Ultra-Low-Dose CT: An Effective Follow-Up Imaging Modality for Ureterolithiasis

Radiation exposure associated with computed tomography for pediatric urolithiasis evaluation: A scoping review of the literature

INTRODUCTION

Computed tomography (CT) imaging is used for assessment of pediatric urolithiasis in cases where ultrasound is inconclusive. The utility of CT imaging must be considered alongside the potential risks of radiation exposure in this patient population due to the increased risk of cancer development. The purpose of this review is to investigate the radiation exposure associated with standard-dose and low-dose computed tomography (CT) imaging for the assessment of pediatric urolithiasis.

METHODS

A scoping literature review over a 23 year period between 2000 and 2023 was conducted of all English-language studies reporting on the use of non-contrast CT imaging for assessment of pediatric urolithiasis. Patients that were specified as pediatric with age ≤20 years at time of intervention and undergoing standard-dose or low/ultra-low-dose CT were included. Low-dose and ultra-low-dose CT were defined as a radiation dose ≤3.0 mSv and ≤1.9 mSv, respectively.

RESULTS

A total of 8121 articles were identified and after screening, 6 articles representing 309 patients were included in this scoping review. Of the articles reviewed, standard non-contrast CT radiation doses for pediatric urolithiasis evaluation ranged from 2.9 to 5.5 mSv and low-dose CT radiation dose was reported to be 1.0-2.72 mSv. Only 2 studies directly evaluated low-dose CT imaging compared to standard-dose CT imaging for pediatric urolithiasis assessment. Radiation reduction approaches did not negatively impact urolithiasis detection or characterization in 2 studies reviewed.

CONCLUSIONS

CT radiation doses for suspected or known pediatric urolithiasis are underreported and vary greatly with underutilization of low-dose/ultra-dose protocols for pediatric urolithiasis especially in comparison to the adult population. Results from this scoping review support that low-dose CTprotocols for pediatric stone disease are feasible to reduce radiation exposure.

Comparison of diagnostic accuracy of ultra low-dose computed tomography and X-ray of the kidneys, ureters and bladder for urolithiasis in the follow-up setting

INTRODUCTION

Urolithiasis is frequently followed up with a low-dose computed tomography of the kidneys ureters and bladder (LD-CTKUB) with doses typically less than 3 millisieverts. Although X-ray is a lower dose (0.5-1.1 mSv) alternative for follow up, it has lower diagnostic accuracy and is limited to radiopaque calculi. This study aims to compare the diagnostic accuracy of sub-millisievert ultra-low dose CT (ULD-CTKUB) against X-ray KUB for the follow up of urolithiasis when both are compared against the standard of care of a low-dose CT KUB (LD-CTKUB).

METHODS

This prospective study included patients with a known diagnosis of urolithiasis on prior CTKUB presenting for follow up. Each patient underwent a repeat reference LD-CTKUB, ULD-CTKUB and X-ray KUB. All imaging studies were interpreted by three readers. The radiation dose and quantitative noise was calculated for each CT. Both CT and X-ray were assessed for the presence, number and size of all calculi ≥2 mm.

RESULTS

A total of 58 patients were included in this study. LD-CTKUB identified 197 calculi. ULD-CTKUB in our study had a mean effective dose of 0.5 mSv compared to X-ray KUB where doses range in the literature from 0.5 to 1.1 mSv. Per-patient pooled analysis for intrarenal calculi when comparing ULD-CTKUB versus X-ray KUB against a reference LD-CTKUB found a sensitivity of 90% versus 67% (P < 0.01) and specificity of 93% versus 98% (P = 0.18) respectively. For ureteric calculi, the sensitivity was 67% versus 33% (P < 0.01) and specificity 94% versus 94% (P = 1.00) respectively. Per-stone pooled analysis detection rate was 79% for ULD-CTKUB versus 48% for X-ray (P < 0.01) when each was compared to the reference LD-CTKUB. Interobserver agreement was high for intrarenal calculi and moderate for ureteric calculi.

CONCLUSION

Sub-millisievert ULD-CTKUB had lower doses and higher sensitivity than X-ray in patients requiring follow up of known urolithiasis.

