Cost-effectiveness treatment strategies for stone disease for the practicing urologist

Percutaneous nephrolithotomy in previously operated patients: A prospective study

Purpose:

To determine the effect of previous renal stone surgery on result and complications of percutaneous nephrolithotomy (PCNL).

Materials and Methods:

Total 300 patients were enrolled in the study. We enrolled 100 surgery-naive cases (those with no history of any renal surgery) as control and labeled them as Group A. Group B comprised 100 cases who had PCNL in the past. Group C constituted 100 patients who had open renal stone surgery in the past. Stones were classified using Guy's stone score. PCNL was performed by standard technique in prone position and technical features encountered during operation and outcomes were compared between groups. Complications were graded using modified Clavien grading system.

Results:

There were no differences between the three groups in age, gender, body mass index, stone burden, and stone opacity. Multiple calyceal stones and distorted pelvicalyceal system anatomy were more in Group C, but stone score showed no statistically significant difference from other groups. The mean operative time (68.91 ± 21.27 min) and fluoroscopy time (264.40 ± 74.90 s) were longer in Group C, but there was no statistically significant difference between the groups. Multiple access was significantly more common in Group C compared to the other two groups (P < 0.001). Access location too did not show any statistically significant difference between the groups. Postoperative complications were more in previous stone surgery patients, but did not show statistically significant difference.

Conclusion:

PCNL is a safe and effective treatment modality for patients with renal stones regardless of history of previous PCNL or open renal surgery.

Feasibility of a Telemedicine-Administered, Pharmacist-Staffed, Protocol-Driven, Multicenter Program for Kidney Stone Prevention in a Large Integrated Health Care System: Results of a Pilot Program

INTRODUCTION

Despite guidelines for prevention of recurrent renal calculi, routine dietary modification and metabolic evaluation are often not performed.

OBJECTIVE

To determine feasibility of a multicenter, pharmacist-staffed program to enroll patients at high risk of recurrent kidney stones and provide dietary instruction, metabolic evaluation, and medical therapy via telemedicine.

METHODS

A total of 536 consecutive adult patients were referred from 3 Northern California Kaiser Permanente facilities. We determined the proportion of patients who enrolled, received dietary counseling, and completed metabolic evaluation at 12 months. The program was staffed by a clinical pharmacist and supervised by urologists following a protocol based on the American Urological Association guidelines. Patients were contacted entirely via telemedicine. Cystine or struvite kidney stones, renal tubular acidosis, and primary hyperoxaluria were exclusion criteria.

RESULTS

Of the 536 patients, 500 agreed to enrollment. Among patients enrolled for 3 months, 99% self-reported compliance with at least 3 of 5 aspects of dietary advice. A complete metabolic evaluation including 24-hour urine collection was performed in 80% of patients by 12 months. A significant improvement in all urinary parameters occurred in 52 patients with calcium stones who repeated 24-hour urine testing. The 12-month dropout rate was 12.4%.

CONCLUSION

A telemedicine-administered, pharmacist-staffed, protocol-driven program can provide dietary advice and obtain compliance with metabolic testing for patients at high risk of recurrent kidney stones. Rates of metabolic testing and dropout compare favorably with previously reported rates. This report represents, to our knowledge, the first telemedicine-administered, pharmacist-staffed, kidney stone prevention program published in the literature.

Combining Mean and Standard Deviation of Hounsfield Unit Measurements from Preoperative CT Allows More Accurate Prediction of Urinary Stone Composition Than Mean Hounsfield Units Alone

INTRODUCTION AND OBJECTIVES

The mineral composition of a urinary stone may influence its surgical and medical treatment. Previous attempts at identifying stone composition based on mean Hounsfield Units (HUm) have had varied success. We aimed to evaluate the additional use of standard deviation of HU (HUsd) to more accurately predict stone composition.

METHODS

We identified patients from two centers who had undergone urinary stone treatment between 2006 and 2013 and had mineral stone analysis and a computed tomography (CT) available. HUm and HUsd of the stones were compared with ANOVA. Receiver operative characteristic analysis with area under the curve (AUC), Youden index, and likelihood ratio calculations were performed.

RESULTS

Data were available for 466 patients. The major components were calcium oxalate monohydrate (COM), uric acid, hydroxyapatite, struvite, brushite, cystine, and CO dihydrate (COD) in 41.4%, 19.3%, 12.4%, 7.5%, 5.8%, 5.4%, and 4.7% of patients, respectively. The HUm of UA and Br was significantly lower and higher than the HUm of any other stone type, respectively. HUm and HUsd were most accurate in predicting uric acid with an AUC of 0.969 and 0.851, respectively. The combined use of HUm and HUsd resulted in increased positive predictive value and higher likelihood ratios for identifying a stone's mineral composition for all stone types but COM.

CONCLUSIONS

To the best of our knowledge, this is the first report of CT data aiding in the prediction of brushite stone composition. Both HUm and HUsd can help predict stone composition and their combined use results in higher likelihood ratios influencing probability.

