What is the initial management approach for a 60-year-old patient with symptoms of small bowel obstruction?

Differential Diagnosis of Small Bowel Obstruction at Age 60

In a 60-year-old patient with small bowel obstruction, adhesions from prior surgery remain the most common cause (55-75% of cases), but you must actively exclude hernias, malignancy, and inflammatory bowel disease—causes that collectively account for 35-45% of cases and require different management strategies. 1

Most Common Etiologies by Frequency

Adhesive Small Bowel Obstruction (55-75%)

• Prior abdominal surgery is the dominant risk factor, with 85% sensitivity and 78% specificity for predicting adhesive etiology 2
• Even remote surgical history (appendectomy decades prior) can cause adhesions 1
• However, do not assume adhesions without imaging confirmation—CT accuracy for identifying adhesive cause is only 52-76% 1

Hernias (10-15%)

• Examine all hernia orifices and previous surgical incision sites during physical examination 2
• Include groin hernias (inguinal, femoral), umbilical, and incisional hernias 1
• Internal hernias are increasingly recognized, particularly in patients with prior bariatric surgery 1

Malignancy (5-10%)

• Primary small bowel tumors or metastatic disease (carcinomatosis, peritoneal metastases) 1
• Document any unexplained weight loss or rectal bleeding in history 2
• Age 60 increases malignancy risk compared to younger patients 1

Inflammatory Bowel Disease (5%)

• Crohn's disease strictures are the primary IBD cause 1, 3
• Ask about chronic diarrhea, prior IBD diagnosis, or extraintestinal manifestations 1

Other Causes (10-15%)

• Gallstone ileus (particularly in elderly patients) 1
• Meckel's diverticulum complications 1
• Intussusception (rare in adults, often has lead point like tumor) 1
• Volvulus 1
• Radiation enteritis (if prior pelvic radiation) 1
• Endometriosis (less likely at age 60 but possible) 1

Critical Initial Assessment to Narrow Differential

History Elements That Guide Diagnosis

• Previous abdominal surgeries: Strongly suggests adhesions (85% sensitivity) 2
• Constipation pattern: Helps predict mechanical obstruction 2, 4
• Last bowel movement/gas passage: Complete vs. partial obstruction 2
• Medication review: Opioids, anticholinergics can cause pseudo-obstruction rather than true mechanical obstruction 1
• Weight loss/rectal bleeding: Raises concern for malignancy 2

Physical Examination Findings

• Abdominal distention has positive likelihood ratio of 16.8 for bowel obstruction 2
• Abnormal bowel sounds (hyperactive early, hypoactive late) predict obstruction 4
• Peritoneal signs indicate strangulation/ischemia requiring emergency surgery, though physical exam sensitivity for strangulation is only 48% 2
• Hernia examination may reveal external cause 2
• Digital rectal exam can detect masses or blood 2

Imaging Strategy to Establish Etiology

CT Abdomen/Pelvis with IV Contrast (First-Line)

• CT is the preferred imaging modality with >90% diagnostic accuracy for identifying obstruction and predicting need for surgery 1, 2
• No oral contrast needed for high-grade obstruction—non-opacified fluid provides adequate contrast 2
• CT helps differentiate causes by excluding hernias, masses, inflammatory changes 1
• CT accuracy for specific adhesive diagnosis is limited (52-76%), so adhesions remain a diagnosis of exclusion 1

Signs on CT Suggesting Specific Etiologies

• Closed loop, mesenteric edema, abnormal bowel wall enhancement: Suggests strangulation/ischemia requiring immediate surgery 1, 2
• Transition point with mass: Malignancy 2
• Transition point at hernia orifice: Hernia 1
• Bowel wall thickening with inflammatory changes: IBD or ischemia 2

Alternative Imaging When CT Unavailable

• Ultrasound has 90% sensitivity and 96% specificity, particularly useful if radiation exposure is a concern 2, 4
• Plain radiography has limited value (50-60% sensitivity) and should not delay CT 2

Key Pitfalls to Avoid

Don't Assume Adhesions Without Excluding Other Causes

• Even with prior surgery history, 25-45% of SBO cases have non-adhesive causes 1
• CT is essential to exclude hernias and malignancy 1

Don't Miss Pseudo-Obstruction

• Review medications carefully—opioids and anticholinergics cause narcotic bowel syndrome mimicking mechanical obstruction 1
• Consider metabolic causes (hypokalemia, hypothyroidism) 1, 2

Don't Delay Surgery for Ischemia

• Mortality increases from 10% to 25-30% with bowel necrosis/perforation 2, 3
• Signs requiring immediate surgery: peritonitis, CT findings of ischemia (pneumatosis, portal venous gas, lack of enhancement) 1, 2

Don't Overlook Malignancy in "Virgin Abdomen"

• In patients without prior surgery, malignancy and hernias become leading causes 1
• Age 60 warrants heightened suspicion for cancer 1

Laboratory Tests to Support Differential

• Marked leukocytosis (>10,000/mm³) suggests peritonitis or ischemia 2, 3
• Elevated lactate indicates possible bowel ischemia 2, 3
• CRP >75 may indicate peritonitis 2
• Electrolyte abnormalities (hypokalemia) need correction and may contribute to ileus 2
• Screen for hypothyroidism, which can cause pseudo-obstruction 1