Rabbits presenting with gastrointestinal obstruction are not uncommon in clinical practice, especially during spring and autumn, when patients are moulting. While previous articles have covered the identification of acute abdomen and diagnosis of gastrointestinal obstruction in rabbits, the swift identification of these cases is only the beginning. Treating gastrointestinal obstruction is relatively straightforward, and treatment can be medical management or surgical management.
The main concern in these cases is the condition of the patient, as rabbits with gastrointestinal obstruction are often in shock, hypothermic and hypovolaemic and have impaired venous return, increasing their anaesthetic risk significantly. However, surgical management of these cases results in rapid improvement in clinical signs and patient recovery.
Initial presentation
Initially, patients often present hypothermic and quiet or even obtunded. Active warming should be commenced as soon as possible in cases presenting with hypothermia.
It is essential that an intravenous cannula be placed in rabbits with gastrointestinal obstruction. This can assist with the induction of anaesthesia in those treated surgically and provide boluses of intravenous fluids to treat shock. Intravenous cannulation can be performed in the marginal ear veins (Figure 1) or cephalic veins. An intravenous cannula should never be placed in the central vessel of the ears, as this is a large artery and obstruction can result in ischaemia of the pinna.
Placement of an intravenous cannula also facilitates the administration of a lidocaine constant rate infusion (CRI). Use of lidocaine CRI has been shown to improve survival rates in rabbits treated for gastrointestinal obstruction (Huckins et al., 2024). Fluid therapy should be instigated using crystalloids; as the patient is likely hypovolaemic, a fluid rate of 10ml/kg/hour of warmed fluids should be used under general anaesthesia.
Premedication and induction
In general, a premedication that has minimal cardiovascular side effects and provides adequate analgesia should be selected. Choice of premedication is often based on the preference of the surgeon, and is beyond the scope of this article; however, the author prefers the use of a partial or full mu opioid receptor agonist and a benzodiazepine, such as midazolam, for muscle relaxation.
Induction should be performed intravenously using alfaxalone, propofol or ketamine. Endotracheal intubation is essential, as gastric reflux is a very real possibility due to the high gastric pressures caused by the build-up of gas and gastric fluid.
Even the removal of a small amount of gas and gastric fluid can dramatically improve patient morbidity and venous return
Once the patient is induced and intubated, the passage of a stomach tube can be very useful to relieve pressure on the stomach wall. This tube will often become blocked before draining most of the fluid and gas, but even the removal of a small amount of gas and gastric fluid can dramatically improve patient morbidity and venous return.
To pass a stomach tube, the patient is placed in sternal recumbency, and the head held in extension. A soft, flexible feeding tube of 20 to 30cm should be premeasured from the tip of the nose to the last rib, and this distance marked on the tube. The tube is passed down the oesophagus, which is possible with minimal effort due to endotracheal intubation protecting the airway. There will be a small amount of resistance when entering the stomach, but excessive force should never be used. In most cases, the gas and fluid will pass out of the tube passively, but in some cases, attaching a syringe to the stomach tube and removing fluid or gas with negative pressure can also be useful (Harcourt-Brown, 2013).
Preparing the patient for surgery
After anaesthesia is induced, the patient must be prepared for surgery. When preparing the patient, care should be taken to elevate the thorax. This is a consideration for anaesthesia in rabbits under routine general anaesthesia due to the volume and weight of the large gastrointestinal tract. The increased volume of the expanded stomach will increase the pressure on the diaphragm further, preventing caudal movement of the diaphragm during inspiration and resulting in patient hypoxia. To elevate the thorax, a foam wedge, sandbag or rolled-up towel is usually sufficient. If available, intermittent positive pressure ventilation should be used to ensure the patient is not hypoventilating.
The ventral abdomen should be clipped of hair from approximately 2.5cm cranial to the xiphoid process to roughly the level of the pubis. Rabbit skin is very thin and fragile, so care should be taken when clipping to prevent clipper rash or tearing of the skin. Surgical preparation should be performed as standard, with either chlorhexidine or iodine-based disinfectants, followed by a final preparation with surgical spirit (Varga, 2013).
Surgical treatment of gastrointestinal obstructions in rabbits
Initial stages
An incision should be made on the ventral midline through the skin to the level of the abdominal musculature, starting with an incision at the level of the umbilicus and extending 5 to 10cm cranially (Figure 2). This incision can be extended during surgery if required.
There is often very little subcutaneous tissue, and you can usually identify the linea alba through the skin incision alone. To enter the abdomen, the linea alba should be grasped with atraumatic forceps and tented upwards. Palpate the tented muscle to ensure no organs are present between the layers of muscle.
The abdomen can be entered with scissors or a reverse stab incision with a scalpel blade to make a roughly 5mm incision (Figure 3). Once this incision has been made, scissors can be introduced through the abdominal wall. Then the abdominal wall can be tented away from the abdominal organs and incised along the length of the skin incision.
If required, a self-retaining retractor can be placed on the edge of the abdominal incision to allow better visualisation of the abdominal viscera. The stomach will likely be very large, obstructing most of the cranial surgical field. Visualisation of the intestinal loops should show two populations of intestines: one distended and fluid-filled, proximal to the obstruction, and the second empty of all material, distal to the obstruction.