Dose Optimization Using a Deep Learning Tool in Various CT Protocols for Urolithiasis: A Physical Human Phantom Study

Background and Objectives: We attempted to determine the optimal radiation dose to maintain image quality using a deep learning application in a physical human phantom. Materials and Methods: Three 5 × 5 × 5 mm3 uric acid stones were placed in a physical human phantom in various locations. Three tube voltages (120, 100, and 80 kV) and four current-time products (100, 70, 30, and 15 mAs) were implemented in 12 scans. Each scan was reconstructed with filtered back projection (FBP), statistical iterative reconstruction (IR, iDose), and knowledge-based iterative model reconstruction (IMR). By applying deep learning to each image, we took 12 more scans. Objective image assessments were calculated using the standard deviation of the Hounsfield unit (HU). Subjective image assessments were performed by one radiologist and one urologist. Two radiologists assessed the subjective assessment and found the stone under the absence of information. We used this data to calculate the diagnostic accuracy. Results: Objective image noise was decreased after applying a deep learning tool in all images of FBP, iDose, and IMR. There was no statistical difference between iDose and deep learning-applied FBP images (10.1 ± 11.9, 9.5 ± 18.5 HU, p = 0.583, respectively). At a 100 kV-30 mAs setting, deep learning-applied FBP obtained a similar objective noise in approximately one third of the radiation doses compared to FBP. In radiation doses with settings lower than 100 kV-30 mAs, the subject image assessment (image quality, confidence level, and noise) showed deteriorated scores. Diagnostic accuracy was increased when the deep learning setting was lower than 100 kV-30 mAs, except for at 80 kV-15 mAs. Conclusions: At the setting of 100 kV-30 mAs or higher, deep learning-applied FBP did not differ in image quality compared to IR. At the setting of 100 kV-30 mAs, the radiation dose can decrease by about one third while maintaining objective noise.

The Incidence and Risk Factors for Emergency Department Imaging in Acute Renal Colic

Objective: To determine the incidence of and risk factors for imaging in patients presenting to the emergency department (ED) with renal colic. Subject/Patients and Methods: We conducted a population-based cohort study in the province of Ontario, utilizing linked administrative health data. Patients who presented to an ED with renal colic between April 1, 2010, and June 30, 2020, were included. The rate of initial imaging (CT scans and ultrasound [U/S]) and repeat imaging within 30 days was determined. Generalized linear models were utilized to evaluate patient and institutional-level characteristics associated with imaging, and specifically CT vs U/S. Results: There were 397,491 index renal colic events, of which 67% underwent imaging (CT 68%, U/S 27%, and CT+U/S same day 5%). Repeat imaging was performed in 21% of events (U/S in 12.5%, CT in 8.4%) at a median of 10 days. Of those with an initial U/S, 28% had repeat imaging compared with 18.5% for those with an initial CT. Undergoing an initial CT was associated with being male, urban residence, later year of cohort entry, history of diabetes mellitus and inflammatory bowel disease, and presentation to nonacademic hospitals of larger size, or with a higher volume of ED visits. Conclusion: Two-thirds of renal colic patients underwent imaging, and CT was the most utilized modality. Patients undergoing an initial CT had a lower likelihood of repeat imaging within 30 days. The utilization of CT increased over time and was more common in males and those presenting to nonacademic hospitals of larger size, or with higher ED volumes. Our study highlights the patient- and institution-level factors that need to be targeted with prevention strategies to reduce the utilization of CT scans, when possible, for cost reduction and to minimize patient exposure to ionizing radiation.

Is it necessary to define new diagnostic reference levels during pandemics like the Covid19-?

Introduction

This study intended to assess the dose length product (DLP), effective cumulative radiation dose (E.D.), and additional cancer risk (ACR) due to a chest CT scan to detect or follow up the Covid-19 disease in four university-affiliated hospitals that used different imaging protocols. Indeed, this study aimed to examine the differences in decision-making between different imaging centers in choosing chest CT imaging protocols during the pandemic, and to assess whether a new diagnostic reference level (DRL) is needed in pandemic situations.

Methods

This retrospective study assessed the E.D. of all chest imagings for Covid-19 for six months in four different hospitals in our country. Imaging parameters and DLP (mGy.cm) were recorded. The E.D.s and ACRs from chest CT scans were calculated using an online calculator.

Results

Thousand-six hundred patients were included in the study. The mean cumulative dose due to chest CT was 3.97 mSv which might cause 2.59 × 10^-2 ACR. The mean cumulative E.D. in different hospitals was in the range of 1.96-9.51 mSv.

