Urinary catheters are a common medical device during surgery, but the details are often glossed over. Reasons for a urinary catheter include the prevention of urinary retention during longer procedures, as well as the need to measure urine output. Urine output is one way to estimate if a patient is appropriately "hydrated" during a surgical procedure. Specific to liposuction and BBL surgery, the factors of time and fluid shifts (ie, "hydration status") may be the reasons a urinary catheter is used. Personally, I generally defer to the anesthesiology provider when deciding on whether or not the patient should have a urinary catheter. These are my general thoughts.