Gastrointestinal stasis is a common presenting problem of small herbivorous mammals. One study showed that the prevalence of gastrointestinal stasis in rabbits presenting to an exotic animal referral practice was 25.1 percent (Huynh et al., 2014). Small mammals are well known for hiding signs of illness, so it is crucial that the clinician fully evaluates the patient and establishes the extent of illness before initiating treatment.
Most importantly, it is essential that you recognise that gastrointestinal stasis is not so much a disease to be treated but often a clinical sign itself. Rabbits and guinea pigs will not stop eating unless they are in severe pain, distress or advanced disease states. In most cases, patients stop eating due to pain, which may have been undetectable to the owner.
Rabbits and guinea pigs with repeated frequent episodes of gastrointestinal stasis should have further investigation to determine the underlying cause of pain. Common reasons for repeated gastrointestinal stasis include dental disease (Figure 1), dental abscessation, otitis media, urolithiasis and chronic liver lobe torsions in rabbits. The role of stress should also be emphasised, as stress in small mammal patients can result in the release of catecholamines, which stimulate the sympathetic nervous system and have a direct effect on gut motility (Richardson, 2016). Pain is also a stressor, and gastrointestinal stasis results in abdominal pain, which can further exacerbate the problem.
Diagnosis
Clinical signs
Owners are often very knowledgeable about the habits and behaviours of their pets. Early warning signs noted by owners, such as hyporexia or ignoring a once well-loved treat food, should not be discounted even if the patient appears normal on physical examination in the consultation room.
Gastrointestinal stasis can range in severity from a few hours of anorexia and a mild reduction in faecal output to patients that present with acute surgical abdomens. They can also be in shock or severely hypothermic and hypovolaemic. Clinical signs can vary; however, common clinical signs include partial or full anorexia, reduced or absent faecal output, lethargy, teeth grinding, hunched posture (Figure 2) and a poor response to external stimuli (Huynh and Pignon, 2013).
Physical examination
Hydration status
A full physical examination is essential, not only to determine the extent of gastrointestinal stasis but to help identify its cause. In particular, an assessment of hydration status is important. The author clinically uses the assumption that all small mammals presenting with gastrointestinal stasis signs are at least 5 percent dehydrated. This is because poor gastrointestinal motility results in the dehydration of gastric and intestinal contents (DeCubellis and Graham, 2013). Once gastrointestinal contents dehydrate, they pull fluid in from the circulation, resulting in dehydration and, in severe cases, hypovolaemia.
Hydration status can be assessed by touching the mucous membranes, assessing skin turgor and palpating the contents of the abdomen. Gentle abdominal palpation can also help determine if there are any areas of pain or gaseous distension in the abdomen. Patients presenting with intestinal obstruction or gastric dilation volvulus will have severely distended stomachs on cranial abdominal palpation.
Rectal temperature
Rectal temperature measurements should be performed on all small mammals presenting with signs of gastrointestinal stasis. A study assessing patient mortality outcomes based on the rectal temperature of rabbits at presentation showed that rabbits that were hypothermic on rectal temperature (under 38.0°C) at admission had a mortality risk three times higher than rabbits who were normothermic on presentation (Di Girolamo et al., 2016). Any small mammal patient that is hypothermic on presentation should be actively warmed in a quiet and dark location (Lichtenberger and Lennox, 2010), with constant monitoring of rectal temperature until they become normothermic.
Any small mammal patient that is hypothermic on presentation should be actively warmed in a quiet and dark location, with constant monitoring of rectal temperature until they become normothermic
Blood glucose
Another simple tool to use as a prognostic indicator is blood glucose measurement in rabbits. A study of 907 rabbits assessed with a hand-held glucometer showed that rabbits presenting with blood glucose over 20mmol/l had a poorer prognosis (Harcourt-Brown and Harcourt-Brown, 2012). Rabbits with intestinal obstructions had a mean blood glucose measurement of 24.7mmol/l, so measurement of blood glucose can be used as a quick screening tool for patients where there is a clinical concern for intestinal obstruction.
Pain scales
Detection of pain can be assessed by using established pain scales. The Rabbit Grimace Scale is a reference guide proposed by Keating et al. (2012) that uses facial changes to assess pain, whereas the Bristol Rabbit Pain Scale, also a useful tool for assessing pain, focuses on patient facial expressions, posturing and activities (Benato et al., 2022). While both pain scales can be useful, any score determined must also be interpreted in light of a full physical examination, as subtle signs of pain can be missed by observers with less experience (Shaw et al., 2020).
