Husain Alenezi

Risk Factors for Postoperative Complications of Percutaneous Nephrolithotomy at a Tertiary Referral Center

PURPOSE We sought to describe and evaluate the complications related to percutaneous nephrolithotomy and identify risk factors of morbidity according to the modified Clavien scoring system. We also sought to specify which perioperative factors are associated with minor and major complications. MATERIALS AND METHODS We retrospectively analyzed data on patients who underwent percutaneous nephrolithotomy from 1990 to 2013. Descriptive statistics were used to analyze patient characteristics, medical comorbidities and perioperative features. Complications were categorized according to the Clavien score for percutaneous nephrolithotomy. The Mann-Whitney and Fisher exact tests were used as appropriate. Logistic regression analysis was performed to look for prognostic factors associated with major complications. RESULTS A total of 2,318 surgeries were evaluated. Mean age of the population was 53.7 years. The stone-free rate at hospital discharge was 81.6%. The overall complication rate was 18.3%. Two deaths occurred. Patients with any postoperative complications were older, had more comorbidities, were more likely to have staghorn calculi and had longer operative time and hospital stay on univariate analysis (p<0.05). Age 55 years or older and upper pole access were independent predictors of major complications on multivariate analysis. Other factors such as a history of urinary tract infections, body mass index, stone composition, previous percutaneous nephrolithotomy and multiple tracts were not associated with a major complication. CONCLUSIONS At our center percutaneous nephrolithotomy is an excellent option for complex kidney stone management with a low overall complication rate. Older patient age and upper pole access are significantly associated with an increased risk of a major complication.

Natural History of Residual Fragments After Percutaneous Nephrolithotomy: Evaluation of Factors Related to Clinical Events and Intervention

OBJECTIVE To determine the natural history of residual fragments (RF) after percutaneous nephrolithotomy in long-term patient follow-up and to identify possible predictive factors for future intervention. MATERIALS AND METHODS We assessed all patients from 2006 to 2013 with postoperative computed tomography scan revealing RF, who did not undergo second-look nephroscopy or immediate ancillary procedures, and with at least 12 months of clinical follow-up. We evaluated factors associated with clinical, radiological, and surgical outcomes. Kaplan-Meier curves were used to calculate the proportion of asymptomatic and treatment-free patients during follow-up. RESULTS From 781 percutaneous nephrolithotomies performed, 202 patients underwent postoperative computed tomography scan and 44 patients with residual stones were included in the analysis. Mean follow-up was 57.9 months. A total of 24 patients (54.5%) developed at least 1 clinical outcome, and 32 (72.7%) patients had a surgical intervention. Only 4 patients had radiological evidence of stone passage. Multivariate analysis found that RF >4 mm and struvite or apatite stones were significant predictors for surgical intervention. The 5-year estimated probability to remain intervention free was 29%. CONCLUSION Despite the size of the RF, the vast majority of patients required an intervention during long-term follow-up. We identified that RFs of diameter >4 mm associate with the need for a surgical therapy, but the rate of clinical events was not affected by the size or location of the stones. Struvite or apatite composition stones had an increased risk of intervention during follow-up. Spontaneous passage was an uncommon event in this cohort.

Flexible ureteroscopy: Technological advancements, current indications and outcomes in the treatment of urolithiasis

The last 3 decades have witnessed great improvements in the technology and clinical applications of many minimally invasive procedures in the urological field. Flexible ureteroscopy (fURS) has advanced considerably to become a widely utilized diagnostic and therapeutic tool for multiple upper urinary tract pathologies. The most common indication for fURS is the treatment of upper urinary tract stones with the aid of Holmium:Yttrium Aluminium Garnet (YAG) laser lithotripsy. Advancements in endoscope technologies and operative techniques have lead to a broader application of fURS in the management of urolithiasis to include larger and more complex stones. fURS has proved to be an effective and safe procedure with few contraindications. Continued progression in fURS may increase its clinical applicability and supplant other procedures as the first line treatment option for urolithiasis.

KIM-1 Is a Potential Urinary Biomarker of Obstruction: Results from a Prospective Cohort Study.

