Gentamicin Irrigation for Urostomy Infection
Gentamicin bladder irrigation is safe and effective for localized urinary tract infections in complex urological cases, including urostomy patients, and should be administered as 8-20 mg gentamicin in 20-50 mL normal saline instilled twice daily for 7 days for treatment, or once daily every other day for prophylaxis. 1, 2
Evidence for Gentamicin Irrigation in Urological Cases
Safety Profile
Gentamicin bladder irrigations demonstrate excellent safety with minimal systemic absorption. In a pediatric series of 80 patients treated for a median of 90 days, no patient had detectable serum gentamicin levels greater than 0.4 mg/dL, and no adverse events were documented. 1
A more recent study of 24 pediatric cases confirmed that no serum gentamicin was detectable secondary to intravesical instillation, and no cases of sensorineural hearing loss were attributable to the treatment. 2
The risk of nephrotoxicity appears minimal when used as irrigation. Only 3 patients (all with pre-existing chronic renal insufficiency) showed small increases in serum creatinine in the larger safety study. 1
Efficacy Data
The treatment regimen achieved 86% success (12/14 cases) in suppressing acute UTI when resistance patterns precluded oral alternatives, avoiding hospitalization for parenteral antibiotics. 2
For prophylaxis, 58% of patients had no breakthrough UTI during a mean prophylaxis duration of 252 days. 2
Breakthrough UTIs occurred in 26% of patients on prophylaxis, with only 24% of these being gentamicin-resistant. 1
Recommended Dosing Regimens
Treatment Protocol (Acute Infection)
- 8 mg gentamicin in 20 mL normal saline OR 20 mg gentamicin in 50 mL normal saline (volume selected based on bladder/stoma capacity) 2
- Instilled twice daily for 7 days 2
- The 14 mg in 30 mL formulation used in earlier protocols is also effective 1
Prophylaxis Protocol (Recurrent Infections)
- Same concentration as treatment regimen 2
- Instilled once daily, every other day 2
- Duration individualized but can be continued for months (mean 252 days in published series) 2
Monitoring Requirements
Initial Risk Stratification
Intensive monitoring is only required for high-risk patients: 1
- Those with pre-existing chronic renal insufficiency
- Very young infants
- Patients with known eighth cranial nerve dysfunction
Low-Risk Patients
- No routine serum gentamicin levels or intensive laboratory monitoring required based on the safety data showing no detectable systemic absorption 1, 2
- Baseline serum creatinine is reasonable but not mandatory 1
High-Risk Patients
- Obtain serum creatinine at baseline and periodically during prolonged therapy 1
- Consider random gentamicin levels if clinical concern for absorption (though none were detected in published series) 1
- Audiology testing if treatment exceeds several months 2
Critical Pitfalls to Avoid
Common Errors
Do not confuse irrigation dosing with systemic dosing. The concentrations used for bladder irrigation (8-20 mg total dose) are far lower than systemic doses (3-5 mg/kg/day), and systemic absorption is negligible. 1, 2
Do not withhold this therapy due to concerns about systemic toxicity in patients with normal baseline renal function. The evidence demonstrates no detectable serum levels and no nephrotoxicity or ototoxicity in appropriately selected patients. 1, 2
Do not use this as first-line therapy when oral antibiotics are available and effective. Gentamicin irrigation is indicated when resistance patterns preclude oral alternatives or for prophylaxis after breakthrough infections on oral prophylaxis. 2
Resistance Considerations
- Gentamicin resistance emergence is rare (4.16% in one series), making this a durable option for recurrent infections. 2
- This compares favorably to the high resistance rates seen with repeated courses of oral antibiotics in complex urological patients 2
Administration Routes for Urostomy
- Gentamicin irrigation is feasible via various routes including catheterizable channels, suprapubic tubes, and urethral catheters in patients with complex lower urinary tract abnormalities. 2
- For urostomy specifically, the irrigation can be instilled directly through the stoma using a catheter, with the patient in a position to retain the solution for 15-30 minutes before drainage 2