Adhesive Intestinal Obstruction

Adhesion-induced obstruction is the most common cause of intestinal obstruction in general. The incidence of postoperative small bowel obstruction in children ranges from 2% to 30% and is greater in neonates. 80% of obstructions occurred within 3 months of the initial operation, and 70% were secondary to a single adhesive band. The incidence was 57% greater in neonates than in infants and children and was more common after procedures for gastroschisis and atresias. In children, the most common inciting operation was appendectomy, and there was no difference in occurrence after perforated, nonperforated, or negative appendectomies. Obstruction occurred most often within 2 years of the initial operation (82%).

Procedures with the highest risk for future adhesive intestinal obstruction in pediatric patients include: colectomy, Ladd's procedure, nephrec­tomy, resection/reduction of intussusception, hepatectomy, Nissen fundoplication.

Etiology

Postoperative intestinal obstruction could occur due to adhesions, intussusception, hernia and tumor. Adhesions are fibrous bands of tissue that form between loops of bowel or between the bowel and the abdominal wall after intra-abdominal inflammation. Obstruction occurs when the bowel is compressed or tethered due to these fibrous bands. This may result in kinking of the bowel, volvulus of a segment, or herniation of bowel between a band and another fixed structure within the abdomen.

Clinical Presentation

Children with mechanical intestinal obstruction present with colicky abdominal pain, distension and vomiting. In cases of prolonged intestinal obstruction, the vomitus may become bilious or even feculent. The child may be hemodynamically stable or may show signs of severe dehydration or sepsis (tachycardia, hypotension and fever). Abdominal examination may reveal a distended abdomen with either hyperactive bowel sounds (obstruction) or a paucity of sounds (ileus). Patients may have obstipation or diarrhea depending on whether they have a complete or partial obstruction.

Diagnosis

The differential diagnosis is ileus versus mechanical obstruction. Differentiating a prolonged postoperative ileus from post­operative bowel obstruction can be difficult. Radiographic demonstration of dilated bowel loops may not distin­guish between the two entities.

The key to the diagnosis of adhesive bowel obstruction is abdominal distention and bilious emesis in a patient with previous abdominal surgery. In the early stages of intestinal obstruction, it may be difficult to discern obstruction from infectious gastroenteritis. Initially, the emesis may be nonbilious, but with time it progresses to bilious or "feculent" emesis. The child complains of crampy abdominal pain and has anorexia. With a partial obstruction there continues to be passage of flatus or small stools. In children with complete obstruction, both cease. As the obstruction progresses, the child becomes increasingly lethargic. The presence of a fever should make one suspect bowel compromise.

Physical findings may not be initially obvious, but abdominal distention with either high-pitched or hypoactive bowel sounds evolves over time. Eventual progression of the obstruction leads to continuous, localized pain that is not relieved by nasogastric decompression.

Nonsurgical, inflammatory and metabolic conditions that may result in ileus must be considered.

Radiographs can help differentiate obstruction from infectious causes. Flat and upright abdominal films are obtained. Obstruction is manifested by dilated bowel loops with air-fluid levels. The presence of air in the colon and rectum may signify a partial bowel obstruction. Free intraperitoneal air is indicative of bowel perforation and requires urgent operative treatment. The diagnosis of intestinal obstruction can be confirmed with computed tomography (CT) or a contrast-enhanced upper gastrointestinal series with small bowel follow-through (UGISBFT). The advantage of a CT scan is that it can rule out other diagnoses, can identify the tran­sition zone of the obstruction, and uses water-soluble contrast that does not become diluted as rapidly as the water-soluble contrast with UGISBFT in the presence of obstruction.

Treatment

Nonoperative management includes resuscitation with isotonic solutions, naso-gastric decompression, correction of electrolyte abnormalities and serial examinations. Within 24-48 hours, children with ileus will improve as indicated by a return of bowel function, normalization of vital signs and normal white blood cell count. Conservative treatment was successful in 74% of patients. However, patients treated conservatively had a 36% incidence of recurrent episodes of obstruction as compared with a 19% incidence in those treated by lysis of adhesions.

Indications for operation include obstipation, progressive or persistent abdominal tenderness, fever or leukocytosis despite adequate resuscitation and medical treatment. Urgent surgical intervention is indicated in these patients and broad-spectrum antibiotics should be administered preoperatively. Surgery may only involve lysis of adhesive bands or it may necessitate bowel resection. Postoperatively, nasogastric decompression and intravenous fluids are continued until bowel function returns and the volume of gastric aspirate decreases to a minimum.

Prevention

A multitude of reports have described the prevention of intra-abdominal adhesions; however, a "magic bullet" to prevent adhesion formation has yet to be found. General principles of gentle bowel handling, careful hemostasis, irrigation of the abdominal cavity, and prevention of prolonged bowel exposure to air have not eliminated the occurrence of adhesions. Commercially available adhesion barriers such as Seprafilm, a hyaluronic acid and carboxymethylcellulose membrane, have been widely used and publicized. The Seprafilm membrane hydrates and becomes a gel within 24 hours and is then slowly absorbed from the abdominal cavity over a period of 7 days. Several clinical trials using Seprafilm have demonstrated a decreased incidence of postoperative adhesions. However, one should avoid wrapping Seprafilm around an anastomosis because it may lead to an increased risk for anastomotic leaks. Other substances that have been used in the peritoneal cavity in an attempt to reduce adhesion formation include high-molecular-weight dextran, oxidized regenerated cellulose (Interceed), fibrin sealant, and hydrogel. The only substance that has shown a consistent reduction in adhesions in clinical trials has been Interceed.