Imaging techniques for stone disease and methods for reducing radiation exposure

Evaluation and comparison of S.T.O.N.E. and Guy's scoring systems for predicting percutaneous nephrolithotomy outcomes in supine position

BACKGROUND

Percutaneous nephrolithotomy (PCNL) was applied in the prone position until recently. But also, in recent years supine positions was applied in patients with kidney stones. Predicting how much renal stones can be cleared after surgery and possibility of complications is an important question for both surgeons and patients. Therefore different scoring systems are used to evaluate outcomes of PCNL before surgery.

PATIENTS AND METHODS

Between 2018 and 2020, 80 patients with renal stone who underwent PCNL in the supine position were evaluated preoperatively by S.T.O.N.E. and Guy's scoring systems (GSS). The predictions of both scoring systems for stone-free and complication rates in patients who underwent PCNL in the supine position were evaluated. Also, these scoring systems were compared among themselves for reliability.

RESULT

In both scoring systems, there was a statistically significant difference between postoperative stone-free (SF) and residual stone (RS) of patients and in predicting the likelihood of complications in patients. No statistically significant difference was found between the two scoring systems in predicting the stone-free rate.

CONCLUSION

Our findings revealed that S.T.O.N.E. nephrolithometry and Guy's score systems can be used effectively to predict stone-free rate, complications, and operation duration in supine position PCNL for renal stones.

What Do We Mean by "Stone Free," and How Accurate Are Urologists in Predicting Stone-Free Status Following Ureteroscopy?

Background and Purpose: No consensus exists on how stone-free rates (SFRs) should be reported after stone treatment. The aim of this study was to assess how accurate urologists predict their patients being stone free after completing ureteroscopy (URS) and to see how various treatment strategies influenced the precision of these predictions. We also wanted to study how different definitions of stone-free status (SFS) affected the results and propose a standard definition of "stone free" to be used in future studies. Materials and Methods: A retrospective evaluation of 1019 URS done for stone treatment at Haukeland University Hospital between 2013 and 2018 was performed. Data on pretreatment status, the surgical procedure, and follow-up were recorded. SFS was defined as either no fragments detected on computed tomography (CT) after 3 months or as practical stone-free status, which also included those with small residual fragments not needing further treatment. Exact chi-squared and independent-samples t-tests were used comparing data between different treatment modalities. Results: The overall SFR, irrespective of treatment strategy and location of stone, using the no residual fragments and practical stone-free definitions were 54.2% and 74.7%, respectively. Urologists predicted intraoperatively that 91.0% of their patients treated with fragmentation and extraction would be stone free compared to 76.8% of patients treated with dusting, p < 0.0001. At follow-up, the actual SFRs with no residual fragments for the two treatment strategies were 68.0% and 35.5%, respectively, p < 0.0001. The practical SFRs for fragmentation and retrieval were 83.1% and 64.8% for dusting, p < 0.0001. Conclusion: The different definitions of SFS have great impact on SFRs. Urologists are far too optimistic predicting their patient being stone free after URS. SFS should be defined as no fragments detected on CT 3 months after the URS procedure when presented in studies.

New Imaging Techniques in the Management of Stone Disease

Recent advances in computed tomography, X-ray-based imaging, and ultrasonography have improved the accuracy of urinary stone detection and differentiation of stone composition while minimizing radiation exposure. Dual-energy computed tomography and digital tomosynthesis show promise in predicting mineral composition to optimize medical and surgical therapy. Electromagnetic tracking may enhance the use of ultrasonography to achieve percutaneous renal access for nephrolithotomy. This article reviews innovations in imaging technology in the contemporary management of urinary stone disease.

External validation and comparison of the scoring systems (S.T.O.N.E, GUY, CROES, S-ReSC) for predicting percutaneous nephrolithotomy outcomes for staghorn stones: A single center experience with 160 cases

