How is an abdominal hernia diagnosed?

Diagnosis of Abdominal Hernia

For most abdominal hernias, clinical examination combined with CT scan with intravenous contrast is the diagnostic approach of choice, as CT provides superior sensitivity and specificity compared to physical examination alone and can identify hernia location, contents, and complications. 1

Initial Diagnostic Approach

Clinical Examination

• Most abdominal wall hernias (inguinal, femoral, umbilical) are diagnosed clinically through physical examination, particularly in non-obese patients without prior abdominal surgery 2, 3
• Clinical diagnosis becomes difficult in obese patients, those with abdominal wall scarring from prior surgery, or when pain limits adequate examination 2, 4

When Imaging is Required

Imaging should be obtained when:

• Physical examination is inconclusive due to obesity, pain, or surgical scarring 2, 3
• Internal hernia is suspected (these cannot be diagnosed clinically) 1
• Complications such as bowel obstruction, strangulation, or incarceration are suspected 5, 2
• Differentiating hernia from other abdominal wall masses (tumors, hematomas, abscesses) is needed 3

Imaging Modalities

CT Scan (Gold Standard)

CT with intravenous contrast is the imaging modality of choice for abdominal hernias 1, 6

• Sensitivity and specificity: CT demonstrates 14-82% sensitivity and 87% specificity for diaphragmatic hernias, with superior accuracy for other abdominal hernias 1, 6

• Key advantages: CT accurately identifies the hernia location, size of the defect, hernial contents (bowel, omentum, other organs), and complications such as obstruction, ischemia, or perforation 1, 3

• Specific CT findings to identify:

  • Discontinuity of the abdominal wall or diaphragm 1, 6
  • "Collar sign" (constriction of herniated organ at the defect) 1, 6
  • Bowel loops or other organs protruding through a fascial defect 7, 3
  • Signs of complications: bowel wall thickening, pneumatosis, lack of contrast enhancement indicating ischemia 1

• Oral contrast: Not routinely needed for most hernias, as intraluminal fluid and gas serve as natural contrast; however, oral contrast helps identify anatomy in post-bariatric surgery patients 1

Ultrasound

Ultrasound is a reasonable alternative in specific situations 2, 4

• Best used for: Superficial abdominal wall hernias (inguinal, umbilical, ventral) where the defect and contents can be directly visualized 4
• Advantages: No radiation, real-time dynamic assessment with Valsalva maneuver, cost-effective 2
• Limitations: Operator-dependent, limited in obese patients, cannot adequately assess internal hernias or deep abdominal structures 2, 4
• Preferred in pregnancy: First-line imaging for pregnant patients to avoid radiation exposure 1

Plain Radiography

Plain abdominal X-rays have limited utility 1, 5

• May show bowel gas pattern abnormalities, air-fluid levels, or bowel loops in unusual locations (such as chest in diaphragmatic hernia) 1, 5
• Sensitivity is poor (2-60% for left-sided diaphragmatic hernias, 17-33% for right-sided) 1, 6
• Should not be relied upon to exclude hernia—if clinical suspicion persists with negative X-ray, proceed to CT 1, 6

MRI

MRI is reserved for specific populations 1

• Indicated in pregnant patients when ultrasound is inconclusive and CT must be avoided 1
• Useful in children to minimize radiation exposure 1
• Demonstrates 95% sensitivity and 100% specificity for bowel obstruction in appropriate populations 1

Special Considerations

Internal Hernias

Internal hernias require CT for diagnosis 1

• Cannot be diagnosed clinically due to nonspecific presentation 1
• CT is the only reliable method to identify internal hernias (paraduodenal, mesenteric, omental, pericecal) before they progress to strangulation 1

Post-Bariatric Surgery Patients

CT with both oral and IV contrast is mandatory 1

• Altered anatomy makes clinical and radiological diagnosis challenging 1
• Internal hernias occur frequently after Roux-en-Y gastric bypass 1
• Critical caveat: Negative CT does not rule out internal hernia in post-bariatric patients—maintain low threshold for diagnostic laparoscopy if symptoms persist 1

Diaphragmatic Hernias

Chest X-ray (anteroposterior and lateral) is recommended as initial study, followed by CT if positive or if suspicion remains high 1, 6

• Chest X-ray findings: abnormal bowel gas pattern in chest, air-fluid levels, hemidiaphragm elevation 1, 6
• CT with contrast is gold standard and identifies diaphragmatic discontinuity, herniated organs, and signs of visceral ischemia 1, 6

Common Pitfalls

• Do not rely on negative imaging alone: A negative CT scan does not completely exclude internal hernia, especially in post-bariatric surgery patients—clinical suspicion should guide decision for diagnostic laparoscopy 1
• Hernias can mimic masses: On ultrasound and CT, hernias may appear as cystic or solid masses; always confirm intraperitoneal communication through a fascial defect to avoid misdiagnosis 4
• Intermittent hernias: Some hernias reduce spontaneously and may not be visible on imaging obtained when the patient is supine; dynamic ultrasound with Valsalva or upright positioning may be needed 4