Gastric dilation and intestinal obstruction
6. astric or intestinal ru ture Gastric or intestinal rupture can occur, either as a result of
intestinal necrosis or as a result of extreme tympany (see Figures 14.8 and 14.9). By this time, affected rabbits are shocked and moribund and usually die within an hour of examination.
ossi le outcomes for ra its ith intestinal o struction
• ontaneous resolution and recovery in ra its ith a moving foreign ody In rabbits with moving foreign bodies, the intestinal and gastric distension can suddenly resolve as the foreign body moves through the ileocolic junction into the hindgut and releases the gas and fluid into the proximal colon and caecum (Figure 14.10). The rabbit then often starts to feel better and become more responsive. This recovery can be dramatic and may occur with or without treatment. It can be misinterpreted as a positive response to remedies such as fluid therapy, pineapple juice, simethicone or stomach massage.
• eath This can be the result of shock,
peritonitis, circulatory failure, acute renal failure or rupture of the stomach or intestine.
• artial im rovement initially ut death ithin a fe days An intestinal obstruction is a painful experience, even if a foreign body passes into the hindgut. The episode can trigger paralytic ileus (Figure 14.11) or acute renal failure, which may be fatal, especially if left untreated.
• ecovery after surgical intervention Surgery to relieve the intestinal obstruction can be successful, especially if it is performed promptly.
• eath during or after surgical intervention There are many reasons why a rabbit might die during or after surgery to relieve an obstruction.
The rabbit will be shocked, with disturbed electrolyte and acid–base status and
compromised cardiorespiratory function due to the dilated stomach. Complications associated with enterotomy or enterectomy can easily occur because of the narrow gut, and thin, friable tissue. Gastrointestinal hypomotility, gut stasis, paralytic ileus or acute renal failure may be triggered by the episode.
aralytic ileus. This radiograph shows the lateral view of the abdomen of a rabbit that had been anore ic for hours before undergoing surgery. t was shocked hypothermic and collapsed. A pellet of hair was found obstructing the small intestine and was milked through to the colon. The rabbit died despite treatment with fluids prokinetic therapy and analgesics. There is gas in the stomach small intestine and ileocaecocolic comple .
14.11
resumed moving foreign body. This radiograph shows the lateral abdomen of a rabbit that had been totally anore ic for a number of hours. The stomach was palpably distended. The radiograph shows a dilated stomach and gas in the hindgut. The diameter of the section of intestine suggests that the gas was in the ileocaecocolic comple and colon arrow . The gas shadow e tends to the rectum. This radiograph suggests that an intestinal obstruction has moved through the ileocolic junction and allowed gas from the stomach and small intestine to escape into the hindgut. The rabbit was treated with analgesics and prokinetic therapy. He started to eat voluntarily within hours of radiography.
14.10
Diagnosis of intestinal obstruction Intestinal obstruction is more difficult to diagnose in rabbits than in other domestic species because they hide their pain. A dog or a cat with an intestinal obstruction would be vomiting, trembling and show-ing signs of illness and distress that are obvious to its owner. Horses show signs of colic and sweat, roll, kick and tremble. It is important to remember that rabbits that are dying with a serious abdominal condition may not look particularly unwell on cursory examination. The course of the disease depends on the cause and site of the obstruction. Clinical his-tory and examination, blood sampling and abdo-minal radiography are the main diagnostic tools.
