Medical management of kidney stones: AUA guideline

PURPOSE

The purpose of this guideline is to provide a clinical framework for the diagnosis, prevention and follow-up of adult patients with kidney stones based on the best available published literature.

MATERIALS AND METHODS

The primary source of evidence for this guideline was the systematic review conducted by the Agency for Healthcare Research and Quality on recurrent nephrolithiasis in adults. To augment and broaden the body of evidence in the AHRQ report, the AUA conducted supplementary searches for articles published from 2007 through 2012 that were systematically reviewed using a methodology developed a priori. In total, these sources yielded 46 studies that were used to form evidence-based guideline statements. In the absence of sufficient evidence, additional statements were developed as Clinical Principles and Expert Opinions.

RESULTS

Guideline statements were created to inform clinicians regarding the use of a screening evaluation for first-time and recurrent stone formers, the appropriate initiation of a metabolic evaluation in select patients and recommendations for the initiation and follow-up of medication and/or dietary measures in specific patients.

CONCLUSIONS

A variety of medications and dietary measures have been evaluated with greater or less rigor for their efficacy in reducing recurrence rates in stone formers. The guideline statements offered in this document provide a simple, evidence-based approach to identify high-risk or interested stone-forming patients for whom medical and dietary therapy based on metabolic testing and close follow-up is likely to be effective in reducing stone recurrence.

As low as reasonably achievable: Methods for reducing radiation exposure during the management of renal and ureteral stones

Imaging for urolithiasis has evolved over the past 30 years. Currently, non-contrast computed tomography (NCCT) remains the first line imaging modality for the evaluation of patients with suspected urolithiasis. NCCT is a dominant source of ionizing radiation for patients and one of its major limitation. However, new low dose NCCT protocols may help to reduce the risk. Fluoroscopy use during operating room (OR) surgical procedures can be a substantial source of radiation for patients, OR staff and surgeons. It is important to consider the amount of radiation patients are exposed to from fluoroscopy during operative interventions for stones. Radiation reduction can be accomplished by appropriate selection of imaging studies and multiple techniques, which minimize the use of fluoroscopy whenever possible. The purpose of this manuscript is to review common imaging modalities used for diagnosing and management of renal and ureteral stones associated with radiation exposure. We also review alternatives and techniques to reduce radiation exposure.

Treatment efficacy and outcomes using a third generation shockwave lithotripter

OBJECTIVES

To evaluate the clinical efficiency of a third generation electromagnetic shock wave lithotripter, the Lithoskop(®) (Siemens, Erlangen, Germany), regarding outcomes, stone disintegration, retreatment and complication rates. To compare the results of the Lithoskop with other currently available systems and the reference standard lithotripter, the HM-3 (Dornier MedTech Europe GmbH, Wessling, Germany).

PATIENTS AND METHODS

We analysed the data from 183 patients, including 13 children, undergoing extracorporeal shock wave lithotripsy (ESWL) for renal and ureteric calculi collected from a prospectively populated database. Outcomes were assessed by plain abdominal film of kidney, ureter and bladder and renal ultrasonography for radiopaque and computerized tomography for radiolucent stones 1 day after treatment and after 3 months. We analysed stone size and location before and after treatment, stone disintegration rate, retreatment rate, stone-free and residual fragment rates after 3 months, along with auxiliary procedures and complications.

RESULTS

The mean (range) patient age was 48.6 (1.3-81.4) years, including 13 children with a mean (range) age of 8.4 (1.3-16.7) years, and 77% of the patients were male. In all, 46% of the calculi were localized in the kidney and 54% in the ureter. Renal stones were localized in the upper, middle and lower calyx and in the renal pelvis in 9, 29, 30 and 32% of patients, respectively. Ureteric stones were localized in the upper, mid- and distal ureter in 29, 19 and 52% of patients, respectively. The median (range) stone size before ESWL was 10 (4-25) mm in the kidney and 8 (4-28) mm in the ureteric calculi. The overall stone-free rate after 3 months was 91% (88% for renal and 93% for ureteric calculi); the mean number of sessions to achieve these rates was 1.3. Stone-free rates and the required number of sessions were determined only by stone size. In 7.1% of the patients (n = 13) post-interventional auxiliary procedures were necessary. We observed one perirenal haematoma as a major complication (0.5%), but this did not require any further therapy.

