What is the diagnosis and management for a 35-year-old female with 3 weeks of abdominal distension, colicky abdominal pain, and flatulence without diarrhea, constipation, or vomiting?

Differential Diagnosis and Management Approach

Most Likely Diagnosis: Irritable Bowel Syndrome (IBS)

Based on the clinical presentation of 3 weeks of abdominal distension, colicky pain, and flatulence without diarrhea, constipation, or vomiting in a 35-year-old female, the most likely diagnosis is Irritable Bowel Syndrome (IBS), specifically the bloating-predominant subtype. 1

Key Diagnostic Features Supporting IBS

The patient meets Rome IV criteria for functional abdominal bloating and distension 1:

• Colicky abdominal pain is the hallmark symptom of IBS, typically occurring at any site but most commonly on the left side 2
• Abdominal distension and flatulence are among the five supportive symptoms that cumulatively support IBS diagnosis 1
• Absence of alarm features: No vomiting, no change in bowel habits (no diarrhea or constipation), and no rectal bleeding 2
• Duration of 3 weeks is consistent with chronic functional symptoms rather than acute surgical pathology 3

Critical Red Flags to Exclude First

Before confirming IBS, you must actively exclude these conditions 1, 4:

Mechanical Obstruction (Unlikely but Must Rule Out)

• Absence of key features argues against obstruction: No vomiting (present in 90% of SBO), no absence of flatus (present in 90% of obstruction), and no absence of bowel movements (present in 80.6% of obstruction) 4, 1
• Physical examination findings to assess: Look for severe abdominal tenderness, guarding, rebound tenderness, or absent bowel sounds—none of which appear present based on the description 4, 5

Sigmoid Volvulus (Less Likely)

• Classic triad is incomplete: While the patient has abdominal distension and colicky pain, she lacks constipation and vomiting, which are part of the classic triad 1
• Age and risk factors don't fit: Sigmoid volvulus typically affects elderly, institutionalized patients on psychotropic medications 1

Recommended Diagnostic Workup

Initial Laboratory Tests

Order these screening tests to exclude organic disease 1, 2:

• Complete blood count to rule out anemia or infection 1
• C-reactive protein (CRP) or ESR to exclude inflammatory bowel disease 2
• Fecal calprotectin if available—a negative test almost certainly rules out inflammatory bowel disease 2, 1
• Celiac disease screening (tissue transglutaminase antibody) is recommended to rule out this condition 2

Imaging Considerations

Plain abdominal radiograph during an acute episode is recommended for patients with pain as the predominant symptom to exclude bowel obstruction and other abdominal pathology 1

CT imaging is NOT routinely needed unless clinical features suggest complications or the diagnosis remains uncertain after initial evaluation 1, 5

Alternative Diagnoses to Consider

Small Intestinal Bacterial Overgrowth (SIBO)

• Consider if: Flatulence and bloating are prominent, especially with postprandial worsening 1
• Testing: Hydrogen breath testing can be performed if symptoms persist despite initial management 1

Carbohydrate Intolerance

• Lactose intolerance can present with bloating, distension, and flatulence without diarrhea 1
• Testing: Lactose/dextrose H2 breath test may be indicated 1

Functional Constipation (Masked)

• Consider: Some patients with "normal" bowel movements may have incomplete evacuation or defecatory disorders 1
• Assessment: Digital rectal examination to assess for fecal impaction or pelvic floor dysfunction 6

Management Strategy

First-Line Therapeutic Approach

For bloating-predominant IBS without constipation or diarrhea 1, 3:

1. Dietary modification with low FODMAP diet: This is the most evidence-based dietary intervention for functional bloating and should be offered with careful attention to nutritional adequacy 1, 3, 2

2. Antispasmodic medication: Can be ordered as a therapeutic trial for colicky abdominal pain 1

3. Education and reassurance: Explain that IBS is a functional disorder without structural abnormality, and set realistic expectations about symptom management 1, 3

Second-Line Options if Initial Treatment Fails

If symptoms persist after 3-6 weeks 1:

• Probiotics may be considered for treatment of functional symptoms 1, 3
• Neuromodulators (low-dose antidepressants) for persistent pain 1
• Psychological therapies (cognitive behavioral therapy, hypnotherapy, mindfulness) should be considered 1

When to Escalate Investigation

Perform colonoscopy or sigmoidoscopy if 1:

• Patient is over age 50 years (due to higher risk of colon cancer)
• Clinical features suggestive of organic disease develop (weight loss, rectal bleeding, nocturnal symptoms)
• Symptoms change in character or severity over time
• No response to appropriate therapeutic trials

Common Pitfalls to Avoid

Do not assume IBS without proper screening: The diagnosis of a functional bowel disorder always presumes the absence of structural or biochemical explanation for symptoms 1

Do not order extensive imaging prematurely: In a young patient without alarm features, starting with laboratory screening and therapeutic trials is appropriate 1, 2

Do not overlook SIBO or carbohydrate intolerance: These conditions can mimic IBS and require specific testing if symptoms persist 1

Avoid opiates for pain management: These should be avoided in functional GI disorders as they worsen constipation and can lead to dependence 1