A common myth of treatment of gastrointestinal stasis is that opioid administration will slow gut transit time further and push the patient further into stasis; however, this is simply not true
Given that pain is usually the underlying cause of gastrointestinal stasis (Malik, 2021), analgesia should always be provided in any small mammal showing signs of stasis. A common myth of treatment of gastrointestinal stasis is that opioid administration will slow gut transit time further and push the patient further into stasis; however, this is simply not true (Deflers et al., 2018; Benato et al., 2019). Patients without adequate analgesia often fail to improve or take far longer to recover than those receiving adequate analgesia. Given the assumption that patients presenting with gastrointestinal stasis signs are likely to be dehydrated, the author avoids the use of non-steroidal anti-inflammatory drugs until the patient has received adequate hydration.
Treatment
To admit or not to admit?
There is often a debate about whether patients should be admitted to hospital or managed by owners at home. It is important to establish a realistic timeline for recovery with the owner when proposing at-home management, as often owners have social or familial obligations that prevent them from providing adequate care to patients with gastrointestinal stasis, and they do not expect to be nursing patients at home for several days. In the author’s experience, rabbits admitted to hospital and provided with adequate analgesia and hydration recover from gastrointestinal stasis episodes faster than those that are managed as outpatients.
It is important to establish a realistic timeline for recovery with the owner when proposing at-home management, as often owners have social or familial obligations that prevent them from providing adequate care
Competent owners are often able to nurse patients at home in their known environment, which is excellent for reducing stressors; however, there are several disadvantages to not admitting gastrointestinal stasis patients to hospital. Small mammals can decompensate quickly, and hospital admission allows close monitoring by trained veterinary staff to assess for signs of pain, changes in condition or the onset of hypothermia. Patients at home are not able to receive opioid analgesia, which is often required in cases of gastrointestinal stasis. Intravenous and subcutaneous fluid therapy is instrumental in helping rehydrate patients but cannot be reliably performed at home by owners unless an intravenous cannula is kept in situ and the owner is trained in fluid administration.
Outpatients
In the author’s experience, rabbits that are completely anorexic on admission do not usually start eating again for 24 to 48 hours post-admission. Rabbits managed as outpatients often do not start eating until two to four days after first presentation, sometimes longer. Some owners may not mind providing around-the-clock care to their pets during this time, but for other owners, this may not be an achievable scenario.
Hospitalisation
Hospitalisation of small mammal patients with gastrointestinal stasis should take place in a ward that is dark, quiet, warm and away from predators (DeCubellis and Graham, 2013).
Intravenous (IV) catheterisation is possible in all rabbits (Figures 3A and 3B), as well as some guinea pigs and chinchillas. Where IV catheterisation is not possible, fluids should be provided based on fluid deficits, body weight and an estimated dehydration percentage (Lichtenburger and Lennox, 2010) and administered subcutaneously in boluses. In rabbits, IV fluids may also need to be given by boluses, as rabbits can chew through IV fluid lines.
One of the most important factors in treating gastrointestinal stasis in small mammals is the provision of supplementary food. A study on post-sedation faecal output in chinchillas showed that administration of a critical care formula had more impact on faecal output and food intake in chinchillas than the use of cisapride (Mans et al., 2021). Several products are available for syringe feeding in cases of gastrointestinal stasis, and all should be mixed up and fed based on manufacturer guidelines. A good rule of thumb is that patients should receive roughly 10ml/kg of supplementary feeding every four hours, around the clock (Figures 4A and 4B). Patients not receiving adequate nutrition due to refusing or dropping food should have a nasogastric tube placed (Lichtenberger and Lennox, 2010).
Pharmacological treatment
In addition to analgesia, several prokinetic drugs have been advocated in treating gastrointestinal stasis in small mammals. Cisapride is well absorbed from the gastrointestinal tract of rabbits and provides good prokinetic effects (Langer and Bramlett, 1997). Metoclopramide has been advocated for use in treatment of gastrointestinal stasis, but no pharmacokinetic or pharmacodynamic studies have been performed in small mammals to validate its use (Huynh and Pignon, 2013). The use of maropitant has been advocated in rabbits, with initial pharmacokinetic studies showing promise (Ozawa et al., 2019).
The use of constant rate infusions is gaining popularity in clinical practice and is excellent for providing analgesia in advanced gastrointestinal cases; however, this is beyond the scope of this article.
Conclusion
Gastrointestinal stasis is a commonly encountered problem in small mammals. Clinicians should take care to fully evaluate each patient presenting with signs of gastrointestinal stasis to determine the underlying cause. Consideration should be given to admitting the patient to hospital for treatment, and appropriate timelines for recovery should be communicated to owners.
