Operative indications

The main diagnostic challenges posed by SBO are to establish the underlining cause, identify any strangulation, and determine which patients can be managed nonoperatively. There is no single laboratory or radiographic parameter that will predict spontaneous resolution of SBO. Volume resuscitation, nasogastric suction, ongoing fluid maintenance, and close clinical observation are the cornerstones of nonoperative management of SBO. Gastric decompression provides symptomatic relief and decreases the need for intraoperative decompression. No definite advantage of using a long (intestinal) tube instead a conventional nasogastric tube has been observed. If the patient remains clinically stable, then a conservative approach can be tolerated almost indefinitely, as long as nutrition can be provided. Some clinicians will proceed to operative intervention if nonoperative management has not resolved the SBO after 48 to 72 hours. The maximal duration of nonoperative management for SBO is controversial; published reports have given cutoff periods ranging from 12 hours to 5 days.

As long as ischemia is not present, however, operative intervention for SBO can be delayed. The caveat to this guideline is that the presence of strangulation increases associated mortality to 30%. Thus, early diagnosis of strangulation in SBO is essential; yet, the detection of ischemia still is a function of clinical suspicion. Clinical symptoms and signs of bowel ischemia in SBO include severe abdominal pain, fever, tachycardia, peritoneal signs, leukocytosis (>18,000 white bloods cells/µL), metabolic acidosis, elevated lactate, and various computed tomography (CT) signs (see later); individually, none of these findings is neither sensitive nor specific for strangulation. The determination of whether a patient with an SBO has underlying bowel ischemia requires that the clinician integrate all the available data, including subjective complaints, physical examination, laboratory tests, and radiology.

Contraindications to laparoscopic adhesiolysis for SBO are listed in Table 23-1. These generally concern the severity or nature of the disease and the surgeon’s ability to deal with these conditions. In general, an ideal candidate for minimally invasive release of SBO would (1) be hemodynamically stable; (2) not have generalized peritonitis; (3) have minimal small bowel dilatation; (4) not have a “frozen” abdomen (i.e., a peritoneal cavity obliterated with adhesions); and (5) not have multiple previous laparotomies. The risk for enterotomy (both recognized and delayed) appears to be higher in patients with multiple previous laparotomies. Successful completion of laparoscopic adhesiolysis for SBO would depend on patient selection as guided by Table 23-1.

Table 23-1 Contraindications to Laparoscopic Adhesiolysis

Preoperative evaluation, testing, and preparation

Most patients with SBO present with abdominal pain, nausea and vomiting, constipation, and abdominal distention. The pain typically is intermittent and colicky in nature. Bowel sounds are often high pitched, increasing with the onset of cramping pain. Visible peristalsis or “laddering” of the small bowel may be observed in the patient with a thin abdominal wall. An obstruction in the proximal small bowel may present with nausea and vomiting without distention and constipation, whereas a more distal obstruction may present with abdominal distention and pain, with vomiting later in the course.

The plain abdominal radiograph (Fig. 23-1) remains the primary radiologic test performed in suspected SBO by virtue of low cost, wide availability, and utility. Identification of level of obstruction (small bowel vs. colon) on the plain film may be possible, although grossly distended small bowel can be mistaken for large bowel, and a colonic volvulus can be mistaken for small bowel. In addition, an obstructing colon cancer can cause an SBO in up to 15% of cases. On the other end of the spectrum, a normal abdominal radiograph does not exclude the diagnosis of SBO.

FIGURE 23-1 Supine abdominal radiograph in a patient with a small bowel obstruction.

The oral ingestion of water-soluble contrast agents has become a common diagnostic and therapeutic procedure for SBO. Gastrografin (a mixture of sodium and meglumine diatrizoates) is a widely used contrast agent. Ingestion of this high-osmolarity substance draws water into the small bowel lumen, which is thought to decrease wall edema and stimulate motility. The therapeutic role of Gastrografin probably is limited to speeding resolution of an obstruction that would have resolved without an operation. Typically, 60 to 100 mL of Gastrografin is administered through the nasogastric tube after the diagnosis of SBO has been made and when there is no concern for strangulation or ischemia. Abdominal radiographs should be repeated 3 to 4 hours after Gastrografin administration (Fig. 23-2). If the contrast has reached the cecum and the patient is clinically well, then the patient may be started on liquids. The diet is advanced as tolerated, and early discharge should be possible. If the contrast does not reach the cecum within 24 hours, then surgical intervention may be required.

FIGURE 23-2 Gastrografin administration in a patient with a small bowel obstruction. A, Upright position, demonstrating contrast in the stomach and duodenum and dilated contrast-filled loops of the small bowel with air-fluid levels, but no distal filling. B, Supine position.