Advancements in Uric Acid Stone Detection: Integrating Deep Learning with CT Imaging and Clinical Assessments in the Upper Urinary Tract.

INTRODUCTION: Among upper urinary tract stones, a significant proportion comprises uric acid stones. The aim of this study was to use machine learning techniques to analyze CT scans and blood and urine test data, with the aim of establishing multiple predictive models that can accurately identify uric acid stones. METHODS: We divided 276 patients with upper urinary tract stones into two groups: 48 with uric acid stones and 228 with other types, identified using Fourier-transform infrared spectroscopy. To distinguish the stone types, we created three types of deep learning models and extensively compared their classification performance. RESULTS: Among the three major types of models, considering accuracy, sensitivity, and recall, CLNC-LR, IMG-support vector machine (SVM), and FUS-SVM perform the best. The accuracy and F1 score for the three models were as follows: CLNC-LR (82.14%, 0.7813), IMG-SVM (89.29%, 0.89), and FUS-SVM (29.29%, 0.8818). The area under the curves for classes CLNC-LR, IMG-SVM, and FUS-SVM were 0.97, 0.96, and 0.99, respectively. CONCLUSION: This study shows the feasibility of utilizing deep learning to assess whether urinary tract stones are uric acid stones through CT scans, blood, and urine tests. It can serve as a supplementary tool for traditional stone composition analysis, offering decision support for urologists and enhancing the effectiveness of diagnosis and treatment.

Patients' poor performance status is an independent risk factor for urosepsis induced by kidney and ureteral stones.

This study was aimed to identify the risk factors for urosepsis caused by kidney and ureteral stones. One hundred and nine patients who had kidney or ureteral stones and who were treated with trans-ureteral lithotripsy (TUL) at our institution from 2016 to 2020 were included. We investigated the risk factors for urosepsis caused by kidney or ureteral stones that occurred prior to TUL. Thirty patients (28%) had urosepsis prior to TUL. Patients were divided into a urosepsis group (n = 30, 28%) and a non-urosepsis group (n = 79, 72%). Patients' characteristics (gender, age, performance status [PS] score, presence of diabetes mellitus, and skeletal muscle mass), as well as their stone and urine characteristics (stone size, presence of obstructive ureteral stones, stone composition, and urine and stone cultures), were compared between the two groups. When compared to the non-urosepsis group, patients with urosepsis were more likely to be older (p < 0.001), female (p < 0.001), with lower skeletal muscle mass (p < 0.001) and with poor PSs (p < 0.001). For stone and urine characteristics, infection stones (p = 0.01), positive urine (p < 0.001) and stone culture (p = 0.007) were more often detected in patients with urosepsis. A multivariate analysis showed patients' poor PS to be an independent risk factor for urosepsis due to kidney and ureteral stones (OR = 15.7; 95% CI = 2.2-115, p = 0.007). Our study revealed that the most significant risk factor for urosepsis caused by kidney and ureteral stones was the patients' poor PS.

Evaluation and comparison of scoring systems for predicting stone-free status after flexible ureteroscopy for renal and ureteral stones.

OBJECTIVE: To evaluate four predictive scores for stone-free rate (SFR) after flexible ureterorenoscopy (f-URS) with holmium-YAG laser fragmentation of renal and ureteral lithiasis. METHODS: We carried out a retrospective analysis of 800 f-URS procedures performed in our institution between January 2009 and December 2016. For each procedure, a single surgeon calculated the following scores: S.T.O.N.E score; Resorlu Unsal Stone Score (RUSS); modified Seoul National University Renal Complexity (S-ReSC) score; and Ito's score. RESULTS: Overall SFR was 74.1%. Univariate analysis demonstrated that stone size (p<0.0001), stone volume (p<0.0001), stone number (p = 0.004), narrow lower pole infundibulopelvic angle (IPA) (p = 0.003) and lower pole location + IPA <45° (p = 0.011) were significantly associated with SFR. All scores differed between the stone-free and non-stone-free groups. Area under the curve of the receiving operator characteristics curve was calculated for each score: 0.617 [95%CI: 0.575-0.660] for the S.T.O.N.E score; 0.644 [95%CI: 0.609-0.680] for the RUSS; 0.651 [95%CI: 0.606-0.697] for the S-ReSC score; and 0.735 [95%CI: 0.692-0.777] for Ito's nomogram. CONCLUSION: All four scores were predictive of SFR after f-URS. Ito's score was the most sensitive. However, the performance of all scores in this analysis was lower than in developmental studies.

