What causes a gaseous abdomen?

Causes of a Gaseous Abdomen

A gaseous abdomen results from six primary mechanisms: dietary carbohydrate malabsorption (most common), air swallowing disorders, functional gastrointestinal disorders with visceral hypersensitivity, small intestinal bacterial overgrowth, motility disorders, and structural/obstructive processes. 1

Dietary and Malabsorptive Causes (Most Common)

Carbohydrate enzyme deficiencies are the leading identifiable cause:

• Lactose intolerance affects approximately 51% of patients presenting with bloating, caused by lactase deficiency leading to osmotic effects from undigested sugars in the colon 2
• Fructose intolerance is even more prevalent at 60% of bloating patients, occurring across most digestive disorders 2
• Sucrase deficiency causes sucrose malabsorption with subsequent gas production 1, 2
• Artificial sweeteners including sugar alcohols and sorbitol cause bloating through malabsorption 1, 2
• Fructans in gluten-containing foods may be the actual culprit in patients with self-reported gluten sensitivity, rather than gluten itself 2

Diagnostic approach: A 2-week dietary restriction trial serves as both diagnostic and therapeutic, with symptom resolution indicating the specific intolerance 2

Air-Related Mechanisms

Three distinct patterns of air accumulation cause gaseous symptoms:

• Aerophagia involves influx of air into the esophagus with swallowing, causing intestinal gas accumulation visible on abdominal X-rays 1, 2
• Supragastric belching (voluntary) occurs when air flows into the esophagus then is expelled orally through the pharynx before reaching the stomach 1, 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 1, 2

Differentiation requires: High-resolution manometry with impedance monitoring for at least 90 minutes, preferably 24-hour impedance studies 1

Functional Gastrointestinal Disorders

Visceral hypersensitivity produces severe bloating despite normal gas volumes:

• Irritable bowel syndrome (IBS) commonly presents with bloating due to lower sensation thresholds to bowel distention, with bloating present in >50% of IBS patients 1, 2
• Functional constipation causes bloating through stool retention and altered gut transit 1, 2
• Functional dyspepsia frequently includes bloating as a prominent symptom 1, 2
• Functional bloating as 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, 2

Critical distinction: Rome IV criteria require that patients with functional bloating should NOT fulfill criteria for IBS, functional constipation, functional diarrhea, or functional dyspepsia 1

Small Intestinal Bacterial Overgrowth (SIBO)

SIBO should be considered in high-risk patients:

• Those with chronic watery diarrhea, malnutrition, weight loss >10%, and systemic diseases causing small bowel dysmotility (e.g., cystic fibrosis, Parkinson disease) 2
• Diagnosis: Hydrogen-based breath testing with glucose or lactulose, or small bowel aspirates 2
• Common pitfall: SIBO is overdiagnosed; testing should be reserved for at-risk patients, not routinely ordered for all bloating 1

Motility and Neuromuscular Disorders

Specific motility patterns produce distinct gaseous symptoms:

• Gastroparesis should be ruled out when nausea and vomiting accompany bloating 1, 2
• Abdominophrenic dyssynergia involves inappropriate diaphragm contraction causing abdominal distention not explained by increased intestinal gas, typically worse after meals 2
• Gastric emptying studies should NOT be ordered routinely for bloating alone, only when nausea and vomiting are present 1

Celiac Disease and Gluten-Related Disorders

Immune-mediated reactions 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 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 2
• If serologies are positive, small bowel biopsy must be done to confirm celiac disease diagnosis 1

GERD-Associated Bloating

• Gastric belching related to GERD responds to PPI therapy and lifestyle modifications 1, 2
• Treatment algorithm: Start PPI therapy if gastric belching is related to GERD; consider baclofen if related to excess transient lower esophageal sphincter relaxations 1

Red Flags Requiring Urgent Evaluation

Alarm features mandate imaging and endoscopy:

• Weight loss >10% suggests malabsorption, malignancy, or serious underlying disease 2
• Iron-deficiency anemia mandates celiac disease testing and possible endoscopy 2
• Recent worsening symptoms or abnormal physical examination findings 1

Abdominal imaging and upper endoscopy should be ordered ONLY in patients with alarm features, recent worsening symptoms, or abnormal physical examination 1