Conclusions

The variety of mean E.D.s shows that different hospitals used different imaging protocols. Since there is no defined DRL in the pandemic, some centers use routine protocols, and others try to reduce the dose but insufficiently.In pandemics such as Covid-19, when CT scan is used for screening or follow-up, DLPs can be significantly lower than in normal situations. Therefore, international regularized organizations such as the international atomic energy agency (IAEA) or the international commission on radiological protection (IRCP) should provide new DRL ranges.

Does unenhanced computerized tomography as imaging standard post-retrograde intrarenal surgery paradoxically reduce stone-free rate and increase additional treatment for residual fragments? Outcomes from 5395 patients in the FLEXOR study by the TOWER group

Background

Assessment of residual fragments (RFs) is a key step after treatment of kidney stones.

Objective

To evaluate differences in RFs estimation based on unenhanced computerized tomography (CT) versus X-rays/ultrasound after retrograde intrarenal surgery (RIRS) for kidney stones.

Design

A retrospective analysis of data from 20 centers of adult patients who had RIRS was done (January 2018-August 2021).

Methods

Exclusion criteria: ureteric stones, anomalous kidneys, bilateral renal stones. Patients were divided into two groups (group 1: CT; group 2: plain X-rays or combination of X-rays/ultrasound within 3 months after RIRS). Clinically significant RFs (CSRFs) were considered RFs ⩾ 4 mm. One-to-one propensity score matching for age, gender, and stone characteristics was performed. Multivariable logistic regression analysis was performed to evaluate independent predictors of CSRFs.

Results

A total of 5395 patients were included (1748 in group 1; 3647 in group 2). After matching, 608 patients from each group with comparable baseline and stone characteristics were included. CSRFs were diagnosed in 1132 patients in the overall cohort (21.0%). Post-operative CT reported a significantly higher number of patients with RFs ⩾ 4 mm, before (35.7% versus 13.9%, p < 0.001) and after matching (43.1% versus 23.9%, p < 0.001). Only 21.8% of patients in the matched cohort had an ancillary procedure post-RIRS which was significantly higher in group 1 (74.8% versus 47.6%, p < 0.001). Age [OR 1.015 95% confidence interval (CI) 1.009-1.020, p < 0.001], stone size (OR 1.028 95% CI 1.017-1.040, p < 0.001), multiple stones (OR 1.171 95% CI 1.025-1.339, p = 0.021), lower pole stone (OR 1.853 95% CI 1.557-2.204, p < 0.001) and the use of post-operative CT scan (OR 5.9883 95% CI 5.094-7.037, p < 0.001) had significantly higher odds of having CSRFs.

Conclusions

CT is the only reliable imaging to assess the burden of RFs following RIRS and urologist should consider at least one CT scan to determine the same and definitely plan reintervention only based on CT rather than ultrasound and X-ray combination.

Retrograde Intrarenal Surgery in Children: Evolution, Current Status, and Future Trends

Introduction: Incidence of urolithiasis in children has increased in recent years and with technological advancements and miniaturization of surgical instruments, pediatric urologists have acquired an impressive arsenal for their treatment. Retrograde intrarenal surgery (RIRS) has gained widespread popularity as it is a natural extension of semirigid ureteroscopy and can be done through natural orifice minimizing the morbidity of percutaneous access. The aim of this narrative review is to describe how RIRS has evolved over the decades in children and if the age-related anatomical difference impacts reported outcomes especially stone-free rate (SFR) and complications. Materials and Methods: An electronic literature search from inception to October 15, 2021 was performed using Medical Subject Heading terms in several combinations on PubMed, EMBASE, and Web of Science without language restrictions. A total of 2022 articles were founded and 165 articles were full-text screening. Finally, 2 pediatric urologists included 51 articles that summarize the available literature regarding the development and use of RIRS in children. Results: RIRS as of today is well established as a superior modality for all stones in all locations compared with extracorporeal shockwave lithotripsy both in children and adults. The passive dilation has decreased the need of active ureteral dilation, but the need to perform prestenting is not defined yet. Regarding the use of the ureteral access sheath, the literature tends to lean toward its placement in most cases, but we do not know its long-term effects over the growth of children. Finally, the SFR has increased as the experience of pediatric urologists increases, as well as the number of complications has decreased. Conclusion: RIRS in pediatrics has crossed many milestones, yet many areas need further research and larger data are required to make RIRS the procedure of choice for renal stone management in children across all age groups.