Oral chemolysis is an effective, non-invasive therapy for urinary stones suspected of uric acid content.

Despite the possible benefit from avoiding stone surgery with all its possible complications, oral chemolysis is rarely performed in patients with urinary stones suspected of uric acid content. Among the reasons for its limited use is the sparse and low-quality data on its efficacy and the lack of reliable factors predicting its outcome. We thus performed a retrospective single-center cohort study of 216 patients (median patient age 63 years) with 272 renal (48%) and/or ureteral (52%) stones treated with oral chemolysis from 01/2010 to 12/2019. Patients with low urine pH (< 6), low stone density upon non-contrast enhanced computed tomography (NCCT), radiolucent urinary stones on plain radiography, and/or a history of uric acid urolithiasis were included. Potassium citrate and/or sodium/magnesium bicarbonate were used for alkalization (target urine pH 6.5-7.2). Median stone size was 9 mm, median stone density 430 Hounsfield Units. Patients with ureteral stones < 6 mm were excluded since stones this small are very likely to pass spontaneously. The stone-free status of each patient was evaluated after 3 months using NCCT. Oral chemolysis was effective with a complete and partial response rate of stones at 3 months of 61% and 14%, respectively; 25% of stones could not be dissolved. Lower stone density (OR = 0.997 [CI 0.994-0.999]; p = 0.008) and smaller stone size (OR = 0.959 [CI 0.924-0.995]; p = 0.025) significantly increased the success rate of oral chemolysis in multivariate logistic regression analysis. More precise stone diagnostics to exclude non-uric-acid stones could further improve outcome.

Hounsfield units-a significant predictor of lasering time and energy in the management of upper urinary tract stones using Holmium: Yttrium-Aluminum Garnet lasers.

PURPOSE: To study the impact of stone density as assessed by Hounsfield units (HU) on total laser energy (TLE) used and total laser time (TLT) spent in complete fragmentation of upper urinary tract stones. In addition, we also studied the impact of stone composition on the laser energy and time required for fragmentation. METHODS: Thirty consecutive patients fulfilling inclusion and exclusion criteria were included in the study. Patients with renal or proximal ureteral stones with a size of 5-20 mm were included. Stone fragmentation was performed using Ho:YAG 100 W laser and TLT and TLE were correlated with the HU and stone composition. RESULTS: The mean stone diameter was 10.83 ± 3.5 mm and the mean HU was 893 ± 315. The mean TLE and TLT were 8.86 ± 3.12 kJ and 18.46 ± 6.9 min, respectively. We observed a strong positive correlation between HU and TLE (r = 0.84, p value < 0.001) and between HU and TLT (r = 0.58, p value = 0.001). However, the stone composition did not influence the lasering energy (p value = 0.36) and lasering time (p value = 0.30). Stone diameter also had significant positive correlation with TLE (r = 0.41; p = 0.02) and TLT (r = 0.54; p- 0.002). When controlling for stone size the correlation of HU with TLE (r = 0.83; p < 0.001) and TLT (r = 0.52; p = 0.004) remained significant. CONCLUSIONS: HU and stone diameter are significant predictors of TLE and TLT when using Ho:YAG laser for stone fragmentation. However, stone composition and stone location failed to show any significant effect on either of these parameters.

Reduced Dose Computed Tomography: The Effects of Voltage Reduction on Density Measurements of Urolithiasis.

