Another possible cause of being unable to pass urine is a neurogenic bladder.
Although the symptoms are similar to that of a distended bladder, a neurogenic bladder fails to empty properly because of nerve damage, often associated with the spinal cord.
Unfortunately, the most effective treatment remains intermittent catheterization, which is used several times a day to empty the bladder.
Patients can also try botulin injections to relax the muscles that control the flow of urine, however.
Not all neurogenic bladders are underactive, however -- in some cases, a neurogenic bladder can actually show up as a weak bladder, or overactive bladder.
Whatever the presentation, a neurogenic bladder is a serious condition, and like a distended bladder, requires prompt medical care.