GI Radiology > Procedures > Outline

Imaging Modalities

Some hernias, such as inguinal hernias, may be diagnosed clinically and therefore do not require imgaging studies. Imaging may be useful, however, for difficult to examine patients (i.e. obese) or for patients with non-palpable abdominal wall hernias. CT, ultrasonography, herniography, and MRI are accepted means of imaging hernias. The choice of imaging technique depends on the clinical scenario.


CT scan

Cross sectional imaging is often used to detect occult hernias. Using CT scans, the sensitivity in detecting abdominal wall hernias is reported as 83 percent with specificity between 67 to 83 percent. (Hojer et al, "CT in the diagnosis of abdominal wall hernias: a preliminary study." Eur Radiol 1997; 7:1416-18). Having patients perform a Valsalva maneuver during a fast helical sequence may increase sensitivity since many hernias spontaneously reduce if the patient lies relaxed in the supine position during the scan. Herniated bowel loops make diagnosis easy with CT, however diagnosis may depend on finding a fascial defect. Real-time imaging with ultrasound and/or herniography may be preferable if specific maneuvers elicit hernia symptoms. CT is particularly useful if another disease process is present that may be mimicking a hernia.


Ultrasonography

Ultrasound is useful in non-urgent cases involving the anterior abdominal wall and groin. It has the advantage of being a real-time examination that allows the patient to perform Valsalva or other maneuvers that elicit hernia symptoms. Ultrasound also allows for visualization of peristalsis in herniated bowel, which may assist in diagnosis. One disadvantage is that fascial defects are difficult to identify with ultrasound. A second drawback is that when herniation of mesenteric fat or omentum is present, sonographic appearance may be nonspecific.


Herniography

When clinical diagnosis is uncertain and patient presents non-urgently, herniography is an appropriate means of identifying groin hernias. This study involves the needle placement on the side opposite to the patient's symptoms at the lateral border of the rectus abdominus, inferior to the umbilicus. Placement is confirmed fluroscopically and contrast is then injected into the peritoneal cavity. PA and oblique radiographs are then obtained before and after 15-20 minutes of walking. Radiographs are also taken in any position or maneuver (i.e. coughing, straining) that cause symptoms. Herniography has a low complication rate of less than 1 percent due to accidental colonic puncture.


MRI

Though generally not a first-line imaging technique, MRI allows for hernia evaluation in multiple imaging planes. Such imaging may be useful in cases difficult to characterize by CT such as Morgagni or traumatic hernias. In the future, increased availability of MRI may increase its use as an imaging modality in hernia assessment.

 

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