CT is a widely used imaging modality in the diagnosis of urolithiasis but subjects patients to ionizing radiation. Reduced dose protocols have recently gained wide acceptance. Stone density measurements have been used to predict composition and help guide treatment in standard dose CT (sCT) but not in reduced dose CT (RdCT). We aimed to compare density measurements obtained through RdCT vs sCT and to determine if there is a correlation between stone composition. A total of 201 patients undergoing evaluation for renal colic were prospectively recruited, whereby each subject underwent an sCT (120 kVp) followed immediately by an RdCT (80 or 100 kVp). All calculi <5 mm were excluded to prevent volume averaging and distortion to Hounsfield units measurements. The iliac bone cortex was utilized as an internal control. We also collected stone compositional analyses. In total 36 stones were identified. When the same calculi were evaluated with 120 kVp vs 80 kVp, the RdCT revealed a higher HU (n = 18, 1214 ± 520 vs 1007 ± 307, p < 0.005). Statistical difference was not achieved when 120 kVp was compared with 100 kVp scans (p = 0.151). The percentage differences were 10.6 ± 21 and 1.4 ± 15, respectively. Measurements of the iliac crest mirrored the findings of calculi, with density measurements in 80 kVp being statistically higher than those obtained through 120 kVp. A total of 41 stone analyses were reviewed in accordance with variable CT dosages. When stratified by CT kVp and stone composition, RdCTs trended toward wider density ranges than sCT. Density measurements of urolithiasis in RdCT, achieved by voltage reduction, corresponds to a paradoxical increase in HU. Although HU can be used as a predictor for stone composition, there can be a wide deviation in measured density, and this can be further magnified in the setting of dose reduction.

Stone composition independently predicts stone size in 18,029 spontaneously passed stones.

PURPOSE: To evaluate whether the size of spontaneously passed stones (SPS) may be associated with clinical parameters. METHODS: A search for SPS was conducted in our electronic stone database, comprising data on stones analyzed over the last 33 years at our institution. Adults with upper urinary tract stones were included. Cases with stenotic urinary tract disease or past history of anastomotic urinary tract surgery were excluded. Stone size expressed as maximal stone diameter (MSD) and stone volume (SV) was compared between groups by one-way ANOVA. Logistic regression analyses were performed to identify predictors of MSD ≥ 6 mm. RESULTS: Overall mean MSD and SV for 18,029 SPS was 4.1 mm and 11.5 mm3, respectively, and significantly differed between stone composition groups (p < 0.001). The lowest mean MSD and SV were found for calcium oxalate monohydrate (3.6 mm and 9.0 mm3, respectively) and the highest mean MSD and SV were found for struvite (7.9 mm and 61.0 mm3, respectively). Stone composition and increasing age were found to be independent predictors of MSD ≥ 6 mm (both p < 0.001). Sex differentiation did not contribute as a predictor of MSD ≥ 6 mm. CONCLUSIONS: Stone composition and-to a lesser extent-age serve as independent predictors of size of spontaneously passed stones. Of particular importance, large spontaneously passed stones of ≥ 6 mm may be frequently found in cystine, brushite or struvite stone formers, whereas a minority of all calcium oxalate stones exceed that cutoff. Future studies shall evaluate these parameters as possible predictors of spontaneous stone passage.

Effect of Stone Composition on the Outcomes of Semi-Rigid Ureteroscopy Using Holmium: Yttrium-Aluminum-Garnet Laser or Pneumatic Lithotripsy.

OBJECTIVE: To compare the effectiveness of laser lithotripsy (LL) and pneumatic lithotripters (PL) in calcium oxalate (CaOx) and calcium phosphate (CaP) stones and assess whether these stone compositions affect the outcomes of LL and PL. STUDY DESIGN: Comparative, descriptive study. PLACE AND DURATION OF STUDY: Istanbul Training and Research Hospital, Turkey, from August 2010 to August 2015. METHODOLOGY: A total of 114 patients underwent ureteroscopy using LL and PL. Fifty-eight (50.9%) had CaOx stones and 56 (49.1%) had CaP stones. The lithotripters were compared in stone composition groups, and stone compositions were compared in lithotripter groups. Patient characteristics, perioperative parameters, and postoperative complications were compared. RESULTS: The baseline patient and stone characteristics were similar in all groups. The operation time of the PL and LL for the patients with CaP stones (68.75 ±32.88 and 44.48 ±34.37 minutes, respectively) was significantly shorter than the operation time of the PL and LL for the patients with CaOx stones (91.56 ±30.54 and 65.75 ±37.74 minutes, (p=0.012 and p=0.009, respectively). Moreover, the patients with CaOx or CaP treated with LL 65.75±37.74 and 44.48 ±34.37 minutes, respectively) had significant shorter operation time than the PL (91.56 ±30.54 and 68.75 ±32.88 minutes, (p=0.046 and p=0.01, respectively). Stone-free rates were similar in all groups. The PL for the patients with CaP stones caused more postoperative fever and infection than the other groups (p=0.050). CONCLUSION: Though both PL and LL are effective in the treatment of CaOx and CaP stones, LL had a significantly shorter operation and hospitalization time and complication rates in patients with CaOx and CaP stones. So LL is a more feasible and safer modality in the treatment of recurrent CaP stones.

