Radiological Density, Atomic Numbers, and Stone Fragmentation of Bego Stones Used for Research in Endourology: Comparison to Real Urinary Stones.

Objective: The aim of the study was to characterize artificial stones used for research in endourology in terms of radiological properties and hardness, based on stone fragmentation, and to compare them with real stones. Materials and Methods: We built artificial stones using BegoStone Plus™ powder (BEGO, Lincoln, RI), with powder (g)-water (mL) ratios ranging from 15:03 to 15:12. The CT Gemstone Spectral Imaging Software® (GE Medical Systems, LLC, Waukesha, WI) was used to evaluate the radiological density in HU and spectral properties. Stone fragmentation was assessed in an in vitro experimental setting. These properties of artificial stones were compared with real urinary calculi. Results: Regarding radiological density in terms of HUs, 15:03 artificial calculi showed similar results when compared with real stones comprising calcium oxalate and calcium phosphate. The 15:03 and 15:04 artificial stones showed similar spectral property results to calcium pyrophosphate stones. The 15:11 artificial stones showed similar stone fragmentation results to real stones comprising uric acid, and 15:03 artificial calculi showed similar results to apatite and cystine stones. Conclusions: Artificial stones are useful for research in endourology. Stones with a powder (g)-water (mL) ratio of 15:03 proved to mimic real hard stones in terms of HUs, atomic number, and stone fragmentation in our study and could be used as artificial hard stones, and 15:11 stones showed similar stone fragmentation to uric acid stones. Our study might suggest that standard Bego stones are useful to investigate different areas in endourology, but not radiological properties because radiological homogeneity is not ensured unless more sophisticated mixing methods are used.

Correlation of the Degree of Hydronephrosis and Computed Tomography Value of Calculi with Efficacy of Ureteroscopic Lithotripsy in Patients with Upper Urinary Tract Infectious Calculi.

OBJECTIVE: The correlation of the degree of hydronephrosis and computed tomography (CT) value of calculi with the efficacy of ureteroscopic lithotripsy (URSL) in patients with upper urinary tract infectious calculi was explored. METHODS: The clinical data of 152 patients with upper urinary tract infectious calculi and on URSL in Shanghai Baoshan District Wusong Central Hospital from November 2019 to November 2021 were collected for retrospective analysis. All patients received CT examination before surgery. According to the therapeutic effect of URSL, all patients were divided into the non-calculi group (NCG, n = 101) and residual calculi group (RCG, n = 51), which were compared in terms of the degree of hydronephrosis and CT value of calculi. Then, the correlation of the degree of hydronephrosis and CT value of calculi with the efficacy of URSL in patients was analysed. RESULTS: No significant difference in clinical data was found between the groups (p > 0.05). Patients in the NCG group had lower degree of hydronephrosis than those in the RCG group (p < 0.05), and the NCG had lower CT value of calculi (p < 0.001). Spearman rank correlation analysis showed that the degree of hydronephrosis in patients with upper urinary tract infectious calculi was negatively correlated with the efficacy of URSL (r = -0.676, p < 0.001), and the CT value of calculi in such patients was negatively correlated with the efficacy of URSL (r = -0.795, p < 0.001). CONCLUSIONS: The degree of hydronephrosis and CT value of calculi were negatively correlated with the efficacy of URSL. Both can be used to predict clinical efficacy and have clinical guiding value for the formulation of treatment plans in patients with urinary tract infectious calculi.

The most common types of uroliths larger than 1 mm are readily visible and accurately measured in an in vitro setting mimicking the canine abdomen using digital radiography.

