Westerners swear by raw oysters and steak tartare.
In Korea, it's snake. And now, increasingly, the mainstream medical community is coming up with its own answers. But, whatever the name, the problem is widespread. The causes are various and, in some cases, unexpected. Added to these are the more standard explanations, such as a fractured pelvis, spinal injury or nerve damage from an operation on the prostate gland or rectum.