[A Case of Atazanavir Urolithiasis Diagnosed by Stone Analysis].

A 70-year-old man was referred to our hospital for right back pain. His past history included human immunodeficiency virus infection, which had been treated with atazanavir for 7 years. Abdominal and pelvic computed tomographic scan showed right hydronephrosis due to a strongly suspected right ureteral radiolucent stone. He underwent indwelling of a right ureteral stent because of obstructive pyelonephritis due to the ureteral stone. After improvement of the pyelonephritis, he underwent transurethral ureterolithotripsy for the right ureteral stone. Stone analysis showed the atazanavir stone. He has been followed up for 8 months without evidence of recurrence. Herein, we report this rare case of an atazanavir stone in Japan, which was confirmed by calculus analysis, and present a review of the literature.

The importance of citrates in treatment and prophylaxis of calcium oxalate urinary stones.

About 10% of the people is the subject of an episode of kidney stones during their lifetime, about 70% of these people undergoes relapses. About 80% of the urinary stones contains calcium, of wich 80% is formed of calcium oxalate, in pure form or associated with calcium phosphate. Therefore we can saythat in most cases (about 65%) the urinary stones are composedof calcium oxalate. Use of supplements of potassium citrate and magnesium citrate can help in the prevention of kidney stones of calcium oxalate, but mostly they can be used in the days before a shockwaves lithotripsy treatment to make the stones more fragile to the effect of the shock waves. A case of successful treatment with magnesium potassium citrate of a SWL resistant ureteral stone is presented.

Predicting the mineral composition of ureteral stone using non-contrast computed tomography.

We investigated the correlation between computed tomography (CT) density of ureteral stones and their mineral composition. A total of 346 patients who underwent ureteroscopic lithotripsy for calculi all fragments of which were acquired at a single institution from 2009 to 2011 were analyzed. The maximum and mean CT densities were measured preoperatively. A mineral analysis revealed calcium oxalate in 203 (58.7 %), mixed calcium oxalate and calcium phosphate in 78 (23.0 %), calcium phosphate in 18 (5.2 %), uric acid in 8 (2.3 %), struvite in 3 (0.9 %), and cysteine in 5 (1.4 %). The mean Hounsfield units (HUs) of the CT density were 1046 HUs in calcium oxalate, 1101 HUs in mixed calcium oxalate and calcium phosphate, 835 HUs in calcium phosphate, 549 HUs in uric acid, 729 HUs in struvite, and 698 HUs in cystine. The HUs in calcium oxalate were significantly higher than those in uric acid (p < 0.01) and struvite (p < 0.01). Those in monohydrate stones were significantly higher, compared with dehydrate stones (p < 0.05). We analyzed the largest number of stones than each published study to correlate their mineral composition and CT density. Calcium component stones showed significantly higher CT densities than other types.

Can a dual-energy computed tomography predict unsuitable stone components for extracorporeal shock wave lithotripsy?

PURPOSE: To assess the potential of dual-energy computed tomography (DECT) to identify urinary stone components, particularly uric acid and calcium oxalate monohydrate, which are unsuitable for extracorporeal shock wave lithotripsy (ESWL). MATERIALS AND METHODS: This clinical study included 246 patients who underwent removal of urinary stones and an analysis of stone components between November 2009 and August 2013. All patients received preoperative DECT using two energy values (80 kVp and 140 kVp). Hounsfield units (HU) were measured and matched to the stone component. RESULTS: Significant differences in HU values were observed between uric acid and nonuric acid stones at the 80 and 140 kVp energy values (p<0.001). All uric acid stones were red on color-coded DECT images, whereas 96.3% of the nonuric acid stones were blue. Patients with calcium oxalate stones were divided into two groups according to the amount of monohydrate (calcium oxalate monohydrate group: monohydrate≥90%, calcium oxalate dihydrate group: monohydrate<90%). Significant differences in HU values were detected between the two groups at both energy values (p<0.001). CONCLUSIONS: DECT improved the characterization of urinary stone components and was a useful method for identifying uric acid and calcium oxalate monohydrate stones, which are unsuitable for ESWL.

