USMLE Prep - Medical Reference Library

Adhesive Small Bowel Obstruction — NG Decompression, Water‑Soluble Contrast, and Operative Triggers

System: General Surgery • Reviewed: Sep 1, 2025 • Step 1Step 2Step 3

Synopsis:

Common post‑operative SBO managed initially with fluid resuscitation, NG decompression, and water‑soluble contrast challenge. Operate urgently for peritonitis, strangulation, or failure of non‑operative management.

Key Points

  • Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
  • Set objective targets (hemodynamic, neurologic, respiratory) and reassess frequently.
  • Plan definitive source control or immunomodulation when indicated; document follow‑up and patient education.

Algorithm

  1. Resuscitate; NG decompression; NPO; correct electrolytes.
  2. CT to confirm level/cause and assess for closed loop/ischemia.
  3. Give water‑soluble contrast; observe for transit to colon within 24 h.
  4. Urgent surgery if peritonitis, ischemia, closed loop, or failure of non‑operative management within 48–72 h.

Clinical Synopsis & Reasoning

Common post‑operative SBO managed initially with fluid resuscitation, NG decompression, and water‑soluble contrast challenge. Operate urgently for peritonitis, strangulation, or failure of non‑operative management.


Treatment Strategy & Disposition

Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced or procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.


Epidemiology / Risk Factors

  • Risk varies by comorbidity and precipitants; see citations for condition‑specific data.

Investigations

TestRole / RationaleTypical FindingsNotes
CT abdomen/pelvis with contrastDiagnosis/severityTransition point, closed loop, ischemia signsGuide operative decision
Lactate/WBCStrangulation riskElevated suggests ischemiaTrend with exam
Water‑soluble contrast studyTherapeutic/prognosticTransit to colon within 24 h predicts successMay reduce OR need

Pharmacology

Medication/InterventionMechanismOnsetRole in TherapyLimitations
Isotonic fluidsResuscitationImmediateCorrect dehydration/AKI riskMonitor electrolytes
NG tube decompressionMechanicalImmediateSymptom relief; nausea/vomiting controlAspiration prevention
Analgesia/antiemeticsSupportiveMinutesSymptom controlAvoid ileus‑worsening opioids when possible

Prognosis / Complications

  • Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.

Patient Education / Counseling

  • Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.

References

  1. WSES/Bologna Guidelines for Adhesive Small Bowel Obstruction (2018) — Link