Gastrointestinal hypomotility is a major differential diagnosis, especially in the early stages of intestinal obstruction. Other differential diagnoses include liver lobe torsion, ureteral obstruction, enterotoxae-mia, peritonitis, pancreatitis and any other painful condition that can cause anorexia.
linical history
e ner’s clinical ist r is ten i l s esti e of an intestinal obstruction. Typical features include:
• a id s eed of onset Most owners say s et in li e he was fine last night’ r she ate all her food this morning’
• Total anore ia Rabbits with intestinal obstruction are completely inappetent and this is usually the reason that owners seek veterinary treatment
• hange in demeanour Rabbits with intestinal obstruction suddenly become very quiet and unresponsive (Figure 14.12)
• nusual ehaviour The owners may have had to search for their rabbit before finding it hiding in an unusual place away from view
• igns of ain Overt signs of abdominal pain are rare, although some owners say they have noticed their rabbit changing its position
suddenly or periodically pressing its abdomen to the ground
• loated a earance In the later stages, many owners notice that their rabbit looks bloated. In the terminal stages, when the rabbit becomes shocked and moribund, it is obvious to the owner that it is seriously ill.
linical e amination
Even in the early stages of intestinal obstruction, the stomach may be palpated as an enlarged structure behind the ribs on the left-hand side. This is a sign that should be checked for in any inappetent rabbit.
A dilated stomach can be felt as a tense, balloon-like structure and is easily palpable unless the rabbit is obese. Further clinical examination is also neces-sary. It can reveal concurrent diseases, such as dental disease, grooming difficulties or upper respir-atory problems, which may affect any decision to go for surgery. An assessment of the degree of de-hydration, shock and pain is helpful. Shocked rabbits are hypothermic and ataxic with pale mucous membranes and poor capillary refill time.
Heart rate is a measurable parameter that is useful in other species to assess shock and pain, but in rabbits the normal heart rate is 150–300 beats per minute (Meredith, 2006), which is too fast to count accurately, and a high rate can be normal. Blood glucose measurement can be more useful (Harcourt-Brown and Harcourt-Brown, 2012).
lood iochemistry
A complete blood profile, including haematology, renal and liver function, calcium, phosphorus, elec-trolytes and acid–base parameters, with immediate results, is ideal for rabbits with suspected intestinal obstruction. For practices without the facilities to perform these tests immediately, a good compro-mise is a quick, informative, in-house profile that is easy to perform and only requires 3–4 drops of blood. It can help to differentiate between gut stasis and abdominal catastrophes with a poor prognosis, such as intestinal obstruction.
A glucose meter, centrifuge and spectrometer are required, to measure blood glucose, packed cell volume (PCV) and total protein, while the serum should be visually examined. Glucose is particularly important; it provides information that can help to decide whether a case of acute onset anorexia is surgical or medical. Blood glucose is easily meas-ured with an inexpensive glucose meter that is avail-able from pharmacists. These are hand-held, battery-powered devices that are used with individ-ual test strips fitted with electrodes that measure glucose electrochemically (as glucose dehydro-genase) from 0.6 µl of blood. Results are displayed in 5 seconds and data is transferred from the strip via an infrared sensor.
In rabbits with serious abdominal conditions, such as intestinal obstruction, blood glucose levels rise rapidly to high levels of up to 30 mmol/l
This rabbit had an inoperable obstruction in the duodenum. His stomach was tympanitic and the intestine was about to rupture at the site of the obstruction. The owner found him hiding in a corner when she returned from work. He had been eating well and behaving normally when she left for work hours previously.
14.12
(Harcourt-Brown and Harcourt-Brown, 2012). Con-versely, rabbits with gut stasis rarely have blood glucose values above 15 mmol/l. In cases where decision making is difficult, blood glucose measure-ment can easily be repeated. Rising blood glucose levels signify a condition with a poor prognosis, in
which surgery may be the only hope of saving the rabbit. Normal or slightly elevated glucose levels are indicative that immediate surgery is not necessary (Figure 14.13).
