Does abdominal ultrasound (abd u/s) better evaluate for hernia?

From the Guidelines

Abdominal ultrasound (abd u/s) is not the preferred imaging modality for evaluating hernias, and CT scan is generally better for hernia evaluation. While a standard abdominal ultrasound may incidentally detect larger hernias, it is not optimized for hernia detection as it typically uses different transducers and imaging protocols than those specifically designed for hernia assessment 1. Dedicated hernia ultrasound uses high-frequency linear transducers that provide better resolution of superficial structures and can evaluate hernias dynamically during maneuvers like Valsalva. However, CT scans offer superior anatomical detail and can better visualize hernia contents, potential complications, and surrounding structures, with a sensitivity and specificity of 14–82% and 87%, respectively 1.

Some key points to consider when evaluating hernias include:

• The use of CT scans to confirm or refute the diagnosis in cases of persistent clinical suspicion 1
• The ability of CT scans to evaluate the intrathoracic complications of the herniated abdominal organs 1
• The various radiological findings that can be described in the literature, including diaphragmatic discontinuity, segmental non-recognition of the diaphragm, and the "Dangling diaphragm" sign 1
• The importance of identifying ischemia and necrosis, especially in adhesive small bowel obstruction and sigmoid volvulus, which can be accurately evaluated with CT scans 1

In terms of diagnostic accuracy, CT scans have been shown to be superior to conventional abdominal radiography and ultrasound, with a sensitivity and specificity that ranges from 75 to 100% and 61 to 93%, respectively 1. Therefore, for suspected hernias, requesting a CT scan rather than a general abdominal ultrasound will yield more accurate diagnostic information.

From the Research

Evaluation of ABD U/S for Hernia Diagnosis

• The use of ultrasound in diagnosing abdominal wall hernias has been studied, and it has been found to be accurate, non-invasive, and relatively inexpensive 2.
• A study comparing dynamic abdominal sonography for hernia (DASH) with computed tomography (CT) for incisional hernia evaluation found that DASH had high sensitivity (98%) and specificity (88%) 3.
• Ultrasound has been shown to be useful in evaluating inguinal hernias, with a sensitivity of 97% and a specificity of 77% in one study 4.
• The diagnostic value of ultrasonography for inguinal hernias has been found to influence the decision for or against surgery, with high sensitivity making it suitable for ruling out an inguinal hernia when the findings are negative 4.

Comparison with Other Imaging Modalities

• CT is considered the imaging modality of choice for assessing known adult abdominal hernias, but it may not be as effective in detecting incisional hernias as DASH or ultrasound 5, 6.
• MRI is beneficial when there is concern that a patient's symptoms could be attributable to a hernia or a musculoskeletal source, but it is not typically used as a first-line imaging modality for hernia diagnosis 6.
• Fluoroscopic herniography is a sensitive radiologic investigation for patients with groin pain in whom a hernia is suspected but cannot be identified at physical examination 6.

Clinical Applications

• Ultrasound can be used to evaluate patients with abdominal pain or a palpable mass of questionable etiology, and can help confirm or rule out a hernia diagnosis 2.
• DASH can be used to detect hernia recurrence and facilitate long-term follow-up of hernia patients, with the added benefits of no radiation exposure and instant bedside interpretation 3.
• Ultrasonography can be used in addition to clinical examination to determine the right indication for surgical intervention in patients with suspected inguinal hernias 4.