What is the recommended assessment and management for an adult presenting with several days of intermittent abdominal pain, nausea, vomiting, abdominal distension, and reduced or absent flatus or stool consistent with sub‑acute intestinal obstruction?

Approach to Subacute Intestinal Obstruction

Begin immediate supportive treatment with IV crystalloid resuscitation, nasogastric tube decompression, and obtain CT abdomen/pelvis with IV contrast—the diagnostic standard with >90% accuracy—while simultaneously assessing for signs of ischemia that mandate emergency surgery. 1, 2

Initial Clinical Assessment

Document the specific pattern of symptoms that characterizes subacute obstruction:

• Intermittent crampy abdominal pain that waxes and wanes, often worse after eating 1, 3
• Recurrent symptoms occurring in approximately 48% of subacute cases 4
• Nausea and vomiting that may be intermittent rather than continuous 1, 3
• Reduced passage of flatus and stool (not necessarily complete absence) 1, 3
• Abdominal distension (present in 25-65% of cases, with positive likelihood ratio of 16.8) 1, 3

Critical History Elements

• Previous abdominal surgeries (85% sensitivity for adhesive obstruction, the cause in 55-75% of cases) 1, 3
• Pattern of symptoms: Ask specifically if pain improves after vomiting or passage of watery diarrhea, as incomplete obstruction can mimic gastroenteritis 1, 3
• Dietary triggers: Patients may report symptoms worsen with solid foods and improve with liquid diet 5
• Medication review: Opioids can cause narcotic bowel syndrome mimicking mechanical obstruction 5, 1
• Previous diverticulitis, rectal bleeding, or weight loss suggesting malignancy or inflammatory causes 1, 3

Physical Examination Priorities

• Examine all hernia orifices and previous surgical scars for incarcerated hernias 1, 3
• Visible peristalsis in thin patients suggests mechanical obstruction 5, 3
• Exaggerated bowel sounds occur in 60% of subacute cases 4
• Palpable bowel loops found in 28% of subacute presentations 4

Red Flags Indicating Ischemia/Strangulation (Requiring Emergency Surgery)

• Fever, tachycardia >110 bpm, tachypnea, or confusion 2
• Intense pain unresponsive to analgesics 2
• Peritoneal signs (guarding, rebound tenderness) 2
• Absent bowel sounds (transition from hyperactive to silent indicates advanced ischemia) 3, 2
• Hypotension, cool extremities, mottled skin 2

Immediate Management

Supportive Treatment (Start Immediately)

• IV crystalloid resuscitation to correct dehydration and electrolyte abnormalities 1, 2
• Nasogastric tube decompression to prevent aspiration and relieve symptoms 1, 2
• Foley catheter to monitor urine output and assess hydration 1
• Bowel rest (NPO status) 1, 2
• Anti-emetics for symptom control 1

Laboratory Evaluation

• Complete blood count: Leukocytosis >10,000/mm³ suggests peritonitis or ischemia 1, 2
• Lactate level: Elevated in intestinal ischemia 1, 2
• Electrolytes: Correct hypokalemia before any surgical intervention 1
• Renal function (BUN/creatinine): Assess dehydration 1
• CRP >75: May indicate peritonitis 1

Diagnostic Imaging Strategy

First-Line: CT Abdomen/Pelvis with IV Contrast

CT with IV contrast is the diagnostic standard with >90% accuracy and should be obtained in all cases of suspected subacute obstruction. 5, 1, 2

• No oral contrast needed in suspected high-grade obstruction (intrinsic bowel fluid provides adequate contrast) 5, 1
• IV contrast is essential to evaluate for bowel ischemia and identify underlying etiology 1

CT Findings Mandating Emergency Surgery

• Abnormal bowel wall enhancement or lack of enhancement 5, 1
• Mesenteric edema or haziness 5, 1
• Bowel wall thickening 5, 1
• Pneumatosis intestinalis or portal venous gas 5, 1
• Closed-loop obstruction 1
• Free intraperitoneal air (perforation) 2

CT Findings Suggesting Partial/Low-Grade Obstruction

• Transition point identified with passage of oral contrast beyond it (can re-image at 24 hours to confirm) 5
• Mild bowel dilation without complete obstruction 5

Special Imaging Considerations for Subacute/Intermittent Obstruction

Standard CT has only 48-50% sensitivity for low-grade obstruction because the bowel may appear normal at the time of imaging. 5

When standard CT is negative but clinical suspicion remains high:

• CT enterography or CT enteroclysis provides optimized bowel distention and improved sensitivity for subtle obstructions 5
• Water-soluble contrast studies can be both diagnostic and therapeutic, potentially reducing hospital stay and need for surgery 1
• Diagnostic laparoscopy has 100% accuracy when CECT is unavailable or inconclusive 4

Alternative Imaging

• Ultrasound: 90% sensitivity and 96% specificity, useful in pregnancy or when CT unavailable 1
• Plain abdominal radiographs: Limited value (50-60% sensitivity, 20-30% inconclusive), should not delay CT if suspicion is high 1

Management Algorithm

Immediate Surgery Required If:

• Any signs of ischemia on CT or clinical examination (mortality increases from 10% to 25-30% with bowel necrosis) 1, 2
• Complete obstruction with peritonitis 2
• Closed-loop obstruction 1, 2
• Hemodynamic instability despite resuscitation 2
• Internal hernia (especially post-bariatric surgery) 2

Conservative Management Trial Appropriate If:

• Partial obstruction without ischemia signs 1, 2
• Hemodynamically stable 2
• No peritoneal signs 2

Conservative Management Protocol

• Continue IV fluids, NG decompression, bowel rest 1, 2
• Serial abdominal examinations every 4-6 hours 6, 7
• Monitor for development of ischemia signs 2
• Most low-grade obstructions resolve with conservative treatment within 48-72 hours 5, 1

Surgical Consultation Timing

• Immediate consultation if any ischemia signs present 2
• Early consultation (within hours) for all cases, even if initially managed conservatively 1, 7
• Failure to improve within 48-72 hours of conservative management indicates need for surgery 6, 7

Critical Pitfall: Identifying Underlying Cause in Subacute Cases

In patients whose symptoms resolve with conservative treatment and who do NOT have a history of previous abdominal surgery, underlying pathology requiring definitive treatment is present in 42% of cases (14 of 33 patients in one series). 4

Investigation Strategy After Symptom Resolution

For patients without previous abdominal surgery whose obstruction resolves conservatively:

• CECT or diagnostic laparoscopy is mandatory to identify underlying pathology 4
• Tuberculous pathology found in 52% of these cases 4
• Small intestinal strictures found in 27% 4
• When advanced imaging unavailable, laparotomy is indicated to prevent recurrence 4

For patients with previous abdominal surgery:

• Adhesions are the presumed cause (found in 32% of subacute cases) 4
• Conservative management success is predicted by surgical history (13/19 vs 7/44 without surgery) 4
• Further investigation may not be necessary if symptoms fully resolve 4

Common Pitfalls to Avoid

• Mistaking incomplete obstruction with watery diarrhea for gastroenteritis—the passage of liquid stool does not exclude obstruction 1, 3
• Overlooking obstruction in elderly patients where pain may be less prominent 1
• Delaying CT when plain films are negative but clinical suspicion remains high 1
• Failing to correct electrolyte abnormalities before surgical intervention 1
• Not investigating resolved subacute obstruction in patients without surgical history—underlying treatable pathology is common 4
• Assuming adhesions without imaging confirmation—hernias (10-15%), malignancy (5-10%), and inflammatory disease (5%) require different management 1