General Considerations
Emergency gastrointestinal surgery presents the clinician with several challenges. Animals with severe diseases are very unstable. During initial resuscitation, the clinician must determine the nature of the problem and decide if surgery is indicated. The animal must be as stable as possible before anesthesia. During surgery, the clinician must do a complete abdominal exploratory and not focus on an obvious lesion. Emergency gastrointestinal surgery often requires critical evaluation of bowel viability and exacting technical skill for best postoperative results. In all cases in which perforation has occurred, samples for aerobic and anaerobic cultures are obtained. Adept postoperative management, including careful monitoring and an index of suspicion for potential complications, is vital.
Animals with surgical gastrointestinal disease are often severely dehydrated. Large amounts of fluid are lost in vomitus and diarrhea. Additional fluid is sequestered in inflamed, non-motile intestines. In cases in which the gastrointestinal tract has ruptured, the inflammation caused by chemicals (gastric acid, bile, pancreatic enzymes) and bacteria causes vasodilation, increased peritoneal vessel permeability, and subsequently loss of intravascular fluid and protein. The fluid losses are often accompanied by dangerous electrolyte and acid-base abnormalities.
Preoperative Resuscitation
Treatment should begin immediately on unstable patients. A rapid examination is performed, concentrating on the degree of dehydration, and the cardiovascular, respiratory and central nervous systems. Two large bore intravenous catheters are inserted and blood obtained for an initial data base, including PCV/TS, serum glucose and electrolytes, and blood gas if available. This will provide valuable information and determine the appropriate fluid for resuscitation. If the animal is in shock, 50-100 ml/kg of fluid are administered in the first 30 minutes. Colloids (whole blood, plasma, hetastarch, dextran) are supplemented as needed. In less severe cases, the animal's dehydration is corrected in the first two to four hours, with additional fluid administered to account for ongoing losses and maintenance requirements.
Once the initial resuscitation is underway, a complete history is obtained and a more complete physical examination is performed. Information on vaccination and worming history, potential ingestion of toxins or foreign bodies, and previous medical conditions is vital. Palpation is an important part of assessing the gastrointestinal system. The tongue should be carefully examined for any evidence of a linear foreign body. Additional diagnostic tests such as radiographs are obtained based on the results of physical examination. Contrast agents for gastrointestinal radiographs should be iodine based, as barium worsens peritonitis if it leaks from the gastrointestinal tract. Abdominal paracentesis is performed if free peritoneal fluid is detected. If paracentesis is negative but peritonitis is strongly suspected, a peritoneal lavage is performed. The presence of intracellular bacteria in peritoneal fluid is a clear indication for exploratory laparotomy.
Complete stabilization of the animal may not be possible until the underlying cause is treated. Anesthetic agents with minimal depressant effects on the cardiovascular and respiratory systems are used. The entire ventral abdomen and chest are clipped and prepared for aseptic surgery. Broad spectrum, bacteriocidal antibiotics are administered if bacterial contamination of the peritoneal cavity is suspected or anticipated. A large incision is made, extending from the xiphoid to caudal to the umbilicus. A complete exploratory laparotomy is performed and all organ systems examined sequentially. Definitive treatment depends on the organ system affected and the nature of the disease.
Esophagus
Esophageal foreign bodies should be suspected in any animal presenting with a history of regurgitation. They tend to lodge at points of narrowing in the esophagus: the thoracic inlet, the heart base, and just cranial to the caudal esophageal sphincter. Esophageal foreign bodies should be treated as emergencies. Contraction of the esophageal muscles around a foreign body worsens mucosal ischemia and makes esophageal perforation more likely. Non-surgical removal should be attempted initially. A rigid or flexible endoscope is passed the level of the foreign body and air insufflated through the scope to distend the esophagus away from the foreign body. The foreign body is either grasped and removed, or in cases of foreign bodies in the distal esophagus, gently moved into the stomach. The esophagus is then redistended and inspected for any mucosal tears. Full thickness tears in the esophageal wall necessitate immediate surgical repair. Surgery is also performed when foreign bodies cannot be removed by endoscopy. The approach is dictated by the foreign body's location. A longitudinal esophagotomy is performed. The esophageal wall opposite the incision is checked for perforation, and the incision closed with single interrupted, appositional sutures. Foreign bodies in the distal esophagus can sometimes be retrieved by manipulation through a gastrotomy incision.
Stomach
Gastric dilatation/volvulus (GDV) is a range of syndromes varying from severe gastric distension without volvulus, to volvulus without distension. Massive distension of the stomach with swallowed food or air results in obstruction of the portal vein and caudal vena cava. Decreased venous return from these vessels results in severely decreased cardiac output and poor tissue perfusion. Ischemia affects the heart, resulting in arrhythmias, and the stomach, causing necrosis in severe cases. Many GDV dogs have disseminated intravascular coagulation (DIC) and are endotoxemic.
Resuscitation with shock doses of crystalloids (or initially hypertonic saline/dextran) prior to anesthesia and surgery is vital. Additional therapies, such as desferoximine have theoretical if not proven clinical benefits. Once resuscitation is underway, the stomach is decompressed by carefully passing an orogastric tube or, if this is not possible, gastric trocharization. Radiographs are made to differentiate dilatation from volvulus.
At surgery, the stomach is decompressed, derotated, and replaced in a normal position. The spleen is exteriorized and examined for viability, venous or arterial thrombosis, and short gastric vessel rupture. A splenectomy is performed if necessary. The remainder of the abdomen is explored, and then the stomach is re-examined for necrosis, particularly along the greater curvature. As a guide, areas of the stomach which are discolored a dark purple or grey/green, which feel paper thin, or do not bleed when incised must be removed. If there is doubt concerning the viability of an area it should be removed, using either a stapling device (TA 90, 4.5mm cartridge, US Surgical) or manual resection and suturing. A permanent gastropexy is performed; the author uses a tube gastropexy to allow for postoperative gastric decompression, but at least seven other "pexy" techniques are described. The abdomen is copiously lavaged and closed.
