Ureteral Strictures Following Ureteroscopy for Kidney Stone Disease: A Population-based Assessment.

PURPOSE: As the prevalence of urolithiasis increases and ureteroscopy is used more frequently, the risks of uncommon complications such as ureteral stricture may become more notable. Our objective is to assess the rate and associated risk factors of ureteral stricture formation in patients undergoing ureteroscopy. MATERIALS AND METHODS: Utilizing the IBM MarketScan research database, we evaluated data from 2008 to 2019 and compared ureteral stricture rates and their management following ureteroscopy to subjects who had shock wave lithotripsy. Shock wave lithotripsy was used as a comparison group to represent the rate of stricture from stone disease alone. A third group of those having both shock wave lithotripsy and ureteroscopy was included. Patients and secondary procedures were identified using Current Procedural Terminology, and International Classification of Diseases-9 and -10 codes. RESULTS: A total of 329,776 patients received ureteroscopy, shock wave lithotripsy, or shock wave lithotripsy+ureteroscopy between 2008 and 2019. Stricture developed in 2.9% of patients after ureteroscopy, 1.5% after shock wave lithotripsy, and 2.6% after shock wave lithotripsy+ureteroscopy. In the multivariable model, rates of stricture were 1.7-fold higher after ureteroscopy vs shock wave lithotripsy (OR:1.71, 95% CI 1.62-1.81). Preoperative hydronephrosis, age, prior stones/intervention, and concurrent kidney and ureteral stones were associated with increased risk of stricture. Of those with strictures incurred after ureteroscopy, 35% required drainage, 21% had endoscopic intervention, 4.8% required reconstructive surgery, and 1.7% underwent nephrectomy. CONCLUSIONS: Ureteral stricture rate after ureteroscopy of nearly 3% was higher than expected and approximately twice the rate attributable to stone disease alone. Factors associated with the stone as well as instrumentation were found to be risk factors. The morbidity of stricture disease following ureteroscopy was significant.

National Imaging Trends after Percutaneous Nephrolithotomy.

PURPOSE: Followup imaging after percutaneous nephrolithotomy serves to detect postoperative complications, residual fragments and silent hydronephrosis. However, the timing and optimal imaging modality remain poorly defined. We describe imaging use patterns after percutaneous nephrolithotomy. MATERIALS AND METHODS: In the MarketScan® database we identified patients 17 to 64 years old who underwent percutaneous nephrolithotomy between 2007 and 2014. Imaging modalities were identified by CPT, and ICD-9 and 10 codes, and tracked for 1 year after percutaneous nephrolithotomy. The modalities included computerized tomography, renal ultrasound, abdominal x-ray and intravenous pyelogram. Cumulative longitudinal use patterns were characterized and the association with demographic factors was assessed by the chi-square test. RESULTS: Of the 6,495 patients included in analysis 29% and 15% had undergone no postoperative imaging by 3 and 12 months, respectively. While abdominal x-ray was the most common modality at 3, 6 and 12 months, performed in 46%, 53% and 62% patients, respectively, nearly 50% underwent computerized tomography by 1 year. Of these patients 34% underwent computerized tomography within 3 months, which was done within the first 3 days in 69%. During the study period renal ultrasound use increased by 13% while computerized tomography and abdominal x-ray use remained relatively stable. Female gender, residence in the Northeast, no health maintenance organization status and treatment in a metropolitan statistical area were independently associated with higher rates of renal ultrasound on multivariate analyses (p <0.05). CONCLUSIONS: Among insured adults national imaging patterns vary following percutaneous nephrolithotomy. Many patients do not receive any followup imaging while approximately half undergo computerized tomography within a year. Imaging patterns may be evolving with the increased use of ultrasound.

The Morbidity of Ureteral Strictures in Patients with Prior Ureteroscopic Stone Surgery: Multi-Institutional Outcomes.

