Short-course Methenamine Hippurate for Prevention of Post-operative UTI

Prevention of post-operative urinary tract infections (UTI) is becoming important for both the individual patient and the health system. Complications of UTI include pyelonephritis and bacteremia, requiring hospitalization and parenteral antibiotics. Additionally, recurrent exposure to antibiotics commonly given for UTIs increases the risk of antibiotic resistance to uropathogens. UTIs also increase economic burdens on the health care system, with each episode costing nearly 600 dollars. UTIs associated with catheterization are particularly costly for hospitals, resulting in decreased hospital quality measures and lack of compensation.

This is particularly important after pelvic reconstructive surgery, as reported rates of UTI reach up to 20-25%. Urinary retention requiring short-term indwelling catheterization, common in these women, contributes to the risk of UTIs by increasing the risk of bacteriuria by 5-10% per day and through the dislodging of bacterial colonies during catheter removal. Balancing prevention and resistance and cost is key. A meta-analysis by Marschall et al indicated the benefit of a short dose of antibiotic prophylaxis at catheter removal in general post-surgical patients. However, data is lacking on the effects of daily antibiotic prophylaxis on resistance and cost.

A possible alternative to antibiotics presents itself in methenamine hippurate, a urinary antiseptic which forms formaldehyde in the presence of acidic urine. It is relatively inexpensive, and does not induce resistance in vivo. Prior studies have shown that daily use of methenamine can decrease the risk of post-operative UTI.

The purpose of our study was to investigate the efficacy of a short course of methenamine hippurate at catheter removal to that of a short course of ciprofloxacin in prevention of UTIs after short-term indwelling catheterization. Additionally, we investigated factors that influence post-operative UTIs, the rate of culture-proven UTIs after prophylaxis, the antibiotic resistance profile of those undergoing prophylaxis, and the cost effectiveness of prophylaxis.

Inclusion criteria

• female;
• patients who are able to read and write English;
• 18 years of age or older;
• underwent surgery for pelvic organ prolapse, urinary incontinence, or both;
• require post-operative short-term transurethral catheterization for greater than 24 hours.

Exclusion criteria

• patients undergoing surgical intervention for sacral neuromodulation, or mesh excision;
• patients requiring long-term catheterization secondary to injury to the urinary tract;
• patients who pass their post-operative trial void and thus, do not require additional catheterization;
• patients requiring catheterization for less than 24 hours;
• pregnant patients;
• patients who are breast-feeding;
• allergy to methenamine hippurate or fluroquinolones (either ciprofloxacin or levofloxacin);
• impaired renal or hepatic function;
• pre-operative urinary retention;
• patients who are currently using sulfonamides;
• patients who have severe dehydration;
• patients using tizanidine;
• patients sensitive to quinolones class;
• patients using theophylline; patients with myasthenia gravis;
• patients with prolongation of QT interval.