The intestine should be handled gently as rabbits tend to form fibrous adhesions following tissue damage with rough organ handling. Warmed sterile saline can be used to keep the viscera moist, and any intestines that need to be elevated from the abdominal cavity can be laid on saline-soaked gauze.
The gastrointestinal obstruction is identified by following empty intestine proximally or distended intestine distally until the obstruction is found (Figure 4). Common sites for obstruction include the descending duodenum, approximately 1 to 2cm from the pyloric outflow, and the ileocolic valve, but obstructions can be identified at any point along the small intestine (Harcourt-Brown, 2013).
Milking the obstruction
Once the obstruction has been identified, there are two described techniques for relieving the obstruction. Milking the obstruction distally to the caecum is advocated in most cases. This is where the obstruction is very gently pushed distally to the ileocolic valve and through into the sacculus rotundus of the caecum (Figure 5). The gastrointestinal diameter from the caecum distally is much wider than the small intestine, so there is no risk of further obstruction as long as the obstruction is milked fully into the caecum.
Milking the obstruction is preferential as it reduces the risk of peritonitis or surgical site breakdown, which can be encountered with an enterotomy. However, enterotomy is unavoidable in some cases, such as intestinal stricture, a very large obstruction or rupture of the intestine. In these cases, the enterotomy site should be packed off with surgical laparotomy pads soaked in warmed saline, and the enterotomy incision closed with a fine 4-0 or 5-0 absorbable monofilament suture. The wall of the intestine is thin and very friable, so a simple interrupted pattern is often the only viable suture pattern. The surgical site should be flushed and leak-tested before returning it into the abdomen. Omentalisation of the enterotomy site is difficult in rabbits as they have a very small omentum (Harcourt-Brown, 2013).
Final steps and closure
Once the gastrointestinal obstruction has been milked to the caecum or removed, the bowel should be run to look for any further obstructions. Often, the intestine will start to resume normal peristalsis as soon as the obstruction has been relieved. The stomach remains severely distended with gas and fluid; however, in the author’s experience, this resolves over the next several hours, and the presence of peristalsis during surgery is an excellent sign that gastric contents are already moving distally through the gastrointestinal tract.
The presence of peristalsis during surgery is an excellent sign that gastric contents are already moving distally through the gastrointestinal tract
Some practitioners advocate gastrotomy and removal of the gastric contents and any further fur or trichobezoars that may still be present in the stomach. If no intestinal obstructions are identified or the obstruction is present within the pyloric outflow and cannot be milked out, then this may need to be performed. However, the author would recommend against performing gastrotomy unless entirely necessary as the risk for abdominal contamination with gastric contents is severe due to the high pressure the stomach is under when an obstruction is present. Significant risks are also present for the formation of peritonitis and surgical site breakdown after surgery.
The abdominal wall can be closed with an absorbable monofilament suture using a simple continuous pattern (Figure 6). The lack of subcutaneous tissue means that a subcutaneous closure is rarely required unless the patient has excess abdominal subcutaneous fat. The skin should be closed using an absorbable monofilament suture with an intradermal pattern to help prevent post-operative patient interference (Figure 7).
Post-operative care
Following the cessation of surgery and anaesthesia, the patient’s temperature should be monitored closely. This is because most rabbits are already hypothermic at the start of the procedure and the open abdominal body cavity, as well as the use of saline on the viscera during surgery, can reduce the body temperature further. Active warming should be used, such as a warm air incubator, warm air blanket or a heat mat (Figure 8); however, patients should not be left on a heat mat if they are unable to move during recovery from anaesthesia. In addition, the rectal temperature of the patient should be monitored closely to ensure hyperthermia is not caused.
If not already started preoperatively, a lidocaine CRI should be considered post-operatively, alongside frequent intravenous opioid analgesia.
Following recovery from anaesthesia, syringe feeding needs to be considered. Most of the gastric contents are gas and liquid, which usually move through the intestinal tract fairly quickly following relief of the obstruction. The author recommends starting syringe feeding within four hours of surgery as long as the patient is able to swallow. Food should be available at all times post-operatively once the patient can stand and swallow without assistance.
Post-operative fluid therapy is important and should be given via intravenous and subcutaneous routes. Rabbits tend to chew through intravenous drip lines, so fluids can be given as frequent intravenous boluses if required. Sucralfate may be useful in treating gastric ulceration that may have occurred due to stretching of the gastric wall and build-up of stomach acid (Reusch, 2005). Usually, rabbits remain in hospital for 24 to 48 hours after surgery to ensure they are eating normally and passing faeces post-operatively.
Conclusion
The surgical treatment of gastrointestinal obstruction in rabbits is fairly straightforward and does not require enterotomy in the vast majority of cases. While these patients are not ideal anaesthetic candidates, proper preparation and placement of an intravenous cannula, endotracheal intubation and elevating the patient’s chest can significantly improve clinical outcomes. All rabbit patients should be provided with opioid analgesia, and the use of a lidocaine CRI can improve patient survival rates significantly.