PCV is another useful parameter. It can easily be measured by collecting blood in a heparinized
alue igni cance ossi le reasons Comments
Blood glucose (mmol/l)
<2 Severely hypoglycaemic Insulinoma; paraneoplastic syndrome;
artefact; metabolic disease
2–4.1 Moderately hypoglycaemic Lack of food Needs syringe feeding
4.2–8.2 Within laboratory reference range Reassuring
8.2–12 Within normal range for pet rabbits
in unfamiliar surroundings Mild stress Reassuring but indicative that the rabbit is stressed
12.1–15 Slightly hyperglycaemic Stress Probably stress-induced but could be start
of serious disease; re-sample if necessary
15.1–20 i ni cantl per l cae ic Stress/pain ssi l t n t de nitel s r ical
re-sample after 30–60 minutes; take radiographs
20.1–25 Severely hyperglycaemic Pain/deranged glucose metabolism Serious disease present; needs diagnosis and surgery is likely
>25 Critically hyperglycaemic Pain/deranged glucose metabolism Surgical or terminal PCV
<20% Severely anaemic Liver lobe torsion; autoimmune haemolytic anaemia; blood loss; chronic heavy metal poisoning
Further investigations are necessary
20–30% Moderately anaemic Chronic disease (e.g. dental disease);
chronic or intermittent blood loss 30–33% Low end or less than laboratory
reference ranges; apparently normal for pet rabbits
Reassuring
33–45% Within normal laboratory reference
range Top end of range is unusual in pet rabbits,
suggesting dehydration
>45% High Dehydration; polycythaemia (rare)
Total protein (g/l)
<54 Low Protein-losing kidney or intestinal disease;
liver disease; haemorrhage; malnutrition;
e cessi e e dati n e stri e
54–75g Normal
>75g High Dehydration
Visual examination of serum
normality ossi le reasons Comments
Lipaemia Obesity; hepatic lipidosis Poor prognostic sign
Jaundice Liver disease; haemolytic disease are t si ni cant
nterpretation of mini laboratory profile that can be used to differentiate between medical and surgical emergencies.
14.13
capillary tube and spinning it in a centrifuge. Acute anaemia is a sign of liver lobe torsion, which is another cause of sudden onset anorexia. After the PCV is measured, the serum is visually inspected for lipaemia or jaundice before the tube is snapped so a drop of plasma can be placed in a spectro-meter to measure total protein, which can indicate the hydration status of the rabbit. An interpretation of the results of this quick blood screen is summar-ized in Figure 14.13.
Abdominal radiography
Interpretation of abdominal radiographs is covered in Chapter 7. In rabbits with a suspected intestinal obstruction, the stomach, small intestine, ileocaeco-colic complex and rectum are special areas of inter-est. The normal appearance of these areas changes throughout the day because of the two phases of digestion (see Figures 14.3 and 14.4).
Excessive amounts of liquid and gas in the gas-trointestinal tract are the radiological features that are most easily identified on radiographs. Gas is an excellent contrast medium, which facilitates radio-graphic interpretation. In rabbits with intestinal obstruction and early gastric dilation, a pocket of gas often collects in the pylorus. If the rabbit is radio-graphed lying on its right side, this pocket of gas can
e seen n radi rap s as a ried e ’ s ape in t e stomach (see Figure 14.5). As gastric dilation pro-gresses, the stomach becomes large and tympanitic (see Figures 14.6 and 14.7). The small intestine proximal to the site of the obstruction also becomes dilated and tympanitic, which can be seen if the obstruction is in the distal small intestine but may not be obvious if it is in the descending duodenum.
Once a moving foreign body has moved through the ileocolic valve, the gas and fluid that was trapped in the stomach and small intestine is released into the ileocaecocolic complex and can be seen on radiographs. This is a good prognostic sign (see Figure 14.10).
Rabbits with intestinal obstruction have both gas-tric dilation and excessive amounts of fluid and/or gas in the stomach. However, there are other causes of either gastric dilation or gas in the stomach. These are summarized in Figure 14.14 and shown in Figures 14.15 to 14.17).
Radiographic sign Cause Gastric dilation and
gas in stomach Intestinal obstruction
Mucoid enteropathy (Figure 14.15) Pyloric obstruction (rare) Paralytic ileus (Figure 14.11) Gastric dilation Intestinal obstruction
Engorgement (Figure 14.16) Gas in stomach but
no gastric dilation Early intestinal obstruction Aerophagia: dyspnoea (Figure 14.17) Oesophageal foreign body Stress
Gut stasis
Causes of dilation or gas in the stomach of rabbits.