Abdominal radiography is an important diagnostic to detect uroliths. Cystine and urate uroliths were historically characterized as nonmineral opaque on survey radiographs. However, recent research and clinical observations indicate that pure urate and cystine uroliths may be detected with digital radiography. The primary purpose of this prospective, in vitro, diagnostic accuracy study was to determine the sensitivity of digital radiography in detecting cystoliths of varying size and composition. Forty canine uroliths of pure composition (10 each of calcium oxalate, struvite, cystine, and urate), acquired from Minnesota Urolith Center and ranging from 1 to 10 mm, were placed in phantoms of three various sizes and radiographed. The radiographs, including three sets of each urolith separately, were evaluated by three blinded radiologists on two separate occasions. Evaluation included presence or absence of urolith, number of uroliths, and maximum diameter of the urolith(s). For all four types of uroliths and all readers, the specificity and PPV were 100% with an associated very high sensitivity (94.4%-98.9%) and NPV (94.8%-98.9%). Calcium oxalate uroliths were the most accurately measured and struvite were the least accurately measured when compared with the gross measurement. Smaller uroliths were more accurately measured than larger uroliths. Uroliths placed in smaller bladder phantoms were more accurately measured than in larger bladder phantoms. Though accurate measurement of uroliths is complicated by and dependent on numerous variables, our results reveal that urate and cystine uroliths are visualized on digital radiography making them a relevant differential diagnosis when seen clinically.

Use of dual energy CT urography in evaluation of urinary stone and complex cyst.

BACKGROUND: Dual-energy computed tomography scans can provide significant benefits to the urinary system. The aim of this study is to determine the limitations and benefits of using dual energy CT urography in patients with urinary system stones and cysts. METHODS: In the analysis of the images, the virtual noncontrasted images obtained from the combined nephrogenicexcretory phase and the true noncontrasted images were evaluated. The true noncontrast images were accepted as the gold standard for stone detection. RESULTS: Eighty-three different stones were detected in 26 of the 115 patients included in the study. Sensibilities of virtual noncontrast images in detecting urinary system stones were 66.7% and 65.4% according to the first and second radiologists, respectively. In this study, 32 hyperdense cysts were detected. According to iodine map images, there was no enhancement in 26 of 32 cysts; only 5 cysts showed minimal contrast enhancement. One patient could not decide on contrast enhancement. DISCUSSION: As a result, if CT urography is performed with dual energy, it can provide additional information in patients with urinary system disorder.

Ultrasound-guided mini-percutaneous nephrolithotomy in the treatment of upper urinary tract stones in children: A single-center evaluation.

To evaluate the safety and efficacy of ultrasound-guided mini-percutaneous nephrolithotomy (mini-perc) for the treatment of upper urinary tract stones in children. We reviewed the records of 70 children with upper urinary tract stones who were treated with a mini-perc technique between July 2015 and April 2020. All puncture site selections and tract dilations were determined by Doppler ultrasonography. Patient age, height, weight, stone size, operation time, stone-free rate (SFR), postoperative complications, tubeless rate, and length of hospital stay (LOS) were recorded. Stone components were analysed using infrared spectroscopy. A total of 47 boys and 23 girls were included. Median weight and height of the patients were 18.5 kg and 110 cm, respectively. Median stone diameter was 2.0 cm. Median time to establish access was 4.0 min and median operation time was 25 min. Patients had median preoperative and postoperative haemoglobin levels of 121 and 113.5 g/L, median haemoglobin levels dropped to 8.0 g/L the day after surgery. No patient needed a blood transfusion. Eight children (11.4%) developed significant complications, including four cases with Clavien Grade I, one with Clavien Grade II, and three with Clavien Grade Ⅲ complications. One-day and 1-month follow-ups revealed a complete SFR of 95.7% (67/70) and 97.1% (68/70), respectively. Fifty-six patients (80.0%) did not require catheters of any type (total tubeless). Median LOS was 2.0 days. Ultrasound-guided mini-perc is safe and effective. The mini-perc technique is a feasible alternative for paediatric stone disease that does not result in major complications.

Thermoluminescence Dosimetry in Abdominal CT for Urinary Stone Detection: Effective Radiation Dose Reduction With Tin Prefiltration at 100 kVp.

