Overview
This lecture discusses how to differentiate constipation from bowel obstruction in hospitalized patients, highlighting key symptoms, risk factors, physical findings, and diagnostic imaging.
Differentiating Constipation from Bowel Obstruction
- Constipation is a common symptom in both small and large bowel obstruction.
- Treating presumed constipation without excluding bowel obstruction can cause serious complications, such as bowel perforation.
- Bowel obstruction often presents with acute-onset constipation plus abdominal pain, nausea, vomiting, and abdominal distension.
History and Risk Factors
- Important risk factors for bowel obstruction include prior abdominal surgeries, Crohn's disease, abdominal radiation, and intra-abdominal cancer.
- Gathering a thorough history helps distinguish between simple constipation and obstruction.
Physical Examination Findings
- Patients with bowel obstruction usually appear sicker than those with simple constipation.
- Signs of dehydration or sepsis may be present in bowel obstruction.
- Abdominal exam often reveals distension and tenderness, but tenderness location doesn’t always correlate with obstruction site.
- High-pitched, hyperactive bowel sounds are typical but can be hypoactive or absent as well.
- Look for peritoneal signs (rebound tenderness, involuntary guarding, rigidity) that suggest need for urgent surgery.
Diagnostic Imaging
- History and exam alone may not distinguish constipation from bowel obstruction or other causes like ileus or colonic pseudo-obstruction.
- Abdominal X-ray may show air-fluid levels, dilated bowel loops, and, in severe cases, free air indicating perforation.
- Obtain X-ray images in at least two positions: dependent (supine) and non-dependent (upright or decubitus).
- CT scan is more sensitive, shows dilated loops, air-fluid levels, the transition point, and helps distinguish high vs. low-grade obstruction.
- CT also detects complications such as bowel ischemia, necrosis, or perforation.
- In ileus or regular constipation, no transition point is seen—just diffusely dilated loops with both stool and air.
Evaluating Equivocal Cases
- If history, physical exam, and labs are inconclusive, imaging is necessary to rule out obstruction in constipated patients.
Key Terms & Definitions
- Constipation — infrequent or difficult bowel movements, often with hard stool.
- Bowel Obstruction — blockage that prevents normal passage of intestinal contents.
- Ileus — temporary paralysis of bowel motility, usually post-operative or medication-induced.
- Peritoneal Signs — clinical findings (rebound tenderness, guarding, rigidity) indicating peritonitis and surgical emergency.
Action Items / Next Steps
- When evaluating constipation in the hospital, always rule out bowel obstruction before treatment.
- Obtain abdominal imaging (X-ray, CT) if clinical suspicion for obstruction remains after history and exam.