Is a computed tomography (CT) scan with or without contrast media effective for diagnosing abdominal hernia?

From the Guidelines

For diagnosing an abdominal hernia, a CT scan with contrast is the most appropriate imaging approach, as it provides detailed information about the hernia and its potential complications, according to the most recent and highest quality study 1. When it comes to diagnosing abdominal hernias, imaging plays a crucial role in confirming the diagnosis and evaluating the extent of the hernia.

• The CT scan is considered the gold standard for diagnosing diaphragmatic hernias, with a sensitivity and specificity of 14–82% and 87%, respectively 1.
• The use of contrast in CT scans can help identify areas of inflammation, differentiate between various soft tissues, and visualize blood flow, which is essential in complex cases such as bowel ischemia or infection 1.
• However, in cases where contrast is not necessary, a non-contrast CT scan can still provide valuable information about the hernia, including the location, size, and contents of the hernia sac.
• The decision to use contrast or not should be made based on the clinical presentation, patient's renal function, and specific diagnostic questions being addressed, as patients with impaired kidney function may need to avoid contrast due to the risk of contrast-induced nephropathy 1.
• It's worth noting that most uncomplicated hernias can be adequately diagnosed with physical examination alone, and imaging is typically reserved for cases that are clinically unclear or complicated 1.
• In addition to CT scans, other imaging modalities such as chest X-rays can be useful in diagnosing diaphragmatic hernias, especially in cases where the nature of the thoracic contents is uncertain 1.

From the Research

Diagnostic Imaging for Abdominal Hernia

• CT scan is the imaging modality of choice for assessing a known adult abdominal hernia in both elective and acute circumstances due to its rapid acquisition, capability of multiplanar reconstruction, good spatial resolution, and anatomic depiction with excellent sensitivity for most complications 2.
• The use of contrast in CT scans for diagnosing abdominal hernias is not strictly necessary, but it can be helpful in certain cases, such as when there is a need to visualize the bowel loops or other internal structures 3.
• A study found that the sensitivity and specificity of CT scans in diagnosing abdominal wall hernias were 0.83 and 0.83, respectively, and the predictive value of a positive CT finding was 0.94, while the predictive value of a negative CT finding was 0.63 3.
• The use of a Valsalva maneuver, oral intake of contrast, and 10/10 mm CT slices can help achieve the highest diagnostic accuracy in CT scans for abdominal hernias 3.
• Another study found that CT scans can be useful in detecting incisional hernias, especially in overweight patients, and that the correlation between clinical examination and CT findings was high, with a Fleiss Kappa value of 0.80 4.
• A study on iodine contrast reduction algorithms found that using a low kV CT technique and a patient size- and weight-based contrast reduction algorithm can reduce the iodine contrast dose by 50% while maintaining acceptable image quality in 95% of exams 5.

Comparison of Imaging Modalities

• Ultrasound is useful for adult groin assessment and is the imaging modality of choice for pediatric abdominal wall hernia assessment 2, 6.
• MRI is beneficial when there is reasonable concern that a patient's symptoms could be attributable to a hernia or a musculoskeletal source 2.
• Fluoroscopic herniography is a sensitive radiologic investigation for patients with groin pain in whom a hernia is suspected but in whom a hernia cannot be identified at physical examination 2.
• CT scans are more sensitive and specific than ultrasound in diagnosing occult hernias, especially in cases where clinical suspicion is high despite negative ultrasound findings 6.