OBJECTIVES: Spectral shaping via tin prefiltration has gained recognition for dose saving in high-contrast imaging tasks. The aim of this phantom dosimetry study was to investigate whether the use of tin filters can also reduce the effective radiation dose in 100 kVp abdominal computed tomography (CT) compared with standard low-dose scans for suspected urolithiasis. METHODS: Using a third-generation dual-source CT scanner, 4 scan protocols each were used on a standard (P1-P4) and a modified obese Alderson-Rando phantom (P5-P8), in which 11 urinary stones of different compositions were placed. Hereby 1 scan protocol represented standard low-dose settings (P1/P5: 110 kVp/120 kVp), whereas 3 experimental protocols used low-kilovoltage spectral shaping (P2/P3/P4 and P6/P7/P8: 100 kVp with tin prefiltration). Radiation dose was recorded by thermoluminescent dosimeters at 24 measurement sites. For objective assessment of image quality, dose-weighted contrast-to-noise ratios were calculated and compared between scan protocols. Additional subjective image quality analysis was performed by 2 radiologists using equidistant 5-point scales for estimation image noise, artifacts, kidney stone detectability, and delineation of bone and soft tissue. RESULTS: Both conventional low-dose protocols without tin prefiltration were associated with the highest individual equivalent doses and the highest effective radiation dose in the experimental setup (P1: 0.29-6.43 mGy, 1.45-1.83 mSv; P5: 0.50-9.35 mGy, 2.33-2.79 mSv). With no false-positive diagnoses, both readers correctly detected each of the 11 urinary calculi irrespective of scan protocol and phantom configuration. Protocols using spectral shaping via tin prefiltration allowed for effective radiation dose reduction of up to 38% on the standard phantom and 18% on the modified obese phantom, while maintaining overall diagnostic image quality. Effective dose was approximately 10% lower in a male versus female anatomy and could be reduced by another 10% if gonadal protection was used ( P < 0.001). CONCLUSIONS: Spectral shaping via tin prefiltration at 100 kVp is a suitable means to reduce the effective radiation dose in abdominal CT imaging of patients with suspected urolithiasis. The dose reduction potential is slightly less pronounced in a modified phantom emulating an obese body composition compared with a standard phantom.

Computed Tomography Radiation Exposure among Urinary Tract Stone Patients at Tikur Anbessa Specialized Hospital: A Retrospective Study.

Background: National and multinational surveys indicate large variability of Computed Tomography urinary tract Stone doses. The wide use of abdominopelvic Computed Tomography in the diagnosis, raised the issue of radiation exposure. Hence, this study was conducted to assess Computed Tomography radiation exposure of urinary tract Stone Patients there by, to compare the results from established reference values and other published studies. Methods: A retrospective cross-sectional was done on 100 urinary tract Stone patients who have at least one computed tomography scan as part of their follow-up or for diagnosis purposes from February 1 to May 31, 2021, at Tikur Anbesa Specialized Hospital. Data were collected using a structured questionnaire format that evaluates the number of Computed Tomography they had, scan parameters, dose indicators, and socio-demographic characteristics. Finally, the collected data were analyzed using statistical software SPSS version 22. Results: Out of 100 patients 3.6%of our patients have radiation exposure of more than 4mSv, which is the standard for low-dose Computed Tomography. The median radiation exposure is 1.27mSv per scan. Exposure factors like tube current, tube current products, dose length product, and scan range all have similar values with an almost null interquartile range. All the scans that overpassed the low dose threshold(4mSv) were done outside Tikur Anbesa Specialized Hospital. Conclusion: Our study showed that Tikur Anbesa Specialized Hospital's low-dose CT protocol for patients with urinary tract Stone is well optimized as opposed to non- Tikur Anbesa Specialized Hospital.

Comparison of radiographic methods for detecting radiolucent uroliths in dogs.

