What type of Computed Tomography (CT) scan is needed for a patient with a suspected abdominal hernia?

CT Scan for Suspected Abdominal Hernia

For a patient with suspected abdominal hernia, order a CT abdomen and pelvis WITH intravenous (IV) contrast. This provides optimal visualization of the hernia defect, herniated contents, and most importantly, allows assessment of vascular perfusion to detect complications like bowel ischemia or strangulation 1, 2.

Rationale for IV Contrast

• IV contrast is the gold standard because it enables detection of bowel wall enhancement abnormalities that indicate ischemia—the most critical complication requiring immediate surgery 1, 2
• Contrast enhancement reveals the "collar sign" (constriction at the hernia neck), engorged mesenteric vessels, and the "whirlpool sign" of twisted vessels, all key diagnostic features 2
• Without IV contrast, you cannot reliably assess whether herniated bowel is perfusing normally or becoming ischemic 3

When to Add Oral Contrast

Add oral contrast specifically for:

• Post-bariatric surgery patients where identifying anatomical landmarks (gastric pouch, Roux limb, jejuno-jejunal anastomosis) is mandatory 2
• Suspected internal hernias where oral contrast helps identify the transition point and clustered bowel loops 2

Do NOT use oral contrast for:

• Suspected high-grade bowel obstruction, as it delays diagnosis, increases patient discomfort, risks aspiration, and masks abnormal bowel wall enhancement 3
• Acute presentations where the fluid-filled bowel provides adequate intrinsic contrast 3

Protocol Specifications

• Scan range: Abdomen AND pelvis (not abdomen alone) to capture the full extent of potential hernias 3
• Technique: Multiplanar reconstructions increase accuracy in locating transition zones and hernia defects 3
• Patient positioning: Consider Valsalva maneuver during scanning to increase intra-abdominal pressure and make subtle hernias more apparent 4

Critical Pitfalls to Avoid

• Never rely on a negative CT to exclude internal hernia, especially post-bariatric surgery—40-60% of surgically confirmed internal hernias had negative CT scans. Maintain a low threshold for diagnostic laparoscopy if clinical suspicion persists 2
• If IV contrast is contraindicated (severe contrast allergy, acute kidney injury), proceed directly to laparoscopic exploration rather than relying on non-contrast CT, which has unacceptably low sensitivity for complications 2
• Do not order CT without contrast as your initial study—it cannot assess vascular status and may miss ischemia, the complication that determines mortality 1, 2

Alternative Imaging Considerations

For specific hernia types, different approaches apply:

• Diaphragmatic hernia: Start with chest X-ray; if negative but suspicion persists, then CT chest and abdomen with IV contrast 1, 2
• Hiatal hernia: Fluoroscopic studies (biphasic esophagram or upper GI series) are more appropriate than CT as first-line imaging 2
• Pregnant patients: Use ultrasound first, then MRI if needed—avoid CT due to radiation exposure 1, 2

When Imaging Should Not Delay Surgery

Proceed directly to diagnostic laparoscopy without imaging if:

• Acute signs of bowel obstruction with peritonitis are present 2
• Patient is hemodynamically unstable 2
• Post-bariatric surgery patient with persistent abdominal pain and high clinical suspicion, even if initially stable 2