What are the major causes of abdominal bloating?

Major Causes of Abdominal Bloating

Abdominal bloating results from six major categories: dietary/malabsorptive causes (most common), functional gastrointestinal disorders, small intestinal bacterial overgrowth, motility disorders, air-related mechanisms, and serious structural diseases that must be excluded. 1, 2

Dietary and Malabsorptive Causes

These represent the most prevalent and readily treatable causes:

• Lactose intolerance affects approximately 51% of patients with bloating, caused by lactase enzyme deficiency leading to osmotic effects from undigested sugars in the colon 2
• Fructose intolerance is even more common at 60% of bloating patients, with similar prevalence across most digestive disorders except IBS with constipation 2
• Artificial sweeteners including sugar alcohols and sorbitol cause bloating through malabsorption 2
• Sucrase deficiency leads to sucrose malabsorption and subsequent bloating 2
• Fructans in gluten-containing foods may be the actual culprit in patients with self-reported gluten sensitivity, rather than gluten itself 3, 2
• A 2-week dietary restriction trial can serve as a diagnostic approach, with symptom resolution serving as a positive predictor 2

Functional Gastrointestinal Disorders

These conditions involve altered gut-brain interactions without structural abnormalities:

• Irritable bowel syndrome (IBS) commonly presents with bloating due to visceral hypersensitivity, where patients have lower sensation thresholds to bowel distention 2
• Functional constipation causes bloating through stool retention and altered gut transit 2
• Functional dyspepsia frequently includes bloating as a prominent symptom 2
• Functional bloating as an isolated diagnosis affects 3.5% of the population (4.6% in women, 2.4% in men) when Rome IV criteria are met without other digestive disorders 2

Small Intestinal Bacterial Overgrowth (SIBO)

SIBO should be considered in specific high-risk populations:

• High-risk patients include those with chronic watery diarrhea, malnutrition, weight loss, and systemic diseases causing small bowel dysmotility (e.g., cystic fibrosis, Parkinson disease) 2
• Diagnosis uses hydrogen-based breath testing with glucose or lactulose, or small bowel aspirates 3, 2
• Patients with structural diseases that cause GI transit delay are at elevated risk and may need empiric treatment 3

Motility and Neuromuscular Disorders

These represent more complex pathophysiological mechanisms:

• Gastroparesis should be ruled out in patients with nausea and vomiting alongside bloating, though symptoms do not correlate with the degree of gastric emptying delay on scintigraphy 3, 2
• Abdominophrenic dyssynergia involves inappropriate diaphragm contraction causing abdominal distention not explained by increased intestinal gas, typically worse after meals 3, 2
• Visceral hypersensitivity produces severe bloating with abdominal pain despite normal gas volumes 3, 2
• Pelvic floor dyssynergia frequently causes constipation and bloating, identifiable by straining even with soft stool, need for digital disimpaction, or splinting 3, 1

Air-Related Mechanisms

Excessive air in the GI tract can manifest as bloating:

• Aerophagia involves influx of air into the esophagus with swallowing, causing intestinal gas accumulation visible on abdominal X-rays 2
• Supragastric belching (voluntary) occurs when air flows into the esophagus then is expelled orally through the pharynx before reaching the stomach 2
• Gastric belching (involuntary) happens when air is transported from the stomach through the esophagus due to transient lower esophageal sphincter relaxation, often associated with GERD 2

Celiac Disease and Gluten-Related Disorders

These immune-mediated conditions require specific testing:

• Celiac disease requires screening with tissue transglutaminase IgA and total IgA levels, particularly in IBS with diarrhea or when alarm symptoms are present 3, 2
• Nonceliac gluten sensitivity (NCGS) is an immune-mediated reaction where fructans in gluten-rich foods may be the actual trigger rather than gluten itself 3, 2
• Small bowel biopsy confirming the diagnosis is recommended if serology is positive before treatment 3

Critical Conditions Requiring Exclusion

Certain alarm symptoms mandate evaluation for serious underlying diseases:

• Bloating and abdominal fullness are often the presenting symptoms in patients with ovarian cancer; the highest risk is in women 50 years or older 3, 1
• Weight loss >10% suggests malabsorption, malignancy, or serious underlying disease 1, 2
• Iron-deficiency anemia mandates celiac disease testing and possible endoscopy 1, 2
• Chronic pancreatitis may present with bloating and pain despite adequate pancreatic enzyme replacement, warranting fecal elastase testing 3
• GI bleeding, visible blood or melena, requires urgent evaluation 1

Common Pitfalls

• Do not assume gastroparesis based on symptoms alone, as bloating, nausea, and fullness do not correlate with the degree of gastric emptying delay on scintigraphy 3, 1
• Do not miss ovarian cancer in older women, as bloating and abdominal fullness are often presenting symptoms in women ≥50 years 3, 1
• Do not ignore pelvic floor dysfunction, as straining with soft stool or need for manual assistance suggests dyssynergia, not just constipation 1
• Do not over-test in functional bloating, as the absence of alarm symptoms makes extensive imaging, endoscopy, and motility testing unnecessary and low-yield 1