Bowel Obstruction

The difference between a partial and complete bowel obstruction dictates whether your patient gets watchful waiting or emergency surgery — and the wrong call can lead to bowel necrosis within hours.

Bowel obstruction occurs when intestinal contents cannot pass through the lumen. Mechanical obstruction has a physical blockage (adhesions are the #1 cause in small bowel; tumors are #1 in large bowel). Functional (paralytic ileus) involves absent peristalsis without a physical blockage, commonly after abdominal surgery or with opioid use. Small bowel obstruction (SBO) presents with rapid-onset colicky pain, profuse vomiting (often bilious), abdominal distension, and high-pitched tinkling bowel sounds above the obstruction. Large bowel obstruction (LBO) develops more gradually with marked distension, deep cramping, absent or low-pitched bowel sounds, and absolute constipation. A critical distinction: complete obstruction produces no flatus and no stool — this is a surgical emergency. Strangulated obstruction means compromised blood supply; signs include sudden constant severe pain, fever, tachycardia, and rebound tenderness, signaling ischemia or perforation. Nursing priorities include NPO status, nasogastric tube to low intermittent suction for decompression, strict I&O with fluid and electrolyte replacement (watch for metabolic alkalosis from NG losses), and frequent abdominal assessments. Monitor for signs of perforation: rigid abdomen, absent bowel sounds, fever, tachycardia.

Key Distinctions

Don't confuse mechanical obstruction (high-pitched, hyperactive bowel sounds proximal to blockage) with paralytic ileus (absent bowel sounds throughout). Students mix up SBO and LBO vomiting patterns — SBO causes early, profuse vomiting while LBO causes late or feculent vomiting. Metabolic alkalosis results from NG suction losses (losing HCl), not acidosis — a frequent test trap.

Clinical Pearl

Adhesions after surgery are the top cause of SBO. If your post-op patient stops passing flatus and develops crampy pain with bilious vomiting, think obstruction before ileus resolves.