Staghorn Calculi in a Woman With Recurrent Urinary Tract Infections

Case of the Month Staghorn Calculi in a Woman With Recurrent Urinary Tract Infections NYU Case of the Month, December 2016 Philip Zhao, MD Department of Urology, NYU Langone Medical Center, New York, NY [Rev Urol. 2016;18(4):237-238 doi: 10.3909/ riu0734c] ® © 2016 MedReviews , LLC A 57-year-old woman presents with recurrent urinary tract infections (UTIs) despite receiving multiple courses of antibiotics over a 6-month period. She undergoes evaluation revealing a left full staghorn calculus. She is asymptomatic. Physical Examination Examination reveals the absence of costovertebral angle tenderness. Evaluation Her serum creatinine level is 1.7 mg/dL. Urinalysis results reveal a pH level of 7.4, and are positive for blood, leukocyte esterase, and nitrite. Urine culture results reveal a Proteus mirabilis count . 100,000 CFUs/mL. The patient was treated with amoxicillin-clavulanic acid. A computed tomography (CT) scan of the abdomen and pelvis shows a dense stone (HU . 1000) extending into every calyx from the renal pelvis (Figure 1). Management After informed consent and sterilization of urine, a left percutaneous nephrolithotomy (PCNL) was performed. Supra-12th rib access was initially obtained into the upper pole and a second access tract was placed into the midpole to allow complete stone removal. A re-entry nephroureteral catheter (NUC) was left in the kidney immediately after the operation. A noncontrast CT scan was performed the next day, showing complete stone clearance. On the second postoperative day, the NUC was removed and the patient was discharged home tube free and stone free. Stone analysis demonstrated struvite and calcium phosphate stone composition. She has been doing well without additional UTIs or recurrent stones. Comment A staghorn calculus is any stone that branches into more than one part of the collecting system. Staghorn calculi are most frequently composed of mixtures of magnesium ammonium phosphate (struvite) and calcium carbonate apatite; they are strongly associated with UTIs caused by organisms that produce the enzyme urease, which promotes the generation of ammonia and hydroxide from urea. This alkaline urinary environment promotes the crystallization of struvite and formation Vol. 18 No. 4 • 2016 • Reviews in Urology • 237 15_4004170006_RIU0734c.indd 237 12/12/16 4:21 pm Staghorn Calculi in a Woman With Recurrent Urinary Tract Infections continued Figure 1. Preoperative computed tomography of the abdomen and pelvis. Figure 2. Postoperative nephrostogram. of exopolysaccharide biofilm with incorporation of microproteins into its matrix, becoming a nidus for repeated urine infections. Over time, staghorn calculi often cause loss of renal parenchyma and function and sometimes lead to potentially fatal sepsis. The primary goal of treatment is to completely remove the stone, preserve renal function, eradicate infections, and relieve obstruction. Failure to completely eradicate the struvite stone virtually ensures the regrowth of the stone. American Urological Association guidelines for the surgical management of stones emphasize PCNL as first-line treatment. Shockwave lithotripsy is a poor modality to treat staghorn calculi and should be avoided. At NYU Langone Medical Center (New York, NY), we are able to obtain percutaneous access directly into the kidney without the assistance of interventional radiology. This allows unfettered entry into any calyx for optimal visualization and stone removal. Access into the posterior upper pole calyx is preferred as this vantage point provides a more favorable angle to visualize the renal pelvis, ureteropelvic junction, proximal ureter, and lower pole calyces. The midpole calyces can usually be assessed from the upper pole, as well. The disadvantage with upper pole access is the risk of hydrothorax associated with supra-12th or 11th rib puncture in 10% and 30% of cases, respectively. Sometimes, a second or even access tract is needed to facilitate complete stone clearance. The goal is to maximize removal of the stone burden before visualization becomes hampered by bleeding or angle torque, for example. Antegrade ureteroscopy is performed at the conclusion of every case to ensure the absence of obstructing ureteral fragments. A stone culture is sent because the discordance rate between the intraoperative stone culture and urine culture organisms has been reported in upwards of 50% of cases. Many PCNLs for staghorn calculi are planned as staged operations with a second look through the original established nephrostomy tract. The re-entry NUC allows tamponade of the tract for 24 hours, which substantially lessens the risk of tract bleeding. We obtain a CT scan after every PCNL to ensure stone clearance and assess need for a second-stage operation. Complete stone clearance after PCNL for staghorn calculi approaches 85% in the literature, and is higher at NYU Langone Medical Center. Patients who are completely stone free have all tubes removed prior to their discharge. We rarely leave a double J ureteral stent after PCNL, as we have demonstrated a significantly better quality of life using a temporary nephrostomy tube that is removed before discharge compared with a stent left in place for over a week. As many as 80% of patients implicated the postoperative ureteral stent as the worst part of their operation, which is why we advocate a tubeless disposition upon discharge with complete stone clearance. Postoperative care should include a complete metabolic work-up with 24-hour urine collection to address any metabolic defects and reimaging in 6 months. Patients with infective struvite stones are generally started on urinary acidification with vitamin C, 1 g daily, and methenamine, 1 g twice daily, for ≥ 6 months, if clinically indicated. Methenamine decomposes at an acidic pH to form formaldehyde and ammonia, both of which are bactericidal. Despite some associated adverse effects including abdominal cramps, nausea, vomiting, and diarrhea, as well as painful or difficult urination, methenamine is particularly suitable for long-term prophylactic treatment of UTIs because bacteria do not develop resistance to formaldehyde (which is especially valuable given the prevalence of antibiotic resistance to common antimicrobials). References Assimos D, Krambeck A1, Miller NL, et al. Surgical ­management of stones: American Urological Association/Endourological Society Guideline, Part I. J Urol. 2016;196:1153-1160. Preminger GM, Assimos DG, Lingeman JE, et al; AUA Nephrolithiasis Guideline Panel. Chapter 1: AUA guideline on management of staghorn calculi: ­diagnosis and treatment recommendations. J Urol. 2005;173: 1991-2000. Zhao PT, Hoenig DM, Smith A, Okeke Z. A randomized controlled comparison of nephrostomy drainage vs ureteral stent following percutaneous nephrolithotomy using the Wisconsin StoneQOL [published online Oct. 12, 2016]. J Endourol. doi:10.1089/end.2016.0235. 238 • Vol. 18 No. 4 • 2016 • Reviews in Urology 15_4004170006_RIU0734c.indd 238 12/12/16 4:21 pm