Management of Acute Intestinal Obstruction

1. Classification - Essential First Step

2. Initial Assessment and Resuscitation ("Drip & Suck")

A. Intravenous Fluid Resuscitation

• SBO leads to loss of up to 6 litres/day of salt-rich fluid by vomiting or sequestration into the bowel lumen
• Aggressive IV crystalloid replacement (normal saline or Hartmann's/Ringer's lactate)
• Correct electrolyte imbalances - monitor K+, Na+, Cl-
• Insert urinary catheter for accurate fluid balance

B. Nasogastric Decompression

• NG tube suction empties the stomach, reduces the risk of pulmonary aspiration and limits further distension from swallowed air
• Long intestinal tubes (Cantor or Baker tube) offer no significant advantage over standard NG tubes - prospective RCTs show no difference in decompression achieved, success of non-operative treatment, or post-operative morbidity. They are associated with longer hospital stay and longer post-operative ileus - Sabiston Textbook of Surgery
• Use should be determined on a case-by-case basis (evidence remains inconclusive for universal use)

C. Monitoring and Work-up

• IV access (large bore x2), blood for FBC, U&E, LFTs, amylase, group & save
• Erect chest X-ray (to exclude pneumoperitoneum)
• Erect and supine plain abdominal X-ray as initial imaging
• CT scan (with IV and oral contrast) - now standard for confirming diagnosis, identifying the level and cause, and detecting strangulation/ischemia

3. Radiological Diagnosis

Plain Abdominal X-Ray

• Multiple air-fluid levels on the erect film ("step-ladder" or "string of pearls" pattern)
• Dilated loops with valvulae conniventes (SBO) vs. haustra (LBO)
• Absence of colonic gas suggests complete SBO

Plain erect abdominal X-ray showing multiple dilated small bowel loops with air-fluid levels and visible valvulae conniventes - classic complete SBO pattern.

Erect abdominal X-ray (right panel) showing the pathognomonic "string of pearls" / "stepladder" appearance of multiple air-fluid levels in acute intestinal obstruction.

CT Abdomen (Gold Standard)

• Identifies the exact transition point, cause (adhesion, hernia, mass), and level
• Detects early features of strangulation: mesenteric edema, free fluid, pneumatosis intestinalis, portal venous gas
• Differentiates benign from malignant causes: malignant obstruction - mass at transition zone, adenopathy, abrupt cutoff, irregular thickening; benign - smooth transition zone, mesenteric vascular changes
• Acute cecal dilatation >12-14 cm is a surgical emergency due to high risk of rupture - Harrison's Principles of Internal Medicine, 22nd Ed.

4. Identifying Strangulation - The Critical Decision Point

"Local tenderness over part of the abdomen may suggest developing strangulation... with developing peritoneal irritation due to strangulation the bowel may become atonic and the bowel sounds ominously quiet." - Pye's Surgical Handicraft

5. Non-Operative (Conservative) Management

Indications

• Partial SBO (up to 85% of partial obstructions resolve without surgery)
• Adhesive SBO without strangulation signs
• Post-operative ileus
• First episode after known pelvic/abdominal malignancy (trial of conservative)
• Crohn's disease-related acute obstruction (often resolves with conservative care + steroids)

Components

1. NG decompression + bowel rest
2. IV fluid and electrolyte replacement
3. Analgesia
4. Regular clinical reassessment (vital signs, abdominal exam, urine output)
5. Serial abdominal X-rays

Water-Soluble Contrast Challenge (Gastrografin)

• 100 mL of water-soluble contrast given via NG tube or orally, with follow-up X-rays at 8 and 24 hours
• If contrast has not reached the colon at 24 hours - conservative management is unlikely to succeed and surgery is indicated
• Evidence supports its use in adhesive SBO specifically; not established for non-adhesive obstruction - Sabiston Textbook of Surgery

Failure of Conservative Management

• Clinical deterioration (increasing pain, fever, tachycardia)
• Increasing distension on serial X-rays
• Failure of contrast to pass at 24 hours
• No improvement after 48-72 hours
• New signs of strangulation at any point

