What are the causes and management approaches for abdominal distension?

Causes of Abdominal Distension

Abdominal distension is most commonly caused by ascites from liver cirrhosis (75%), followed by malignancy (10%), heart failure (3%), and functional gastrointestinal disorders, with specific treatment approaches required for each underlying cause. 1

Pathophysiological Causes

1. Fluid Accumulation

• Ascites (most common cause of visible distension)
  • Portal hypertension due to liver cirrhosis (75% of all ascites cases) 1
  • Malignancy (10%) 1
  • Heart failure (3%) 1
  • Pancreatitis (1%) 1
  • Other causes (11%) 1

2. Gastrointestinal Disorders

• Functional Disorders

  • Functional bloating and distension 2
  • Irritable bowel syndrome 2
  • Functional dyspepsia 2
  • Functional constipation 2

• Motility Disorders

  • Small intestinal dysmotility 3
  • Chronic intestinal pseudo-obstruction (CIPO) 3
  • Enteric neuropathies causing disrupted gut coordination 3

• Mechanical Obstruction

  • Sigmoid volvulus (presenting with asymmetric gaseous distention) 3
  • Small bowel obstruction
  • Large bowel obstruction

3. Gas-Related Causes

• Small intestinal bacterial overgrowth (SIBO) 3
  • Results from gut stasis and ineffective migrating motor complex
  • Causes malabsorption, steatorrhea, and gas production

4. Neuromuscular Mechanisms

• Abdominophrenic dyssynergia 4
  • Diaphragmatic descent with simultaneous relaxation of anterior abdominal wall
  • Present in 34 of 35 patients with functional abdominal distension 4

Diagnostic Approach to Abdominal Distension

Physical Examination

• Shifting dullness (83% sensitivity, 56% specificity) - requires approximately 1.5 liters of fluid 1
• Asymmetric gaseous distention with emptiness of left iliac fossa (pathognomonic for sigmoid volvulus) 3

Laboratory Testing

• Complete blood count, liver function tests, renal function
• Blood gas and lactate levels (to detect bowel ischemia) 3
• Serum-ascites albumin gradient (SAAG) for ascites:
  • SAAG ≥1.1 g/dL indicates portal hypertension (97% accuracy)
  • SAAG <1.1 g/dL indicates non-portal hypertension causes 1

Imaging

• Abdominal ultrasound (confirms ascites, evaluates liver appearance) 1
• Plain abdominal radiographs (for bowel obstruction, volvulus "coffee bean sign") 3
• CT imaging with contrast (when ischemia or perforation is suspected) 3

Management Based on Underlying Cause

1. Ascites Management

• Grade 1 (mild): Sodium restriction only 3
• Grade 2 (moderate): Sodium restriction + diuretics 3
  • Spironolactone (starting at 50-100 mg/day, max 400 mg/day)
  • Furosemide may be added if needed
• Grade 3 (large): Sodium restriction + diuretics + paracentesis 3
  • Target weight loss: 0.5 kg/day without edema, 1 kg/day with edema 1

2. Functional Bloating and Distension

• Dietary modifications:
  • Low FODMAP diet 2
  • Reduced fiber intake to decrease bacterial fermentation 3
• Pharmacological approaches:
  • Antispasmodics (peppermint oil, hyoscine butylbromide) 3
  • Rifaximin for bacterial overgrowth 2
  • Prokinetics for impaired motility 2
  • Neuromodulators for visceral hypersensitivity 2

3. Small Intestinal Dysmotility

• Nutritional support:
  • Oral supplements/dietary adjustments first 3
  • If unsuccessful, consider gastric or jejunal feeding 3
  • Parenteral nutrition if enteral feeding fails 3
• Symptom management:
  • Venting gastrostomy for recurrent vomiting 3
  • Pain management (avoid high doses of opioids) 3

4. Mechanical Obstruction (e.g., Sigmoid Volvulus)

• Urgent diagnostic imaging 3
• Surgical consultation for definitive management 3

Common Pitfalls and Caveats

1. Misdiagnosis: Abdominal distension is often incorrectly attributed solely to gas accumulation, when objective studies show abdominophrenic dyssynergia is the predominant mechanism in functional disorders 4

2. Delayed diagnosis: Delay in diagnosing complications like spontaneous bacterial peritonitis increases mortality (3.3% per hour of delay) 1

3. Inappropriate dietary restrictions: Patients often self-impose restrictive diets that fail to resolve distension while risking nutritional deficiencies 5

4. Medication side effects: Some medications can cause or worsen dysmotility, including clozapine, baclofen, buserelin, clonidine, fludaribine, phenytoin, and verapamil 3

5. Overlooking surgical emergencies: Abdominal distension may indicate serious conditions requiring urgent intervention, such as bowel ischemia or perforation 3