Focused Dual-energy CT Maintains Diagnostic and Compositional Accuracy for Urolithiasis Using Ultralow-dose Noncontrast CT.

OBJECTIVE: To evaluate the diagnostic accuracy of a new energy and radiation dose-reduced protocol for noncontrast computed tomography (NCCT) with dual-energy CT (DECT) analysis and its potential for the compositional analysis of uric acid (UA)- or non-uric acid (N-UA)-containing calculi. METHODS: A retrospective evaluation was carried out in 61 patients who underwent dose-reduced DECT (tube A: 140 kV/55 mAs; tube B: 80 kV/303 mAs) with a tube current 38.8% lower than that set by the manufacturer. A protocol combining low-dose CT and targeted DE scans was used. Urinary stones were detected and classified as UA- or N-UA-containing or mixed based on DE software results. The accuracy of the compositional analysis was controlled by correlation with conventional infrared-based analysis. RESULTS: The compositional stone differentiation was correct in 58 of 61 (95.1%) patients. The sensitivity of detecting pure UA-containing and pure N-UA-containing stones was 100%. The specificity of detecting UA- and pure N-UA-containing stones was 100% and 78.57%, respectively, as 3 of 7 mixed urinary stones (small fragments <4 mm) were classified as N-UA calculi. The total radiation dose in patients with body mass index <25 and >25 kg/m(2) was 1.2 and 2.5 mSv, respectively. CONCLUSION: Lowering the DECT tube current by up to 38% of the manufacturer's recommendations allows a reduced radiation dose without impairing detection accuracy and stone compositional analysis. Compared with previous studies, this protocol might significantly decrease patient radiation exposure without affecting the quality of results.

Evaluation of low-dose dual energy computed tomography for in vivo assessment of renal/ureteric calculus composition.

PURPOSE: This study aimed to assess the accuracy of low-dose dual-energy computed tomography (DECT) in predicting the composition of urinary calculi. MATERIALS AND METHODS: A total of 52 patients with urinary calculi were scanned with a 128-slice dual-source DECT scanner by use of a low-dose protocol. Dual-energy (DE) ratio, weighted average Hounsfield unit (HU) of calculi, radiation dose, and image noise levels were recorded. Two radiologists independently rated study quality. Stone composition was assessed after extraction by Fourier transform infrared spectroscopy (FTIRS). Analysis of variance was used to determine if the differences in HU values and DE ratios between the various calculus groups were significant. Threshold cutoff values to classify the calculi into separate groups were identified by receiver operating characteristic curve analysis. RESULTS: A total of 137 calculi were detected. FTIRS analysis differentiated the calculi into five groups: uric acid (n=17), struvite (n=3), calcium oxalate monohydrate and dihydrate (COM-COD, n=84), calcium oxalate monohydrate (COM, n=28), and carbonate apatite (n=5). The HU value could differentiate only uric acid calculi from calcified calculi (p<0.001). The DE ratio could confidently differentiate uric acid, struvite, calcium oxalate, and carbonate apatite calculi (p<0.001) with cutoff values of 1.12, 1.34, and 1.66, respectively, giving >80% sensitivity and specificity to differentiate them. The DE ratio could not differentiate COM from COM-COD calculi. No study was rated poor in quality by either of the observers. The mean radiation dose was 1.8 mSv. CONCLUSIONS: Low-dose DECT accurately predicts urinary calculus composition in vivo while simultaneously reducing radiation exposure without compromising study quality.

Changes in stone composition over two decades: evaluation of over 10,000 stone analyses.