6. Operative Management

Indications for Urgent/Emergency Surgery

• Strangulation or vascular compromise (closed-loop obstruction, volvulus, hernia with vascular compromise)
• Complete obstruction with failure of conservative management
• Peritonitis / perforation (pneumoperitoneum on CXR)
• Signs of strangulation on CT
• Cecal dilatation >12 cm (LBO)

Approach by Etiology

Laparoscopic vs. Open

• Laparoscopic approach for SBO - multiple studies confirm lower morbidity and mortality, shorter length of stay
• Conversion to open if extensive adhesions, ischemic bowel, or dense inflammation
• Sabiston Textbook of Surgery

Assessing Bowel Viability Intraoperatively

1. Wrap segment in warm saline-moistened sponges for 15-20 minutes and re-examine
2. If normal color returns and peristalsis resumes - safe to retain
3. Doppler flow probe - identifies mesenteric flow but adds little to surgeon's clinical judgment
4. Fluorescein or indocyanine green (ICG) fluorescence - useful in difficult borderline cases
5. If viability still uncertain - temporary abdominal closure with second-look laparotomy at 18-24 hours

• Sabiston Textbook of Surgery

7. Large Bowel Obstruction - Special Considerations

SEMS (Self-Expanding Metal Stents)

• Endoscopic colonic stenting increasingly used in malignant LBO
• "Bridge to surgery": converts emergency to elective operation, allowing bowel preparation and reduction of stoma rate
• Definitive palliation in patients with advanced/metastatic disease
• Fischer's Mastery of Surgery, 8th Ed.

Colonic Pseudo-Obstruction (Ogilvie's Syndrome)

• Functional obstruction - treat the underlying cause (stop opioids, correct electrolytes, mobilize)
• Neostigmine 2 mg IV - effective first-line pharmacological treatment
• Colonoscopic decompression for cecal diameter >10-12 cm or failure of neostigmine
• Surgery only if perforation or failure of all other measures
• Current Surgical Therapy, 14th Ed.

Sigmoid Volvulus

• Flexible sigmoidoscopy / rigid sigmoidoscopy + rectal tube: first-line decompression (>90% success)
• High risk of recurrence (~40-60%) - elective sigmoid resection after recovery
• Emergency surgery if signs of gangrene/perforation or failed endoscopic decompression

8. Malignant Bowel Obstruction (Palliative Setting)

• Median survival with malignant obstruction is only 3-4 months
• ~25-30% have a benign cause (adhesions, drug-induced ileus) - exclude before declaring palignant
• Conservative approach preferred for known advanced disease: NG decompression, IV fluids, antiemetics, antispasmodics, analgesia
• Octreotide - reduces GI secretions, relieves obstructive symptoms
• Glucocorticoids - anti-inflammatory, may reduce edema at obstruction site
• Venting gastrostomy (PEG) - palliates nausea/vomiting without major surgery
• SEMS for accessible colonic/duodenal obstruction
• Harrison's Principles of Internal Medicine, 22nd Ed.

9. Summary Algorithm

Acute Intestinal Obstruction
        |
        ├── Resuscitation (IV fluids, NG tube, catheter, monitoring)
        ├── Investigations (AXR, CT scan, bloods)
        |
        ├── SIGNS OF STRANGULATION / PERITONITIS / PERFORATION?
        |       YES → Emergency laparotomy / laparoscopy
        |
        └── NO → Conservative Management (48-72 hrs)
                    |
                    ├── SBO
                    |    ├── Partial → 85% resolve; water-soluble contrast challenge at 24-48h
                    |    └── Complete → Careful trial; contrast challenge; operate if no resolution at 24-48h
                    |
                    └── LBO
                         ├── Malignancy → SEMS (bridge/palliation) or urgent resection
                         ├── Volvulus → Endoscopic detorsion (sigmoid) / surgery (cecal)
                         └── Pseudo-obstruction → Neostigmine / colonoscopic decompression

• Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice - Operative and non-operative management
• Pye's Surgical Handicraft, 22nd Ed. - Clinical features and initial assessment
• Current Surgical Therapy, 14th Ed. - LBO etiology and management
• Harrison's Principles of Internal Medicine, 22nd Ed. - Malignant obstruction
• Fischer's Mastery of Surgery, 8th Ed. - SEMS in LBO