In a patient with vomiting, epigastric pain, weight loss and food fear, is a plain abdominal X‑ray (FPA) or a contrast‑enhanced CT scan the preferred initial imaging modality to diagnose gastric outlet obstruction?

CT Scan is the Preferred Initial Imaging for Suspected Gastric Outlet Obstruction

For a patient presenting with vomiting, epigastric pain, weight loss, and food fear concerning for gastric outlet obstruction, contrast-enhanced CT abdomen and pelvis is the preferred initial imaging modality over plain abdominal X-ray. 1

Why CT is Superior to Plain Film

Diagnostic Performance

• CT scan provides comprehensive anatomic evaluation of the gastric outlet, identifying the site, cause, and complications of obstruction with 93-96% sensitivity and 93-100% specificity 1
• Plain abdominal X-ray has markedly inferior performance with only 74-84% sensitivity and 50-72% specificity for confirming obstruction, and cannot reliably identify the cause (0% sensitivity) or precise site (60% specificity) 1
• Malignancy is now the most common cause of gastric outlet obstruction in adults due to widespread H2 blocker and PPI use reducing peptic ulcer disease incidence, making detailed anatomic assessment critical 1

Critical Information CT Provides That Plain Film Cannot

• Identifies the underlying etiology: CT detects nodular/irregular wall thickening, soft tissue attenuation masses, ulcerated lesions, and distinguishes malignant from benign causes 1, 2
• Detects life-threatening complications: Perforation (extraluminal gas, focal wall defects with 95% sensitivity and 93% specificity), active bleeding (hyperdense blood products or contrast extravasation), and lymphadenopathy/metastases 1, 3, 2
• Assesses the mechanism of obstruction: Differentiates luminal narrowing from edema versus chronic inflammation versus mass effect 1, 2

Optimal CT Technique

Essential Technical Requirements

• IV contrast is mandatory to assess mucosal hyperenhancement, nodular wall thickening, soft tissue attenuation, and distinguish inflammatory from neoplastic processes 1
• Neutral oral contrast (water or dilute barium 600-800 mL) should be used rather than positive contrast to avoid obscuring mucosal enhancement and allow assessment of intraluminal bleeding 1, 2
• Include the pelvis to evaluate for distant metastases, as CT abdomen and pelvis is preferred over CT abdomen alone when nonspecific symptoms are present 1

Common Pitfalls to Avoid

• Inadequate gastric distension can cause false-positive wall thickening and obscure masses—ensure proper oral contrast administration 3, 2
• CT without IV contrast will miss critical findings like interrupted mucosal enhancement and has significantly reduced sensitivity 1
• Positive oral contrast impedes assessment of mucosal enhancement and precludes evaluation of intraluminal bleeding 1, 2

Clinical Algorithm

When Plain Film May Have Limited Utility

• Plain X-ray may show gastric distension and suggest obstruction but provides no information about the cause (0% sensitivity for identifying etiology) 1
• In the clinical context described (vomiting, epigastric pain, weight loss, food fear), these constitutional symptoms raise concern for malignancy, which requires CT for proper evaluation 1, 4

Next Steps After CT

• If malignancy is identified: Upper endoscopy with biopsy is mandatory as the reference standard for tissue diagnosis, followed by complete staging 1, 3
• If benign obstruction from peptic ulcer disease: Endoscopy provides both diagnosis and therapeutic intervention 4, 2
• If perforation is detected: Early surgical involvement is required; CT should not delay appropriate treatment if diffuse peritonitis is present 1

Why This Matters for Morbidity and Mortality

• Early identification of malignant gastric outlet obstruction allows for timely oncologic intervention, critical given gastric adenocarcinoma's 32% five-year survival rate 1
• Detection of perforation (present in 2-10% of peptic ulcer disease cases) is life-saving, as perforation carries up to 30% mortality if not promptly treated 1
• Plain film's inability to identify the cause (0% sensitivity) means it cannot guide definitive management and will necessitate additional imaging anyway, causing harmful delays 1