Mister B
Just be aware retention comes in two forms, ""Acute urinary retention is the sudden and often painful inability to void despite having a full bladder. Chronic urinary retention is painless retention associated with an increased volume of residual urine,i.e.not voiding the bladder ""
There are a number of things that can slow the flow apart from a restriction in the urethra, constipation is often cited as a cause of acute retention.
Acute retention is quite unpleasant and if you do get into that situation get help straight away.
Thanks Chris