What are the causes of bloating?

Causes of Bloating

Bloating arises from multiple distinct mechanisms including food intolerances (particularly carbohydrate malabsorption), visceral hypersensitivity, aerophagia, small intestinal bacterial overgrowth (SIBO), constipation-related disorders, and abdominophrenic dyssynergia—with the specific cause determining the appropriate diagnostic and treatment approach. 1

Primary Dietary and Malabsorptive Causes

Food intolerance and carbohydrate malabsorption represent the most common and readily treatable causes of bloating:

• Lactose intolerance affects approximately 51% of patients with bloating, caused by lactase enzyme deficiency leading to osmotic effects in the colon from undigested sugars 1
• Fructose intolerance is even more prevalent at 60% of bloating patients, with similar prevalence across most digestive disorders except IBS with constipation 1
• Artificial sweeteners including sugar alcohols and sorbitol cause bloating through malabsorption 1
• Sucrase deficiency leads to sucrose malabsorption and subsequent bloating 1
• Fructans in gluten-containing foods may cause symptoms in patients with self-reported gluten sensitivity, where fructans rather than gluten itself are the culprit 1

The simplest diagnostic approach is a 2-week dietary restriction trial, with symptom resolution serving as a positive predictor—this is more economically sound than immediate breath testing 1

Functional Gastrointestinal Disorders

Bloating is highly prevalent (>50%) when associated with other digestive disorders:

• Irritable bowel syndrome (IBS) commonly presents with bloating due to visceral hypersensitivity, where patients have lower sensation thresholds to bowel distention 1
• Functional constipation causes bloating through stool retention and altered gut transit 1
• Functional dyspepsia frequently includes bloating as a prominent symptom 1
• 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 1

Air-Related Mechanisms

Excessive air in the gastrointestinal tract produces bloating through distinct mechanisms:

• Aerophagia involves influx of air into the esophagus with swallowing, causing intestinal gas accumulation visible on abdominal X-rays 1
• Supragastric belching (voluntary) occurs when air flows into the esophagus then is expelled orally through the pharynx before reaching the stomach 1
• 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 1

High-resolution manometry with impedance monitoring can differentiate these mechanisms when clinically significant 1

Small Intestinal Bacterial Overgrowth

SIBO causes bloating through bacterial fermentation of carbohydrates:

• 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) 1
• Diagnosis uses hydrogen-based breath testing with glucose or lactulose, or small bowel aspirates 1
• Rifaximin is the most studied nonabsorbable antibiotic for SIBO-related bloating, though not FDA-approved for this indication 1

Motility and Neuromuscular Disorders

Altered gut motor function and abdominal wall mechanics contribute to bloating:

• Gastroparesis should be ruled out in patients with nausea and vomiting alongside bloating 1
• Pelvic floor dyssynergia causes constipation-related bloating, diagnosed by anorectal manometry when patients strain with soft stool or require digital disimpaction 1, 2
• Abdominophrenic dyssynergia involves inappropriate diaphragm contraction causing abdominal distention not explained by increased intestinal gas, typically worse after meals 1
• Visceral hypersensitivity produces severe bloating with abdominal pain despite normal gas volumes 1

Celiac Disease and Gluten-Related Disorders

Immune-mediated reactions to gluten or fructans cause bloating:

• Celiac disease requires screening with tissue transglutaminase IgA and total IgA levels, particularly in IBS with diarrhea or when alarm symptoms are present 1
• Nonceliac gluten sensitivity (NCGS) is an immune-mediated reaction where fructans in gluten-rich foods may be the actual trigger rather than gluten itself 1
• Small bowel biopsy confirms celiac disease if serology is positive, and is mandatory when alarm symptoms (weight loss, iron-deficiency anemia) are present 1

GERD-Associated Bloating

Gastroesophageal reflux disease contributes to bloating through specific mechanisms:

• Gastric belching related to GERD responds to PPI therapy and lifestyle modifications 1, 3
• Aerophagia associated with GERD requires behavioral interventions rather than acid suppression 3
• Supragastric belching typically involves non-acidic reflux episodes, making PPIs ineffective 3

Critical Diagnostic Considerations

Alarm symptoms warrant immediate investigation to exclude serious pathology:

• Weight loss >10% suggests malabsorption, malignancy, or serious underlying disease 1, 2
• GI bleeding requires urgent evaluation 2
• Iron-deficiency anemia mandates celiac disease testing and possible endoscopy 1, 2
• Family history of inflammatory bowel disease or colorectal cancer increases risk of these conditions 2
• Women ≥50 years with new-onset bloating require evaluation for ovarian cancer 2
• Persistent or severe vomiting may indicate gastroparesis or obstruction 2

Common Pitfalls to Avoid

• Over-testing in functional bloating: Extensive imaging, endoscopy, and motility testing are unnecessary and low-yield in the absence of alarm symptoms 2
• Assuming gastroparesis based on symptoms alone: Bloating, nausea, and fullness do not correlate with gastric emptying delay on scintigraphy 2
• Missing pelvic floor dysfunction: Straining with soft stool or need for manual assistance suggests dyssynergia, not simple constipation 2
• Ignoring ovarian cancer in older women: Bloating and abdominal fullness are often presenting symptoms in women ≥50 years 2