What are the causes and treatments of abdominal distention?

Abdominal Distention: Causes and Treatment

Immediate Assessment Priority

Begin by identifying alarm features that mandate urgent investigation: unintentional weight loss >10%, gastrointestinal bleeding, persistent vomiting, iron-deficiency anemia, or family history of inflammatory bowel disease or colorectal cancer. 1, 2, 3

Key Clinical Features to Assess

• Timing relative to meals: Distention during or immediately after eating suggests abdominophrenic dyssynergia, while constant symptoms suggest small intestinal bacterial overgrowth (SIBO) 1, 4
• Relationship to specific foods: Lactose affects 51% and fructose affects 60% of patients with bloating 1, 2
• Stool patterns: Use Bristol Stool Scale to identify constipation (suggests pelvic floor disorder) versus diarrhea (suggests celiac disease or SIBO) 3
• Associated symptoms: Nausea and vomiting suggest gastroparesis; straining with soft stool suggests pelvic floor dysfunction 1, 2

Diagnostic Testing Strategy

Reserve abdominal imaging and upper endoscopy exclusively for patients with alarm features, recent worsening symptoms, or abnormal physical examination. 1, 2, 3

Selective Laboratory Testing

• Celiac disease screening: Tissue transglutaminase IgA with total IgA levels in patients with bloating, particularly with diarrhea or weight loss 1, 3
• Complete blood count and comprehensive metabolic panel: Only when alarm symptoms present or systemic disease suspected 1, 2
• Avoid routine gastric emptying studies: Consider only if nausea and vomiting are prominent features 1

Specialized Testing When Indicated

• Anorectal physiology testing: For patients with constipation or difficult evacuation to rule out pelvic floor disorder 1
• Breath testing: For SIBO in high-risk patients (chronic watery diarrhea, malnutrition, systemic diseases causing dysmotility like cystic fibrosis or Parkinson disease) 1
• Carbohydrate intolerance testing: Dietary restriction trial for 2 weeks is more economical than breath testing 1

Treatment Algorithm

First-Line: Dietary Modifications (3-4 weeks)

Implement dietary changes before considering pharmacological interventions. 2, 3

• Low-FODMAP diet: For suspected carbohydrate intolerance 1, 2, 3
• Gluten and fructan restriction: For self-reported gluten sensitivity, as fructans rather than gluten may cause symptoms 1, 2
• Small evening meals with longer intervals before lying down: For gastroparesis-related symptoms 2
• Gastroenterology dietitian consultation: Essential to avoid malnutrition from prolonged restrictions 1, 3

Second-Line: Pharmacological Management

Match treatment to underlying mechanism:

• For constipation-related bloating: Secretagogues (linaclotide, lubiprostone) show superiority over placebo 1, 2, 3
• For gastroparesis symptoms: Prokinetic agents (metoclopramide 10-20 mg every 6-8 hours) as first-line therapy 2, 3
• For SIBO in high-risk patients: Rifaximin (non-absorbable antibiotic), though expensive and not FDA-approved for this indication 1, 2, 3
• For visceral hypersensitivity: Central neuromodulators (antidepressants) to reduce hypersensitivity, raise sensation threshold, and improve psychological comorbidities 1, 2, 3

Third-Line: Brain-Gut Behavioral Therapies

Psychological therapies are effective, particularly when anxiety or depression coexist (present in one-third of IBS patients). 2, 3

• Hypnotherapy and cognitive behavioral therapy: For persistent bloating and distention 1, 3
• Diaphragmatic breathing: Specifically for abdominophrenic dyssynergia (paradoxical diaphragm contraction causing meal-triggered distention) 1, 2, 4
• Biofeedback therapy: When pelvic floor disorder identified 1, 3

Understanding the Mechanisms

Abdominophrenic Dyssynergia (Most Common in Functional Disorders)

Objective distention results from paradoxical diaphragmatic contraction (downward movement) with anterior abdominal wall relaxation, not from increased intestinal gas. 4, 5, 6

• In functional disorders, total abdominal volume increases minimally (0.3L), but visible distention occurs due to diaphragmatic descent and ventro-caudal redistribution of contents 5
• This mechanism is confirmed by EMG showing diaphragmatic contraction in 34 of 35 patients and CT showing diaphragmatic descent in 82 of 103 patients 6

True Volume Increase (Dysmotility Disorders)

• In intestinal dysmotility, total abdominal volume increases substantially (1.4L) with cephalic diaphragm displacement and marked gas pooling in the small bowel 5, 7

Critical Pitfalls to Avoid

• Over-testing in functional bloating: Extensive imaging, endoscopy, and motility testing are unnecessary and low-yield without alarm symptoms 2
• Assuming gastroparesis from symptoms alone: Bloating, nausea, and fullness do not correlate with gastric emptying delay on scintigraphy 1, 2
• Using probiotics: Not recommended for abdominal bloating and distention 1, 2, 3
• Ignoring pelvic floor dysfunction: Straining with soft stool or need for manual assistance suggests dyssynergia requiring anorectal testing 2
• Ovarian cancer screening: Consider in women ≥50 years with new-onset bloating and fullness 1