The purpose of this study was to evaluate and compare positive cystography techniques at 5%, 10%, and 20%, as well as three different double-contrast protocols for detecting radiolucent uroliths with a diameter of less than 3.0 mm in dogs. Six cadavers were used, one was selected at random to represent the negative control, and the others were submitted to urolith implantation in the bladder by urethral catheter. Three radiology professionals blindly accessed ventrodorsal and -lateral projections of each test. Contrast at 20% showed greater diagnostic sensitivity, but with greater difficulty identifying the number and size of the uroliths. Consequently, double-contrast techniques are better and should be used for diagnostic and therapeutic planning. Sensitivity and specificity tests demonstrated that positive 5% cystography and different concentrations of double contrast obtained better results in terms of sensitivity and specificity. However, due to the presence of a greater amount of artifacts in the 5% cystography, it is suggested that double contrast is used for this purpose, especially with the removal of contrast excess (protocol 2).

Computed tomographic assessment of retrograde urohydropropulsion in male dogs and prediction of stone composition using Hounsfield unit in dogs and cats.

BACKGROUND: Persistent uroliths after a cystotomy in dogs are a common cause of surgical failure. OBJECTIVES: This study examined the following: the success rate of retrograde urohydropropulsion in male dogs using non-enhanced computed tomography (CT), whether the CT mean beam attenuation values in Hounsfield Units (mHU) measured in vivo could predict the urolithiasis composition and whether the selected reconstruction kernel may influence the measured mHU. METHODS: All dogs and cats that presented with lower urinary tract uroliths and had a non-enhanced CT preceding surgery were included. In male dogs, CT was performed after retrograde urohydropropulsion to detect the remaining urethral calculi. The percentage and location of persistent calculi were recorded. The images were reconstructed using three kernels, from smooth to ultrasharp, and the calculi mHU were measured. RESULTS: Sixty-five patients were included in the study. The success rate of retrograde urohydropropulsion in the 45 male dogs was 55.6% and 86.7% at the first and second attempts, respectively. The predominant components of the calculi were cystine (20), struvite (15), calcium oxalate (8), and urate (7). The convolution kernel influenced the mHU values (p < 0.05). The difference in mHU regarding the calculus composition was better assessed using the smoother kernel. A mHU greater than 1,000 HU was predictive of calcium oxalate calculi. CONCLUSIONS: Non-enhanced CT is useful for controlling the success of retrograde urohydropropulsion. The mHU could allow a prediction of the calculus composition, particularly for calcium oxalate, which may help determine the therapeutic strategy.

Silica Urinary Stones: A Case Report and A Brief Review of Literature.

Silicate stones are extraordinarily rare in human beings, but when present, they are often associated with ingestion of Magnesium Trisilicate, an antacid medication. However, there have been few case reports of patients who developed silicate stones, without ingestion of Magnesium Trisilicate. Hereby, we present the case of a 67-year-old man who developed acute kidney injury due to obstructive uropathy, detected during his scheduled chemotherapy for his relapsing multiple myeloma. Abdominal ultrasound and CT scan imaging demonstrated multiple non-mobile calcifications in the bladder neck/prostate bed. Stone analysis showed a material resembling silica. This case with silicate urinary tract stone highlights this extra-rare urinary stone in a patient without any identified source of silicate.  DOI: 10.52547/ijkd.7044.

Clinicopathologic findings and urolith composition for green iguanas (Iguana iguana) with urolithiasis: 21 cases and 132 stones (1996-2020).

