Spiral Computerized Tomography in the Evaluation of Acute Flank Pain: A Replacement for Excretory Urography

The role of serum and urinary markers in predicting obstructing ureteral stones and reducing unjustified non-contrast computerized tomographic scans in emergency departments

INTRODUCTION

The reported yield of non-contrast computed tomography (NCCT) in assessing flank pain and obstructive urolithiasis (OU) in emergency departments (EDs) is only ~ 50%. We investigated the potential capability of serum and urinary markers to predict OU and improve the yield of NCCT in EDs.

METHODS

All consecutive ED patients with acute flank pain suggestive of OU and assessed by NCCT between December 2019 and February 2020 were enrolled. Serum white blood cells (WBC), C-reactive protein (CRP) and creatinine (Cr) levels, and urine dipstick results were analyzed for association with OU, and unjustified NCCT scan rates were calculated.

RESULTS

NCCTs diagnosed OU in 108 of the 200 study patients (54%). The median WBC, CRP, and Cr values were 9,100/µL, 4.3 mg/L, and 1 mg/dL, respectively. Using ROC curves, WBC = 10,000/µL and Cr = 0.95 mg/dl were the most accurate thresholds to predict OU. Only WBC ≥ 10,000/µL (OR = 3.7, 95% CI 1.6-8.3, p = 0.002) and Cr ≥ 0.95 mg/dl (OR = 5, 95% CI 2.3-11, p < 0.001) were associated with OU. Positive predictive value and specificity for detecting OU among patients with combined WBC ≥ 10,000 and Cr ≥ 0.95 were 83% and 89%, respectively. Patients negative to the serum markers criteria underwent significantly more unjustified NCCTs (p = 0.03). The negative predictive value of the serum criteria for justified NCCT scanning was 81%.

CONCLUSIONS

WBC and Cr may be valuable serum markers in predicting OU among patients presenting to EDs with acute flank pain. They may potentially reduce the number of unjustified NCCT scans in the ED setting.

Renal stone density on native CT-scan as a predictor of treatment outcomes in shock wave lithotripsy

Extracorporeal shock wave lithotripsy (ESWL) is considered a standard treatment for nephrolith or kidney stones measuring less than 20 mm. Anatomical, machine-related, and stone factors play pivotal roles in treatment outcomes, the latter being the leading role. This paper examined the relationship between stone density on native CT scans and ESWL treatment to remove renal stones concerning several treatments. One hundred and twenty patients (64 males and 56 females) were enrolled and completed the study from April 2019 to September 2020. Inclusion criteria were a single renal pelvis stone of 5-20 mm to be treated for the first time in adult patients with no urinary or musculoskeletal anatomical abnormalities. We assessed patients' renal function and obtained stone characteristics using a native CT scan. Patients were then scheduled for ESWL by the same machine and operator under fluoroscopy, with two-week intervals between treatment sessions when more than one treatment session was required. Before each new session, a new KUB-US was performed to reevaluate the stone. One hundred and twenty patient records were analyzed, 64 (53.3%) males and 56 (46.7%) females, with a mean age of 38.6 years and a mean stone size of 13.15 mm. Treatment with ESWL cleared stones in 76 (63.3%) patients, while 44 (36.7%) failed the treatment. The mean stone density in patients whose stones were cleared was significantly lower (661 vs. 1001) (P<0.001). Estimating renal calculus (or kidney stone) density on a native CT scan might help prognosticate ESWL treatment outcomes regarding stone clearance rates and the number of sessions required to clear a stone.

Doppler-Assessed Ureteric Jet Frequency: A Valuable Predictor of Ureteric Obstruction

Objectives: To compare ureterovesical jet frequency in non-obstructed versus obstructed ureter secondary to ureteric stone using ultrasonography in patients presenting with ureteral stones.

Study design: Cross-sectional prospective study.

Place of study and duration: Urology Department, The Kidney Centre Post Graduate Training Institute from May 16 to November 15, 2019.

Methods: This study included 97 patients having presented in the emergency department with acute renal colic and were diagnosed as having ureteral stones on a non-contrast-enhanced computed tomography (NCCT). The ureteric jet frequency was measured by Doppler ultrasonography by our radiologist with the Hitachi Aloka F-37 ultrasound machine after they underwent CT. Patients were asked to drink 750-1000 ml of liquids 15-20 minutes before their ultrasonographic examination of both kidneys, ureters, and urinary bladder. The kidney size (length and width) and presence/absence of hydronephrosis were evaluated by grayscale ultrasound. Then, with the help of color Doppler ultrasonography, the frequency of the ureteric jet was recorded.

