“How long does urinary retention last after anesthesia?”

Not everyone gets a urinary retention. It is commoner after spinal or epidural

Not all patients get urinary retention after anesthesia. There are some strategies to attempt to minimize the risk. Many hospitals and surgery centers have being able to void urine (that is to say, no urinary retention) as a condition of discharge.

Urinary retention related to surgery and anesthesia is multifactorial, including patient conditions (BPH, urethral strictures, advanced age, and others), length of surgery (longer surgeries require the placement of a Foley urine catheter to avoid bladder distention, longer duration of Foley catheter presence increases the risk of urine retention after removal of the Foley catheter), type of surgery (surgery on the penis, urethra, prostate, or bladder can increase the risk of urine retention), and more painful surgeries (higher doses of opioids to control pain may increase the risk of urine retention), and spine surgeries (neurogenic bladder is a potential side effect of surgery on or near the spinal cord).

Urinary retention is a side effect of narcotics, so all long as you take them postop, you can have retention. It is also a side effect of spinal anesthesia and can last several hours with a spinal.

Interesting question. Answer is...well, it depends on one's sensitivity to narcotics on the vesciculo-urethral sphincter, the junction of the bladder with the urethra. Narcotics increase the tone of the sphincter there and cause urinary retention. If it persists past 10-12 hours, the patient will need catheterization in the bladder to relieve the urinary pressure.