The best test to diagnose an inguinal hernia is a physical exam. A standard groin hernia exam can easily be performed to diagnose a hernia. That is why if you suspect a hernia, you should see a doctor initially before obtaining an x-ray or other radiologic exam (US, CT or MRI). This has been proven in many, many scholarly articles.
Infrequently, it is difficult to tell whether a hernia is present on physical exam. At this point, a radiologic exam may be ordered.
Most commonly, an ultrasound or MRI of the groin will be ordered. Each of these tests has their own benefits and downsides in the determination of a groin hernia.
An umbilical hernia can usually be diagnosed by a physical exam as well. Sometimes an ultrasound or CT may need to be performed to determine if a hernia is present.
Other abdominal wall hernias or incisional hernias (hernias in a prior surgical scar) are very similar to umbilical hernias in terms of diagnosis. Most can be diagnosed by a physical exam as well. Sometimes an ultrasound or CT may need to determine if a hernia is present.