Small Bowel Obstruction and Resection

Small bowel obstruction is a blockage of the passage of intestinal contents through the small intestine and is one of the most common reasons for emergency abdominal surgical assessment. Most cases arise from adhesions following previous surgery; management ranges from non-operative bowel rest and decompression to operation, and resection of small intestine is required when bowel is strangulated, ischaemic, or otherwise non-viable.

Definition

Small bowel obstruction is a mechanical or functional interruption of the normal aboral passage of contents through the small intestine; its surgical management includes relief of the obstruction and, where bowel is non-viable, resection of the affected segment with restoration of continuity.

Scope

This entry covers the principal causes of small bowel obstruction, the distinction between simple and strangulated (or complicated) obstruction, the rationale for an initial trial of non-operative management in selected cases, and the indications for operation and small-bowel resection. It is a reference description of the condition and its surgical management, not a clinical protocol or source of individualized advice.

Core questions

• What are the common causes of small bowel obstruction, and why are adhesions predominant?
• How is simple obstruction distinguished from strangulation that threatens bowel viability?
• When is a trial of non-operative management appropriate and when is it unsafe?
• What are the indications for surgery and for small-bowel resection?

Key concepts

• Mechanical bowel obstruction
• Adhesions
• Strangulation and bowel ischaemia
• Closed-loop obstruction
• Non-operative management
• Water-soluble contrast challenge
• Bowel resection and anastomosis

Mechanisms

Obstruction interrupts the forward flow of intestinal contents, causing proximal distension with fluid and gas, increased intraluminal pressure, and impaired venous drainage of the bowel wall; if the blood supply is compromised — as in a closed-loop or strangulating obstruction — the bowel becomes ischaemic and may perforate, which is the principal threat to life. Most obstructions are caused by postoperative adhesions, with hernias and tumours the other major mechanical causes. Many simple adhesive obstructions resolve with bowel rest, nasogastric decompression, and fluid resuscitation, and a water-soluble contrast study can both predict resolution and hasten transit; signs of strangulation, closed-loop obstruction, or failure to resolve mandate operation, at which non-viable bowel is resected and continuity restored (ten Broek et al., 2018). Postoperative complications are graded by the Clavien-Dindo system (Clavien et al., 2009).

Clinical relevance

Recognizing the features that distinguish a safely observed obstruction from one that requires urgent operation is a core competency in acute general surgery, because delayed recognition of strangulation increases the risk of resection and death. This entry is descriptive and educational and is not a basis for individual diagnostic or treatment decisions.

Epidemiology

Adhesive disease following previous abdominal or pelvic surgery is the leading cause of small bowel obstruction in populations where such surgery is common, while hernia and malignancy account for most of the remainder; obstruction is a frequent reason for emergency hospital admission and abdominal operation (ten Broek et al., 2018).

History

Surgical understanding of intestinal obstruction advanced through the twentieth century with the recognition of adhesions as a dominant cause and the development of fluid resuscitation and nasogastric decompression, which made non-operative management of simple obstruction feasible. The use of water-soluble contrast studies to predict resolution and the consolidation of practice into evidence-based consensus, such as the World Society of Emergency Surgery's Bologna guidelines, reflect the modern emphasis on selecting patients for operation rather than operating on all.

Debates

How long should non-operative management continue before operation?

An initial non-operative trial is appropriate for many simple adhesive obstructions, but the safe duration before declaring failure is debated, since prolonged observation risks missing evolving strangulation while early operation exposes patients who would have resolved spontaneously to surgical risk.

Seminal works

• tenbroek-2018

Frequently asked questions

What most often causes small bowel obstruction?

Adhesions from previous abdominal or pelvic surgery are the most common cause, followed by hernias and tumours.

Does every small bowel obstruction need surgery?

No. Many simple adhesive obstructions settle with bowel rest, decompression, and fluids, but signs of strangulation or failure to resolve indicate the need for operation, sometimes with resection of non-viable bowel.