Urinary catheterization is the insertion of a hollow tube through the urethra (or, less commonly, a suprapubic stoma) into the bladder to drain urine. The NCLEX-RN tests the two main approaches the registered nurse must distinguish. An indwelling (Foley) catheter has a retention balloon inflated with sterile water inside the bladder and remains in place to provide continuous drainage; it is reserved for clear indications such as acute urinary retention, accurate measurement of output in a critically ill patient, perioperative use during prolonged surgery, healing of sacral or perineal wounds in an incontinent patient, and comfort in end-of-life care. Intermittent (straight) catheterization is a single in-and-out drainage with no balloon, used to relieve transient retention, obtain a sterile specimen, measure a post-void residual, or empty the bladder on a schedule in patients with neurogenic bladder. The central nursing principle is that every urinary catheter carries risk. Catheter-associated urinary tract infection (CAUTI) is one of the most common healthcare-associated infections, and the single most effective prevention strategy is to avoid unnecessary catheters and remove them as soon as they are no...