CONCLUSIONS

Clinical stone-free rates with the Lithoskop are high and similar to those of other available systems, including the reference standard HM-3 lithotripter. Retreatment and complication rates are low, supporting the use of ESWL as first-line therapy for urinary calculi <10 mm, independent of stone location.

Contemporary Management of Struvite Stones Using Combined Endourologic and Medical Treatment: Predictors of Unfavorable Clinical Outcome

BACKGROUND AND PURPOSE

Struvite stones have been associated with significant morbidity and mortality, yet there has not been a report on the medical management of struvite stones in almost 20 years. We report on the contemporary outcomes of the surgical and medical management of struvite stones in a contemporary series.

PATIENTS AND METHODS

A retrospective review of patients who were treated with percutaneous nephrolithotomy (PCNL) for struvite stones at Duke University Medical Center between January 2005 and September 2012 identified a total of 75 patients. Of these, 43 patients had adequate follow-up and were included in this analysis. Stone activity, defined as either stone recurrence or stone-related events, and predictors of activity were evaluated after combined surgical and medical treatment.

RESULTS

The study included 43 patients with either pure (35%) or mixed (65%) struvite stones with a median age of 55±15 years (range 21-89 years). The stone-free rate after PCNL was 42%. Stone recurrence occurred in 23% of patients. Postoperatively, 30% of patients had a stone-related event, while 60% of residual stones remained stable with no growth after a median follow-up of 22 months (range 6-67 mos). Kidney function remained stable during follow-up. Independent predictors of stone activity included the presence of residual stones >0.4 cm(2), preoperative large stone burden (>10 cm(2)), and the presence of medical comorbidities (P<0.05).

CONCLUSIONS

Struvite stones can be managed safely with PCNL followed by medical therapy. The majority of patients with residual fragments demonstrated no evidence of stone growth on medical therapy. With careful follow-up and medical management, kidney function can be maintained and stone morbidity can be minimized. Initial large stone burden, residual stones after surgery, and associated medical comorbidities may have deleterious effect on stone recurrence or residual stone-related events.

Emergent ureteric stent vs percutaneous nephrostomy for obstructive urolithiasis with sepsis: patterns of use and outcomes from a 15-year experience

OBJECTIVES

To characterize the use of emergent JJ ureteric stent placement and percutaneous nephrostomy (PCN) for patients with obstructive urolithiasis with sepsis, and to determine whether outcomes differ between the two treatment methods.

PATIENTS AND METHODS

A total of 130 patients with obstructive urolithiasis and systemic inflammatory response syndrome criteria were identified retrospectively from a single health system database from 1995 to 2011. Primary outcomes included stone-related and clinical variables which predicted the use of each treatment method. Secondary outcomes included the length of hospital stay, risk of intensive care unit (ICU) admission, and surgical approach used for definitive stone management.

RESULTS

The overall rate of failed procedures was 2.3% (3/130), with one in-hospital death (0.8%). Patients treated with PCN had larger stones (10 vs 7 mm, P = 0.031), and were more acutely ill (acute physiology, age, chronic health evaluation [APACHE] II scores of 15 vs 11, P = 0.036) than those treated with JJ stent placement. Patients treated with PCN were more likely to require ICU admission (odds ratio: 3.23, 95% confidence interval [CI]: 1.24-8.41, P = 0.016), and demonstrated longer length of hospital stay (β: 0.47, 95% CI: 0.20-0.74, P = 0.001), even when adjusting for age, APACHE II score, and Charlson Comorbidity Index score. After resolution of sepsis, patients treated with PCN were more likely to be treated definitively with a percutaneous approach, while patients treated with JJ stent placement were more likely to be treated ureteroscopically.

CONCLUSIONS

Both JJ stent placement and PCN drainage appear effective. Patients with larger stones and who are more acutely ill are more likely to be treated with PCN. Additional randomized clinical trials of adequate power are warranted to define the optimum management of these often complex cases.

