Treatment of Triple Phosphate Crystals with Urease-Producing UTI
Complete surgical removal of all stone material is mandatory and must be combined with appropriate antibiotic therapy, as bacteria embedded within struvite stones cannot be eradicated by antibiotics alone. 1
Immediate Diagnostic and Treatment Steps
Mandatory Initial Workup
- Obtain urine culture and susceptibility testing before starting antibiotics, as all UTIs with urease-producing organisms are complicated UTIs by definition 1
- Culture stone fragments if available, since bacteria within stones may differ from urine cultures 1
- Look for urease-producing organisms including Proteus mirabilis (most common), Klebsiella, Pseudomonas, and less commonly Ureaplasma urealyticum and Corynebacterium urealyticum which require special culture techniques 2, 3
Empirical Antibiotic Selection While Awaiting Culture
- Avoid fluoroquinolones if recent exposure or local resistance >10% 1
- Consider trimethoprim-sulfamethoxazole for empiric coverage if local resistance is acceptable, but adjust based on susceptibilities 4, 5
- Monitor for hyperkalemia with trimethoprim use, especially in patients with renal insufficiency or underlying potassium disorders 5
Definitive Management: Surgical Stone Removal
Primary Treatment Approach
- Percutaneous nephrolithotomy (PNL) is the primary modality for staghorn calculi 1
- Combinations of PNL and shock wave lithotripsy (SWL) may be used for complex cases 1
- Open surgery (anatrophic nephrolithotomy) is reserved only for cases where endoscopic approaches fail 1
Critical Surgical Principle
- Achieve complete stone clearance—any residual fragments will harbor bacteria and cause recurrence 1, 6
- Residual fragments should be treated with chemolysis via ureteral catheter/nephrostomy or citrate administration 6
Why Surgery Cannot Be Avoided
- Untreated staghorn calculi will destroy the kidney and/or cause life-threatening sepsis over time 1
- Antibiotics alone cannot penetrate the stone matrix where bacteria are embedded 1, 2
Post-Operative Medical Management
Metabolic Stone Prevention
- Administer potassium citrate to increase nucleation pH (pHn) more than urinary pH, which reduces struvite crystallization risk 1, 6
- Increase fluid intake to maintain high urine output 1
- Implement sodium restriction and encourage ample fruits/vegetables 1
Monitoring Protocol
- Obtain 24-hour urine specimen for stone risk factors within 6 months of treatment initiation 1
- Monitor for recurrent UTIs, as patients remain at increased risk even after stone removal 1
Alternative Medical Therapies (Limited Role)
- Acetohydroxamic acid (AHA) may benefit patients at high risk for recurrence, though extensive side effects limit use 1, 6
- Urinary acidification with NH₄Cl or NH₄NO₃ is difficult to achieve long-term in infected urine and has limited efficacy 6, 7
Common Pitfalls to Avoid
- Never rely on antibiotics alone without addressing stone burden—this is the most critical error 1
- Do not treat contaminated cultures showing mixed flora with no predominant organism, as this drives antimicrobial resistance 4
- Do not assume negative conventional cultures rule out infection—Ureaplasma urealyticum requires special culture techniques 3
- Avoid incomplete stone removal, as even small fragments perpetuate infection 1, 6
Special Considerations for Risk Factors
Evaluate for underlying conditions that predispose to infection stones 2:
- Urinary tract obstruction
- Neurogenic bladder or voiding dysfunction
- Indwelling catheters
- Distal renal tubular acidosis
- Medullary sponge kidney