The aim of this study was validation and comparison of stone scoring systems (S.T.O.N.E, GUY, CROES, S-ReSC) used to predict postoperative stone-free status and complications after percutaneous nephrolithotomy (PCNL) for staghorn stones. A total of 160 patients who had staghorn renal stones and underwent PCNL between January 2012 and August 2015 were included in the current retrospective study. Guy, S.T.O.N.E., S-ReSC (Seoul National University Renal Stone Complexity) and CROES (Clinical Research Office of the Endourological Society) nephrolithometry scores were calculated for each patient, and their potential association with stone-free status, operative and fluoroscopy time, and length of hospital stay (LOS) were evaluated. Postoperative complications were graded according to the modified Clavien classification, and the correlation of scoring systems with postoperative complications was also investigated. The mean CROES, S.T.O.N.E, Guy and S-ReSC scores were 143.5 ± 33.6, 9.7 ± 1.6, 3.5 ± 0.5 and 6.2 ± 2.0 respectively. The overall stone-free rate was 59%. All scoring systems were significantly correlated with stone-free status in univariate analysis. However, Guy and S-ReSC scores were the only significant independent predictor in multivariate analysis. And all four nomograms failed to predict complication rates. Current study demonstrated that Guy and S-ReSC scoring systems could effectively predict postoperative stone-free status for staghorn stones. However all four scoring systems failed to predict complication rates.

External Validation and Comparisons of the Scoring Systems for Predicting Percutaneous Nephrolithotomy Outcomes: A Single Center Experience with 506 Cases

BACKGROUND

To validate and compare the stone scoring systems (stone size [S], tract length [T], obstruction [O], number of involved calices [N], and essence or stone density [E] [S.T.O.N.E.], Guy's Stone Score [GSS], Clinical Research Office of the Endourological Society [CROES], and Seoul National University Renal Stone Complexity [S-ReSC]) used to predict postoperative stone-free status and complications after percutaneous nephrolithotomy (PCNL).

METHODS

A total of 567 patients who underwent PCNL for renal stones between January 2012 and August 2015 were included in the recent retrospective study. Sixty-one patients who had not done preoperative CT were excluded from the study. GSS, S.T.O.N.E., S-ReSC, and CROES nephrolithometry scores were calculated for each patient, and their potential association with stone-free status, operative and fluoroscopy time, and length of stay (LOS) was evaluated. Postoperative complications were graded according to the modified Clavien classification, and the correlation of scoring systems with postoperative complications was also investigated.

RESULTS

The mean CROES, S.T.O.N.E., GSS, and S-ReSC scores were 203.7 ± 59.8, 7.52 ± 1.8, 2.08 ± 0.9, and 3.35 ± 2.2, respectively. The overall stone-free rate was 77.9%. All scoring systems were significantly correlated with stone-free status and operation time. While GSS, S.T.O.N.E., and CROES systems were significantly correlated with complication rates (CR), S-ReSC score failed to predict CR. All scoring systems except S.T.O.N.E. were significantly correlated with LOS. CROES and S-ReSC scores were predictive of estimated blood loss (EBL), while GSS and S.T.O.N.E. failed to predict EBL.

CONCLUSIONS

Recent study demonstrated that S.T.O.N.E., GSS, CROES, and S-ReSC scoring systems could effectively predict postoperative stone-free status. Although S-ReSC scoring system failed to predict CR, the rest three scoring systems were significantly correlated with postoperative CR.

Semi-rigid ureteroscopic lithotripsy versus laparoscopic ureterolithotomy for large upper ureteral stones: a meta - analysis of randomized controlled trials

Introduction:

To provide a systematic review and meta-analysis of randomized controlled trials (RCT) comparing semi-rigid ureteroscopic lithotripsy (URS) with laparoscopic ureterolithotomy (LU) for the treatment of the large proximal ureteral stone.

Materials and methods:

A systematic literature review was performed in June 2015 using the PubMed, Scopus, and Web of Science databases to identify relevant studies. Article selection proceeded according to the search strategy based on Preferred Reporting Items for Systematic Reviews and Meta-analysis criteria.

Results:

Six RCT including 646 patients were analyzed, 325 URS cases (50.3%) and 321 LU cases (49.7%). URS provided a significantly shorter operative time (weighted mean difference [WMD] = −31.26 min; 95%CI −46.88 to −15.64; p<0.0001) and length of hospital stay (WMD = −1.48 days; 95%CI −2.78 to −0.18; p=0.03) than LU. There were no significant differences in terms of overall complications (OR = 0.78; 95%CI 0.21-2.92; p=0.71) and major complications – Clavien ≥3 – (OR = 1.79; 95%CI 0.59-5.42; p=0.30). LU led to a significantly higher initial stone-free rate (OR = 8.65; 95%CI 4.18-17.91; p<0.00001) and final stone-free rate (OR = 6.41; 95%CI 2.24-18.32; p=0.0005) than URS. There was a significantly higher need for auxiliary procedures in URS cases (OR = 6.58; 95%CI 3.42-12.68; p<0.00001).