Radiation exposure in the follow-up of patients with urolithiasis comparing digital tomosynthesis, non-contrast CT, standard KUB, and IVU

OBJECTIVE

To compare the effective doses (EDs) associated with imaging modalities for follow-up of patients with urolithiasis, including stone protocol non-contrast computed tomography (NCCT), kidney, ureter, and bladder radiograph (KUB), intravenous urogram (IVU), and digital tomosynthesis (DT).

METHODS

A validated Monte-Carlo simulation-based software PCXMC 2.0 (STUK) designed for estimation of patient dose from medical X-ray exposures was used to determine the ED for KUB, IVU (KUB scout plus three tomographic images), and DT (two scouts and one tomographic sweep). Simulations were performed using a two-dimensional stationary field onto the corresponding body area of the built-in digital phantom, with actual kVp, mAs, and geometrical parameters of the protocols. The ED for NCCT was determined using an anthropomorphic male phantom that was placed prone on a 64-slice GE Healthcare volume computed tomography (VCT) scanner. High-sensitivity metal oxide semiconductor field effect transistors dosimeters were placed at 20 organ locations and used to measure organ radiation doses.

RESULTS

The ED for a stone protocol NCCT was 3.04±0.34 mSv. The ED for a KUB was 0.63 and 1.1 mSv for the additional tomographic film. The total ED for IVU was 3.93 mSv. The ED for DT performed with two scouts and one sweep (14.2°) was 0.83 mSv.

CONCLUSIONS

Among the different imaging modalities for follow-up of patients with urolithiasis, DT was associated with the least radiation exposure (0.83 mSv). This ED corresponds to a fifth of NCCT or IVU studies. Further studies are needed to demonstrate the sensitivity and specificity of DT for the follow-up of nephrolithiasis patients.

Lithotrites and postoperative fever: does lithotrite type matter? Results from the Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study

OBJECTIVE

To compare the risks of fever from different lithotrites after percutaneous nephrolithotomy (PNL).

MATERIALS AND METHODS

The Clinical Research Office of the Endourological Society (CROES) PNL database is a prospective, multi-institutional, international PNL registry. Of 5,803 total patients, 4,968 received preoperative antibiotics, were supplied with complete information and included in this analysis. The lithotrites assessed included no fragmentation, ultrasonic, laser, pneumatic and combination ultrasonic/pneumatic. Risk of fever was estimated using multivariate logistic regression with adjustment for diabetes, steroid use, a history of positive urine culture, the presence of staghorn calculi or preoperative nephrostomy, stone burden and lithotrite.

RESULTS

The overall fever rate was 10%. Pneumatic lithotrites were used in 43% of the cohort, followed by ultrasonic (24%), combination ultrasonic/pneumatic (17.3%), no fragmentation (8.4%) and laser (7.3%). Fever rates were no different between patients who underwent no or any fragmentation (p = 0.117), nor among patients when stratified by lithotrite (p = 0.429). On multivariate analysis, fragmentation was not significantly associated with fever [Odds Ratio (OR) 1.17, p = 0.413], while diabetes (OR 1.32, p = 0.048), positive urine culture (OR 2.08, p < 0.001), staghorn calculi (OR 1.80, p < 0.001) and nephrostomy (OR 1.65, p < 0.001) increased fever risk. Fever risk among lithotrites did not differ (p ≥ 0.128).

CONCLUSIONS

Risk of post-PNL fever was not significantly different among the various lithotrites used in the CROES PNL study.

Radiation exposure in urology: a genitourinary catalogue for diagnostic imaging

PURPOSE

Computerized tomography use increased exponentially in the last 3 decades, and it is commonly used to evaluate many urological conditions. Ionizing radiation exposure from medical imaging is linked to the risk of malignancy. We measured the organ and calculated effective doses of different studies to determine whether the dose-length product method is an accurate estimation of radiation exposure.

MATERIALS AND METHODS

An anthropomorphic male phantom validated for human organ dosimetry measurements was used to determine radiation doses. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations to measure specific organ doses. For each study the phantom was scanned 3 times using our institutional protocols. Organ doses were measured and effective doses were calculated on dosimetry. Effective doses measured by a metal oxide semiconductor field effect transistor dosimeter were compared to calculated effective doses derived from the dose-length product.