INTRODUCTION Partial or complete obstruction of the urinary tract is a common and challenging urological condition that may occur in patients of any age. Serum creatinine is the most commonly used method to evaluate global renal function, although it has low sensitivity for early changes in the glomerular filtration rate or unilateral renal pathology. Hence, finding another measurable parameter that reflects the adaptation of the renal physiology to these circumstances is important. Several recent studies have assessed the use of new biomarkers of acute kidney injury (AKI), but the information among patients with stone disease and those with obstructive uropathy is limited. MATERIAL AND METHODS A prospective cohort study was conducted to determine the urinary levels of kidney injury molecule-1 (KIM-1), Total and Monomeric neutrophil gelatinase-associated lipocalin (NGAL) in patients with hydronephrosis secondary to renal stone disease, congenital ureteropelvic junction obstruction or ureteral stricture. Comparison between patients with hydronephrosis and no hydronephrosis was carried out along with correlation analysis to detect factors associated with biomarker expression. RESULTS Urinary levels of KIM-1 significantly decreased after hydronephrosis treatment in patients with unilateral obstruction (1.19 ng/mL vs 0.76 ng/mL creatinine, p = 0.002), additionally KIM-1 was significantly higher in patients with hydronephrosis compared to stone disease patients without radiological evidence of obstruction (1.19 vs 0.64, p = 0.006). Total and Monomeric NGAL showed a moderate correlation with the presence of leukocyturia. We found that a KIM-1 value of 0.735 ng/mg creatinine had a sensitivity of 75% and specificity of 67% to predict the presence of hydronephrosis in preoperative studies (95% CI 0.58-0.87, p = 0.006). CONCLUSION Our results show that KIM-1 is a promising biomarker of subclinical AKI associated with hydronephrosis in urological patients. NGAL values were influenced by the presence of leukocyturia, limiting its usefulness in this population.

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 stones 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.

Novel Methods of Determining Urinary Calculi Composition: Petrographic Thin Sectioning of Calculi and Nanoscale Flow Cytometry Urinalysis

Accurate determination of urinary stone composition has significant bearing on understanding pathophysiology, choosing treatment modalities and preventing recurrence. A need exists for improved methods to determine stone composition. Urine of 31 patients with known renal calculi was examined with nanoscale flow cytometry and the calculi collected during surgery subsequently underwent petrographic thin sectioning with polarized and fluorescent microscopy. Fluorescently labeled bisphosphonate probes (Alendronate-fluorescein/Alendronate-Cy5) were developed for nanoscale flow cytometry to enumerate nanocrystals that bound the fluorescent probes. Petrographic sections of stones were also imaged by fluorescent and polarized light microscopy with composition analysis correlated to alendronate +ve nanocrystal counts in corresponding urine samples. Urine samples from patients with Ca2+ and Mg2+ based calculi exhibited the highest alendronate +ve nanocrystal counts, ranging from 100–1000 nm in diameter. This novel urine based assay was in agreement with composition determined by petrographic thin sections with Alendronate probes. In some cases, high alendronate +ve nanocrystal counts indicated a Ca2+ or Mg2+ composition, as confirmed by petrographic analysis, overturning initial spectrophotometric diagnosis of stone composition. The combination of nanoscale flow cytometry and petrographic thin sections offer an alternative means for determining stone composition. Nanoscale flow cytometry of alendronate +ve nanocrystals alone may provide a high-throughput means of evaluating stone burden.

The Effect of Renal Cysts on the Fragmentation of Renal Stones During Shockwave Lithotripsy: A Comparative In Vitro Study

PURPOSE To assess the potential effect of simple renal cysts (SRC) on stone fragmentation during shockwave lithotripsy (SWL) in an in vitro model. MATERIALS AND METHODS The in vitro model was constructed using 10% ordnance gelatin (OG). Models were created to mimic four scenarios: Model A-with an air-filled cavity (suboptimal for stone fragmentation); model B-without a cavity (normal anatomy); model C-with a 3-cm serum filled cavity (to represent a small SRC); model D-with a 4-cm serum filled cavity (to represent a larger SRC). SWL was applied to 24 standardized phantom stones (weight of 2±0.1 g) in each model using a standardized protocol. Stone fragments were retrieved, then dried overnight at room air temperature. Fragmentation coefficient (FC) was calculated for each stone, for fragments<4 mm and <2 mm. RESULTS The OG in vitro model was robust enough for the proposed research. There was no fragmentation evident in model A as expected. The mean FC was 29.7 (±20.5) and 39.7 (±23.7) for <4 mm fragments (P=0.069) and 7.6 (±4.1) and 10.6 (±6.7) for <2 mm fragments (P=0.047), for noncystic and cystic models, respectively. The mean FC was 29.7 (±20.5), 38.8 (±26.2) and 40.7 (±21.3) for <4 mm fragments (P=0.213) and 7.6 (±4.1), 11.1 (±8) and 10.2 (±5.3) for <2 mm fragments (P=0.138), for models B, C, and D, respectively. CONCLUSION Our in vitro experiment confirms better stone fragmentation associated with SWL in the presence of adjacent SRC.