PURPOSE: Nephrolithiasis is an increasingly common ailment in the United States. Ureteroscopic management has supplanted shockwave lithotripsy as the most common treatment of upper tract stone disease. Ureteral stricture is a rare but serious complication of stone disease and its management. The impact of new technologies and more widespread ureteroscopic management on stricture rates is unknown. We describe our experience in managing strictures incurred following ureteroscopy for upper tract stone disease. MATERIALS AND METHODS: Records for patients managed at four tertiary care centers between December 2006 and October 2015 with the diagnosis of ureteral stricture following ureteroscopy for upper tract stone disease were retrospectively reviewed. Study outcomes included number and type (endoscopic, reconstructive, or nephrectomy) of procedures required to manage stricture. RESULTS: Thirty-eight patients with 40 ureteral strictures following URS for upper tract stone disease were identified. Thirty-five percent of patients had hydronephrosis or known stone impaction at the time of initial URS, and 20% of cases had known ureteral perforation at the time of initial URS. After stricture diagnosis, the mean number of procedures requiring sedation or general anesthesia performed for stricture management was 3.3 ± 1.8 (range 1-10). Eleven strictures (27.5%) were successfully managed with endoscopic techniques alone, 37.5% underwent reconstruction, 10% had a chronic stent/nephrostomy, and 10 (25%) required nephrectomy. CONCLUSIONS: The surgical morbidity of ureteral strictures incurred following ureteroscopy for stone disease can be severe, with a low success rate of endoscopic management and a high procedural burden that may lead to nephrectomy. Further studies that assess specific technical risk factors for ureteral stricture following URS are needed.

National Imaging Trends after Ureteroscopic or Shock Wave Lithotripsy for Nephrolithiasis.

PURPOSE: The study of diagnostic imaging after procedural intervention for nephrolithiasis is limited. We sought to characterize actual national imaging patterns and longitudinal trends after ureteroscopic or shock wave lithotripsy. MATERIALS AND METHODS: We analyzed the MarketScan® database and identified a nationally representative sample of insured, employed patients, 17 to 64 years old who underwent ureteroscopic or shock wave lithotripsy for nephrolithiasis between 2007 and 2014. Patients were excluded from study if they lacked at least 1 year of postoperative database enrollment or underwent a repeat nephrolithiasis procedure of any type within 90 days after the initial procedure. We identified and tracked postoperative imaging modalities by medical billing codes. RESULTS: We identified 101,554 patients treated with ureteroscopy, of whom 55% and 39% underwent no postoperative imaging within 3 and 12 months, respectively. Of the 101,590 patients treated with shock wave lithotripsy 23% and 16% underwent no postoperative imaging within 3 and 12 months, respectively. Abdominal x-ray was the most common imaging modality after either procedure type. Ultrasound use increased with time while computerized tomography decreased. In about 25% of ureteroscopy and shock wave lithotripsy cases at least 1 postoperative computerized tomography was done within a year. Female gender and older age were associated with higher imaging rates. Ultrasound was more commonly performed in the northeast region and in more densely populated areas. CONCLUSIONS: A notable portion of patients treated with ureteroscopy and a smaller percent treated with shock wave lithotripsy do not undergo any followup imaging within 1 year. In the majority who undergo imaging abdominal x-ray is done, precluding the ability to screen for hydronephrosis or silent obstruction in almost 75% of patients treated with ureteroscopy.

Quantification of Renal Stone Contrast with Ultrasound in Human Subjects.

PURPOSE: Greater visual contrast between calculi and tissue would improve ultrasound (US) imaging of urolithiasis and potentially expand clinical use. The color Doppler twinkling artifact has been suggested to provide enhanced contrast of stones compared with brightness mode (B-mode) imaging, but results are variable. This work provides the first quantitative measure of stone contrast in humans for B-mode and color Doppler mode, forming the basis to improve US for the detection of stones. MATERIALS AND METHODS: Using a research ultrasound system, B-mode imaging was tuned for detecting stones by applying a single transmit angle and reduced signal compression. Stone twinkling with color Doppler was tuned by using low-frequency transmit pulses, longer pulse durations, and a high-pulse repetition frequency. Data were captured from 32 subjects, with 297 B-mode and Doppler images analyzed from 21 subjects exhibiting twinkling signals. The signal to clutter ratio (i.e., stone to background tissue) (SCR) was used to compare the contrast of a stone on B-mode with color Doppler, and the contrast between stone twinkling and blood-flow signals within the kidney. RESULTS: The stone was the brightest object in only 54% of B-mode images and 100% of Doppler images containing stone twinkling. On average, stones were isoechoic with the tissue clutter on B-mode (SCR = 0 dB). Stone twinkling averaged 37 times greater contrast than B-mode (16 dB, p < 0.0001) and 3.5 times greater contrast than blood-flow signals (5.5 dB, p = 0.088). CONCLUSIONS: This study provides the first quantitative measure of US stone to tissue contrast in humans. Stone twinkling contrast is significantly greater than the contrast of a stone on B-mode. There was also a trend of stone twinkling signals having greater contrast than blood-flow signals in the kidney. Dedicated optimization of B-mode and color Doppler stone imaging could improve US detection of stones.

