Brian P. Jacob, David C. Chen, Bruce Ramshaw, Shirin Towfigh (eds.) - The SAGES Manual of Groin Pain-Springer International Publishing (2016)

6. Groin Pain Etiology: The Inguinal Hernia, the Occult…
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meta-analysis, has a sensitivity of 86 % and specificity of 77 % [ 9 ].
Towfigh and colleagues recently published a review of their series and
found that when an occult hernia is suspected, an MRI was the best
image modality to order [ 16 ].
All of the above diagnostic modalities have unique drawbacks.
Herniography, though seemingly the most accurate, is the most invasive,
second only to surgery, and utilizes contrast medium, which can elicit an
allergic reaction. It is also of no use in determining alternative causes for
the complaint of groin pain, and is thus rarely used in clinical practice.
CT carries with it the risk of radiation exposure, and the patient is unable
to stand for the study [ 10 ]. Ultrasound is largely operator dependent,
though inexpensive and noninvasive. With ultrasound, there is also
added benefit of the capability to image the patient in various positions
with certain maneuvers to better elicit the hernia impulse.
Not included in the meta-analysis discussed above is the study by
Garvey, which looks exclusively at the use of CT in the diagnosis of
occult inguinal hernia. This was chosen because it helps to evaluate
hernia in obese patients, where ultrasound may be limited. CT is more
affordable than MRI, for which there is still limited data on its use in
occult hernia diagnosis. CT was found to have an accurate diagnosis
94 % of the time in a carefully selected group of patients. The author of
this one study, however, continues to use ultrasound as his preferred
imaging method, and reserves CT for obese patients [ 10 ].
Although most of the studies mentioned above focus on a mixed
population, they favor diagnosis in men. Imaging to diagnose women
with occult hernia is similar, with herniography as a popular method in
Europe [ 12 ]. Given the invasive nature of herniography, Grant et al.
looked at ultrasound specifically for the diagnosis of groin hernia in
women with normal or inconclusive physical exam findings. The ultrasound
was used to look for occult direct, indirect, and femoral hernias.
The main benefit of ultrasound is that fact that the Valsalva maneuver
can be performed, often making the hernia apparent [ 12 ]. Though the
literature reports that indirect inguinal hernias consist of 70 % of the
groin hernia diagnoses in women, the study by Grant et al. found that
direct hernias were more common in those with normal exam findings.
Of the hernias found on ultrasound and confirmed in the operating room,
48 % were direct hernias. This discordance is likely due to the fact that
direct hernias are more difficult to detect on physical examination. This
study showed that ultrasound in women with groin pain has a 95 %
sensitivity and 75 % specificity [ 12 ].