Does previous open renal surgery or percutaneous nephrolithotomy affect the outcomes and complications of percutaneous nephrolithotomy

In this study, we aim to evaluate the effectiveness and safety of PNL in patients with a history of open renal surgery or PNL by comparing with primary patients and to compare impact of previous open renal surgery and PNL on the success and complications of subsequent PNL. Charts of patients, who underwent PNL at our institute, were analyzed retrospectively. Patients were divided into three groups according to history of renal stone surgery. Patients without history of renal surgery were enrolled into Group 1. Other patients with previous PNL and previous open surgery were categorized as Group 2 and Group 3. Preoperative characteristic, perioperative data, stone-free status, and complication rates were compared between the groups. Stone-free status was accepted as completing clearance of stone and residual fragment smaller than 4 mm. Eventually, 2070 patients were enrolled into the study. Open renal surgery and PNL had been done in 410 (Group 2) and 131 (Group 3) patients, retrospectively. The mean operation time was longer (71.3 ± 33.5 min) in Group 2 and the mean fluoroscopy time was longer (8.6 ± 5.0) in Group 3 but there was no statistically significant difference between the groups. Highest stone clearance was achieved in primary PNL patients (81.62%) compared to the other groups (77.10% in Group 2 and 75.61% in Group 3). Stone-free rate was not significantly different between Group 2 and Group 3. Fever, pulmonary complications, and blood transfusion requirement were not statically different between groups but angioembolization was significantly higher in Group 2. Percutaneous nephrolithotomy is a safe and effective treatment modality for patients with renal stones regardless history of previous PNL or open renal surgery. However, history of open renal surgery but not PNL significantly reduced PNL success.

Are stone analysis results different with repeated sampling?

INTRODUCTION

We assessed differences in results of stone analyses on subsequent sampling.

METHODS

A retrospective review of patients with stone analyses at a tertiary stone centre between March 2006 and July 2012 was performed. All stones were analyzed at a centralized laboratory using infrared spectroscopy. Patients were grouped according to the first predominant stone type on record, as defined by the predominant stone component of at least 60%. Stone groups included calcium oxalate (CaOx), calcium phosphate (CaP), uric acid (UA), cystine, struvite, mixed CaOx-CaP and mixed CaOx-UA. All patients had a full metabolic stone workup.

RESULTS

Of the 303 patients with stone analyses, 118 (38.9%) patients had multiple stone analyses. The mean age was 53.4 ± 15.1 years, and 87 (73.7%) were males. Of the 118, the initial stone analysis showed 43 CaOx, 38 CaP, 21 UA, 4 CaOx-CaP, 2 CaOx-UA, 6 cystine, and 4 struvite. There was a different stone composition in 25 (21.2%) patients with a median time delay of 64.5 days. Different compositions were found in 7 CaOx (to 3 CaP, 2 CaOx-CaP, and 2 UA), 5 CaP (to 3 CaOx and 2 CaOx-CaP), 3 UA (to 3 CaOx), 4 CaOx-CaP (to 2CaOx, 1 UA and 1 CaP), 2 CaOx-UA (to 2 CaOx) and 4 struvite (to 3 CaP and 1 UA).

CONCLUSIONS

Stone composition was different in 21.2% of patients on subsequent analyses.

In vitro fragmentation efficiency of holmium: yttrium-aluminum-garnet (YAG) laser lithotripsy--a comprehensive study encompassing different frequencies, pulse energies, total power levels and laser fibre diameters

OBJECTIVE

To assess the fragmentation (ablation) efficiency of laser lithotripsy along a wide range of pulse energies, frequencies, power settings and different laser fibres, in particular to compare high- with low-frequency lithotripsy using a dynamic and innovative testing procedure free from any human interaction bias.

MATERIALS AND METHODS

An automated laser fragmentation testing system was developed. The unmoving laser fibres fired at the surface of an artificial stone while the stone was moved past at a constant velocity, thus creating a fissure. The lithotripter settings were 0.2-1.2 J pulse energies, 5-40 Hz frequencies, 4-20 W power levels, and 200 and 550 μm core laser fibres. Fissure width, depth, and volume were analysed and comparisons between laser settings, fibres and ablation rates were made.

RESULTS

Low frequency-high pulse energy (LoFr-HiPE) settings were (up to six times) more ablative than high frequency-low pulse energy (HiFr-LoPE) at the same power levels (P < 0.001), as they produced deeper (P < 0.01) and wider (P < 0.001) fissures. There were linear correlations between pulse energy and fragmentation volume, fissure width, and fissure depth (all P < 0.001). Total power did not correlate with fragmentation measurements. Laser fibre diameter did not affect fragmentation volume (P = 0.81), except at very low pulse energies (0.2 J), where the large fibre was less efficient (P = 0.015).

CONCLUSIONS

At the same total power level, LoFr-HiPE lithotripsy was most efficient. Pulse energy was the key variable that drove fragmentation efficiency. Attention must be paid to prevent the formation of time-consuming bulky debris and adapt the lithotripter settings to one's needs. As fibre diameter did not affect fragmentation efficiency, small fibres are preferable due to better scope irrigation and manoeuvrability.

Comparison of shock wave lithotripsy, flexible ureterorenoscopy and percutaneous nephrolithotripsy on moderate size renal pelvis stones

To compare success and complication rates of shock wave lithotripsy (SWL), flexible ureterorenoscopy (F-URS) and percutaneous nephrolithotripsy (PNL) according to modified clavien grading system of renal pelvis stones between 1 and 2 cm. The results of 149 patients were evaluated retrospectively. Patients were divided into three groups as 52 for SWL, 47 for F-URS and 50 for PNL. Complications were evaluated by modified Clavien grading system. In the first group, stone-free rates after a mean of 2, 6 sessions was 86 % (45/52). In Group 2, this ratio was 91.4 % (43/47), and in Group 3, it was 98 % (49/50). The success rate in Group 3 was significantly higher than other groups. Complication rates for Group 1, 2 and 3 were 7.6 % (4/52), 6.3 % (3/47) and 12 % (6/50), respectively. Although PNL was the most successful technique compared with other techniques, complications were also higher in this group. Even though PNL is the most successful, it should be performed for selected patient groups and indications should be carefully evaluated.