Conclusions:

Outcomes with LU for larger proximal ureteral calculi are favorable compared to semi-rigid URS and should be considered as a first-line alternative if flexible ureteroscopy is not available. Utilization of flexible ureteroscopy in conjunction with semi-rigid ureteroscopy may impact these outcomes, and deserves further systematic evaluation.

Imaging Advances in Urolithiasis

The prevalence of urinary stones in the United States has been described as 1 in 11 persons reporting a history of stones. Imaging plays a crucial role in diagnosis, management, and follow-up for these patients and imaging technology over the last 100 years has advanced as the disease prevalence has increased. CT remains the gold standard for imaging urolithiasis and changes in this technology, with the addition of multidetector CT and dual-energy CT, as well as the changes in utilization of CT, have decreased the radiation dose encountered by patients and allowed for improved stone detection. The use of digital tomography has been introduced for follow-up of recurrent stone formers offering the potential to lower radiation exposure over the course of a patient's lifelong treatment. However, there is still a demand for improved imaging techniques to detect smaller stones and stones in larger patients at lower radiation doses as well as the continued need for the judicious use of all imaging modalities for healthcare cost containment and patient safety.

Predictors of radiation exposure to providers during percutaneous nephrolithotomy

Background:

Limited studies have reported on radiation risks of increased ionizing radiation exposure to medical personnel in the urologic community. Fluoroscopy is readily used in many urologic surgical procedures. The aim of this study was to determine radiation exposure to all operating room personnel during percutaneous nephrolithotomy (PNL), commonly performed for large renal or complex stones.

Materials and Methods:

We prospectively collected personnel exposure data for all PNL cases at two academic institutions. This was collected using the Instadose™ dosimeter and reported both continuously and categorically as high and low dose using a 10 mrem dose threshold, the approximate amount of radiation received from one single chest X-ray. Predictors of increased radiation exposure were determined using multivariate analysis.

Results:

A total of 91 PNL cases in 66 patients were reviewed. Median surgery duration and fluoroscopy time were 142 (38–368) min and 263 (19–1809) sec, respectively. Median attending urologist, urology resident, anesthesia, and nurse radiation exposure per case was 4 (0–111), 4 (0–21), 0 (0–5), and 0 (0–5) mrem, respectively. On univariate analysis, stone area, partial or staghorn calculi, surgery duration, and fluoroscopy time were associated with high attending urologist and resident radiation exposure. Preexisting access that was utilized was negatively associated with resident radiation exposure. However, on multivariate analysis, only fluoroscopy duration remained significant for attending urologist radiation exposure.

Conclusion:

Increased stone burden, partial or staghorn calculi, surgery and fluoroscopy duration, and absence of preexisting access were associated with high provider radiation exposure. Radiation safety awareness is essential to minimize exposure and to protect the patient and all providers from potential radiation injury.

Imaging for Urinary Stones: Update in 2015

CONTEXT

Imaging is essential for the diagnosis and the clinical decision-making process of patients with urinary stones.

OBJECTIVE

To assess the benefits and limitations of various imaging techniques by specifically focusing on different phases of stone patients' management.

EVIDENCE ACQUISITION

PubMed and Web of Science databases were used to identify studies published in the last 10 yr on this argument. Search terms included 'urolithiasis', nephrolithiasis', or 'urinary stones' in combination (AND) with the terms 'imaging', 'computer tomography', 'ultrasonography', 'intravenous pyelogram', or 'radiation exposure'. Study selection was based on an independent peer-review process of all the authors after the structured data search.

EVIDENCE SYNTHESIS

Noncontrast-enhanced computer tomography (CT) provides the highest value of diagnostic accuracy for urinary stones. Stone composition can be specifically assessed through the use of dual-energy CT. When information about the anatomy of the renal collecting system is required or alternative pathologies are suspected, CT with contrast injection is recommended. Low-dose protocols allowed a drastic reduction of the effective dose administered to the patient, thus limiting the biological risk due to ionising radiations. Other strategies to contain the radiation exposure include the dual-split bolus dual energy CT and the adaptive statistical image reconstruction. Abdomen ultrasound may be a valid alternative as an initial approach since it does not change the outcome of patients compared with CT, and should be the imaging of choice in children and pregnant women.

