Catheterization is a process where a tube is inserted into a patient's urethra to drain urine from the bladder independently for collection. It is commonly performed to manage incontinence in comatose patients, obtain urine cultures, and carefully monitor urine output in intensive care situations. Acute renal failure occurs when the kidneys fail to remove waste from the blood, causing fluids and waste to build up. It can be caused by lack of blood flow to the kidneys due to injury, lack of fluids like dehydration, or long term use of certain medications. Common symptoms include little urine, swelling, nausea, and flank pain.