What is the initial management for suspected intestinal obstruction?

Initial Management of Suspected Intestinal Obstruction

Begin immediate resuscitation with intravenous isotonic crystalloids, insert a nasogastric tube for decompression, place a Foley catheter, enforce strict bowel rest (NPO), and obtain CT abdomen/pelvis with IV contrast as the primary diagnostic imaging. 1, 2

Immediate Resuscitation and Stabilization

Fluid Resuscitation:

• Establish IV access and begin aggressive isotonic crystalloid resuscitation (isotonic dextrose-saline or balanced crystalloid solutions) to correct hypovolemia from third-spacing and vomiting 1, 2
• Add supplemental potassium to replacement fluids in equivalent volume to losses, as vomiting causes significant potassium depletion 1
• Monitor adequacy of resuscitation by urine output via Foley catheter (target >0.5 mL/kg/hr) 1, 2

Gastric Decompression:

• Insert nasogastric tube immediately to decompress the proximal bowel and prevent aspiration pneumonia 1, 2
• Feculent gastric aspirate is characteristic of distal small bowel or large bowel obstruction 1

Supportive Measures:

• Enforce strict NPO status (bowel rest) 1, 2
• Administer antiemetics cautiously; avoid prokinetic agents in complete obstruction 2
• Insert Foley catheter to monitor urine output and assess resuscitation adequacy 1, 2

Essential Laboratory Workup

Order the following tests immediately to assess for complications and guide management:

• Complete blood count - marked leukocytosis with left shift suggests ischemia or peritonitis 1, 2
• Lactate level - elevated lactate is highly concerning for bowel ischemia 1, 2
• Comprehensive metabolic panel - assess for electrolyte abnormalities (hypokalemia, hypomagnesemia, hypercalcemia) and pre-renal acute kidney injury 1, 2
• C-reactive protein - elevated CRP suggests inflammation, ischemia, or peritonitis 2, 3
• Coagulation profile - essential given potential need for emergency surgery 1, 2
• Arterial blood gas - low pH and low bicarbonate may indicate intestinal ischemia 1
• Amylase - hyperamylasemia can be useful in diagnosing intestinal ischemia 1

Diagnostic Imaging Strategy

CT Abdomen/Pelvis with IV Contrast (Preferred Initial Study):

• CT has >90% diagnostic accuracy for confirming obstruction, identifying the transition point, determining the cause, and detecting complications 1, 2
• IV contrast is essential to assess bowel perfusion and identify ischemia, though CT is not highly sensitive for ischemia (sensitivity only 15-52% even with expert review) 1
• Do NOT give oral contrast in suspected high-grade obstruction - it delays diagnosis, increases patient discomfort, risks aspiration, and obscures bowel wall enhancement needed to detect ischemia 1
• Multiplanar reconstructions increase accuracy in locating the transition zone 1
• CT signs requiring urgent surgery include: intraperitoneal fluid, mesenteric edema, absence of small-bowel feces, closed-loop obstruction, pneumoperitoneum, or signs of ischemia 1, 2

Plain Abdominal Radiographs (Limited Role):

• Sensitivity for small bowel obstruction is only 50-60%, with misleading findings in 10-20% of cases 1
• May be diagnostic in 50-60% of cases but inconclusive in 20-30% 1
• For large bowel obstruction, sensitivity is 84% and specificity 72% 1
• Skip plain films and proceed directly to CT in most cases given CT's superior accuracy 1

Water-Soluble Contrast Administration

Diagnostic and Therapeutic Role:

• Administer 50-150 mL of water-soluble contrast (Gastrografin) orally or via nasogastric tube after adequate gastric decompression 1, 2
• If contrast has NOT reached the colon on abdominal X-ray at 24 hours, this predicts failure of non-operative management with high accuracy 1, 2
• Water-soluble contrast has both diagnostic value (predicting need for surgery) and therapeutic benefit (may reduce time to resolution and need for surgery) 1, 2, 3

Critical Safety Precautions:

• Only administer after the stomach has been adequately decompressed via nasogastric tube to prevent aspiration pneumonia 1
• High osmolarity can cause further dehydration by shifting fluid into bowel lumen; ensure adequate IV hydration first, especially in elderly and children 1
• Consider giving at 48 hours rather than immediately to reduce aspiration and dehydration risk, and dilute with water 1
• Rare anaphylactoid reactions have been reported 1

Timeline for Conservative Management

72-Hour Rule:

• A 72-hour trial of non-operative management is safe in partial obstruction without signs of peritonitis, strangulation, or ischemia 2, 3
• Reassess at 24 hours after water-soluble contrast administration 2
• Failure of conservative management after 72 hours mandates surgical consultation 2, 3
• Non-operative management is successful in approximately 70-90% of adhesive small bowel obstructions 3

Absolute Indications for Immediate Surgery

Do NOT attempt conservative management if any of the following are present:

• Signs of peritonitis on physical examination (rebound tenderness, guarding, rigidity) 2, 3
• Evidence of bowel ischemia or strangulation (elevated lactate, marked leukocytosis, metabolic acidosis, CT signs of ischemia) 2, 3
• Closed-loop obstruction on CT imaging 2, 3
• Pneumoperitoneum with free fluid in an acutely unwell patient 2
• Hemodynamic instability despite adequate resuscitation 2

Important caveat: Classical clinical signs (fever, tachycardia, leukocytosis, local tenderness) are poor predictors of gangrenous bowel, explaining only 14% of variance 4. Therefore, maintain a low threshold for surgical consultation and do not rely solely on clinical examination to rule out ischemia.

Reversible Medical Causes to Identify Early

Before committing to prolonged conservative management or surgery, evaluate for:

• Electrolyte abnormalities - hypokalemia, hypomagnesemia, hypercalcemia can cause pseudo-obstruction 2
• Opioid-induced dysmotility - even small doses can cause prolonged colonic inertia; reduce or discontinue if feasible 2
• Severe fecal impaction - may mimic obstruction 2
• Small bowel bacterial overgrowth - consider trial of antibiotics if suspected 2