Renal and Urological Disorders Associated With Inflammatory Bowel Disease

Renal and urinary tract complications related to inflammatory bowel disease (IBD) have been relatively understudied in the literature compared with other extraintestinal manifestations. Presentation of these renal manifestations can be subtle, and their detection is complicated by a lack of clarity regarding the optimal screening and routine monitoring of renal function in IBD patients. Urolithiasis is the most common manifestation. Penetrating Crohn's disease involving the genitourinary system as an extraintestinal complication is rare but associated with considerable morbidity. Some biologic agents used to treat IBD have been implicated in progressive renal impairment, although differentiating between drug-related side effects and deteriorating kidney function due to extraintestinal manifestations can be challenging. The most common findings on renal biopsy of IBD patients with renal injury are tubulointerstitial nephritis and IgA nephropathy, the former also being associated with drug-induced nephrotoxicity related to IBD medication. Amyloidosis, albeit rare, must be diagnosed early to reduce the chance of progression to renal failure. In this review, we evaluate the key literature relating to renal and urological involvement in IBD and emphasize the high index of suspicion required for the prompt diagnosis and treatment of these manifestations and complications, considering the potential severity and implications of acute or chronic loss of renal function. We also provide suggestions for future research priorities.

Multi-institutional variation in performance of low dose computerized tomography for the evaluation of suspected nephrolithiasis

Introduction and Objective Guidelines from the American Urological Association (AUA) and American College of Radiology (ACR) recommend that patients with suspected nephrolithiasis undergo low dose computerized tomography (LD CT KUB) as opposed to higher dose conventional imaging. We hypothesized that even at institutions with established LD protocols, higher dose imaging is common. Methods We identified four academic medical centers where LD CT KUB protocols were implemented to yield an Effective Dose (EDose) consistent with national guidelines. Fifty consecutive adult patients who underwent CT KUB specifically for the evaluation of nephrolithiasis were retrospectively reviewed at each site. Patient age, sex, BMI, imaging location, and EDose (millisieverts, mSv) were recorded. Results 200 patients with a mean age of 54 years were identified. 46 patients (23%) underwent CT KUB with EDose ≤ 4 mSv, accounting for 10-48% of each institution's cohort. 116 patients had a BMI < 30, and would have been expected to receive LD CTs by the AUA criteria for LD CT KUB. Within this subset, only 37 patients (32%) actually underwent LD CT KUB. The highest dose CT KUB at each institution resulted in EDose of 33.8-44.6 mSv, exceeding the recommended exposure of LD CT KUB by tenfold. Conclusions At academic institutions where LD CT KUB was implemented for the evaluation of nephrolithiasis, a minority of patients with BMI < 30 receive guideline-concordant imaging. Differences in patient BMI did not account for the variation in radiation exposure. Further research is necessary to elucidate barriers to low dose CT implementation.

Using Intraoperative Portable CT Scan to Minimize Reintervention Rates in PCNL: A Prospective Trial

BACKGROUND AND PURPOSE

More than 40% of patients undergoing PCNL are left with residual stone fragments and often require secondary procedures. Portable CT (PCT) technology allows surgeons to obtain intraoperative cross-sectional imaging, identify and extract residual stones immediately, and thereby reduce the need for subsequent procedures. This prospective trial evaluates how incorporation of PCT during PCNL affects perioperative outcomes.

PATIENTS AND METHODS

We prospectively enrolled eligible patients undergoing initial PCNL for this trial (n=60), which entailed a single intraoperative CT-abdomen and ipsilateral antegrade ureteroscopy when the surgeon felt stone treatment was visually complete. If residual fragments were identified, the surgeon continued nephroscopy to find and remove them; if not, the procedure was concluded. These patients were compared to a retrospective cohort (n=174) who underwent initial PCNL with post-operative imaging performed the following day.

RESULTS

The two cohorts had similar demographic properties and stone characteristics, and location of percutaneous access. In the prospective arm, 50% of intraoperative PCT scans identified residual fragments, prompting continuation of surgery to remove them. This cohort had significantly higher stone-free rate (82% vs. 36%, p<0.01), lower rate of planned reintervention (7% vs. 32%, p<0.01), lower rate of urgent presentation with ureteral obstruction (0% vs. 7%, p=0.04), lower total CT-based effective radiation dose (8.4 vs. 14.6 mSv, p<0.01), and shorter length of stay (2.3 vs. 3.5 days, p<0.01) when compared to the retrospective cohort that did not use intraoperative PCT.