Results: The patient's mean age was 46.66 ± 3.21 years ranging from 37 to 56 years. There were 58 (59.8%) male and 39 (40.2%) female cases. The mean cumulative stone size was 9.77 ± 2.65 mm. According to stone location, 44 (45.4%) cases had upper ureteric, 24 (24.7%) cases had mid ureteric, and 29 (29.9%) cases had lower ureteric stone. The mean obstructive side jet frequency was 0.70/min ± 0.49, and the non-obstructive side jet frequency was 2.89/min ± 1.29 (P < 0.05).

Conclusions: The mean obstructive side jet frequency was 0.70 ± 0.49/min, which, if we compare to the non-obstructed normal ureter, is significantly less. Hence, color Doppler ultrasonography can be helpful to patients who were previously diagnosed with ureteral stones on NCCT to see if their stone has passed. This can be a very cost-effective modality especially in resource-poor countries where repeat CT can be very expensive. The results from this study can also be used in a specific population (i.e., pregnancy) where the use of imaging modalities that involve ionizing radiation is prohibited.

The Outcomes of Extracorporeal Shock Wave Lithotripsy for High-Density Renal Stone on Non-Contrast Computed Tomography

Introduction Urinary lithiasis is usually managed by extracorporeal shock wave lithotripsy (ESWL). Patients are examined using non-contrast computed tomography (NCCT) in order to evaluate the feasibility of ESWL, according to where the stone is located and how big is its size. The objective of this study is to determine the outcomes of ESWL in patients having high-density renal stone, evaluated using NCCT. Materials and methods A descriptive case series study was conducted in the Department of Urology, Sindh Institute of Urology & Transplantation, Karachi for six months. Patients of either gender aged between 25-50 years, who presented with solitary renal and ureteric calculi of 0.5-2 cm in diameter and high-density renal stones [>750 hounsfield units (HU)] were enrolled. ESWL was performed and a satisfactory outcome was defined as complete stone clearance in less than or equal to three ESWL sessions. Statistical Package for Social Sciences (SPSS) (IBM Corp., Armonk, NY) was used to analyze frequencies and percentages of the number of ESWL sessions, complete renal stone clearances, and satisfactory outcomes at the end of 12 weeks. A p-value of <0.05 was considered significant. Results The mean age of the patient was reported to be 34.08 ± 9.53 years. 51.6% male preponderance was noticed. Renal and ureteric stones were found in 69.7% and 30.3% of patients, respectively. 21.3% of patients showed stone clearance after two ESWL sessions, 27% of patients after three ESWL sessions, and 51.6% of patients after four ESWL sessions. Stone clearance was found in 58.2% of patients and a satisfactory outcome was found in 42.6% of patients. Conclusions Our results signify a satisfactory outcome of extracorporeal shock wave lithotripsy for high-density renal stone on non-contrast computed tomography. Further studies on a larger scale are needed to validate these results.

Clinical and Radiological Predictors of Early Intervention in Acute Ureteral Colic

PURPOSE

Acute ureteric colic (AUC) is generally one of the most common reasons for emergency department attendance. Expectant management is recommended in non-complicated ureteral calculi. However, data regarding the optimal duration of observation or indications of early intervention (EI) are not well understood. This article describes the clinical and radiological factors that promote EI in AUC.

PATIENTS AND METHODS

This was an observational and retrospective cohort study. Patients with AUC diagnosed based on non-contrast computerized tomography (NCCT) between 2019 and 2020 were enrolled in the study. These patients were classified into two main categories: spontaneous passage of stone (SSP) and EI. In addition, a comparative analysis was performed to identify clinical and radiological variables that promote EI.

RESULTS

One-hundred and sixty-one patients were included. High WBCs are associated with a significant increase in EI. Forty-three percent (n=37) of patients with serum WBCs higher than 10 had an EI, while 23% had SSP (n=17;p<0.001). High CRP level is also significantly associated with EI (n=36; 86%; p<0.001). Upper and middle ureteral calculi are statistically associated with EI (n=54; 62%) in comparison to the SSP cohort (n=22; 30%;p<0.001). EI is also linked to the maximal length of ureteric calculi (MCL) of 9 mm (6-13mm), and HU density of stone of 700 (430-990) H.U (p<0.001). Ureteric stone volume of 0.2 (0.06-0.3) cm³ is significantly associated with EI (p<0.001). Ureteral wall thickness of 3 (2-3 mm), the presence of extrarenal pelvis (n=20; 23%), and AP diameter of renal pelvis 18 (13-28 mm) are all significantly associated with a higher rate of EI (p<0.001). Multiple binary logistic regression analysis showed that MCL is the strongest predictor of EI.