OBJECTIVE: To document the clinical signs, diagnosis, and treatment of urolithiasis in green iguanas (Iguana iguana) and to report on the composition of uroliths from green iguanas submitted to the Minnesota Urolith Center for analysis. ANIMALS: 21 green iguanas with urolithiasis. PROCEDURES: Medical record databases of multiple veterinary teaching hospitals were searched from 1996 through 2020. Emails were sent to all facilities that submitted a urolith from a green iguana to the Minnesota Urolith Center from 1996 through 2020. Signalment; presenting complaint; physical examination findings; hematologic, biochemical, and diagnostic imaging findings; treatment; necropsy results; and survival times were described for each patient. RESULTS: Iguanas most commonly presented with nonspecific clinical signs, but 9 of the 21 iguanas had clinical signs associated with the urogenital tract. Twelve iguanas had a palpable mass in the caudal coelom. All uroliths were visible on radiographs. Surgery was performed on 15 iguanas; 3 died secondary to intra- or postoperative complications. Iguanas that underwent surgery had a median survival time of 39 months. Necropsy was performed on 5 iguanas, and urolithiasis contributed to the decision to euthanize or was the cause of death for 4. Uroliths from 132 iguanas were analyzed, and all were composed of 100% uric acid salts. CLINICAL RELEVANCE: Green iguanas with urolithiasis may not have clinical signs or physical examination findings associated with the urinary system, and hematologic and biochemical abnormalities are nonspecific. Green iguanas should be routinely examined for uroliths, and surgical treatment should be pursued.

Analysis of the Application Value of X-Ray Digital Tomographic Fusion Technique in Urinary System Diseases.

OBJECTIVE: To explore the application value of the X-ray digital tomographic fusion technique in the diagnosis of urinary system diseases. METHODS: 500 patients with suspected urinary diseases in our hospital were examined by three methods: X-ray digital tomographic fusion imaging (DTS), intravenous pyelography (IVP), and abdominal plain film (KUB), and the image quality before and after tomographic fusion was objectively evaluated. The image quality could be divided into three grades: excellent, good, and poor. RESULTS: The image excellent rate of DTS (88%) was higher than that of IVP (27.5%). The sensitivity of DTS in the diagnosis of renal cyst and space occupying of the bladder was higher than that of IVP (P < 0.05). The accuracy rate of DTS in the diagnosis of urinary calculi was 93.33%, higher than 63.3% of KUB (P < 0.001). The accuracy rate of DTS in the diagnosis of ureteral stricture was 90%, higher than 65% of IVP (P=0.03). The accuracy of DTS in the diagnosis of hydronephrosis was higher than that of IVP and KUB (P < 0.05). CONCLUSION: In the examination of urinary system-related diseases, high-definition images can be obtained by timely using sectional fusion technology. Compared with conventional IVP, space occupying lesions such as the bladder and kidney can be displayed more clearly with the help of the tomographic fusion technique, which is helpful to improve the possibility of finding lesions and is of great significance in clinical application.

In Vivo Comparison of Radiation Exposure in Third-Generation vs Second-Generation Dual-Source Dual-Energy CT for Imaging Urinary Calculi.

Purpose: To investigate the potential for decreasing radiation dose when utilizing a third-generation vs second-generation dual-source dual-energy CT (dsDECT) scanner, while maintaining diagnostic image quality and acceptable image noise. Materials and Methods: Retrospective analysis of patients who underwent dsDECT for clinical suspicion of urolithiasis from October 2, 2017, to September 5, 2018. Patient demographics, body mass index, abdominal diameter, scanning parameters, and CT dose index volume (CTDIvol) were recorded. Image quality was assessed by measuring the attenuation and standard deviation (SD) regions of interest in the aorta and in the bladder. Image noise was determined by averaging the SD at both levels. Patients were excluded if they had not undergone both third- and second-generation dual-energy CT (DECT), time between DECT was more than 2 years, or scan parameters were outside the standard protocol. Results: A total of 117 patients met the inclusion criteria. Examinations performed on a third-generation DECT had an average CTDIvol 12.3 mGy, while examinations performed on a second-generation DECT had an average CTDIvol 13.3 mGy (p < 0.001). Average image noise was significantly lower for the third-generation DECT (SD = 10.3) compared with the second-generation DECT (SD = 13.9) (p < 0.001). Conclusions: The third-generation dsDECT scanners can simultaneously decrease patient radiation dose and decrease image noise compared with second-generation DECT. These reductions in radiation exposure can be particularly important in patients with urinary stone disease who often require repeated imaging to evaluate for stone development and recurrence as well as treatment assessment.

