Foley catheter

**Design:** Introduced by Frederic Foley in the 1930s. It is a flexible latex or silicone tube, usually two-way (one lumen for drainage, one for balloon inflation) or three-way (an extra lumen for continuous bladder irrigation). Size is given in French (Fr; 1 Fr = 0.33 mm in outer diameter), and adult sizes are usually 14–18 Fr. The balloon is inflated with sterile water, not saline, because saline can crystallize and block the balloon channel. The balloon sits above the internal urethral sphincter in the bladder and anchors the catheter.

**Indications:** - Acute urinary retention or bladder outlet obstruction (BPH, clots, urethral stricture) - Neurogenic bladder with retention - Accurate urine output monitoring in critically ill or unstable patients (shock, sepsis, AKI) - Perioperative use (prolonged surgery, urologic or pelvic surgery, epidural anesthesia) - Continuous bladder irrigation (three-way catheter) for gross hematuria and clots - Sacral or perineal pressure ulcers in incontinent patients (to promote healing) - Comfort care at end of life

**Not indications:** convenience, nursing ease, or incontinence alone. Do not use it to obtain a urine specimen in a patient who can void.

**Contraindications:** - Suspected urethral injury: blood at the urethral meatus, a high-riding or "floating" prostate, or perineal or scrotal ecchymosis after pelvic fracture or straddle trauma. Get a retrograde urethrogram (RUG) first. If there is a urethral injury, place a suprapubic catheter. - Acute prostatitis (relative) - Recent urethral surgery (relative)

**Complications:** - **CAUTI:** the most common healthcare-associated infection. Risk rises about 3–7% per day of catheterization. Biofilm formation is the key mechanism. Common organisms are *E. coli*, *Klebsiella*, *Proteus*, *Pseudomonas*, *Enterococcus*, and *Candida*. *Proteus* is urease-positive, so it causes alkaline urine and struvite stones, which can encrust and block the catheter. Do not treat asymptomatic bacteriuria in catheterized patients (except in pregnancy or before urologic procedures with mucosal trauma). Treat symptomatic CAUTI and replace the catheter if it has been in place for more than 2 weeks. - Urethral trauma, false passage, and later stricture - Paraphimosis if the foreskin is not reduced after insertion - Bladder spasms and discomfort - Hematuria - Bladder stones - Urethral erosion with long-term use - Rarely, squamous cell carcinoma of the bladder with chronic indwelling catheters - Post-obstructive diuresis after relief of chronic retention - Hypotension with rapid decompression (historically cited, but not well supported)

**Prevention (CDC bundle):** - Insert only when indicated. - Use aseptic technique and a closed drainage system. - Keep the bag below bladder level and off the floor. - Review daily for necessity and remove early. - Consider alternatives: external (condom) catheter, intermittent straight catheterization (preferred for neurogenic bladder), or suprapubic catheter. - Antibiotic prophylaxis and routine catheter changes are not recommended.

**Foley vs. other catheters:** - A straight (in-and-out) catheter has no balloon and is removed right away. It is used for intermittent catheterization or a one-time sterile specimen or residual volume. - A Coudé catheter has a curved tip and is used in BPH or when a standard catheter cannot pass. - A suprapubic catheter goes through the abdominal wall directly into the bladder.

**Boards pearls:** - The most common cause of nosocomial UTI is catheter use. - Blood at the meatus after trauma means no Foley until a RUG is done. - Postoperative urinary retention and fever on days 3–5 may point to CAUTI (the "5 W's" of postoperative fever list "Water" for UTI). - Patients with chronic Foley use who have recurrent *Proteus* infections can form staghorn calculi (struvite: magnesium ammonium phosphate). - Foley placement is a common simple-procedure scenario in Step 2 CK and CS-style questions. Know the sterile technique, the balloon inflation, and what to do if urine does not return (check for kinking, advance further, and flush).