Small bowel obstruction

Common causes of SBO in adults include:

• Previous surgery with the formation of intra-abdominal adhesions, including colorectal/gynaecological surgery, resection of intra-abdominal tumours, laparotomy for trauma

• Inguinal hernia with incarceration; ventral, incisional, umbilical, and parastomal hernias

• Crohn's disease

• Intestinal malignancy

• Appendicitis.

Rare causes include radiation enteritis, intra-abdominal abscess (from perforated appendicitis/diverticulitis), gallstone ileus, foreign body, and intestinal bezoar.

SBO represents an interruption in the patency of the gastrointestinal tract. The proximal dilation of the intestine, together with peristalsis, leads to abdominal cramping (colic), which can become severe. The abdominal pain may also be accompanied by vomiting, while the distal interruption of faecal flow leads to absolute constipation. In acute cases, there can be hyperperistalsis distal to the obstruction, leading to the finding of diarrhoea. Obstructed bowel will, over time, prevent appropriate venous drainage with the possible result of decreased arterial perfusion. Untreated patients develop progressive intestinal ischaemia, necrosis, and perforation.

According to the nature of the obstruction

Partial (incomplete) bowel obstruction

• The situation in which the blockage of the intestine is not complete, resulting in partial passage of flatus and occasionally stool. This is not a surgical emergency and it may resolve with non-operative therapy.

Complete bowel obstruction

• Emergency situation in which the blockage of the intestine completely obstructs the lumen of the intestine, resulting in failure to pass flatus and stool, is generally associated with peritonitis. This is considered to be a surgical emergency and, except in rare cases (e.g., Crohn's disease), will not respond to non-operative therapy.

Simple bowel obstruction

• An intestinal blockage in the absence of peritonitis; generally reflects early or partial obstruction and may respond to non-operative therapy.

Complicated bowel obstruction

• A surgical emergency in which the obstruction has progressed to intestinal ischaemia/gangrene and/or perforation. This is a life-threatening situation that requires urgent resuscitation and surgical intervention.

Combined terms

Partial (incomplete) and simple SBO are diagnosed and treated in the same way; complete SBO may progress to complicated SBO when intestinal ischaemia, necrosis, and/or perforation develop.