Postoperatively, GDV patients require intensive care and monitoring. The rate of intravenous fluid administration is based on an assessment of perfusion. Tissue perfusion is estimated from clinical examination, blood pressure and urine output measurements, and laboratory parameters. Cardiac arrhythmias often develop in the first 24 to 48 hours after surgery. They are not necessarily associated with a poor prognosis as previously thought. Antiarrhythmic therapy is given if the abnormality is associated with poor cardiac function (subjectively assessed from mucus membrane color, heart rate, and arterial blood pressure) or severe electrical disturbance (R on T phenomena).
Most gastric foreign bodies are not true surgical emergencies. However, needles should be removed as soon as possible to prevent migration or perforation. In most cases, this is readily accomplished using a flexible endoscope.
Occasionally, severe gastric ulceration and bleeding can be successfully treated surgically. Gastric ulceration and hemorrhage is associated with gastric neoplasia, mast cell tumors, gastrinomas, stress and exogenous corticosteroids. However, cases of severe hemorrhage occur most frequently after non-steroidal antiinflammatory medication. Surgery is considered for those cases with massive bleeding in which medical therapy fails. The animal is stabilized with transfusions of packed red blood cells and plasma. Rapid endoscopy is useful to differentiate focal from diffuse gastric hemorrhage. The peritoneal cavity is explored, a large gastrotomy incision made, and the stomach mucosa examined. Focal bleeding ulcers are resected.
Small Intestine
Foreign bodies are the most common small intestinal condition requiring emergency surgery. The clinical signs, degree of dehydration, and electrolyte and acid base imbalance seen in small intestinal obstructions varies with the location, duration, and severity of the obstruction. Many foreign bodies can be detected on abdominal palpation. Plain and sometimes contrast radiographs are useful in making a diagnosis of obstruction. Surgery involves a thorough, sequential examination of the entire gastrointestinal tract. The affected area is packed off from the remained of the peritoneal cavity with moistened laparotomy sponges. In cases in which the bowel is healthy, the foreign body is removed through an incision made in the antimesenteric boarder of the bowel immediately distal to the foreign body. This ensures that the suture line is placed in healthy bowel. The enterotomy is closed with single interrupted appositional sutures. 3/0 polydioxanone (PDS) is used in medium and large dogs, and 4/0 PDS in small dogs and cats. In cases where the bowel is of questionable viability, a generous area of small intestine is resected and an end to end anastomosis is performed. The area can be "reinforced" by omental wrapping or serosal patching.
Linear foreign bodies pose some specific challenges. The clinician must examine the tongue carefully; the author has seen several cases in which the string cut through the lingual frenulum, which subsequently healed. At laparotomy, the plicated area of bowel should be isolated from the peritoneal cavity before cutting the "anchor" under the tongue. Mesenteric areas of the plicated bowel can perforated but be prevented from leaking until the tension on the string is released and the plications relax. The entire length of string is removed, necessitating multiple enterotomies. Large sections of the intestine may have multiple mesenteric perforations, necessitating resection and anastomosis.
Intussusceptions are common in younger animals. Although a cause is often not apparent, all affected animals should be treated for intestinal parasites. At surgery, gentle traction on the intussusceptum and pressure on the intussuscipiens aids reduction. Resection and anastomosis is required in cases in which the lesion cannot be reduced, or if the involved bowel is necrotic. This often means apposing bowel segments with different lumen diameters, as the majority of intussusceptions involve the ileocolic junction. This can be managed by an incision on the antimesenteric surface of the smaller bowel loop, or oversewing of the larger bowel loop.
Small intestinal neoplasms are rarely true emergencies; however, when they cause obstruction, hemorrhage, or intestinal rupture, immediate surgical intervention is warranted. Thoracic radiographs should be made before surgery to check for metastatic disease if neoplasia is suspected. Similarly, the abdominal contents, especially the liver and regional lymph nodes should be carefully examined during the exploratory laparotomy. Intestinal neoplasms are removed by resection and anastomosis, with generous margins. Enlarged lymph nodes are removed or biopsied.
Mesenteric torsion is rare in dogs. The root of the mesentery twists, completely occluding the mesenteric veins and partly to completely occluding the mesenteric arteries. The intestines are rapidly compromised, allowing bacteria to translocate into peritoneal cavity. Animals present with signs of acute abdominal crisis and deteriorate rapidly. Even with immediate surgery and derotation of the mesenteric root, the prognosis is grave.
Large Intestine
Surgical emergencies of the colon are uncommon, but include obstruction, perforation, and hemorrhage. Perforation of the colon is a true emergency because of the high colonic bacterial content. Untreated, colonic perforations are rapidly fatal. Perforation occurs secondary to trauma (ie gunshot), rupture of mural neoplasia, or rarely from foreign bodies. At surgery, the peritoneal cavity is lavaged, and the affected area is packed off and either debrided and sutured or resected.
Rectal perforation and prolapse: See notes from Colorectal Surgery lecture
Pancreas
Emergency surgery of the pancreas is usually limited to abscess drainage or removal. The surgeon should be thoroughly familiar with the anatomy of the pancreatic blood supply to avoid damaging vessels supplying the duodenum and stomach, the pancreatic papillae, or the common bile duct. Abscesses are treated by removing the affected area of the pancreas, generous lavage, and local drainage or open peritoneal drainage.