What is the initial workup for a general adult patient presenting with abdominal distention?

Initial Workup for Abdominal Distention in Adults

Begin with a plain abdominal radiograph to assess for bowel dilation and gas patterns, followed by CT abdomen/pelvis with oral and IV contrast if mechanical obstruction or serious pathology is suspected. 1

Immediate Clinical Assessment

History - Key Elements to Elicit

• Onset and pattern: Determine if distention is constant versus episodic, and relationship to meals 1, 2
• Associated symptoms: Document presence of pain (location, character), nausea, vomiting (bilious vs non-bilious), early satiety, and changes in bowel habits 1, 2
• Bowel movement characteristics: Use Bristol Stool Scale to assess consistency, frequency, straining, sensation of incomplete evacuation, and need for digital disimpaction 2
• Dietary triggers: Specifically ask about lactose, fructose, and gluten intake and their correlation with symptoms 1, 2
• Medication review: Identify all drugs that impair motility, particularly opioids, anticholinergics, and cyclizine 1, 3
• Red flag symptoms: Weight loss, gastrointestinal bleeding, persistent vomiting, family history of inflammatory bowel disease or colorectal cancer 2
• For women over 50: Consider ovarian malignancy presenting with bloating, ascites, and pelvic symptoms 1

Physical Examination - Critical Findings

• Abdominal examination: Measure girth with tape measure at umbilical level, assess for visible peristalsis, palpate for masses or pulsatile structures, percuss for tympany versus dullness (ascites) 1
• Digital rectal examination: Essential to detect fecal impaction, which requires different management than simple constipation 3
• Neuromuscular assessment: Evaluate for autonomic dysfunction (orthostatic pulse changes), joint hypermobility, and signs of systemic disease 1
• Pelvic examination in women: If ovarian pathology suspected based on symptoms 1

Initial Laboratory Studies

Order the following baseline tests 1:

• Complete blood count
• Comprehensive metabolic panel (including potassium, magnesium)
• Liver function tests
• Thyroid-stimulating hormone
• Anti-tissue transglutaminase antibodies (celiac screening)
• Fasting glucose
• For women of childbearing age: Pregnancy test 1
• If ovarian malignancy suspected: CA-125, though not for routine screening 1

Imaging Strategy

First-Line: Plain Abdominal Radiograph

Obtain upright and supine abdominal X-rays to assess for 1:

• Dilated small bowel (>3 cm) or large bowel (>6 cm)
• Air-fluid levels suggesting obstruction
• Transition point between dilated and normal bowel (indicates mechanical obstruction)
• Overall gas distribution pattern

Second-Line: CT Abdomen/Pelvis with Contrast

Proceed to CT with both oral and IV contrast if 1, 3:

• Plain films show dilated bowel or transition point
• Clinical concern for mechanical obstruction (colicky pain, loud bowel sounds, vomiting)
• Suspicion of malignancy (weight loss, palpable mass, ascites)
• Need to exclude vascular pathology
• Severe or progressive symptoms despite initial management

CT helps distinguish 1:

• Mechanical obstruction from severe dysmotility
• Functional bloating from true intestinal pseudo-obstruction
• Identifies underlying pathology (masses, inflammation, vascular issues)

Ultrasound

Reserve for specific indications 1:

• Suspected ovarian pathology in women with pelvic mass, ascites, or concerning symptoms
• Initial evaluation of pelvic masses before CT
• Assessment for ascites

Differential Diagnosis Framework

Mechanical Obstruction (Requires Urgent Evaluation)

Look for 1, 3:

• Transition point on imaging
• Colicky abdominal pain
• High-pitched bowel sounds
• Vomiting (especially bilious)
• Prior abdominal surgery (adhesions)

Severe Intestinal Dysmotility

Suspect when 1:

• Diffusely dilated bowel without transition point
• Severe pain after eating
• Early satiety and nausea
• History of multiple negative laparotomies
• Associated autonomic symptoms

Functional Bloating/Distention (Abdominophrenic Dyssynergia)

Characterized by 1:

• Episodic visible distention
• Normal or near-normal imaging
• Behavioral component with diaphragmatic dysfunction
• Absence of significant gas accumulation on CT

Constipation-Related Distention

Features include 3, 2:

• Fecal loading on examination or imaging
• Straining, incomplete evacuation
• May have pelvic floor dysfunction

Malignancy

Consider in 1:

• Women over 50 with new-onset bloating, ascites, pelvic mass
• Unexplained weight loss
• Progressive symptoms

Common Pitfalls to Avoid

• Never assume distention is purely functional without excluding mechanical obstruction first 1
• Do not order gastric emptying studies routinely for distention alone; reserve for patients with prominent nausea and vomiting 1
• Avoid whole gut transit studies unless treatment-refractory symptoms warrant evaluation for neuromyopathic disorders 1
• Do not perform upper endoscopy or colonoscopy routinely; order only if alarm features present or abnormal physical examination 1
• Recognize that CT may appear normal in early intestinal dysmotility despite significant symptoms 1

When to Pursue Advanced Testing

Small Bowel Manometry

Consider after 1:

• Mechanical obstruction excluded
• Nutritional status optimized
• Patient off motility-affecting drugs
• Persistent symptoms suggesting chronic intestinal pseudo-obstruction

Anorectal Physiology Testing

Indicated when 1, 4:

• Distention associated with constipation or difficult evacuation
• Suspicion of pelvic floor disorder
• Prolonged balloon expulsion predicts distention in constipated patients

Breath Testing

May be useful to 1:

• Rule out carbohydrate enzyme deficiencies (lactose, fructose)
• Evaluate for small intestinal bacterial overgrowth in select at-risk patients (use glucose or lactulose-based hydrogen breath tests)

Immediate Management Considerations

While completing workup 1, 3:

• If fecal impaction present: Use suppositories and enemas first-line, not oral laxatives
• Review and discontinue: Opioids, anticholinergics, and other constipating medications when possible
• Nutritional assessment: Calculate BMI and percentage weight loss; address refeeding risks if malnourished
• Exclude refeeding syndrome risk: Check and replete electrolytes before aggressive nutritional support