Emergency surgery of the gastrointestinal tract - Part 2
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 remainder 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 border of the bowel immediately distal to the foreign body. This ensures that the suture line is placed in a healthy bowel. The enterotomy is closed with single interrupted appositional sutures. 3/0 PDS is used in medium and large dogs, and 4/0 PDS in small dogs and cats (Figure 4). 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 (Figure 5). 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. The mesenteric surface of the plicated bowel loops can be perforated but prevented from leaking until the tension on the string is released and the plications relax. The entire length of string is removed, sometimes necessitating several enterotomies. Sections of the intestine with multiple mesenteric perforations are resected and the bowel ends anastomozed.
Intussusceptions are common in younger animals. Although a cause is often not apparent, all affected animals should be evaluated and if necessary treated for intestinal parasites, Coccidia and Giardia. 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 bowel involved 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. Enteroplication to prevent recurrence of the intussusception is controversial. Enteroplication involves sewing adjacent loops of intestine together and although it has been shown to decrease the incidence of recurrence (4), the procedure has been associated with sporadic reports of serious postoperative complications (5).
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 the 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.
Surgical emergencies of the large intestine 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 (i.e. gunshot), rupture of mural neoplasms, such as cecal leiomyosarcomas or stromal cell tumors, or rarely from foreign bodies. Non-traumatic perforation is reported in dogs with intervertebral disc disease after the parental administration of corticosteroids (Dexamethasone). Perforation leads to rapidly progressive peritonitis and septic shock. The diagnosis is suspected from clinical signs including lethargy, depression, pyrexia, and abdominal pain. Cytology and analysis of fluid obtained by ultrasound guided abdominocentesis confirms the diagnosis. The animal is stabilized before anesthesia and broad spectrum, bacteriocidal antibiotics are administered perioperatively. At surgery, the peritoneal cavity is lavaged and the affected area is packed off and either debrided and sutured or resected. Samples are taken for aerobic and anerobic bacterial culture and sensitivity. The abdomen is thoroughly lavaged with a large volume of balanced electrolyte solution which is then completely aspirated. The abdomen is either closed, drained, or left open depending on the amount of peritoneal contamination and degree of regional or general peritoneal inflammation.
Rectal prolapse occurs in young, unthrifty, parasitized animals, in association with tumors in older cats, and following perineal hernia repair in dogs. Clinical signs are obvious, however it is necessary to distinguish the prolapse from a prolapse of anus and rectum containing an intussusception of the ileum. The prolapse must be amputated if it is necrotic. In other cases the prolapsed rectum is reduced. The edema is removed by gentle pressure and massage using soft cloth moistened with warm saline. Following reduction a loose purse-string suture is inserted in the anus. This is removed in 3-5 days. A sedative to prevent straining is necessary. A low residue diet is fed for several days and any underlying parasitic infection (for example Trichuris spp.) is treated. In animals with recurrent prolapse, a colopexy is performed. A caudal ventral midline laparotomy is performed and the descending colon is identified. The surgeon places gentle cranial traction on the colon whilst a non-sterile assistant helps reduce the prolapsed anus and rectum. Once the prolapse is reduced, the descending colon is sutured to the abdominal wall using a double row of single interrupted sutures to fix it in place (Figure 6) (6).
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 best treated by opening the abscess cavity, flushing it thoroughly, then packing the cavity with omentum.
Septic peritonitis is a severe, life-threatening condition that poses many challenges for the small animal veterinarian. Obtaining an accurate and timely diagnosis, understanding peritoneal fluid and protein loss, hypovolemia, the Systemic Inflammatory Response Syndrome (SIRS)/sepsis, and effective resuscitation are vital to successful treatment of peritonitis. Septic peritonitis results from bowel perforation, extension of a urogenital infection (ruptured pyometra or prostatic abscess), leakage of bile from the common bile duct, a ruptured gall bladder or damaged hepatic ducts, penetrating wounds, or surgical contamination.
The diagnosis is suspected based on the animal’s history, clinical signs and physical examination findings. Peritonitis should be strongly suspected in any animal where free peritoneal gas is evident on abdominal radiographs, provided the animal has not had a recent exploratory laparotomy. Cytology and analysis of free peritoneal fluid can definitively diagnose peritonitis. Free peritoneal fluid is suspected based on a loss of abdominal detail on plain abdominal radiographs and can be confirmed and sampled using ultrasound. The presence of intracellular bacteria on a peritoneal fluid sample is diagnostic for peritonitis. If the concentration of glucose in the peritoneal fluid is 20 mg/dL or less, or lower than the simultaneous blood glucose concentration it is diagnostic for peritonitis (7).
Aggressive resuscitation using intravenous crystalloids and colloids is required before anesthesia and surgery. Goals for initial resuscitation in humans include a central venous pressure (CVP) of 8-12 mmHg, a mean arterial pressure (MAP) >65 mmHg, urine output (UOP) >0.5 mL/ kg/hr, and central venous or mixed venous oxygen saturation >70% (8). Broad spectrum, bacteriocidal antibiotics are administered intravenously, pending results of culture and sensitivity testing on samples obtained at exploratory laparotomy.
Control of the source of peritoneal contamination remains the primary goal of exploratory laparotomy in cases of generalized septic peritonitis. Once this has been achieved, lavage with a warm, balanced electrolyte solution is used to remove gross peritoneal contamination. It is vital to aspirate all lavage fluid from the peritoneal cavity before closure (9).
Anticipation of significant post-operative fluid production due to inability to control the source of contamination, generalized peritonitis, or severe local peritonitis is an indication for postoperative peritoneal drainage. Peritoneal defense mechanisms may be inhibited by a large volume of fluid, either from ongoing effusion or residual lavage. Bacterial phagocytosis within fluid depends on the presence of opsonins that can become depleted. A large volume of fluid may also limit the localization of the contamination and speed the systemic absorption of bacteria and endotoxin.
Drainage of localized peritonitis (prostatic or pancreatic abscesses) has largely been replaced by omentalization. Drainage of the entire peritoneal cavity can be accomplished by open peritoneal drainage, in which the linea is loosely apposed leaving a 3-6 cm gap between the edges and sterile bandage material is applied to the incision. Closed suction drains and more recently vacuum assisted closure devices have also been used for peritoneal drainage. There are no randomized, double blind studies comparing outcomes (i.e. survival) of animals with peritonitis treated with these difference drainage methods. Clinical case series of animals with peritonitis treated with primary closure, closed suction drains, and open peritoneal drainage all document reasonably comparable survivals.
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This article was previously on VetGrad.co.uk in 2013.