I am not familiar with this matter either. I hope the pain will subside soon. I am also guessing from shaky's description about timing of bladder spasm that it happens when either bladder neck sphincter (extension of smooth muscle of bladder) or external sphincter (different muscle) below prostate squeezes to close to stop urination. Shaky says no spasm while urinating. While urinating, smooth muscle of bladder wall constricts, but bladder neck sphincter and external urethral sphincter relaxes so urine can be voided outside. When bladder is empty or some signal sends to brain through nerves, External urethral sphincter and bladder neck sphincter squeezes urethra so urine will stay in bladder. Incidentally, bladder neck sphincter is controlled autonomous and involuntary, meaning just like hear or lung, squeezing and relaxing are done without a specific nerve signal. External urethral sphincter is controlled specific nerve signal from brain. My guess is that it is bladder neck sphincter's action to squeeze at the end of urination to stop urination is causing the bladder spasm. The reason is that external urethral sphincter was not likely affected by TURBT or BCG unless it was injuring during catheterization for BCG. On the other hand, Bladder neck sphincter (muscle) could have been injured by TURBT or BCG as BCG stays longest in the bladder neck area. Note that both sphincters surround urethra.
According to Google,
Myrbetriq is used to treat overactive bladder (OAB) with symptoms of urgency, frequency and leakage
Uribel is a cocktail of 5 different mediations (hyoscyamine, methenamine, methylene blue, phenyl salicylate, and sodium phosphate) of which hyoscyamine is used to treat a variety of stomach /intestinal problems such as
cramps
and
e
. It is also used to treat other conditions such as and bowel control problems, cramping pain . Methenamine and methylene blue are antiseptic drugs, which help clear a urinary tract infection. bacteria that cause UTI. Phenyl salicylate is a pain reliever. Sodium phosphate makes the urine more acidic, which helps methenamine work better.