CONCLUSIONS

Noncontrast-enhanced CT is the most accurate imaging technique to identify urinary stones. Abdomen ultrasound seems to be a valid alternative in the initial evaluation of urinary colic. New low-dose protocols and strategies have been developed to contain radiation exposure, which is a major issue especially in specific circumstances.

PATIENT SUMMARY

Noncontrast-enhanced computer tomography has been increasingly used for the diagnosis and management of urinary stones. Low-dose protocols as well as alternative imaging should be considered by clinicians in specific circumstances to minimise radiation exposure.

Prospective evaluation of outcome of percutaneous nephrolithotomy using the 'STONE' nephrolithometry score: A single-centre experience

Objective

To assess the prediction of stone clearance and complications of percutaneous nephrolithotomy (PCNL) using the ‘STONE’ nephrolithometry score, assessing stone size, tract length (skin-to-stone distance), degree of obstruction, number of calyces involved and stone essence (density).

Patients and methods

This was a prospective study of patients undergoing single-tract PCNL while prone, conducted at a university hospital. All patients had non-contrast-enhanced computed tomography within 3 weeks of the procedure. Only patients with a unilateral procedure and radio-opaque stones were included. The five variables of the STONE nephrolithometry score were calculated before the procedure. The stone-free rates were assessed with a plain abdominal film at 4 weeks and complications were graded using the modified Clavien system.

Results

In all, 107 patients were included in the final analysis. Overall, 80% of patients were rendered stone-free. Among the individual variables, a larger stone (P = 0.002) and the involvement of multiple calyces (P = 0.04) were associated with residual stones, while tract length (skin-to-stone distance), stone density and presence of hydronephrosis were not. Patients who were rendered stone-free had a statistically significant lower overall STONE score than those with residual stones, at 7.24 vs. 8.14 (P = 0.02). The score also correlated with operative duration, which was significantly longer with a higher STONE score (P = 0.03). The complication rate was 18% and most complications were Clavien grade 2, with bleeding requiring a blood transfusion (11 patients) being the commonest. There were no deaths within 30 days of surgery, but there was no correlation between the STONE score and complications.

Conclusion

The STONE nephrolithometry score is a simple and easy to apply system for predicting complexity in stone clearance with PCNL.

Radiation dosage in the urolithiasis population: Do we over-radiate our patients?

Introduction:

There is increasing concern about the amount of radiation that patients with urolithiasis receive. Ensuring patients are exposed to the minimum necessary radiation is imperative. Here we review the radiation dosages that newly diagnosed urolithiasis patients received in the year following their presentation, both those presenting acutely and those referred electively.

Patients and methods:

A retrospective study of 95 treatment-naïve patients (47 acute, 48 elective) referred for management of urolithiasis was undertaken. The analysis included all imaging modalities related to stone disease for both patient groups within one year following presentation. The total effective dose (mSV) in one year was calculated by summing the dose for each individual radiation exposure.

Results:

An average of 5.6 radiological investigations (range 1–14) was carried out for acute patients and 4.57 for elective patients (range 1–11). The mean total effective dose was 14.45 mSV for the acute cases and 12.87 mSV for the elective cases. The maximum radiation dose reached 30.1 mSV in acute patients and 36.51 mSV in elective ones. None of the patients exceeded the maximal annual dose recommended by the International Commission on Radiological Protection (ICRP) of 50 mSV.

Conclusion:

Management of acute and elective urolithiasis patients can be achieved with acceptable radiation dose exposure. It is extremely important to keep the hazards of radiation in mind whilst managing patients with urolithiasis and clinicians need to remember adherence to the ALARA principle.

Does the nephrostomy tract length impact the outcomes of percutaneous nephrolithotomy (PNL)?

PURPOSE

Different factors can determine the outcomes of percutaneous nephrolithotomy (PNL). We analyzed the effect of tract length (TL) on outcomes after PNL.

METHODS

We performed a retrospective review of patients undergoing PNL between 2006 and 2011. Patients with preoperative computed tomography (CT), one percutaneous access tract and follow-up imaging within 3 months were included. TL was defined as distance between the skin to the calyx of puncture as measured on preoperative CT. Measurements were independently performed by two urologists and the average was used for analysis. Stone-free rate (SFR) was defined as zero fragments on follow-up imaging. Factors independently associated with the likelihood of being stone-free after PNL were determined using multivariable analysis adjusted for TL, location of access, the presence of incomplete or complete staghorn calculi and type of follow-up imaging. Complications (Clavien score) were independently assessed.