14.14
Engorgement. This lateral view of the abdomen was taken because an enlarged stomach was palpated during clinical examination of a rabbit presented for vaccination. The rabbit had just eaten a large bowl of dried food, which it did not normally have access to. She showed no other clinical abnormalities and was not ill.
14.16
Mucoid enteropathy is a non-inflammatory condition that mainly affects the hindgut. The aetiology is not clear and dysautonomia has been confirmed in some outbreaks. The motility of the hindgut is affected so the caecum becomes impacted with hard dry ingesta (arrow) and the colon fills with mucus. Gastric dilation occurs in the late stages, as in this case. The ventrodorsal abdominal radiograph is of a 14-week-old rabbit that was one of number that had died at the same breeding establishment.
14.15
Site of obstruction escending duodenum
The diameter suddenly narrows approximately 1–2 cm from the pylorus and this is a common site for obstruction. Affected rabbits carry a grave prog-nosis. The course of the disease is rapid and severe. Intestinal necrosis at the site of obstruction is common (Figure 14.18).
Aerophagia. This lateral view of the chest and abdomen shows hyperinflated lungs and a stomach full of gas. There is gas in the small intestine and rectum. The rabbit was presented for veterinary treatment because of a nasal foreign body which was subsequently snee ed out.
14.17
leocolic valve
The ileocolic valve is another common site of obstruction. In these cases, abdominal radiographs show lots of gas-filled intestine. The course of the disease is more protracted and the clinical signs less dramatic than in rabbits with a duodenal obstruction.
indgut
Obstruction of the hindgut is seldom due to an ingested foreign body. It is more likely to be due to a tumour, intussusception or a large piece of impacted caecal content that has moved into the colon. The fusus coli is the most likely site for obstruction of the colon by a caecolith or accumulation of foreign material. The diameter of the colon narrows at its entrance and strands of indigestible material, such as synthetic carpet fibre, can collect at this point and cause an obstruction.
Causes of intestinal obstruction ellets of im acted fur
A pellet of impacted fur is the most common cause of intestinal obstruction. The pellet is similar in size and appearance to a hard faecal pellet but is com-posed of tightly matted hair rather than plant mat-erial (Figure 14.19). The origin of these pellets has not been proven, although various suggestions have been put forward. For example, it has been postu-lated that the pellets are felts of matted hair that
Duodenal obstruction. This image taken during post mortem e amination shows an inflamed necrotic section of pro imal duodenum containing a pellet of compacted hair see igure . . The patient was a
year old male neutered e house rabbit that was reluctant to eat at pm the previous evening. y am he was moribund and tympanitic. He died shortly after admission.
14.18
mall intestine
The small intestine can be obstructed anywhere along its length. The clinical signs and course of the disease depend on whether it is a foreign body that is causing a complete obstruction or moving and periodically obstructing. Tumours or other chronic abnormalities, such as strictures or diverticula, which partially occlude the intestinal lumen, may show more intermittent clinical signs, but gastric dilation is still a feature.
Typical pellet of hair that obstructs the small intestine. (a) The hard pellet that was obstructing the duodenum of the rabbit shown in igure
. . (b) The same pellet after it was washed dried and teased out.
14.19 (a)
(b)
have been removed from the coat and ingested dur-ing groomdur-ing, or that they are pieces of impacted stomach content that have broken off and passed into the small intestine. Current evidence indicates that neither of these explanations is correct.
Although the pellets are more common during moulting and in long-haired rabbits, they also occur in short-coated breeds, such as Rexes. They have even been found in captive wild rabbits.
