Gastric Dilation and Intestinal Obstruction – Rabbit

Gastric stasis must be differentiated from gastric dilation which is usually associated with intestinal obstruction. See Harcourt Brown F M (2007), Gastric dilation and intestinal obstruction in 76 rabbits Veterinary Record 161 409 – 414 and Harcourt Brown T R (2007) Management of Acute Gastric Dilation in Rabbits Journal of Exotic Pet Medicine 16 (3) 168 – 174.

Description

The difference between gastric dilation and gut stasis is that gastric dilation develops rapidly, suddenly and unexpectedly, whereas gut stasis develops slowly and insidiously, usually followed by a painful or stressful episode. Note that a moving foreign body could mimic gut stasis except that the stomach is not impacted (stomach may or may not be impacted).

Pathophysiology

(Pathological) obstruction of small intestine accompanied by (physiological) continuous production of saliva which leads to:

• Accumulation of fluid in stomach and small intestine cranial to obstruction
• Fermentation => gas production
• Painful gastrointestinal dilation
• Reduced gut motility
• Secondary ileus.
• Sequestration of fluid => electrolyte and acid-base imbalances and hypovolaemia (and the necessity of fluid therapy.
• Passage of blockage to hind gut
  • note dilation of gut proximal to obstruction
• Non-passage of the blockage leads to devitalisation and necrosis of intestine

Clinical Signs of Gastric Dilation

• Anorexia
• Depression
• Moribund/unresponsive
• Death (due to peritonitis or shock)
• Distended stomach palpable in left epigastric area caudomedial to left last rib and confirmed radiographically
• Abdominal pain or flaccidity

Causes of intestinal obstruction

• Compressed hair
• Intestinal neoplasia
  • Lymphoma
• Foodstuff
• Post-spay adhesions
• Post-castration strangulated hernia
• Foreign fibre
• Tapeworm cysts
• Diverticulosis

Pellets of compressed hair are acquired by

• grooming/moulting
• Ingestion of matted hair
• Ingestion of hair in caecotrophs
• Predisposed by low-fibre diets

Sites and causes of obstruction

• Pylorus (Deeb 2000 Jenkins 2003)
• Proximal duodenum
  • foreign bodies
  • mid-small intestine
  • foreign bodies
  • neoplasia
  • strangulated hernia
  • diverticulosis
• ileocaecocolic junction
  • foreign bodies
  • neoplasia
• Large intestine
  • neoplasia
  • carpet fibre at fusus coli
  • postspay adhesions
  • tapeworm cysts along attachment with small intestine

NB: Severity of prognosis is directly proportional to closeness of site of obstruction to pylorus

Case assessment Clinical signs Radiographic signs Conclusion Unresponsive Collapsed Hypothermic Abdominal pain +/- gastric dilation Gas in stomach and intestine Free gas in peritoneal cavity Ruptured gut Explorotomy Euthanasia Unresponsive Abdominal pain Gastric dilation palpable Gas/fluid in stomach Minimal gas in intestine Cranial sm int obstruction Gastric decompression and surgery ?Euthanasia Unresponsive Abdominal pain Gastric dilation palpable Gas/fluid in stomach Much gas in small intestine Caudal sm int obstruction Repeat rads (30-60 mins) or perform gastric decompression Depressed Not collapsed Palpably enlarged stomach Gas in caecum Foreign body has passed through Medical treatment

“Performing surgery only to find that the obstruction has moved is preferable to performing a post-mortem examination on a rabbit that required surgical intervention”. Harcourt Brown T R (2007) Journal of Exotic Pet Medicine 16 (3) 168-174 						

Procedure with a case of gastric dilation • Radiograph under opiate analgesia - fentanyl/fluanisone ((Hypnorm; Janssen-Cilag) 0.2-0.3ml/kg SC once only or buprenorphine 0.01-0.05mg/kg SC/IM/IV q 6-12hrs (Vetergesic; Alstoe) plus meloxicam (Metacam; Boehringer Ingelheim) 0.1-0.3mg/kg SC/IM q24h or carprofen (Rimadyl; Pfizer) 2-4mg/kg SC/IM q24hr. Prepare orthogonal radiographs - lateral and dorso-ventral with legs extended or ventro-dorsal views. Observe the dilation of the stomach and the presence and distribution of fluid (liquid and gas) in the gastrointestinal tract to identify location of obstruction. Note the degree of contact of the dilated stomach with the ventral abdominal wall. Assess the amount of gas in the small intestine and look for gas in the large intestine. If no gas in hindgut and stomach severely dilated it may be best to go for euthanasia. Free gas in peritoneum indicates rupture of the gastrointestinal tract and justifies euthanasia. A search for other pathology may indicate other problems like bladder stones, spinal arthritis etc and may also indicate euthanasia. • Pit-falls of radiography: Caecum and large intestine generally do not have large amounts of gas in normal rabbits BUT caecum and large intestine generally do not have no gas in obstructed rabbits Caecum and large intestine with gas and dilated stomach seen in cases carrying a better prognosis. • Search for peritoneal gas in rabbits with severe depression If found, this is an indication of rupture of the intestine and indicates euthanasia. Remember euthanasia always an option • Serial radiographs (every 30 – 90 minutes) looking for gas in hindgut. If gas in hind gut this indicates that the obstruction is moving - administer NSAIDs (carprofen or meloxicam) if not already administered (see above) - followed by prokinetics if still anorectic after 2-3 hours. • Fluid accumulation in stomach leads to deficit in intra- and extra-cellular compartments. Parenteral fluids required. Give 10-20 ml Hartmann’s/kg /hr IV • Exploratory surgery may be attempted. Decision of whether to embark on surgery or conservative treatment depends on o the time of presentation: • Day => conservative treatment • Night=> surgery more likely o and on financial considerations

Surgical Procedure • Insert stomach tube to decompress: if it blocks, remove, flush and replace o Procedure of gastric decompression  +/- sedation  mouth to last rib  gentle gastric massage  patience  minimal suction  intermittent retropulsion  if tube is placed inadvertently endotracheally there will be • a change in breathing pattern • the presence of breath sounds at the free end of the tube • intraluminal condensation • Gastric rupture => euthanasia • Intestinal rupture => euthanasia • Intestinal neoplasm => euthanasia • Intestinal FB milked through ileocaecocolic junction into the hind gut or perform an enterotomy. • Note small omentum so omentalisation may not be possible • Postoperatively give antibiotics, prokinetics, food (force fed with Oxbow Critical Care Formula and baby cereal)

Practical approach to exploratory laparotomy in rabbits with intestinal obstruction 1. Opiate premedication, oxygenation, gastric and tracheal intubation and isoflurane maintenance. 2. Incision midline, sternum to umbilicus 3. Inspect retroperitoneum for fluid/ingesta 4. Palpate stomach and descending duodenum 5. Palpate ascending duodenum (under caecum) 6. Palpate jejunum cranially and caudally 7. Look for flattened intestine caudal to obstruction 8. Examine site of obstruction for contributive or subsequent pathology  Cytology/biopsy? 9. Milk obstruction to hindgut or stomach 10. Gastrotomy/enterotomy/ectomy??? 11. Closure with Vicryl (not catgut) Complications of rabbit intestinal surgery • Insufficient omentum for omentalisation • Intestine small and thin-walled • Food cannot be withheld during post-operative period o danger of hepatic lipidosis Postoperative care • Warmth, quiet • Fluid therapy • Analgesia • Antibiotics • Prokinetics • Food (grass, dandelions) • Gavage with Oxbow CCF and Baby cereal