CONCLUSION

MCL is an independent and robust predictor of EI in AUC. Biochemical variables and radiological characteristics can also act as an adjunct to promote EI.

Development of a computational tool for estimating computed tomography dose parameters

BACKGROUND

Computed Tomographic (CT) imaging procedures have been reported as the main source of radiation in diagnostic procedures compared to other modalities. To provide the optimal quality of CT images at the minimum radiation risk to the patient, periodic inspections and calibration tests for CT equipment are required. These tests involve a series of measurements that are time consuming and may require specific skills and highly-trained personnel.

OBJECTIVE

This study aims to develop a new computational tool to estimate the dose of CT radiation outputs and assist in the calibration of CT scanners. It may also provide an educational resource by which radiological practitioners can learn the influence of technique factors on both patient radiation dose and the produced image quality.

METHODS

The computational tool was developed using MATLAB in order to estimate the CT radiation dose parameters for different technique factors. The CT radiation dose parameters were estimated from the calibrated energy spectrum of the x-ray tube for a CT scanner.

RESULTS

The estimated dose parameters and the measured values utilising an Adult CT Head Dose Phantom showed linear correlations for different tube voltages (80 kVp, 100 kVp, 120 kVp, and 140 kVp), with R2 nearly equal to 1 (0.99). The maximum differences between the estimated and measured CTDIvol were under 5 %. For 80 kVp and low tube currents (50 mA, 100 mA), the maximum differences were under 10%.

CONCLUSIONS

The prototyped computational model provides a tool for the simulation of a machine-specific spectrum and CT dose parameters using a single dose measurement.

Dual-energy computed tomography: A reliable and established tool for In vivo differentiation of uric acid from nonuric acid renal Stones

Background

Dual-energy computed tomography (DECT) utilises the technique of simultaneous image acquisition of a body part at two different energy levels of the X-ray tubes. We used the DECT in this project to study its accuracy in non-invasive in vivo differentiation of uric acid (UA) calculi from non-UA calculi using the 3^rd generation dual-source computed tomography (CT) scanner.

Materials and Methods

The DECT ratios of the various stones were noted and compared with the postextraction analysis of stones for composition. Sixty stones from 53 patients were included in the study, and their DECT results were compared with the post-extraction analysis (by infrared spectroscopy as the standard comparative method).

Results

DECT was highly sensitive and specific in the diagnosis of various types of calculi based on their dual-energy ratio. It was found to be 100% sensitive and specific for differentiating UA stones from the non-UA stones. The DE ratio for the UA stones was found to be 0.98-1.13. Most of the stones belonged to non-UA category (85%), and only 15% were UA calculi. The sensitivity and specificity in differentiating a calcium oxalate from non-calcium oxalate calculus was 97.8% and 92.3%, respectively.

Conclusion

DECT using the 3^rd generation CT scanners is highly sensitive in the determination of urinary calculi composition which will be very helpful to the treating surgeon in selecting the optimal modality of treatment as UA stones are amenable to medical therapy while most of the non-UA stones require surgical intervention.

A novel method for prediction of stone composition: the average and difference of Hounsfield units and their cut-off values

PURPOSE

The purpose of the study was to investigate the predictive value of stone measurements by including a novel method on non-contrast computed tomography (NCCT) images for stone composition.

METHODS

We retrospectively evaluated patients who had stone analysis, NCCT images, and underwent percutaneous nephrolithotomy between 2013 and 2016. Patient characteristics, stone measurements on NCCT images, and stone analysis results were evaluated. Hounsfield unit (HU) values (maximum (HU_max), minimum (HU_min), and average (HU_ave) of HU values) were investigated on NCCT images. HU_diff was calculated as the difference between the HU_max and the HU_min values. Patients were divided into seven stone groups and data were compared. Then patients were separately divided into two groups according to mineral complexity (mono-mineral and multi-mineral groups) and calcium-based (calcium and other stone groups) evaluation.

