Symptoms of Small Bowel Obstruction
Small bowel obstruction classically presents with colicky abdominal pain, distension, vomiting, and obstipation (complete obstruction) or alternating constipation with diarrhea (partial obstruction). 1, 2
Classic Symptom Presentation
Complete Obstruction
- Regular vomiting or absolute constipation with abdominal distension are the hallmark features, constituting a surgical emergency 1
- Total mechanical blockage prevents any passage of intestinal contents through the obstructed segment 1
- Patients develop progressive abdominal distension with absent bowel movements 1
Partial Obstruction
- Intermittent colicky abdominal pain with distension, loud bowel sounds, episodes of no bowel action followed by diarrhea when obstruction resolves, and vomiting characterize partial obstruction 2
- Pain is typically colicky and worsens after oral intake 1
- The bowel secretes excess fluid proximal to the blockage during obstructive episodes, and when the obstruction temporarily resolves, this accumulated fluid is expelled as diarrhea 2
- Imaging demonstrates partial passage of intestinal contents through the narrowed segment 1
Critical Diagnostic Pitfall
Do not dismiss bowel obstruction simply because the patient has diarrhea 2. This is a common error that delays diagnosis. Look for the pattern of intermittent colicky pain, abdominal distension with loud bowel sounds, and obstipation alternating with diarrhea 2.
Physical Examination Findings
- Prior abdominal surgery, history of constipation, abdominal distension, and abnormal bowel sounds are the most reliable clinical findings 3
- Visible peristalsis may be observed on abdominal inspection 4
- Abdominal distension with stenosis on digital rectal examination followed by a gush of liquid stool is pathognomonic for distal obstruction (the "gush sign") 4
Signs of Strangulation (Surgical Emergency)
Fever, hypotension, diffuse abdominal pain, and peritonitis indicate strangulation requiring immediate surgical intervention 3. These patients need urgent operative management as strangulation leads to mucosal ischemia, necrosis, and perforation 3.
High-Risk Populations
- Adhesions account for 55-75% of small bowel obstructions, with history of abdominal surgery having 85% sensitivity and 78% specificity for predicting adhesive obstruction 2
- Multiple prior laparotomies significantly increase risk of intermittent obstruction from adhesions 2
- Up to 54% of Crohn's disease patients develop small bowel obstruction requiring surgery due to fibrostenotic strictures 2
- Colorectal cancer causes approximately 60% of large bowel obstructions, and peritoneal carcinomatosis can cause extrinsic compression leading to intermittent obstruction 2
Diagnostic Approach
- CT scan during an acute pain episode is most helpful for demonstrating the transition point between dilated and normal-sized bowel, which suggests mechanical obstruction 2
- Early CT imaging is required to understand the anatomy of the obstruction and exclude cancer recurrence 1
- Plain radiographs are often ordered but cannot exclude the diagnosis 3
- Fixed bowel from adhesions may not dilate, making diagnosis more challenging 2
Management Algorithm
Initial Resuscitation
- Mechanical obstruction requires aggressive resuscitation and consideration for surgical intervention 1
- Intravenous fluid resuscitation and correction of electrolyte disturbances are essential 5, 3
- Nasogastric tube decompression is useful for patients with significant distension and vomiting by removing contents proximal to the obstruction 3
Operative vs. Non-Operative Decision
Proceed to surgery if:
- Evidence of strangulation (fever, hypotension, peritonitis) 1, 3
- Complete obstruction that fails to resolve with adequate decompression 1
- Signs of bowel ischemia or perforation 3
Non-operative trial may be appropriate if:
- Partial small bowel obstruction without signs of strangulation 1
- Water-soluble contrast agents can be both diagnostic and therapeutic in partial obstruction 1
- However, patients with high-grade obstruction managed non-operatively have a significantly higher recurrence rate (24% vs 9%) and shorter time to recurrence (39 days vs 105 days) compared with operative intervention 6
Medication Considerations
Prokinetic agents like metoclopramide should not be used in complete obstruction as they can cause perforation, but may be beneficial in incomplete obstruction 1. Metoclopramide is the mainstay of therapy for gastroparesis but must be avoided when complete mechanical obstruction is present 5.