MP51-17 IMPACT OF PERCUTANEOUS NEPHROLITHOTRIPSY ON EARLY AND LONG-TERM RENAL FUNCTION IN PATIENTS WITH A SOLITARY KIDNEY

INTRODUCTION AND OBJECTIVES: The impact of percutaneous nephrolithotripsy (PCNL) on renal function is an especially important consideration in stone formers with solitary kidneys. The objectives of this study were to evaluate the effect of PCNL on kidney function and further characterize patient demographics and perioperative outcomes of this unique cohort. METHODS: A retrospective review of medical records was performed on patients with a solitary or single functioning renal unit who underwent PCNL at a single institution between 1990 and 2013. Data on early and long-term post-operative renal function were collected and analyzed. Patient demographics and perioperative factors were compared to our larger cohort of PCNL patients and evaluated as potential predictors of post-operative renal function. RESULTS: Of 2318 patients, there were 76 PCNL events for patients with a solitary renal unit (40 female and 36 male). Long-term data (over 2 years post-operatively) was available for 48 PCNL events (24 female and 24 male). Estimated glomerular function (eGFR) slightly worsened in the early post-operative period, from 51 2.9 to 47 2.7 ml/min/1.73m2 (p <0.01). In the long-term however, eGFR improved, from 48 3.7 to 57 5.9 ml/min/1.73m2 (p <0.02). Predominant stone compositions included 19.7% cysteine, 19.7% calcium oxalate monohydrate and 11.8% and struvite. Compared to the larger cohort of PCNL patients, age, sex, complications, and stone free rates were consistent. Patients with solitary kidneys had more medical co-morbidities (64.7% vs 45%), with higher rates of diabetes (18.4% vs 13%) and pre-existing renal impairment (18.4% vs 3%). Univariate analyses of patient age, sex, comorbidities, stone composition, stone size, number of tracts and stone free rates were unable to identify a significant predictor of early and long-term postoperative renal function. CONCLUSIONS: These results show that while in the early post-operative period renal function slightly declines, it recovers in the long-term post PCNL for patients with solitary kidneys. Based on these findings, PCNL correlates with overall improved long-term renal function in patients with solitary kidneys. Given the higher rate of pre-existing medical co-morbidity and likely history of recurrent stone disease (high rates of cysteine and struvite stones), this solitary kidney cohort is presumably a high-risk population for future renal impairment. This further emphasizes the need to preserve renal function with PCNL in stone formers with solitary kidneys.

Assessing the Magnitude of Effect of Bone Structures on Shockwave Lithotripsy Fragmentation: Results from an In Vitro Study

INTRODUCTION Several anatomic and clinical factors have been implicated in the failure rates of shock wave lithotripsy (SWL), including the attenuating effects of bony structures. We designed an in vitro model that incorporates the lumbar spine, including vertebral bodies and transverse processes along the pathway of shockwaves, to mimic the clinical scenario during SWL of upper ureteral stones. We hypothesized that the presence of bone structures in the SWL pathway significantly affects the fragmentation rate. MATERIALS AND METHODS An ordnance gelatin (OG) model was conceptualized and created to allow a pigs lumbar spine to be embedded within it. Artificial urinary calculi weighing 2 ± 0.1 g (1.2-cm diameter) were prepared using BegoStone plaster. The trial was divided into two arms: group 1 models had OG only and served as the control and group 2 models had the bone embedded in the gelatin with stone wells placed above the transverse processes. Twenty-four stones per group were subjected to SWL using the STORZ MODULITH SLX-F2 lithotripter, using the same treatment parameters. Fragments were sieved through 2- and 4-mm filters, and the fragmentation coefficients (FC) were calculated. The Mann-Whitney test was used to compare FC between the two groups. RESULTS The mean fragmentation rate of group 1 was statistically significantly higher compared with group 2 using a 4-mm sieve (43% vs 0.62%, p < 0.001) and the 2-mm filter (18% vs 0.52%, p < 0.001). CONCLUSIONS The presence of bone structures dramatically reduces the fragmentation rate of phantom stones using an OG in vitro model. The OG model is inexpensive and simple to use to simulate clinical situations during SWL.