CONCLUSIONS

Obtaining an intraoperative portable CT scan during PCNL can substantially improve perioperative outcomes. Further evaluation of this modality through a randomized-controlled trial is warranted.

Expanding the Utilization of Low-Dose Computed Tomography in Plastic and Reconstructive Surgery Based on Validated Practices Among Surgical Specialties

INTRODUCTION

As computed tomography (CT) usage increases, so have concerns over radiation-induced malignancy. To mitigate these risks, low-dose CT (LDCT) has emerged as a versatile alternative by other specialties, although its use in plastic surgery remains sparse. This study aimed to investigate validated uses of LDCT across surgical specialties and extrapolate these insights to expand its application for plastic surgeons.

METHODS

A systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using search terms "low dose CT" OR "low dose computed tomography" AND "surgery," where the name of each surgical specialty was substituted for word "surgery" and each specialty term was searched separately in combination with the 2 CT terms. Data on radiation dose, outcomes, and level of evidence were collected. Validated surgical applications were correlated with similar procedures and diagnostic tests performed routinely by plastic surgeons to extrapolate potential applications for plastic surgeons.

RESULTS

A total of 3505 articles were identified across surgical specialties, with 27 ultimately included. Depending on the application, use of LDCT led to a 25% to 97% reduction in radiation dose and all studies reported noninferior image quality and diagnostic capability compared with standard-dose CT. Potential identified uses included the following: evaluation of soft tissue infections, preoperative and postoperative management of facial and hand fractures, flap design, 3D modeling, and surgical planning.

DISCUSSION

Low-dose CT is a valid imaging alternative to standard-dose CT. Expanded utilization in plastic surgery should be considered to minimize the iatrogenic effects of radiation and to promote patient safety without compromising outcomes.

Patients’ perception of radiation safety of radiological investigations in urology

Background:

This study analyses patients’ knowledge of common radiological investigations.

Methods:

At a university teaching hospital, 100 patients attending urological clinics, who had had a plain X-ray of the kidney, ureter and bladder, magnetic resonance imaging (MRI), computed tomography (CT) or ultrasound scan (USS), completed a 14-item Likert scale questionnaire assessing patients’ perception of safety (both qualitatively and quantitatively) and the hazards of radiological investigations.

Results:

Using a radiation risk score, patients perceived the following investigations to be in rank order of increasing radiation risk: USS (0.84), MRI (1.4), CT (1.5) and plain X-ray (1.6). On the same scale (0–5), only 17% of patients correctly attributed a risk score of 3 or 4 for a CT scan, and 49% were able to identify a plain X-ray’s risk score correctly as 1 or 2. In addition, more patients identified CT (34%) as having a lower risk of 0 than an X-ray (24%). The mean (1.35 vs. 1.60), median (1 vs. 1) and mode (0 vs. 1) for the CT risk scores are less than those for a plain X-ray, demonstrating that patients perceived CT scans to be safer. Further, the majority of patients understood USS to have no radiation exposure (56%) but thought that MRI posed a radiation risk (62%). Patients were unable to quantify radiation exposure correctly: USS (37% correctly attributed – 0 mSv), MRI (22% – 0 mSv), X-ray (47% – 1 mSv) and CT scan (28% – 10 mSv).

Conclusion:

This demonstration of suboptimal patient awareness of radiation exposure of common radiological investigations highlights the need to educate patients in order to improve patient autonomy and possibly reduce the demand for unnecessary radiological investigations such as CT.

Level of evidence:

Level 2.

Resolution of Hydronephrosis and Pain to Predict Stone Passage for Patients With Acute Renal Colic

OBJECTIVE

To study patients who presented to the Emergency Department with acute renal colic to determine if resolution of hydronephrosis and pain accurately predicts stone passage on follow-up CT.

MATERIALS AND METHODS

This is a secondary analysis of a multicenter prospective randomized clinical trial of patients diagnosed by computed tomography (CT) scan with a symptomatic ureteral stone < 9 mm in diameter. Participants were followed after randomization to evaluate for analgesic use and to assess stone passage and hydronephrosis on a repeat CT scan obtained at 29-36 days.

