Although small bowel obstructions have been recognized for centuries, certain aspects of management remain problematic. This is due primarily to the various etiologies of the obstructive process and the difficulties in distinguishing simple from reversible, strangulating obstruction.

Adhesions from a previous laparotomy are responsible for approximately 50-75% of all cases of small bowel obstruction in the United States. Lower abdominal and pelvic operations have a higher incidence of ensuing bowel obstruction than upper gastrointestinal procedures, probably due to the greater mobility of the small bowel distally with its elongated mesentery. The incidence of small bowel obstruction has been estimated to range from 5-10% following a number of intra-abdominal procedures. Malignancy and hernias are the next most common etiologies of small bowel obstruction. The malignant cases are usually secondary to metastatic type disease rather than primary small bowel neoplasms. Hernias have decreased in frequency as an etiology of obstruction in industrialized nations but continue to account for approximately 10% of cases of small bowel obstruction in the U.S.A.

Clinically, the diagnosis should be suspected with the quartet of cramping abdominal pain, nausea and vomiting, abdominal distention, and obstipation. One must remember, however, that more proximal obstruction can be present with minimal distention. Also, with obstruction and the initial increased peristalsis, frequent loose stools may occur in the early hours. The physical exam is especially pertinent as relates to the degree of distention (remember above), the presence of scars from previous surgery (adhesions), and the evaluation for external abdominal wall hernia.

There are no specific laboratory values diagnostic of small bowel obstruction and/or strangulation.

Advances in x-ray imaging have contributed to improved diagnosis and patient management. Flat and upright abdominal radiographs should be done initially, however, they may be nondiagnostic in a number of cases. Small amounts of oral contrast material may be given, and follow-up films in 12-24 hours may demonstrate whether contrast has passed into the cecum or not confirming partial and/or complete obstruction. Contrast enemas may be used to exclude a colonic process and document distal collapsed small bowel if the ileocecal valve is incompetent. Upper GI series may also be used to evaluate the degree and level of obstruction. Recently, CT scanning has been applied to patients with small bowel obstruction demonstrating both dilated proximal small bowel, documenting collapsed loops of distal small bowel, and sometimes demonstrating the actual site of obstruction. Specific etiologies may even be suggested by CT findings. More importantly, generalized distention compatible with an adynamic ileus can be diagnosed, and surgical intervention avoided. The small bowel enteroclysis study likewise may define the degree and location of the obstruction and also its improvement or failure to improve with time.

Once the diagnosis of small bowel obstruction is established, replacement of intravascular volume should begin, and tube decompression of the GI tract should be initiated. Use of antibiotics to combat "bacterial translocation" may be worthwhile, but currently remains unproven.

The most controversial aspect of small bowel obstruction remains the role of early surgery vs. a trial of nonoperative management. The adage "never let the sun set or rise" on a bowel obstruction, which implies the need for immediate operation, clearly does not apply to all patients.

Advances in imaging techniques now allow better distinction between partial and complete obstruction. Unfortunately, we cannot diagnose early reversible strangulation prior to progressing to irreversible ischemia; but, this is much more common with complete obstruction. Sixty to eighty percent of patients with partial obstruction will resolve their symptoms and be discharged without surgery. Those with complete obstruction benefit from 12-24 hours of resuscitation and decompression followed by surgery as indicated.

Certain specific problems warrant additional comment. Recurrent adhesive small bowel obstruction treated surgically can have recurrence rates as high as 30% making nonoperative management desirable, especially in patients with multiple recurrences. Early postoperative small bowel obstruction does not always clear with decompression and may require surgical intervention in a significant number of patients. A history of neoplasm does not imply carcinomatosis or recurrence as the etiology of obstruction, and up to 40% of patients with obstruction and concomitant or a past malignancy may have a benign remedial cause of obstruction.

Bass. Advances in Surgery. Volume 31.

Current Management of Small-Bowel Obstruction. Current Surgical Therapy, Fourth Edition.