Acute Colonic Pseudo-Obstruction (ACPO / Ogilvie’s Syndrome)

Definition

Acute colonic pseudo-obstruction (ACPO) is a condition characterized by massive dilatation of the colon (especially caecum and ascending colon) without any mechanical obstruction, occurring in severely ill, postoperative, or hospitalized patients.

📌 It is a functional obstruction due to autonomic dysregulation of colonic motility.

Eponym

• Ogilvie’s syndrome
• First described by Sir William Heneage Ogilvie (1948) in patients with retroperitoneal malignancy

Epidemiology

• Typically occurs in:
• Hospitalized patients
• ICU patients
• Postoperative patients
• Age: Elderly (>60 years)
• Male predominance
• Incidence:
• Common after orthopedic surgery, trauma, cardiac surgery, sepsis

Pathophysiology (HIGH-YIELD)

Core Mechanism

➡️ Autonomic imbalance
➡️ ↓ Parasympathetic activity (sacral plexus S2–S4)
➡️ Unopposed sympathetic tone
➡️ Colonic atony and progressive dilatation

Why caecum is most vulnerable?

• Largest diameter
• According to Laplace’s law:

Wall tension ∝ Radius
➡️ Caecum dilates first → highest risk of ischemia and perforation

Cellular / Functional Changes

• ↓ Acetylcholine release
• ↓ Enteric neuronal activity
• Smooth muscle paralysis
• Colonic gas + fecal accumulation

Common Precipitating Factors

Medical Conditions

• Sepsis
• Severe electrolyte disturbances
• Stroke, spinal cord injury
• Parkinson’s disease
• Dementia
• Heart failure
• Renal failure

Postoperative States

• Orthopedic surgery (hip, spine)
• Abdominal surgery
• Cesarean section
• Cardiac surgery

Drugs (VERY IMPORTANT )

• Opioids
• Anticholinergics
• Tricyclic antidepressants
• Antipsychotics
• Calcium channel blockers
• Benzodiazepines
• Dopamine agonists

Metabolic Abnormalities

• Hypokalemia
• Hypomagnesemia
• Hypocalcemia
• Uremia

Clinical Features

Symptoms

• Progressive abdominal distension (hallmark)
• Abdominal discomfort or pain
• Nausea, vomiting
• Constipation or paradoxical diarrhea
• Anorexia

Signs

• Distended, tympanitic abdomen
• Bowel sounds:
• Normal, reduced, or absent
• Mild tenderness (severe pain → suspect ischemia/perforation)
• Fever, tachycardia → complications

📌 Peritonitis = late & ominous sign

Differential Diagnosis 

Diagnosis

Laboratory Tests

• Usually nonspecific
• Evaluate:
• Electrolytes (K, Mg, Ca)
• Renal function
• Sepsis markers
• Lactate (ischemia)

Imaging 

Plain Abdominal X-ray

• Colonic dilatation
• Predominantly caecum + ascending colon
• No air-fluid levels typical of obstruction

📌 Caecal diameter is CRITICAL

CT Abdomen with Contrast (Gold Standard)

• Excludes mechanical obstruction
• Uniform colonic dilatation
• No transition point
• Assesses ischemia, perforation

📌 CT is mandatory before pharmacologic therapy

Complications

• Caecal ischemia
• Colonic necrosis
• Perforation (mortality up to 40%)
• Sepsis
• Electrolyte imbalance

Management (STEPWISE – EXAM FAVORITE)

1️⃣ Conservative (Initial Management)

🔹 Indicated when:

• Caecum < 12 cm
• No ischemia/perforation
• Hemodynamically stable

Measures

• NPO
• Nasogastric decompression
• Rectal tube
• Stop precipitating drugs
• Correct electrolytes
• Treat underlying illness
• Mobilization
• Frequent abdominal girth monitoring
• Serial abdominal X-rays (every 12–24 h)

📌 Success rate: ~70% within 48–72 h

2️⃣ Pharmacologic Therapy – Neostigmine

Indications

• Failure of conservative therapy (48–72 h)
• Caecal diameter ≥ 10–12 cm
• No perforation or ischemia

Drug of Choice: NEOSTIGMINE

📌 Response usually within 30 minutes

Contraindications 

• Mechanical bowel obstruction
• Bowel perforation
• Ischemic colitis
• Severe bradycardia
• Recent MI
• Asthma
• Uncontrolled arrhythmias

Adverse Effects

• Bradycardia
• Hypotension
• Bronchospasm
• Excess salivation
• Nausea

📌 Atropine must be at bedside

Efficacy

• Success rate: 85–90%
• Recurrence: 20–30%

➡️ Second dose may be given after 24 h if partial response

3️⃣ Colonoscopic Decompression

Indications

• Failed neostigmine
• Contraindication to neostigmine
• Rapid decompression needed

Procedure

• Flexible sigmoidoscopy or colonoscopy
• Decompression ± decompression tube placement

Risks

• Perforation (2–3%)
• Bleeding
• Recurrence

📌 Preferred over surgery when feasible

4️⃣ Surgical Management 

Indications

• Perforation
• Ischemia
• Peritonitis
• Failure of all other measures

Options

• Cecostomy
• Segmental colectomy
• Subtotal colectomy

📌 Mortality extremely high in critically ill patients

Prognosis

• Overall mortality: 10–15%
• With perforation: 30–40%
• Early diagnosis dramatically improves outcomes

Special ICU Considerations

• Avoid excessive opioids
• Aggressive electrolyte correction
• Early mobilization
• Vigilant abdominal monitoring
• Multidisciplinary care (ICU + GI + Surgery)

ACPO vs Paralytic Ileus