RESULTS

Four-hundred-three patients were randomized in the original study and patients were included in this analysis if they did not have surgery for stone removal and had a CT scan and information on pain medication at follow-up (N = 220). Hydronephrosis was detected in 181 (82%) on initial CT. At follow-up CT, 43 (20%) participants had a persistent ureteral stone. Of these patients, 36 (84%) had no pain, 26 (60%) did not have hydronephrosis, and 23 (53%) had neither pain nor hydronephrosis. Resolution of hydronephrosis was associated with stone passage (RR 4.6, 95% CI 1.9, 11.0), while resolution of pain was not (RR 1.1, 95% CI 0.9, 1.4).

CONCLUSION

In patients with urinary stone disease, stone passage is associated with resolution of hydronephrosis but not resolution of pain. In patients with persistent ureteral stones, neither pain nor hydronephrosis are consistently present. These findings have important implications on follow-up imaging of patients with urinary stone disease.

Diagnostic performance of ultra-low dose versus standard dose CT for non-traumatic abdominal emergencies

PURPOSE

The purpose of this study was to compare the diagnostic performance of ultra-low dose (ULD) to that of standard (STD) computed tomography (CT) for the diagnosis of non-traumatic abdominal emergencies using clinical follow-up as reference standard.

MATERIALS AND METHODS

All consecutive patients requiring emergency abdomen-pelvic CT examination from March 2017 to September 2017 were prospectively included. ULD and STD CTs were acquired after intravenous administration iodinated contrast medium (portal phase). CT acquisitions were performed at 125mAs for STD and 55mAs for ULD. Diagnostic performance was retrospectively evaluated on ULD and STD CTs using clinical follow-up as a reference diagnosis.

RESULTS

A total of 308 CT examinations from 308 patients (145 men; mean age 59.1±20.7 (SD) years; age range: 18-96 years) were included; among which 241/308 (78.2%) showed abnormal findings. The effective dose was significantly lower with the ULD protocol (1.55±1.03 [SD] mSv) than with the STD (3.67±2.56 [SD] mSv) (P<0.001). Sensitivity was significantly lower for the ULD protocol (85.5% [95%CI: 80.4-89.4]) than for the STD (93.4% [95%CI: 89.4-95.9], P<0.001) whereas specificities were similar (94.0% [95%CI: 85.1-98.0] vs. 95.5% [95%CI: 87.0-98.9], respectively). ULD sensitivity was equivalent to STD for bowel obstruction and colitis/diverticulitis (96.4% [95%CI: 87.0-99.6] and 86.5% [95%CI: 74.3-93.5] for ULD vs. 96.4% [95%CI: 87.0-99.6] and 88.5% [95%CI: 76.5-94.9] for STD, respectively) but lower for appendicitis, pyelonephritis, abscesses and renal colic (75.0% [95%CI: 57.6-86.9]; 77.3% [95%CI: 56.0-90.1]; 90.5% [95%CI: 69.6-98.4] and 85% [95%CI: 62.9-95.4] for ULD vs. 93.8% [95%CI: 78.6-99.2]; 95.5% [95%CI: 76.2-100.0]; 100.0% [95%CI: 81.4-100.0] and 100.0% [95%CI: 80.6-100.0] for STD, respectively). Sensitivities were significantly different between the two protocols only for appendicitis (P=0.041).

CONCLUSION

In an emergency context, for patients with non-traumatic abdominal emergencies, ULD-CT showed inferior diagnostic performance compared to STD-CT for most abdominal conditions except for bowel obstruction and colitis/diverticulitis detection.

Minimizing radiation dose in management of stone disease: how to achieve 'ALARA'

PURPOSE OF REVIEW

Exposure to radiation is known to have adverse effects such as secondary malignancies. Patients with nephrolithiasis are exposed to radiation in the workup and treatment of their condition. Furthermore, exposure to radiation is often repeated due to the high recurrence rate of nephrolithiasis.

RECENT FINDINGS

We discuss practices inside and outside of the operating room to strive to keep radiation exposure as low as reasonably achievable (ALARA) for patients being treated for nephrolithiasis. These efforts include reduced dose computed tomography scans, fluoroless surgical techniques and new alternative technologies.

SUMMARY

Maintaining radiation exposure ALARA for our patients is increasingly practical. The urologist must make every effort to adhere to ALARA principles to protect patients from the stochastic effects of radiation.