Revolution spectral CT for urinary stone with a single/mixed composition in vivo: a large sample analysis.

PURPOSE: To analyze various compositions of urinary stones using revolution spectral CT (rapid kV switching dual-energy CT) in vivo. METHODS: 202 patients with urinary stones underwent spectral CT before surgery. Zeff peak, overall scope and CT values were detected. Moreover, water/iodine attenuating material images were obtained. Removed stones were subjected to infrared spectroscopy after surgery. The results of infrared spectroscopy were compared with CT. RESULTS: 28 stones (14.08%) with single composition, 165 stones with two mixed compositions (81.68%), and 9 stones with three mixed compositions (4.46%) were observed. When Zeff peaks of stones with single/mixed compositions were summarized together, 146 peaks of calcium oxalate monohydrate, 119 peaks of calcium oxalate dihydrate, 55 peaks of carbapatite, 38 peaks of urate, 16 peaks of struvite, and 11 peaks of brushite were totally observed. 93.8% of calcium oxalate monohydrate had Zeff peaks between 13.3 and 14.0. 91.6% of calcium oxalate dihydrate had peaks between 12.0 and 13.3. For carbapatite, 90.9% of stones had peaks from 14.0 to 15.0. A total of 94.8% of urate had peaks between 7.0 and 11.0. 93.8% of struvite had peaks between 11.0 and 13.0, and 90.9% of brushite had peaks between 12.0 and 14.0. Moreover, densities of urate, struvite and brushite were low density in iodine-based images and high-density in water-based images. CONCLUSION: The in-vivo analysis of spectral CT in urinary stone revealed characteristics of different compositions, especially mixed compositions. An in-vivo predictive model may be constructed to distinguish stone compositions.

[Urinary stone imaging tests.] / Diagnóstico por imagen de la litiasis urinaria.

Imaging in urolithiasis has a wide group of techniques, with different characteristics, limitations, and indications, which together allow the management of this prevalent pathology. Plain abdominal radiography and ultrasound are very accessible and in expensive techniques that combined present an acceptable sensitivity and specificity. They are widely used for monitoring the evolution of stone disease and for evaluation after treatments (surgery or SWL). Ultrasound is the primary radiological diagnostic tool in the pediatric population and in pregnant women. CT has prevailed over IVP in the anatomical assessment of the urinary tract and the description of the characteristics of the lithiasis, although it shows a greater exposure to ionizing radiation, so the use of low and ultra-low dose CT is spreading. In this article we also discuss other imaging techniques suchas Digital to mosynthesis, Fluoroscopy and DMSA Scintigraphy.

El diagnóstico por imagen de la urolitiasis comprende un amplio grupo de técnicas, con diferentes características, limitaciones e indicaciones, que en su conjunto permiten el manejo de esta patología tan prevalente. La radiografía simple de abdomen y la ecografía son técnicas muy accesibles y económicasque combinadas presentan una aceptable sensibilidad y especificidad. Siendo ampliamente utilizadas para el seguimiento de la evolución de la enfermedad litiásica y para la valoración tras tratamientos (cirugía o LEOC). La ecografía es la técnica de elección en la población pediátrica y en gestantes. El TC se ha impuesto sobre la UIV en la valoración anatómica de la vía urinaria y la descripción de las características de la litiasis,  aunque presenta una mayor exposición a radiaciones ionizantes, por lo que se está extendiendo el uso del TC de baja y ultrabaja dosis. Tratamos también en este artículo otras técnicas como la Tomosíntesis digital, la Fluoroscopiay la Gammagrafía DMSA.

Virtual Unenhanced Dual-Energy CT Images Obtained with a Multimaterial Decomposition Algorithm: Diagnostic Value for Renal Mass and Urinary Stone Evaluation.