The most plausible explanation is that the pel-lets are formed by compression of ingested hair during its passage through the large intestine, especially when large quantities pass through the digestive tract during moulting. Fur is not broken down by digestive enzymes as it passes through the gastrointestinal tract so is compressed into pel-lets during its passage through the colon. These are sometimes seen as chains of faeces attached by strands of hair. Although rabbits are known to eat their caecotrophs, they are also coprophagic, and some rabbits will ingest hard faecal pellets as well as caecotrophs (Ebino et al., 1993). This is not a problem if the pellet is small enough to pass through the small intestine, but if it is slightly larger it may periodically obstruct the small intestine on its way through. If the pellet is too large to pass through the small intestine then it will obstruct com-pletely. Large amounts of hair (during moulting), large faeces (from a large companion), long fine mattable hair (angoras), intestinal abnormalities (adhesions, intestinal hypertrophy, diverticulitis) or slow gut motility (insufficient indigestible fibre) may be contributory factors.
ngested foreign odies
Occasionally, rabbits will swallow an object or mat-erial that can obstruct the intestine. At one time in the UK, locust bean seeds were a common cause of small intestinal obstruction but the incidence has reduced because locust beans are now excluded from most muesli mix diets. Other hard spherical objects, such as dried sweetcorn kernels, can also obstruct the small intestine.
Ingestion of large amounts of synthetic fibres (e.g. carpet) may obstruct the small intestine or they can pass, undigested, into the hindgut where they are separated from the rest of the ingesta and pass through the colon as large clumps. Occasionally obstruction can occur at the fusus coli.
eo lasia
Intestinal neoplasia, especially lymphoma, is not unusual in rabbits. Affected rabbits may have a his-tory of weight loss and inappetence before an acute episode of gastric dilation because the intestinal lumen is narrowed and eventually obstructed by the tumour. Other parts of the digestive tract, such as the caecum or rectum, can be involved and the clini-cal signs vary with the site of the lesion. Abdominal masses may or may not be palpable prior to sur-gery. Intestinal lymphomas are often aggressive and in many instances there is metastatic spread throughout the lymph nodes. There may be several tumours in the gut wall at the time of surgery.
dhesions and other intestinal a normalities
Adhesions with neighbouring structures can cause functional obstructions by creating bends or stric-tures in the intestine that impede the passage of a foreign object or pellet of fur through the intestinal tract. The adhesions may be chronic and long-standing, or acute. Long-standing adhesions may be the result of previous surgery or infection, or due to inflammation of a neighbouring structure, such as an abscess or a uterus full of pus. In acute cases, the adhesions may have formed because of periton-itis, which may be due to a perforated gut or from peracute enteritis or enterotoxaemia.
The author has encountered some other intesti-nal abnormalities that have caused intermittent bouts of obstruction. These include diverticulosis, and intestinal hypertrophy. These conditions were diagnosed during exploratory surgery or at post-mortem examination.
Torsions and strangulations
Gastric torsion in rabbits is not reported in the litera-ture and has not been encountered by the author.
Torsion of the intestine also appears to be very rare.
Strangulations are more common and can be the result of adhesions or surgery, such as castration or laparotomy, where the abdominal repair has failed (Figure 14.20).
Strangulated herniated section of intestine.
A lateral view of the abdomen of a rabbit that was presented ill hours after castration. A section of small intestine had herniated through the inguinal canal and strangulated arrow . The stomach was dilated and filled with gas and fluid.
14.20
aecoliths
Occasionally, a large piece of impacted ingesta from the caecum (caecolith) may obstruct the colon, usu-ally at the fusus coli, where the diameter of the colon suddenly decreases. This is a secondary problem.
The primary cause is caecal impaction, which can be caused by intestinal hypomotility, mucoid entero-pathy, inflammatory conditions, ingestion of small undegradable particles (e.g. chalk, barium, finely ground lignified material, clay cat litter) or chronic dehydration due to chronic renal failure. Ingestion of indigestible fine particulate material causes prob-lems when it reaches the hindgut because, as the small particles are not degraded by bacteria, when they move into the caecum, they compress and can impact the caecum.