Overview
This lecture covers bowel obstruction, including types (mechanical and functional), causes, clinical presentation, key diagnostic features, complications, and management strategies.
Types of Bowel Obstruction
- Mechanical obstruction involves a physical blockage of the intestinal lumen with intact bowel muscle.
- Functional obstruction (also called paralytic ileus) is caused by impaired muscle motility, not a physical blockage.
- Mechanical obstructions show increased motility early, but loss of motility in late stages.
- Functional obstructions have decreased motility with no transition point on imaging.
Causes of Obstruction
- Small bowel obstructions: most commonly from adhesions (post-surgery), hernias, and intussusception (children).
- Large bowel obstructions: usually from tumors (e.g., colorectal cancer) or volvulus (twisting of bowel, especially in the elderly).
- Functional small bowel obstruction (paralytic ileus): caused by peritonitis, recent surgery, hypokalemia, or opioid use.
- Functional large bowel obstruction (colonic pseudo-obstruction/Ogilvie syndrome): similar causes as paralytic ileus.
Clinical Features & Diagnosis
- Common symptoms: cramping abdominal pain, abdominal distension, vomiting, obstipation (no passage of gas/stool).
- Mechanical obstruction shows proximal bowel distension and distal decompression with a visible transition point on imaging.
- Functional obstruction shows diffuse bowel distension without a transition point.
- Diagnosis starts with abdominal x-ray and is confirmed with CT scan for transition points, bowel dilatation, or air in the peritoneum.
- Auscultation: mechanical obstruction has hyperactive (early) then hypoactive (late) bowel sounds; functional has absent sounds.
Complications
- Hypovolemia from vomiting and poor absorption/secretion of fluids and electrolytes.
- Electrolyte imbalances: hypokalemia and metabolic alkalosis due to loss of potassium and protons (vomiting).
- Bowel ischemia (mesenteric ischemia) from prolonged pressure, leading to necrosis, high lactate, sepsis.
- Perforation: leakage of bacteria and air into the peritoneum causing peritonitis and pneumoperitoneum, seen on x-ray.
Management
- Supportive care: NPO (nothing by mouth), nasogastric (NG) tube for decompression, IV fluids, and electrolyte correction.
- Gastrografin may help partial obstructions by drawing fluid out of edematous bowel wall (not for complete obstructions).
- Surgery or endoscopy: needed for complete, closed-loop, or complicated (ischemia, perforation) mechanical obstructions.
- Functional obstruction: supportive care, rectal tube, laxatives, or neostigmine for unresponsive Ogilvie syndrome.
- Surgical intervention for perforation or ischemia.
Key Terms & Definitions
- Mechanical Bowel Obstruction — physical blockage in the intestine with intact bowel movement.
- Functional Bowel Obstruction (Paralytic Ileus) — bowel paralysis due to loss of muscle activity, not a blockage.
- Transition Point — spot on imaging where bowel changes from dilated (proximal) to decompressed (distal).
- Ogilvie Syndrome — acute colonic pseudo-obstruction, usually functional and without a physical blockage.
- Volvulus — twisting of the intestine causing obstruction.
- Intussusception — telescoping of one part of the bowel into another, common in children.
- Peritonitis — inflammation of the peritoneum, often from perforation.
- Pneumoperitoneum — presence of air in the peritoneal cavity, often due to perforation.
Action Items / Next Steps
- Review abdominal x-ray and CT findings for bowel obstruction patterns.
- Know common causes and complications for both small and large bowel obstructions.
- Study management steps for both mechanical and functional obstructions.