To examine the changes in stone composition from 1990 to 2010. A retrospective review was performed of all renal and ureteral stones submitted from the state of Massachusetts to a single laboratory (Laboratory for Stone Research, Newton, MA) for the years 1990 and 2010. Stone composition was determined by infrared spectroscopy and/or polarizing microscopy. A total of 11,099 stones were evaluated (56.7% from 1990, 43.3% from 2010). From 1990 to 2010, the percentage of stones from females (i.e., female/male ratio) increased significantly (29.8% in 1990 to 39.1% in 2010, p < 0.001). Among women, from 1990 to 2010, there was a significant increase in stones which were >50% uric acid (7.6-10.2%, p < 0.005) and a significant decrease in struvite stones (7.8-3.0%, p < 0.001). Among women with calcium stones, the % apatite per stone decreased significantly (20.0 vs. 11.7%, p < 0.001). Among men, there were no changes in stones which were majority uric acid (11.7-10.8%, p = 0.2). Among men with calcium stones, the % apatite per stone increased significantly (9.8 vs. 12.5%, p < 0.001). Males also demonstrated a significant increase in both cystine (0.1-0.6%, p < 0.001) and struvite stones (2.8-3.7%, p = 0.02). The epidemiology of stone disease continues to evolve and appears to vary according to gender. While some of these findings may be related to population changes in body mass index and obesity, the etiology of others remains unclear.

Evaluation of Hounsfield Units as a predictive factor for the outcome of extracorporeal shock wave lithotripsy and stone composition.

The objective of this study was to evaluate the utility of the Hounsfield Unit (HU) values as a predictive factor of extracorporeal shock wave lithotripsy outcome for ureteral and renal stones. We also assessed the possibility that HU values could be used to predict stone composition. A retrospective study was performed to measure stone HU values in 260 patients who underwent extracorporeal shock wave lithotripsy (ESWL) for solitary renal and ureteral stones from July 2007 to January 2012. Stone volume, location, skin-to-stone distance, stone HU values, and stone composition were assessed. Success of ESWL was defined as: (1) being stone-free or (2) residual stone fragments <4 mm after 3 months by radiography. Of the 260 assessed patients, 141 (54.2%) were stone-free, 32 (12.3%) had residual stone fragments <4 mm (clinically insignificant stone fragments), and 87 (33.5%) had residual stone fragments ≥4 mm after one round of ESWL. Multivariate analysis revealed that stone location and mean HU were significant predictors of ESWL success. Receiver operating characteristic curves defined cutoff values for predicting treatment outcome. Treatment success rates were significantly higher for stones <815 HU than with stones >815 HU (P < 0.0265). HU of calcium oxalate and calcium phosphate stones were higher than those of uric acid stones, but we could not differentiate between calcium oxalate monohydrate and calcium oxalate dihydrate stones. Evaluation of stone HU values prior to ESWL can predict treatment outcome and aid in the development of treatment strategies.

Stone size limits the use of Hounsfield units for prediction of calcium oxalate stone composition.

OBJECTIVE: To evaluate the role of stone size in predicting urinary calculus composition using Hounsfield units on noncontrasted computed tomography (CT) scan. METHODS: A retrospective review was performed for all patients who underwent ureteroscopy or percutaneous nephrolithotomy during a 1-year period, had a stone analysis performed, and had CT imaging available for review. All CT scans were reviewed by a board-certified radiologist. Variables evaluated included age, sex, body mass index, stone size, stone location, Hounsfield units (HUs), and stone composition. RESULTS: We identified a total of 91 patients (41 men and 50 women) with CT imaging and stone analysis available for review. Stone analysis showed 41 calcium oxalate monohydrate (CaOxMH), 13 calcium oxalate dihydrate, 29 calcium phosphate, 5 uric acid, 2 struvite, and 1 cystine stone. Average age was 46 years, and average body mass index was 32 kg/m2. Measured HUs varied significantly with size for CaOxMH and calcium oxalate dihydrate stones (P values <.05), but not for calcium phosphate stones (P = .126). Using a CaOxMH identification value of 700-1000 HUs, 28 of 41 stone compositions (68%) would not have been correctly identified, including all 10 (100%) small (<5 mm) stones, 13 of 22 (59%) medium (5-10 mm) stones, and 5 of 9 large (>10 mm) stones (55%). CONCLUSION: For calcium stones, the ability of CT HUs to predict stone composition was limited, likely due to the mixed stone composition. Within a cohort of CaOxMH stone formers, measured HUs varied linearly with stone size. All stones <5 mm were below thresholds for CaOxMH composition.