RESULTS

The mean±SD effective dose on dosimetry for stone protocol, chest and abdominopelvic computerized tomography, computerized tomography urogram and renal cell carcinoma protocol computerized tomography was 3.04±0.34, 4.34±0.27, 5.19±0.64, 9.73±0.71 and 11.42±0.24 mSv, respectively. The calculated effective dose for these studies Was 3.33, 2.92, 5.84, 9.64 and 10.06 mSv, respectively (p=0.8478).

CONCLUSIONS

The effective dose varies considerable for different urological computerized tomography studies. Renal stone protocol computerized tomography shows the lowest dose, and computerized tomography urogram and the renal cell carcinoma protocol accumulate the highest effective doses. The calculated effective dose derived from the dose-length product is a reasonable estimate of patient radiation exposure.

Increasing dwell time of mitomycin C in the upper tract with a reverse thermosensitive polymer

Abstract Background and Purpose: Topical chemotherapy for urothelial cancer is dependent on adequate contact time of the chemotherapeutic agent with the urothelium. To date, there has not been a reliable method of maintaining this contact for renal or ureteral urothelial carcinoma. We evaluated the safety and feasibility of using a reverse thermosensitive polymer to improve dwell times of mitomycin C (MMC) in the upper tract.

MATERIALS AND METHODS

Using a porcine model, four animals were treated ureteroscopically with both upper urinary tracts receiving MMC mixed with iodinated contrast. One additional animal received MMC percutaneously. The treatment side had ureteral outflow blocked with a reverse thermosensitive polymer plug. MMC dwell time was monitored fluoroscopically and intrarenal pressures measured. Two animals were euthanized immediately, and three animals were euthanized 5 days afterward.

RESULTS

In control kidneys, drainage occurred at a mean of 5.3±0.58 minutes. Intrarenal pressures stayed fairly stable: 9.7±14.0 cm H20. In treatment kidneys, dwell time was extended to 60 minutes, when the polymer was washed out. Intrarenal pressures in the treatment kidneys peaked at 75.0±14.7 cm H20 and reached steady state at 60 cm H20. Pressures normalized after washout of the polymer with cool saline. Average washout time was 11.8±9.6 minutes. No histopathologic differences were seen between the control and treatment kidneys, or with immediate compared with delayed euthanasia.

CONCLUSIONS

A reverse thermosensitive polymer can retain MMC in the upper urinary tract and appears to be safe from our examination of intrarenal pressures and histopathology. This technique may improve the efficacy of topical chemotherapy in the management of upper tract urothelial carcinoma.

Imaging techniques for stone disease and methods for reducing radiation exposure

Imaging plays a critical role in the evaluation of patients with urolithiasis. It is essential for the diagnosis of stones and provides important information to aide in determining the appropriate treatment of renal or ureteral calculi. Imaging for urolithiasis has evolved over the past 30 years. Currently, noncontrast computed tomography remains the first-line imaging modality for the evaluation of patients with suspected urolithiasis. Proper imaging modality selection helps to minimize radiation exposure. Following the principles of As Low As Reasonably Achievable in the operating room can help reduce the amount of radiation patients are exposed to from fluoroscopy.

Clinical effectiveness protocols for imaging in the management of ureteral calculous disease: AUA technology assessment

PURPOSE

This technology assessment addresses the optimal use of imaging in the evaluation and treatment of patients with suspected or documented ureteral stones.

MATERIALS AND METHODS

A comprehensive literature search addressing 4 guiding questions was performed for full text in English articles published between January 1990 and July 2011. The search focused on major subtopics associated with the imaging of ureteral calculi, and included specific imaging modalities used in the diagnosis and management of ureteral calculous disease such as unenhanced (noncontrast) computerized tomography, conventional radiography, ultrasound, excretory urography, magnetic resonance imaging and nuclear medicine studies. Protocols (in the form of decision tree algorithms) were developed based on this literature review and in some instances on panel opinion. The 4 questions addressed were 1) What imaging study should be performed for suspected ureteral calculous disease? 2) What information should be obtained? 3) After diagnosis of a ureteral calculus, what followup imaging should be used? 4) After treatment of a ureteral calculus, what followup imaging studies should be obtained?

