Possible causes for the bladder not emptying include nerve problems, bladder muscle weakness, blockage of the urethra and the side effects of certain medications, explains National Institute of Diabetes and Digestive and Kidney Diseases. Each of these basic problems can come about in a variety of ways.
Nerve problems that lead to an inability to empty the bladder can arise from trauma, including childbirth or injury, as well as from heavy metal poisoning, stroke, diabetes or multiple sclerosis, National Institute of Diabetes and Digestive and Kidney Diseases says. Weakened muscles generally are a consequence of aging. Blockage of the urethra can have many causes, including urinary tract stones, a displacement of the bladder or rectum that pinches the urethra, constipation, scarring of the urethra from infection or surgery, or enlargement of the prostate.
The inability to empty the bladder, or urinary retention, can be either acute or chronic, says National Institute of Diabetes and Digestive and Kidney Diseases. Acute urinary retention is sudden and leaves the person completely unable to urinate. This is a very dangerous condition that requires immediate medical attention and can cause severe pain and discomfort. Chronic urinary retention, on the other hand, persists over time, and may cause no symptoms at all until complications arise from it.