What is the differential diagnosis (ddx) and initial management approach for a patient presenting with bloating?

Differential Diagnosis of Bloating

Begin with a systematic algorithmic approach prioritizing common functional causes while ruling out serious organic disease through targeted history and selective testing based on alarm features.

Primary Differential Diagnosis Categories

Functional Disorders (Most Common)

• Irritable Bowel Syndrome (IBS) - particularly IBS with constipation (IBS-C) or diarrhea (IBS-D), diagnosed using Rome IV criteria 1
• Functional bloating/distention - primary disorder when Rome IV criteria are met but patient doesn't fulfill IBS, functional constipation, or functional dyspepsia criteria 1
• Functional constipation - assess using Rome IV criteria 1
• Functional dyspepsia - consider when upper abdominal symptoms predominate 1

Food Intolerances and Malabsorption

• Carbohydrate enzyme deficiencies - lactase deficiency (51% prevalence in DGBI patients), sucrase deficiency 1
• Fructose intolerance - most common at 60% prevalence in IBS patients 1
• Celiac disease - must be ruled out with serologic testing (tissue transglutaminase IgA and total IgA) 1, 2, 3
• Nonceliac gluten sensitivity - consider after celiac disease excluded 1
• Artificial sweeteners - sugar alcohols and sorbitol cause osmotic effects 1

Motility Disorders

• Gastroparesis - consider only when nausea and vomiting are prominent symptoms 2, 3
• Pelvic floor dyssynergia - evaluate with anorectal manometry (ARM) when constipation present with straining despite soft stool 1, 4
• Small intestinal bacterial overgrowth (SIBO) - reserve testing for at-risk patients refractory to dietary restrictions 1

Mechanical/Structural Causes

• Aerophagia - diagnosed by manometry showing air influx into esophagus with intestinal gas accumulation on abdominal X-rays 1
• Gastroesophageal reflux disease (GERD) - may present with bloating and belching 1

Critical "Cannot Miss" Diagnoses

• Ovarian cancer - maintain high suspicion in women ≥50 years, as bloating and abdominal fullness are often first presenting symptoms 2, 3
• Gastrointestinal malignancy - consider with alarm features 2, 3
• Inflammatory bowel disease - assess family history 4

Initial Management Approach

Step 1: History and Physical Examination

Assess for alarm features requiring immediate investigation:

• Unintentional weight loss 2, 3, 4
• Gastrointestinal bleeding (visible blood or melena) 2, 3, 4
• Persistent vomiting 2, 3, 4
• Iron-deficiency anemia 2, 3
• Family history of GI malignancy or inflammatory bowel disease 2, 4
• In women ≥50 years: maintain high suspicion for ovarian cancer 2, 3

Key history elements:

• Relationship between bloating and meals, specific food triggers 4
• Bowel movement patterns using Bristol Stool Scale - constipation, diarrhea, or alternating patterns 4
• Straining during defecation, digital disimpaction, splinting, or incomplete evacuation (suggests pelvic floor dysfunction) 1, 4
• Lactose, fructose, wheat, dairy, and coffee consumption 3, 4
• Complete medication list (many drugs cause constipation and bloating) 4
• Comorbid conditions affecting gut motility (diabetes, Parkinson's disease) 4

Step 2: Diagnostic Testing Algorithm

If alarm features present:

• Order abdominal imaging (CT/ultrasound) and upper endoscopy 1, 2, 3
• In patients >40 years with dyspeptic symptoms, consider endoscopy especially in high H. pylori prevalence regions 2

If no alarm features:

• First-line: Serologic testing for celiac disease (tissue transglutaminase IgA and total IgA) in all patients with bloating 1, 2, 3
• If celiac serology positive, perform small bowel biopsy for confirmation 1
• Consider thyroid function testing 3

For suspected food intolerance:

• Start with 2-week dietary restriction trial - this is the simplest and most cost-effective approach 1, 2
• Reserve breath testing (hydrogen/methane) for patients who fail dietary restriction, testing for lactose, fructose, or sucrose intolerance 1, 2
• Small bowel aspiration and glucose- or lactulose-based breath testing for SIBO only in at-risk patients refractory to dietary measures 1, 2

For constipation-predominant bloating:

• Anorectal physiology testing (ARM) to rule out pelvic floor disorder when difficult evacuation or straining present 1, 2

Avoid routine testing:

• Do NOT order gastric emptying studies routinely for bloating alone; reserve for patients with prominent nausea and vomiting 1, 2, 3
• Do NOT order whole gut motility studies unless treatment-refractory lower GI symptoms warrant evaluation for neuromyopathic disorders 1
• Avoid excessive testing in functional bloating without alarm features - yield is extremely low 2, 3

Step 3: Initial Therapeutic Interventions

Dietary modifications (first-line):

• Start with simple dietary changes targeting excessive non-digestible carbohydrates, fruits, or caffeine 3
• Low-lactose diet if consuming >280 ml milk per day 3
• Low-FODMAP diet for IBS patients, but ONLY under supervision of trained gastroenterology dietitian to avoid eating disorders and malnutrition 1, 3
• Gastroenterology dietitian should be part of multidisciplinary care for celiac disease and nonceliac gluten sensitivity 1

Pharmacologic options:

• Do NOT use probiotics to treat abdominal bloating and distention 1
• Rifaximin (non-absorbable antibiotic) is most studied for SIBO but expensive and not FDA-approved for this indication; requires careful patient selection 1, 5
• PPI therapy if GERD-related 1
• Baclofen if related to excess transient lower esophageal sphincter relaxations 1

Behavioral therapies:

• Biofeedback therapy effective when pelvic floor disorder identified 1
• Brain-gut behavioral therapies (cognitive behavioral therapy, diaphragmatic breathing) for supragastric belching 1

Critical Pitfalls to Avoid

• Missing ovarian cancer in women ≥50 years - bloating may be the only presenting symptom despite benign examination 2, 3
• Over-testing patients with functional bloating without alarm features 2, 3
• Implementing overly restrictive diets without dietitian supervision - risk of eating disorders and malnutrition 3
• Ordering gastric emptying studies routinely for bloating alone 1, 2, 3
• Using probiotics as treatment - not recommended 1