Postoperative urinary retention (PUR) is a common complication of surgery and anesthesia. The risk of retention is especially high after anorectal surgery, hernia repair, and orthopedic surgery and increases with advancing age. Certain anesthetic and analgesic modalities, particularly spinal anesthesia with long-acting local anesthetics and epidural analgesia, promote the development of urinary retention. Portable ultrasound provides rapid and accurate assessment of bladder volume and aids in the diagnosis and management of PUR. Catheterization is recommended when bladder volume exceeds 600 mL to prevent the negative sequelae of prolonged bladder overdistention.