What is the best initial imaging study for a patient with suspected upper gastrointestinal (GI) pathology, comparing KUB (Kidney, Ureter, Bladder) X-ray versus Small Bowel Follow Through (SBFT)?

Fluoroscopy Upper GI with KUB vs Small Bowel Follow-Through (SBFT)

Neither fluoroscopy upper GI with KUB nor SBFT should be used as initial imaging for suspected upper gastrointestinal pathology or small bowel obstruction—CT abdomen and pelvis with IV contrast is the definitive first-line study with >90% diagnostic accuracy. 1, 2

Why CT is Superior to Both Modalities

Diagnostic Accuracy

• CT with IV contrast achieves >90% diagnostic accuracy for detecting small bowel obstruction, determining the exact location and cause, and identifying life-threatening complications such as ischemia, strangulation, and closed-loop obstruction 1, 2, 3
• Plain radiography (KUB) demonstrates highly variable and inconsistent performance with accuracy ranging only 30-70%, and can be misleading in 20-40% of patients 1
• SBFT has no current literature support for evaluating patients with acute abdominal pain, fever, or suspected obstruction 1

Critical Information CT Provides That Fluoroscopy Cannot

• CT identifies the transition point and underlying cause in 95% of cases where obstruction is present 3, 4
• CT detects bowel ischemia through assessment of bowel wall enhancement, mesenteric edema, and vascular perfusion—findings that fluoroscopy cannot evaluate 1, 5
• CT reveals complications including perforation, closed-loop obstruction, and strangulation that directly impact surgical decision-making 1

When Fluoroscopy Studies Have Limited Role

Upper GI Series with SBFT

• SBFT is only appropriate for low-grade or intermittent partial obstruction after an equivocal CT scan as a problem-solving tool 5
• The American College of Radiology states that opinions remain divided on the usefulness of SBFT, and it should never be used as initial imaging 5
• SBFT cannot be performed in acute obstruction because patients cannot tolerate oral contrast administration when the bowel is obstructed 1

Plain Radiography (KUB)

• KUB sensitivity for small bowel obstruction ranges only 30-90% with highly inconsistent results across studies 1
• Radiographs provide no information about the cause of obstruction or presence of ischemia 1
• Abdominal radiographs after CT add no diagnostic value and should not be routinely performed for follow-up 5

Specific Clinical Scenarios

For Suspected Small Bowel Obstruction

• Order CT abdomen and pelvis with IV contrast immediately rather than starting with KUB or fluoroscopy 1, 2
• CT provides diagnostic accuracy of 90% compared to plain radiography's 50-60% sensitivity 5
• Multiplanar reconstructions increase accuracy in locating transition zones 1

For Upper GI Pathology

• Upper GI endoscopy has become the primary modality for investigating upper gastrointestinal symptoms, not fluoroscopy 6
• Dynamic contrast studies remain useful only for specific conditions like hiatal hernia evaluation, where biphasic esophagram achieves 88% sensitivity 7

For Inflammatory Bowel Disease

• Small bowel capsule endoscopy (SBCE) or cross-sectional imaging (CT/MR enterography) should be considered for patients with suspected Crohn's disease and normal endoscopy 1
• SBFT is not mentioned as an appropriate modality in current IBD diagnostic guidelines 1

Common Pitfalls to Avoid

• Do not order KUB or SBFT when CT is available—this prolongs evaluation without adding diagnostic information and can delay critical surgical intervention by 12-72 hours 3
• Do not use oral contrast for suspected high-grade obstruction—the intraluminal fluid already present serves as natural contrast, and oral contrast delays diagnosis and increases aspiration risk 1, 5
• Do not rely on plain radiographs to exclude obstruction—normal radiographs occur in up to 52% of cases with actual obstruction 3

Protocol Specifications When CT is Ordered

• Use IV contrast to assess bowel perfusion and detect ischemia through evaluation of bowel wall enhancement 1, 5
• Scan both abdomen and pelvis to capture the full extent of pathology 7
• Oral contrast is generally not required for suspected obstruction as nonopacified fluid provides adequate intrinsic contrast 1, 5