RESULTS

Based on these protocols, noncontrast computerized tomography is recommended to establish the diagnosis in most cases, with a low energy protocol advocated if body habitus is favorable. Conventional radiography and ultrasound are endorsed for monitoring the passage of most radiopaque stones as well as for most patients undergoing stone removal. Other studies may be indicated based on imaging findings, and patient, stone and clinical factors.

CONCLUSIONS

The protocols generated assist the clinician in establishing the diagnosis of ureteral calculous disease, monitoring stone passage and following patients after treatment. The protocols take into account not only clinical effectiveness but also cost-effectiveness and risk/harm associated with the various imaging modalities.

In-vitro assessment of a new portable ballistic lithotripter with percutaneous and ureteroscopic models

BACKGROUND AND PURPOSE

The EMS Swiss LithoBreaker is a new, portable, electrokinetic lithotripter. We compared its tip velocity and displacement characteristics with a handheld, pneumatic lithotripter LMA StoneBreaker.™ We also evaluated fragmentation efficiency using in vitro models of percutaneous and ureteroscopic stone fragmentation.

MATERIALS AND METHODS

Displacement and velocity profiles were measured for 1-mm and 2-mm probes using a laser beam aimed at a photo detector. For the percutaneous model, 2-mm probes fragmented 10-mm spherical BegoStone phantoms until the fragments passed through a 4-mm mesh sieve. The ureteroscopic model used 1-mm probes and compared the pneumatic and electrokinetic devices to a 200-μm holmium laser fiber. Cylindrical (4-mm diameter, 4-mm length) BegoStone phantoms were placed into silicone tubing to simulate the ureter; fragmented stones passed through a narrowing in the tubing.

RESULTS

For both 1-mm and 2-mm probes, the electrokinetic device had significantly higher tip displacement and slower tip velocity, P<0.01. In the percutaneous model, the electrokinetic device needed an average of 484 impulses over 430 seconds to fragment one BegoStone, while the pneumatic device needed 29 impulses over 122 seconds to fragment one stone. Both clearance times and number of impulses needed for percutaneous stone clearance were significantly different at P<0.01. Ureteroscopically, the mean clearance time was 97 seconds for the electrokinetic lithotripter, 145 seconds for the pneumatic lithotripter, and 304 seconds for the laser. Comparing the pneumatic device with the electrokinetic device ureteroscopically, there was no significant difference in clearance time, P=0.55. Both the pneumatic and electrokinetic lithotripters, however, demonstrated decreased clearance times compared with the laser, P=0.027.

CONCLUSIONS

The portable electrokinetic lithotripter may be better suited for ureteroscopy instead of percutaneous nephrolithotomy. It appears to be comparable to the portable pneumatic device in the ureter. Further clinical studies are needed to confirm these findings in vivo.

Outcomes of metallic stents for malignant ureteral obstruction

PURPOSE

Malignant ureteral obstruction often necessitates chronic urinary diversion and is associated with high rates of failure with traditional ureteral stents. We evaluated the outcomes of a metallic stent placed for malignant ureteral obstruction and determined the impact of risk factors previously associated with increased failure rates of traditional stents.

MATERIALS AND METHODS

Patients undergoing placement of the metallic Resonance® stent for malignant ureteral obstruction at an academic referral center were identified retrospectively. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction (recurrent hydroureteronephrosis or increasing creatinine). Predictors of time to stent failure were assessed using Cox regression.

RESULTS

A total of 37 stents were placed in 25 patients with malignant ureteral obstruction. Of these stents 12 (35%) were identified to fail. Progressive hydroureteronephrosis and increasing creatinine were the most common signs of stent failure. Three failed stents had migrated distally and no stents required removal for recurrent infection. Patients with evidence of prostate cancer invading the bladder at stent placement were found to have a significantly increased risk of failure (HR 6.50, 95% CI 1.45-29.20, p = 0.015). Notably symptomatic subcapsular hematomas were identified in 3 patients after metallic stent placement.

CONCLUSIONS

Failure rates with a metallic stent are similar to those historically observed with traditional polyurethane based stents in malignant ureteral obstruction. The invasion of prostate cancer in the bladder significantly increases the risk of failure. Patients should be counseled and observed for subcapsular hematoma formation with this device.