What do u think????Its like asking "from what sea a drop of water came",,,
There are many causes related to this symptom,,,
Are u male or female?, How old are u?, Is there any pain at the abdomen or back or any other (not only during micturation)?, do u use alcohol?r u under medication treat.?
In general the most common cause of the retention is the prostatic problem(if u r male),and pelvic mass(if a female),
if meant with ur words the anuria so the presence of kidney stones is the main cause and ultrasound is suggestive to be used,,,
go to a doctor to diagnose it(the earlier the problem detected , the easier the treatment)and whenever there was no real problem then, 2b sure z better then 2b sorry,,,