Detection and Evaluation of Renal Injury in Burst Wave Lithotripsy Using Ultrasound and Magnetic Resonance Imaging.

PURPOSE: Burst wave lithotripsy (BWL) is a transcutaneous technique with potential to safely and effectively fragment renal stones. Preclinical investigations of BWL require the assessment of potential renal injury. This study evaluates the capabilities of real-time ultrasound and MRI to detect and evaluate BWL injury that was induced in porcine kidneys. MATERIALS AND METHODS: Ten kidneys from five female farm pigs were treated with either a 170 or 335 kHz BWL transducer using variable treatment parameters and monitored in real-time with ultrasound. Eight kidneys were perfusion fixed and scanned with a 3-Tesla MRI scanner (T1-weighted, T2-weighted, and susceptibility-weighted imaging), followed by processing via an established histomorphometric technique for injury quantification. In addition, two kidneys were separately evaluated for histologic characterization of injury quality. RESULTS: Observed B-mode hyperechoes on ultrasound consistent with cavitation predicted the presence of BWL-induced renal injury with a sensitivity and specificity of 100% in comparison to the histomorphometric technique. Similarly, MRI detected renal injury with a sensitivity of 90% and specificity of 100% and was able to identify the scale of lesion volumes. The injuries purposefully generated with BWL were histologically similar to those formed by shock wave lithotripsy. CONCLUSIONS: BWL-induced renal injury can be detected with a high degree of sensitivity and specificity by real-time ultrasound and post-treatment ex vivo MRI. No injury occurred in this study without cavitation detected on ultrasound. Such capabilities for injury detection and lesion volume quantification on MRI can be used for preclinical testing of BWL.

Stone-Mode Ultrasound for Determining Renal Stone Size.

PURPOSE: The purpose of this study was to measure the accuracy of stone-specific algorithms (S-mode) and the posterior acoustic shadow for determining kidney stone size with ultrasound (US) in vivo. MATERIALS AND METHODS: Thirty-four subjects with 115 renal stones were prospectively recruited and scanned with S-mode on a research US system. S-mode is gray-scale US adjusted to enhanced stone contrast and resolution by minimizing compression and averaging, and increasing line density and frequency. Stone and shadow width were compared with a recent CT scan and, in 5 subjects with 18 stones, S-mode was compared with a clinical US system. RESULTS: Overall, 84% of stones identified on CT were detected on S-mode and 66% of these shadowed. Seventy-three percent of the stone measurements and 85% of the shadow measurements were within 2 mm of the size on CT. A posterior acoustic shadow was present in 89% of stones over 5 mm versus 53% of stones under 5 mm. S-mode visualized 78% of stones, versus 61% for the clinical system. S-mode stone and shadow measurements differed from CT by 1.6 ± 1.0 mm and 0.8 ± 0.6 mm, respectively, compared with 2.0 ± 1.5 mm and 1.6 ± 1.0 mm for the clinical system. CONCLUSIONS: S-mode offers improved visualization and sizing of renal stones. With S-mode, sizing of the stone itself and the posterior acoustic shadow were similarly accurate. Stones that do not shadow are most likely <5 mm and small enough to pass spontaneously.

Ultrasonic propulsion of kidney stones.

PURPOSE OF REVIEW: Ultrasonic propulsion is a novel technique that uses short bursts of focused ultrasonic pulses to reposition stones transcutaneously within the renal collecting system and ureter. The purpose of this review is to discuss the initial testing of effectiveness and safety, directions for refinement of technique and technology, and opinions on clinical application. RECENT FINDINGS: Preclinical studies with a range of probes, interfaces, and outputs have demonstrated feasibility and consistent safety of ultrasonic propulsion with room for increased outputs and refinement toward specific applications. Ultrasonic propulsion was used painlessly and without adverse events to reposition stones in 14 of 15 human study participants without restrictions on patient size, stone size, or stone location. The initial feasibility study showed applicability in a range of clinically relevant situations, including facilitating passage of residual fragments following ureteroscopy or shock wave lithotripsy, moving a large stone at the ureteropelvic junction with relief of pain, and differentiating large stones from a collection of small fragments. SUMMARY: Ultrasonic propulsion shows promise as an office-based system for transcutaneously repositioning kidney stones. Potential applications include facilitating expulsion of residual fragments following ureteroscopy or shock wave lithotripsy, repositioning stones prior to treatment, and repositioning obstructing ureteropelvic junction stones into the kidney to alleviate acute renal colic.