disease process, but later gut sounds are reduced or absent. Signs of pain may be observed and include a hunched posture or bruxism.

Radiographic findings include intestinal loops distended with gas and a very small cecum. It is not uncommon to see a gas shadow surrounding the gastric contents. This gas bubble, at times caused by aerophagia during induction with inhalant anesthetics, outlines the dehydrated mass of gastric contents.

Intensive supportive care is often necessary to nurse a rabbit patient through a bout of gastrointestinal stasis.

  • Ileus is an extremely painful condition. Provide liberal analgesia using agents such as meloxicam (0.1-0.2mg/kg SC, PO q 24h) and/or buprenorphine (0.01-0.05mg/kg SC, IP, IV q 6-12 hrs).
  • Give appropriate crystalloid fluids such as lactated ringers or normal saline with vitamin B complex either intravenously, intraosseously, or subcutaneously, depending on the severity of disease. Oral administration of electrolyte solution is also helpful in restoring normal hydration. Maintenance is approximately 60-100 ml/kg per day and most rabbits with ileus require at least 1.5 to 2-times maintenance.
  • Syringe feed high-fiber gruel such as Emeraid Herbivore or Oxbow Critical Care. A pureed pellet and vegetable mix may also be used short-term. Provide ad lib amounts of hay and leafy greens. Regular feedings every 3-6 hours will prevent hepatic lipidosis, which develops quickly in rabbits, while promoting gastrointestinal motility.
  • Nasogastric tube feeding can be less stressful for critically ill rabbits that are too weak or nauseous to eat from a syringe.
  • Pharmacological agents used in the treatment of ileus include prokinetics such as metoclopromide (0.5mg/kg PO, SC q 4-12 h) and cisapride (0.5mg/kg PO q8-12 h). Cisapride may be obtained through a compounding pharmacy.
  • Simethicone, in the form of a commercial infant anti-gas preparation (Mylicon©, Merck), may also be useful in breaking down GIT gas (1 mL PO q 4-8 h).
  • Stimulate intestinal motility and breakdown impacted gastrointestinal contents with gentle, deep abdominal massage. If the rabbit is not critical, encourage exercise to stimulate gastrointestinal motility.
  • Another reported adjunct is cholestyramine (Questran©). This product acts as an ion exchange resin to adsorb enterotoxins that can potentially damage the liver. The published dose is 2g (one-eighth teaspoon)/rabbit PO q24h gavaged in 20mL of water.

Gastrointestinal obstruction and acute gastric dilation

Rabbits have a very tight esophageal sphincter and cannot vomit or eructate. Rabbits also normally produce large amounts of saliva and gastric secretions. As a result, obstruction of gastric outflow quickly leads to distension of the stomach. The distended stomach compresses the acute angle of the pyloric outflow tract in the rabbit creating a self-perpetuating cycle of further distension and obstruction. The distended stomach may place excess pressure on the diaphragm, which compromises the rabbit’s already small lung volume.

Rabbits are often obstructed because of a small mass of dehydrated ingesta or hair-filled cecal pellet. Less commonly, a trichobezoar, a mass lesion, or an ingested foreign body may cause obstruction. The most common locations for intestinal obstruction are the distal duodenum and the ileocolic junction.

Clinical signs of bloat and gastrointestinal obstruction often include sudden onset anorexia, abdominal pain, and depression. This condition can very quickly become life threatening if left untreated, and rabbits often present severely compromised and hypothermic.

Survey radiographs are helpful in distinguishing between gastric and/or intestinal obstruction and ileus. Radiographically, with upper GIT obstruction the stomach is filled with gas and/or fluid and food and loops of dilated intestine proximal to site of obstruction may be seen. Serial radiographs may be helpful in determining whether an obstructed bowel is responding to medial therapy. If the obstruction passes through the ileocecocolic junction, gas is seen in the cecum and more gas-filled loops of intestine are seen radiographically. If the obstruction is not moving, as determined by serial radiographs, then the case becomes surgical. Contrast studies are rarely useful, because the normal gastrointestinal transit time is relatively slow in rabbits.

Patients often respond to intravenous fluid therapy, prudent use of metoclopromide, and decompression. If the patient is stable enough to be anesthetized, place the patient in left lateral recumbency, and pass a gastric tube such as a 12 Fr red rubber catheter with extra fenestrations to immediately relieve pressure. Remove as much fluid and gas as possible, provide analgesia and monitor the patient closely. If the condition has not resolved within 2-6 hours, surgical intervention is necessary. As a general rule, rabbits do not tolerate surgery of the GIT as well as other species. Take great care to provide pre-emptive analgesia and supportive care.

 

Rectal polyps

Rectal polyps are seen fairly commonly in the rabbit GIT. These polyps are usually benign papilomas that may be removed surgically if they cause bleeding or irritation. These pedunculated papillomas are removed easily by placing a cerclage ligature around the base of the mass.

 

Conclusion

Gastrointestinal problems are common in rabbits. Important conditions include coccidiosis in young rabbits, mucoid enteropathy in rabbits housed in commercial or laboratory settings, cecal dysbiosis, gastrointestinal stasis, as well as gastrointestinal obstruction and gastric dilation. Aggressive supportive care is often necessary to nurse a rabbit with gastrointestinal disease. Although treatment varies with the underlying cause, management frequently relies upon analgesia, fluid therapy, enteral feedings, and gastrointestinal motility agents. An appropriate diet, high in fiber and low in simple carbohydrates and concentrates, is the most important factor for maintaining normal gastrointestinal health. Proper husbandry that minimizes stress and ensures ample hydration is also crucial.

References