Percutaneous Nephrolithotomy with Intraoperative Computed Tomography Scanning Improves Stone-Free Rates

Introduction: The use of fluoroscopy during percutaneous nephrolithotomy (PCNL) may lead to an overestimation of stone-free rates. The objective of this study is to demonstrate the feasibility of intraoperative CT-guided PCNL compared with standard of care (SoC) PCNL. Patients and Methods: A prospective feasibility study (20 patients undergoing PCNL with an intraoperative CT scan between June 2017 and February 2020) and a retrospective study of a historical cohort (20 consecutive patients undergoing SoC PCNL between September 2015 and September 2016) were conducted. All procedures were performed by an expert endourologist in a tertiary referral hospital. Follow-up was performed at 6 weeks postoperatively. The primary goal is to investigate the practicality and potential benefits and harms of intraoperative CT scanning during PCNL. Secondary outcomes are a stone-free rate after the 6-week follow-up, perioperative radiation exposure, the need for postoperative imaging, and peri- and postoperative complications. Statistical significance was considered at p < 0.05. Results: The initial stone-free rate in the CT scan group was 65% (n = 13). In 25% (n = 5) of patients, residual stone fragments were removed after the perioperative CT scan. In the SoC group, 85% (n = 17) of patients were thought to be stone free perioperatively. At the 6-week follow-up, 80% (n = 16) in the CT scan group vs 50% in the SoC group (n = 10) were found to be stone free. Radiation exposure, perioperatively, was higher in the CT scan group. Complications were comparable between groups. Limitations of the study are the nonrandomized design of the study and nonstandardized follow-up imaging. Conclusions: Intraoperative CT scanning during PCNL is feasible and gives a better estimate of any remaining stone fragments compared with fluoroscopy only.

THE USE OF LOW-DOSE CT WITH ADAPTIVE STATISTICAL ITERATIVE RECONSTRUCTION FOR THE DIAGNOSIS OF URINARY CALCULI

This study aimed to explore the diagnosis of urinary calculi through utilisation of low-dose computed tomography (LDCT) with adaptive statistical iterative reconstruction (ASIR). Data from 140 patients that had undergone pathological or operative diagnosis with urinary calculi were analysed. Patients were divided into two groups based on whether they received conventional-dose computed tomography (CDCT) or LDCT, respectively, followed by filtered back projection or ASIR. Average CDCT radiation doses were roughly 4-fold higher than LDCT doses. Despite this difference, there were no significant differences between groups with respect to stone size or location, image quality (P = 0.261), image noise (P = 0.153) and diagnostic efficacy (P = 0.371). LDCT is an effective approach to urinary calculi diagnosis, performing to ASIR while decreasing the effective radiation dose, improving the safety of this procedure.

A prospective, matched comparison of ultra-low and standard-dose computed tomography for assessment of renal colic

OBJECTIVE

To determine the diagnostic accuracy of ultra-low-dose computed tomography (ULDCT) compared with standard-dose CT (SDCT) in the evaluation of patients with clinically suspected renal colic, in addition to secondary features (hydroureteronephrosis, perinephric stranding) and additional pathological entities (renal masses).

PATIENTS AND METHODS

A prospective, comparative cohort study was conducted amongst patients presenting to the emergency department with signs and symptoms suggestive of renal or ureteric colic. Patients underwent both SDCT and ULDCT. Single-blinded review of the image sets was performed independently by three board-certified radiologists.

RESULTS

Among 21 patients, the effective radiation dose was lower for ULDCT [mean (SD) 1.02 (0.16) mSv] than SDCT [mean (SD) 4.97 (2.02) mSv]. Renal and/or ureteric calculi were detected in 57.1% (12/21) of patients. There were no significant differences in calculus detection and size estimation between ULDCT and SDCT. A higher concordance was observed for ureteric calculi (75%) than renal calculi (38%), mostly due to greater detection of calculi of <3 mm by SDCT. Clinically significant calculi (≥3 mm) were detected by ULDCT with high specificity (97.6%) and sensitivity (100%) compared to overall detection (specificity 91.2%, sensitivity 58.8%). ULDCT and SDCT were highly concordant for detection of secondary features, while ULDCT detected less renal cysts of <2 cm. Inter-observer agreement for the ureteric calculi detection was 93.9% for SDCT and 87.8% for ULDCT.

CONCLUSION

ULDCT performed similarly to SDCT for calculus detection and size estimation with reduced radiation exposure. Based on this and other studies, ULDCT should be considered as the first-line modality for evaluation of renal colic in routine practice.