Urinary Catheterisation
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Direct answer
Urinary catheterisation is the introduction of a catheter through the urethra into the bladder, performed as a sterile procedure to drain urine when the patient cannot void, to monitor output in critical illness, or before certain surgeries. Adult indwelling (Foley) catheters are commonly 14–16 French, the balloon is inflated with 5–10 mL sterile water, and the catheter is inserted about 5–7.5 cm in females and 17–22.5 cm in males, advanced a further 2.5–5 cm after urine flows before the balloon is inflated.
What you must remember
- Catheter sizes are measured in French units — higher numbers mean larger diameter — and the smallest size that drains adequately is chosen.
- Female catheterisation: knees flexed, the meatus identified after separating the labia, and the perineum cleaned front to back from above the meatus downward.
- Male catheterisation: clean from the meatus outward, hold the penis perpendicular to the body while advancing past the bulbar urethra, and instill generous lubricant (ideally lignocaine jelly).
- Never inflate the balloon until urine flows and the catheter has advanced a further 2.5–5 cm — inflating in the urethra causes trauma and bleeding.
- Maintain a closed drainage system: the bag stays below bladder level and never on the floor, the catheter is secured to the thigh or abdomen, and specimens come from the sampling port.
- CAUTI prevention: catheterise only when clearly indicated, use strict asepsis, review daily whether the catheter is still needed, remove at the earliest, and avoid routine bladder irrigation.
- Expected urine output in a hydrated adult is about 0.5–1 mL per kg per hour; report oliguria, haematuria, blockage, leakage or suprapubic discomfort promptly.
Common confusion
Insertion lengths get swapped: the male urethra is about 20 cm against the female 4–5 cm, and resistance in the male at the external sphincter is managed by pausing, reassuring and letting the patient breathe out — never forcing. The other confusion is bag management: raising the bag above the bladder lets urine reflux and invites infection, while routine clamping or irrigation is not recommended. On removal, fully deflate the balloon with a syringe before withdrawal.
Exam-focused takeaway
Procedure-order questions dominate: explanation and consent, privacy, sterile field, cleaning direction, insertion length, urine-flow check, balloon inflation, fixation and documentation. Know the CAUTI bundle — avoid, asepsis, closed system, early removal — plus the numbers for size, balloon volume and length. Scenario stems test balloon-related trauma (blood at the meatus, no urine) where the first action is to stop and notify, not force.
Frequently asked questions
What size catheter is used for adults?
Commonly 14–16 French for women and 14–18 French for men, always the smallest that drains adequately; larger sizes serve bleeding or clot drainage.
How far is the catheter inserted?
About 5–7.5 cm in females and 17–22.5 cm in males, then 2.5–5 cm further after urine flows, before balloon inflation with sterile water.
How is catheter-associated urinary tract infection prevented?
Catheterise only when indicated, maintain asepsis and a closed system, keep the bag below the bladder, secure the catheter and remove it early.
When is urinary catheterisation indicated?
Retention, accurate output monitoring in critical illness, protection of pressure wounds in incontinent patients, before selected pelvic surgery, and palliation in terminal illness.
How is a urine specimen collected from a catheter?
From the sterile sampling port with a syringe after cleaning — never from the drainage bag, which holds pooled stale urine.