What is the sensitivity of contrast‑enhanced CT for detecting gastric outlet obstruction in adults?

CT Sensitivity for Gastric Outlet Obstruction

Contrast-enhanced CT demonstrates 93-96% sensitivity for detecting gastric outlet obstruction, making it the diagnostic modality of choice when this condition is suspected. 1

Diagnostic Performance of CT

CT achieves excellent diagnostic accuracy for gastric outlet obstruction with the following performance characteristics:

• Sensitivity: 93-96% for detecting the presence of obstruction 1
• Specificity: 93-100% for confirming obstruction 1
• Accuracy: 90-94% for determining both the site and cause of obstruction 1

These figures represent data from large bowel obstruction studies, which include gastric outlet obstruction as part of the upper gastrointestinal obstruction spectrum. 1

CT Protocol Recommendations

Perform CT with intravenous contrast only—do not routinely add oral contrast. 1

• IV contrast is essential to assess for mucosal hyperenhancement, submucosal edema, focal wall defects, and interrupted mucosal enhancement that characterize peptic ulcer disease and other causes of gastric outlet obstruction 1
• Neutral oral contrast (water or dilute barium) may be used if gastric pathology assessment is the primary goal, but positive oral contrast should be avoided as it impedes mucosal enhancement evaluation and obscures intraluminal bleeding 1
• Multiphase CT is not routinely needed unless acute GI bleeding is suspected as a complication 1

Key CT Findings in Gastric Outlet Obstruction

CT reliably identifies:

• Dilated stomach with fluid and food debris proximal to the obstruction 1
• Collapsed or normal-caliber duodenum distal to the transition point 2
• The exact site of obstruction (pylorus, duodenum) in 90-94% of cases 1
• The underlying cause in 66-87% of cases, including peptic ulcer disease, malignancy, or extrinsic compression 1

Critical Complications CT Can Detect

CT is superior for identifying life-threatening complications that require urgent surgical intervention:

• Perforation: Extraluminal gas (97% sensitivity), focal wall defect/ulcer (84% sensitivity), and extraluminal contrast if oral contrast was given 1
• Active bleeding: Hyperdense blood products or active contrast extravasation at the ulcer site 1
• Wall thickening and inflammatory changes suggesting transmural involvement 1

The combination of focal wall defect and wall thickening shows 95% sensitivity and 93% specificity for localizing perforation sites. 1

Comparison with Alternative Imaging

CT vastly outperforms other modalities for gastric outlet obstruction:

• Plain radiography: Only 74-84% sensitivity and 50-72% specificity for any bowel obstruction 1
• Ultrasound: 88% sensitivity but only 76% specificity, with limited ability to determine cause (23%) or site (70%) 1
• Fluoroscopy (upper GI series): May be used for functional assessment or when CT is equivocal, but provides less information about extraluminal pathology and complications 1

Common Pitfalls to Avoid

• Do not rely on plain films when gastric outlet obstruction is suspected—they miss 16-26% of obstructions and provide no information about the cause 1
• Do not perform CT without IV contrast unless there is a true contraindication, as non-contrast CT cannot assess mucosal enhancement patterns critical for diagnosing peptic ulcer disease and ischemia 1
• Do not delay CT if clinical suspicion is high, even if initial plain films appear normal—CT detects obstruction in patients with false-negative plain radiographs 3, 2
• Do not assume benign etiology without CT confirmation of the cause, as malignancy accounts for a significant proportion of gastric outlet obstruction in adults 1