Paralytic Ileus (Adynamic Ileus) 

Definition

Paralytic ileus is a functional inhibition of propulsive intestinal motility without a mechanical obstruction, leading to diffuse bowel dilatation, gas and fluid accumulation, and failure of intestinal transit.

➡️ It is neurogenic–inflammatory–metabolic, not obstructive.


Terminology & Related Entities

Term

Meaning

Paralytic ileus

Complete gut hypomotility

Adynamic ileus

Synonym

Postoperative ileus (POI)

Ileus after surgery

Acute colonic pseudo-obstruction

Ogilvie syndrome (colon-specific)


Normal GI Motility 

Segment

Recovery after surgery

Small intestine

4–8 hours

Stomach

24–48 hours

Colon

48–72 hours (last to recover)

➡️ Ileus mainly reflects colonic dysmotility


Pathophysiology 

Paralytic ileus is multifactorial:


1. Neural Reflex Inhibition

  • Surgical handling → visceral afferent activation
  • ↑ Sympathetic tone
  • ↓ Parasympathetic (vagal) activity
  • Result: Inhibition of peristalsis


2. Inflammatory Mediator Release

  • Local bowel manipulation → macrophage activation
  • Release of:
    • Nitric oxide
    • Prostaglandins
    • IL-6, TNF-α
  • Causes smooth muscle paralysis


3. Opioid-Induced Dysmotility—> Most important iatrogenic factor

4. Electrolyte & Metabolic Disturbance

  • Hypokalemia (most common)
  • Hypomagnesemia
  • Uremia
  • Metabolic acidosis


5. Hormonal & Neurohumoral Factors

  • ↑ Catecholamines
  • ↑ Vasopressin
  • ↓ Motilin


Etiology / Causes

Postoperative (Most Common)

  • Abdominal surgery
  • Bowel manipulation
  • Open > laparoscopic
  • Prolonged surgery
  • Excess IV fluids


Medical Causes

Category

Examples

Electrolyte

Hypokalemia, hypomagnesemia

Metabolic

DKA, uremia

Infection

Sepsis, pneumonia

Cardiac

MI

Endocrine

Hypothyroidism

Drugs

Opioids, anticholinergics, TCAs

Trauma

Spine, retroperitoneal hematoma


Critical Care–Specific Causes

  • Mechanical ventilation
  • Sedatives and opioids
  • Sepsis-associated ileus
  • Vasopressor use
  • Immobility


Clinical Features

Symptoms

  • Abdominal distension (progressive)
  • Abdominal discomfort (not colicky)
  • Nausea and vomiting
  • Failure to pass flatus or stool
  • Early satiety


Signs

  • Distended abdomen
  • Tympanic on percussion
  • Absent or hypoactive bowel sounds
  • No peritoneal signs (unless complicated)


Ileus vs Mechanical Obstruction 

Feature

Paralytic Ileus

Mechanical Obstruction

Pain

Mild, constant

Colicky, severe

Bowel sounds

Absent

High-pitched, tinkling

Gas pattern

Diffuse (small + large bowel)

Proximal dilatation

Air–fluid levels

Few, long

Multiple, step-ladder

Rectal gas

Present

Absent (late)

CT transition point

No

Yes


Investigations

1. Laboratory

  • Electrolytes (K⁺, Mg²⁺, Ca²⁺)
  • Renal function
  • Sepsis markers if suspected
  • ABG (metabolic derangements)


2. Imaging

Plain X-ray Abdomen

  • Dilated loops of both small and large bowel
  • Uniform gas distribution
  • No transition point
  • Gas in rectum


CT Abdomen (Gold Standard)

  • Diffuse bowel dilatation
  • No obstructing lesion
  • No transition point
  • Rules out:
    • Obstruction
    • Ischemia
    • Anastomotic leak


Special ICU Variant

Sepsis-Associated Ileus

  • Cytokine-mediated dysmotility
  • Marker of severe illness
  • Associated with:
    • Poor enteral feed tolerance
    • Increased mortality


Management (STEPWISE & GUIDELINE-BASED)

1. Supportive Care 

Measure

Rationale

NPO

Prevent aspiration

NG tube

Decompression (if vomiting/distension)

IV fluids

Correct hypovolemia

Electrolyte correction

Especially K⁺, Mg²⁺

Early mobilization

Stimulates gut

Minimize opioids

Reduce gut inhibition


2. Treat Underlying Cause

  • Correct hypokalemia
  • Treat sepsis
  • Stop offending drugs
  • Manage metabolic derangements


3. Pharmacologic Therapy

Prokinetics (Limited Role)

Drug

Comment

Metoclopramide

Upper GI effect only

Erythromycin

Tachyphylaxis

Neostigmine

❌ Not for generalized ileus (used in Ogilvie)

➡️ No strong evidence for routine use


4. Enhanced Recovery After Surgery (ERAS) Measures

ERAS Component

Effect

Early feeding

Reduces ileus

Chewing gum

↑ Vagal stimulation

Goal-directed fluids

Avoid bowel edema

Minimally invasive surgery

↓ Inflammation


6. Nutrition

  • Start enteral nutrition once bowel sounds / flatus return
  • If prolonged (>7 days):
    • Consider parenteral nutrition


Duration & Prognosis

Type

Expected duration

Physiologic postoperative ileus

2–4 days

Prolonged ileus

>4–5 days

ICU / sepsis-associated

Variable, worse prognosis


Complications

  • Aspiration pneumonia
  • Electrolyte imbalance
  • Bowel ischemia (rare)
  • Abdominal compartment syndrome
  • Malnutrition
  • Prolonged hospital stay


Ogilvie Syndrome vs Paralytic Ileus

Feature

Paralytic Ileus

Ogilvie Syndrome

Segment

Entire gut

Colon only

Cause

Generalized dysmotility

Autonomic imbalance

Cecal diameter

Mild

>10–12 cm

Treatment

Supportive

Neostigmine / decompression