Background Virtual unenhanced (VUE) images obtained by using a dual-energy CT (DECT) multimaterial decomposition algorithm hold promise for diagnostic use in the abdomen in lieu of true unenhanced (TUE) images. Purpose To assess VUE images obtained from a DECT multimaterial decomposition algorithm in patients undergoing renal mass and urinary stone evaluation. Materials and Methods In this retrospective Health Insurance Portability and Accountability Act-compliant study, DECT was performed in patients undergoing evaluation for renal mass or urinary stone. VUE images were compared quantitatively to TUE images and qualitatively assessed by four independent radiologists. Differences in attenuation between VUE and TUE images were summarized by using 95% limits of agreement. Diagnostic performance in urinary stone detection was summarized by using area under the receiver operating characteristic curve, sensitivity, and specificity. Results A total of 221 patients (mean age ± standard deviation, 61 years ± 14; 129 men) with 273 renal masses were evaluated. Differences in renal mass attenuation between VUE and TUE images were within 3 HU for both enhancing masses (95% limits of agreement, -3.1 HU to 2.7 HU) and nonenhancing cysts (95% limits of agreement, -2.9 HU to 2.5 HU). Renal mass classification as enhancing mass versus nonenhancing cyst did not change (reclassification rate of enhancing masses, 0% [0 of 78]; 95% CI: 0, 5; reclassification rate of nonenhancing cysts, 0% [0 of 193]; 95% CI: 0, 2) with use of VUE in lieu of TUE images. Among 166 urinary stones evaluated, diagnostic performance of VUE images for stone detection was lower compared with that of TUE images (area under the receiver operating characteristic curve, 0.79 [95% CI: 0.73, 0.84] vs 0.93 [95% CI: 0.91, 0.95]; P < .001) due to reduced sensitivity of VUE for detection of stones 3 mm in diameter or less compared with those greater than 3 mm (sensitivity, 23% [25 of 108; 95% CI: 12, 40] vs 88% [126 of 144; 95% CI: 77, 94]; P < .001). Conclusion Compared with true unenhanced images, virtual unenhanced (VUE) images were unlikely to change renal mass classification as enhancing mass versus nonenhancing cyst. Diagnostic performance of VUE images remained suboptimal for urinary stone detection due to subtraction of stones 3 mm or less in diameter. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Sosna in this issue.

Tubeless percutaneous nephrolithotomy (PCNL) for forgotten and retained stent in renal allograft recipient: an interesting case report and lessons learnt.

Complications after renal allograft transplantation are not so uncommon. Most complications are related to graft rejection, immune-suppressive drug toxicity and the operative procedure. Stents are placed after a transplant to prevent urine leak at the site of ureteric reimplantation, to facilitate an early healing in immune-suppressed individuals and to prevent obstruction at the site of ureteral anastomosis. We report a case of a renal allograft recipient with a forgotten ureteral double J stent. where the stent remained in situ for more than 4 years and further complicated by encrustation and stone formation at both the bladder and renal pelvic ends. The stone over the bladder coil was removed by holmium laser cystolithotripsy while the encrusted renal pelvic coil was removed by percutaneous approach. This case is presented for its rarity and also to emphasise on the need for maintenance of a stent register in order to ensure avoidance of such preventable complications.

Non-contrast computed tomography characteristics in a large cohort of cystinuria patients.