RESULTS

A total of 222 patients were included. Median stone burden and body mass index (BMI) was 239.4 mm(2) and 30.5 [interquartile range (IQR): 25.7-36.2]. The median TL was 85.0 mm (IQR: 70.3-100.0) and highly correlated with BMI (ρ = 0.66, p < 0.001). A total of 101 patients (45.5 %) were stone-free. TL was not associated with SFR (p = 0.53). Clavien 1 and 2 complications occurred in 38 (17 %) while Clavien 3 and 4 complications occurred in 17 (8 %) patients. Multivariable analysis revealed no association between complications and TL even when adjusted for gender.

CONCLUSIONS

Percutaneous TL is not associated with outcomes of PNL. PNL is a safe and effective treatment for stones in patients with differing body habitus.

Urinary evaluation after RYGBP: a lithogenic profile with early postoperative increase in the incidence of urolithiasis

BACKGROUND

The objective of this study was to assess predictors for new-onset stone formers after Roux-en-Y gastric bypass (RYGBP).

METHODS

One hundred and fifty-one obese patients underwent RYGBP and were followed for 1 year. The analysis comprised two study time points: preoperative (T0) and 1 year after surgery (T1). They were analyzed for urinary stones, blood tests, and 24-h urinary evaluation. Nonparametric tests, logistic regression, and multivariate analysis were conducted using SPSS 17.

RESULTS

Median BMI decreased from 44.1 to 27.0 kg/m2 (p < 0.001) in the postoperative period. Urinary oxalate (24 versus 41 mg; p < 0.001) and urinary uric acid (545 versus 645 mg; p < 0.001) increased significantly postoperatively (preoperative versus postoperative, respectively). Urinary volume (1310 versus 930 ml; p < 0.001), pH (6.3 versus 6.2; p = 0.019), citrate (268 versus 170 mg; p < 0.001), calcium (195 versus 105 mg; p < 0.001), and magnesium (130 versus 95 mg; p = 0.004) decreased significantly postoperatively (preoperative versus postoperative, respectively). Stone formers increased from 16 (10.6 %) to 27 (17.8%) patients in the postoperative analysis (p = 0.001). Predictors for new stone formers after RYGBP were postoperative urinary oxalate (p = 0.015) and uric acid (p = 0.044).

CONCLUSIONS

RYGBP determined profound changes in urinary composition which predisposed to a lithogenic profile. The prevalence of urinary lithiasis increased almost 70% in the postoperative period. Postoperative urinary oxalate and uric acid were the only predictors for new stone formers.

Comparison of Nephrolithiasis Prevalence in Two Bottlenose Dolphin (Tursiops truncatus) Populations

In humans, ammonium urate (AU) nephrolithiasis is rare in the Western hemisphere and more common in Japan and developing countries. Among a variety of risk factors, insulin resistance has been associated with urate nephrolithiasis in people. Bottlenose dolphins (Tursiops truncatus) are susceptible to AU nephrolithiasis, and it is believed that some populations are more likely to develop nephrolithiasis compared to others. In an effort to better understand population-based risk factors for AU nephrolithiasis in dolphins and their comparative value to humans, sonographic evaluation was performed on dolphins from a managed collection in San Diego Bay, CA (n = 40) and dolphins from a free-ranging, nearshore population in Sarasota Bay, FL (n = 39) to look for evidence of nephrolithiasis. While 14 (35%) of San Diego Bay dolphins evaluated for the study had sonographic evidence of nephrolithiasis, none of the Sarasota Bay dolphins had evidence of disease. Presence or absence of stones was confirmed by computed tomography in a subset of the San Diego collection (n = 10; four dolphins with stones, six without stones). Age was identified as a risk factor, as dolphins with stones in the San Diego collection were significantly older than dolphins without stones (25.4 vs. 19.1 years, respectively; P = 0.04). Additionally, San Diego dolphins included in the study were significantly older than Sarasota Bay dolphins (21.3 vs. 13.8 years, respectively; P = 0.008). In addition to the previously reported risk factors of hypocitraturia and hyperinsulinemia in bottlenose dolphins, other potential factors include geographic location, managed vs. free-ranging status, prey species, and feeding schedules.