So true -- you are now official smarter than the head of surgery of Columbia Univerity in NY, who told me "if there's no bulge, there's no hernia". DORK. Just the fact you can Google "nonpalpable hernia" or "occult hernia" proves him wrong.

But CT scans are probably not the best way to diagnose an occult hernia, and sometimes they can be detected by herniography or "dynamic" ultrasound ("ultrasound" is the same thing as sonogram, and in both cases the dynamic part means you move around while they're doing the imaging).

See below.

luck!

Spy

HERNIOGRAPHIES AND DYNAMIC ULTRASOUNDS MIGHT REVEAL HERNIAS, BUT CT SCANS DO NOT
[1] http://www.riainvision.com/invision/patientinfo/conditions/patinfo_cond_hernia_sub.asp

Dynamic Ultrasound versus a CT or MRI Scan for Diagnosing Hernias

Your physician may order a dynamic ultrasound to diagnose a hernia or to characterize the contents of a hernia and determine its reducibility. The ultrasound examination is dynamic because it is performed in real time, showing motion live, and because it can be performed while the patient is lying on his/her back or standing upright. It can also be performed when the patient is breathing quietly or straining vigorously. Finally, ultrasound can be performed while the hernia is being compressed with the ultrasound transducer. CT and MR scans, on the other hand, can only be done with the patient lying on his/her back and generally without straining. Because of the ability of ultrasound to show motion during dynamic maneuvers, ultrasound has several advantages over more expensive CT and MR scans in evaluating for groin and anterior abdominal wall hernias.

CT and MR can show only non-reducible hernias – those hernias that are “out all the time”. Only a minority of hernias are non-reducible. Most hernias are reducible and will fall back into the abdomen when the patient is quietly lying on his/her back on a CT or MR table.

Ultrasound, like CT and MR, can show larger non-reducible hernias, but can also smaller show reducible hernias that CT and MR cannot show. Because ultrasound images show real time motion, we can see reducible hernias moving in and out during dynamic maneuvers.

During the ultrasound examination, any hernia that is found can be compressed with the ultrasound probe to determine if the hernia is reducible or tender. CT and MR, on the other hand, even when they show a hernia, cannot determine whether the hernia is tender. Tenderness is important, because hernias are so common, that we often find “incidental” small hernias that are not the cause of the patient’s pain. If a hernia is tender when compressed by the ultrasound probe, it is far more likely that the hernia is, indeed, the cause of pain, and not merely a common incidental finding.

Ultrasound can identify hernias that are completely reducible when the patient is lying down, but become non-reducible and more tender when the patient is standing. CT and MRI cannot.

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[2] http://www.aafp.org/afp/991015ap/1687.html

Patients with nonpalpable (occult) hernias generally have a history of chronic activity-related groin pain. In patients with nerve entrapment, pain or numbness in the appropriate nerve distribution has been reported.18 Inguinal examination may demonstrate pain at the superficial ring. Imaging, with the possible exception of herniography (Figure 6) or ultrasonography to identify occult hernias, has not proved useful.

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[3] ISMJ, 1(1), March 2000, Copyright © 2000 Pathophysiology of Chronic Groin Pain in the Athlete

Authors: John Orchard, John W Read, Geoffrey M Verrall, John P Slavotinek

Dynamic real-time ultrasound has been reported recently as an aid in the diagnosis of indirect inguinal hernia in nonathletes and is further suggested as an aid to the diagnosis of incipient direct inguinal hernia in athletes. Like contrast herniography, ultrasound can show hernia lesions but does not necessarily predict clinical relevance. UltraSound is the only imaging modality capable of demonstrating the dynamic function of the inguinal canal in real-time, but it is very dependent on the skill of the operator.