PURPOSE: Cystine stones are widely considered hard and difficult to treat. Hounsfield Units (HU) are used in other stone types to estimate 'hardness' and treatments based on that finding. Our objective was to report mean HU of cystine stones in vivo in a large case series of cystinuria patients and assess for differences in genotype. METHODS: A prospective case series of cystinuria patients referred to a specialist centre was analysed. CT imaging was assessed by two independent radiologists to determine in vivo attenuation of cystine calculi. Mean HU was compared for both cystinuria genes (SLC3A1 and SLC7A9) using an independent t-test. RESULTS: 164 adult cystinuric patients were identified (55% male), median age 43 years (range 18-80). Median follow up was 31 months (IQR 10-62). Genetic data available for 153/164 (93%) demonstrated 97 SLC3A1 (63%) and 55 (36%) SLC7A9 mutations (39 homozygous, 16 heterozygous) and one heterozygous for both SLC3A1/SLC7A9. 107 patients had CT images available demonstrating calculi. Median HU across the cohort was 633 (5th to 95th centile 328-780). There was no difference in mean HU between SLC3A1 and SLC7A9 genotypes (p = 0.68) or homo and heterozygous SLC7A9 (p = 0.70). Mean HU correlated with stone size (Pearson correlation coefficient = 0.51, p < 0.001). CONCLUSION: In this large single centre cystinuria cohort, mean HU was low for stones that are difficult to treat. Calculi of < 800 HU should prompt consideration of a cystinuria diagnosis. Attenuation was not associated with genotype, and distinct 'smooth' and 'rough' stones were not observed. Calculi with HU > 1000 are unlikely pure cystine, and in a known cystinuric would suggest conversion to another stone type.

Fluoroless versus conventional ureteroscopy for urinary stones: a systematic review and meta-analysis.

INTRODUCTION: The aim of this review was to comprehensively assess the effectiveness and safety of fluoroless ureteroscopy (URS) vs. conventional URS for urinary stones. EVIDENCE ACQUISITION: An exhaustive search on PubMed, EMBASE, Web of Science and Cochrane Library were performed to find eligible research before May 2020. Result parameters including stone-free rate (SFR), operation time, repeat procedure rate and complication rate were assessed using RevMan 5.3 (Cochrane Training; https://training.cochrane.org/online-learning/core-software-cochrane-reviews/revman/revman-5-download). EVIDENCE SYNTHESIS: Seven studies (5 retrospective studies and 2 prospective randomized controlled trials) involving 1404 individuals were included. Pooled results demonstrated that the operation time in fluoroless URS group was slightly longer than conventional URS group (weighted mean difference [MD]=2.79, P=0.0001), but no statistically significant differences regarding SFR (odds ratio [OR]=1.18, P=0.57), repeat procedure rate (OR=1.32, P=0.52), and total complication rate (OR=0.75, P=0.16) were observed between two techniques. CONCLUSIONS: Flourless URS is equally safe and effective to conventional URS procedure with zero radiation exposure. However, it needs to be cautiously conducted in selected patients and fluoroscopy equipment should always be available intraoperatively.

Artificial intelligence in the diagnosis, treatment and prevention of urinary stones.

PURPOSE OF REVIEW: There has a been rapid progress in the use of artificial intelligence in all aspects of healthcare, and in urology, this is particularly astute in the overall management of urolithiasis. This article reviews advances in the use of artificial intelligence for the diagnosis, treatment and prevention of urinary stone disease over the last 2 years. Pertinent studies were identified via a nonsystematic review of the literature performed using MEDLINE and the Cochrane database. RECENT FINDINGS: Twelve articles have been published, which met the inclusion criteria. This included three articles in the detection and diagnosis of stones, six in the prediction of postprocedural outcomes including percutaneous nephrolithotomy and shock wave lithotripsy, and three in the use of artificial intelligence in prevention of stone disease by predicting patients at risk of stones, detecting the stone type via digital photographs and detecting risk factors in patients most at risk of not attending outpatient appointments. SUMMARY: Our knowledge of artificial intelligence in urology has greatly advanced in the last 2 years. Its role currently is to aid the endourologist as opposed to replacing them. However, the ability of artificial intelligence to efficiently process vast quantities of data, in combination with the shift towards electronic patient records provides increasingly more 'big data' sets. This will allow artificial intelligence to analyse and detect novel diagnostic and treatment patterns in the future.