The gastrointestinal (GI) system comprises the mouth, oesophagus, stomach, small intestines (duodenum, ileum and jejunum) and the large intestine (colon). There are many complications that can arise in these areas which may require emergency intervention.
The oesophagus is a muscular structure that connects the mouth to the stomach and can become obstructed by foreign bodies including bone/cartilage or fish hooks: both require emergency treatment. The clinical signs may include regurgitation, a change in posture, drooling (blood may be present), repeated attempts to swallow, anorexia and coughing due to pneumonia (Cook, 2020). Clinical signs and a history from the owner will be highly suggestive of an oesophageal foreign body (FB), radiography will identify fish hooks (due to the high contrast/radiopacity) whereas bone or bulky FBs vary and may appear as an ill-defined soft tissue density in the caudal thorax (Hotston Moore, 2008).
There are a variety of methods that can be used to remove the FB and sometimes it requires a combination of flexible endoscopy, rigid endoscopy and/or surgical intervention. Medical management using endoscopy is the preferred method, with oesophagoscopy allowing for visualisation of the oesophagus. A retrospective study by Burton et al. (2007) found that the success rates are high for oesophageal foreign body removal by this method. Surgery is indicated if there is an oesophageal perforation or the FB can not be removed via endoscopy.
Endoscopy is not recommended for the removal of a linear foreign body (LFB) due to the material becoming anchored in different parts of the GI tract. LFBs are more commonly found in cats and can consist of a variety of materials, from hair bands to string. Clinical signs of an LFB vary, but can include vomiting, lethargy, abdominal pain, inappetence and anorexia. Sometimes owners may report witnessing the ingestion or seeing the FB within the mouth (Pope, 2003). LFBs are found to have a less favourable prognosis in cats due to multiple incisions being made into the GI tract (Taylor, 2016). However, one study found that the survival rates for dogs with LFBs and non-LFBs were the same at 96 percent (Hobday et al., 2014). If an FB is suspected in a cat, it is always advisable to check under the tongue during the clinical examination where the FB may be seen wrapped around the base of the tongue. An exploratory laparotomy is recommended with a gastrotomy and enterotomies to remove the foreign body. If intestinal tissue is not viable then an intestinal enterectomy and anastomosis may be required.
Gastric dilatation volvulus
A common GI emergency that affects the stomach is a gastric dilatation volvulus (GDV). This involves the stomach filling with gas and twisting, which compromises the blood supply to the stomach and spleen, resulting in cardiogenic and hypovolaemic shock (Homer, 2020). Clinical signs of shock include tachycardia, pale mucous membranes, prolonged capillary refill time (CRT), weak peripheral pulses and hypotension. A GDV is a life-threatening condition which mainly affects large deep-chested breeds including Boxers, Great Danes, Rottweilers and Irish Setters.
Patients with GDV present with varying degrees of shock. Previously, shock rates using crystalloids of 90ml/kg/hr have been recommended; however, to be able to titrate the intravenous fluid therapy correctly, bolus therapy of 10 to 20ml/kg while monitoring the patient’s response prevents possible complications from over infusion (Poli, 2017).
Gastric decompression can be achieved using a stomach tube or trocharisation to remove gas and stomach contents prior to surgery. Surgery has three goals: repositioning the stomach, evaluating the abdominal viscera and performing a gastropexy by creating a permanent adhesion between the stomach and the body wall (Rosselli, 2017). Benitez et al. (2013) investigated the use of an incisional gastropexy and the prevention of a GDV; they found that no dogs had a recurring GDV but gastric bloat recurred in 8.8 percent of patients that had a gastropexy during surgery for a GDV and 11 percent for those having a gastropexy prophylactically.
Gut motility can be altered by underlying disease processes and can result in an intussusception, where a portion of the GI tract invaginates into the lumen of the adjacent segment; it is commonly recognised in patients less than one year of age (Thomason and Latimer, 2020). Intussusception is diagnosed using ultrasonography and clinical signs, and once diagnosed surgery is recommended. An exploratory laparotomy is performed, with the entire GI tract being examined. Manual reduction may be successful if there are no or minor adhesions present, and the GI tract appears viable. Enterectomy and anastomosis is performed when the intestinal segment cannot be reduced, is perforated or not viable. A 2008 study of 88 dogs showed 82 percent required anastomosis due to necrosis (Barreau, 2008).
Intravenous fluid therapy is essential not only in stabilising patients prior to surgery but also post-operatively. Fluid losses occur via respiration, urine and faeces at 50ml/ kg/24 hours; patients with gastrointestinal disease may have increased losses through vomiting and diarrhoea. It is important to continue intravenous fluid therapy until the patient can independently replace the fluid loss (Hill and Crompton, 2011) and until the clinical signs resolve.
|For animals between 2 and 45kg bodyweight (BW), use the simpler linear formula:|
(BW x 30) + 70 = RER (kcal/24 hours)
For all animals, the allometric formula can be used:
70 x (BW)0.75 = RER (kcal/24 hours)
Post-operative management of cases that have had an oesophageal FB will depend on the degree of mucosal damage caused to the oesophagus. Those with minimal mucosal damage will require a combination of a cytoprotective (sucralfate), proton pump inhibitor (omeprazole) or an H2 receptor agonist (ranitidine, famotidine). Those with more severe mucosal damage should have a gastrostomy tube placed for enteral feeding for 5 to 10 days (White, 2014). Feeding tubes that can be used to bypass the oesophagus include gastrostomy or percutaneous endoscopic gastrostomy (PEG) tubes which are placed into the stomach either surgically or endoscopically. These tubes have a larger diameter than other feeding tubes such as naso-oesophageal or oesophagostomy tubes which means specific tube feeding diets can be used or tinned/wet food diets blended with water. The patient’s resting energy requirement (RER) should be calculated daily based on the patient’s weight (Box 1). If the patient requires additional nutrition the daily calorific intake can be increased by 25 percent at a time.
It is important to provide nutrition early post-operatively and different methods may be required to get a patient to eat such as warming food, hand feeding or placement of feeding tubes until the patient is maintaining their daily nutritional requirement independently. Normal motility returns to the small intestine almost immediately after an insult such as GI surgery. However, the stomach and large intestine are compromised for 24 to 36 hours, so using liquid foods to deliver nutrition can help as minimal mechanical digestion is needed. Early enteral nutrition after surgery or hospitalisation has been shown to lower complications, shorten hospital stays and improve patient outcomes (Firth, 2013).
A possible complication of gastrointestinal surgery is peritonitis (leakage of intestinal contents into the abdominal cavity caused by the breakdown of the intestinal suture line) which occurs around three to five days after surgery (Stanley, 2012). A second exploratory laparotomy is performed to find the affected area of intestine; resection and anastomosis is followed by abdominal lavage using copious volumes of crystalloid fluids and placement of a closed abdominal suction drain. Suction drains should be monitored frequently to check for signs of complications or infection around the insertion site (redness, swelling, exudate and pain). The accumulating fluid should be emptied (wearing gloves) every four to six hours and the volume and appearance of the fluid and any complications recorded each time. Drainage can be affected by fibrin, omentum and blood clots but also by patient interference (Yon, 2020), which can be prevented by using a buster collar or body suit. Any blood clots can be removed by flushing crystalloid fluids via the tubing connecting to the drain. Removal of a suction drain depends on the quantity and quality of the fluid produced; drains should be removed when the fluid production is less than 0.2ml/kg/hr. It is important to remember that the fluid production will never be zero due to the body identifying the drain as foreign material and inducing fluid production (Van Goethem, 2015).