What are some possible causes of urinary retention?
For a person to be able to urinate, there must be no obstruction to the bladder outlet and the bladder muscle must be able to contract to allow the urine to be drained from the bladder. At the same time, the sphincter (the muscle that maintains continence) has to relax as the bladder contracts.
The most common cause of urinary retention would be an obstruction to the bladder outlet eg due to an enlarged prostate in men, stricture (narrowing) along the urethra. A stone wedged in the urethra can also cause an obstruction and hence result in urinary retention. These are usually patients who present with acute urinary retention with lower abdominal discomfort.
Other less common causes would be neurological conditions (eg spinal cord injuries, stroke) that cause weak contractions of the bladder muscle or inability of the sphincter to relax or even lack of coordination between bladder contraction and sphincter relaxation.
These patients tend to have chronic urinary retention (less likely to have abdominal pain) and are more prone to kidney failure as the pressures build up from the bladder and are transmitted back to the kidneys.
Urinary retention needs to be evaluated and the aim of treatment is to maintain good function of the bladder (both as a storage organ for urine as well as a good voiding organ for urination) and to prevent kidney failure.
Possible causes of urinary retention can be broadly divided into outflow versus bladder conditions.
For males, this is usually caused by an enlarged prostate. Other causes can be due to narrowing of the urethra due to scar formation (stricture) or obstruction by a stone.
For females, outflow obstruction also can be caused by narrowing of the urethra due to scar formation (stricture), obstruction by a stone, or other mass lesions.
If there are no outflow obstructions, urinary retention can be caused by a simple urinary tract infection or more complex due to weakness of the bladder wall.
Weakness of the bladder wall can be due to damage of nerve supply to the bladder in conditions such as spinal cord injuries, post-stroke, brain tumour, or diabetes mellitus.
I would recommend that you get a full assessment by a specialist urologist as sudden onset of urinary retention is not normal.