RESULTS

In the study, 115 patients were evaluated. Age, gender, HU_min, HU_max, and HU_ave were significantly different between the stone groups. HU_diff and HU_ave were found to be 341.5 HU (AUC = 0.719, p = 0.017) and 1051.5 HU (AUC = 0.701, p = 0.029) as cut-off, respectively. Seventy of 72 > 341.5 HU_diff patients and 64 of 67 > 1051.5 HU_ave patients had multi-mineral stones (p = 0.001, OR 9.26, and p = 0.028, OR 4.27), respectively. In multivariate analysis, > 341.5 HU_diff rate was significantly higher in multi-mineral and calcium stone groups; HU_ave was also significantly higher in the calcium stone group.

CONCLUSIONS

HU_diff and HU_ave were significant predictors of mineral complexity. HU_diff of < 341.5 HU showed 81.8% sensitivity and 67.2% specificity for identification of mono-mineral stones.

Sensitivity of Noncontrast Computed Tomography for Small Renal Calculi With Endoscopy as the Gold Standard

OBJECTIVE

To compare the sensitivity of noncontrast computed tomography (CT) with endoscopy for detection of renal calculi. Imaging modalities for detection of nephrolithiasis have centered on abdominal x-ray, ultrasound, and noncontrast CT. Sensitivities of 58%-62% (abdominal x-ray), 45% (ultrasound), and 95%-100% (CT) have been previously reported. However, these results have never been correlated with endoscopic findings.

METHODS

Idiopathic calcium oxalate stone formers with symptomatic calculi requiring ureteroscopy were studied. At the time of surgery, the number and the location of all calculi within the kidney were recorded followed by basket retrieval. Each calculus was measured and sent for micro-CT and infrared spectrophotometry. All CT scans were reviewed by the same genitourinary radiologist who was blinded to the endoscopic findings. The radiologist reported on the number, location, and size of each calculus.

RESULTS

Eighteen renal units were studied in 11 patients. Average time from CT scan to ureteroscopy was 28.6 days. The mean number of calculi identified per kidney was 9.2 ± 6.1 for endoscopy and 5.9 ± 4.1 for CT (P <.004). The mean size of total renal calculi (sum of the longest stone diameters) per kidney was 22.4 ± 17.1 mm and 18.2 ± 13.2 mm for endoscopy and CT, respectively (P = .06).

CONCLUSION

CT scan underreports the number of renal calculi, probably missing some small stones and being unable to distinguish those lying in close proximity to one another. However, the total stone burden seen by CT is, on average, accurate when compared with that found on endoscopic examination.

Predicting the stone composition of children preoperatively by Hounsfield unit detection on non-contrast computed tomography

INTRODUCTION

Many studies have been performed on adult patients to reveal the relationship between Hounsfield unit (HU) value and composition of stone, but none have focused on childhood.

OBJECTIVE

We aimed to predict stone composition by HU properties in pre-intervention non-contrast computed tomography (NCCT) in children. This could help to orient patients towards more successful interventions.

MATERIALS AND METHODS

Data of 94 children, whose pre-intervention NCCT and post-interventional stone analysis were available were included. Stones were grouped into three groups: calcium oxalate (CaOx), cystine, and struvite. Besides spot urine PH value, core HU, periphery HU, and Hounsfield density (HUD) values were measured and groups were compared statistically.

RESULTS

The mean age of patients was 7 ± 4 (2-17) years and the female/male ratio was 51/43. The mean stone size was 11.7 ± 5 (4-24) mm. There were 50, 38, and 6 patients in the CaOx, cystine, and struvite groups, respectively. The median values for core HU, periphery HU, and mean HU in the CaOx group were significantly higher than the corresponding median values in the cystine and struvite groups. Significant median HUD difference was seen only between the CaOx and cystine groups. No difference was seen between the cystine and struvite groups in terms of HU parameters. To distinguish these groups, mean spot urine PH values were compared and were found to be higher in the struvite group than the cystine group (Table).

DISCUSSION

The retrospective nature and small number of patients in some groups are limitations of this study, which also does not include all stone compositions. Our cystine stone rate was higher than childhood stone composition distribution in the literature. This is because our center is a reference center in a region with high recurrence rates of cystine stones. In fact, high numbers of cystine stones helped us to compare them with calcium stones more accurately and became an advantage for this study.

CONCLUSIONS

NCCT at diagnosis can provide some information for determination of stone composition. While CaOx stones can be discriminated from cystine and struvite stones using HU parameters, a simple spot urine pH assessment must be added to distinguish cystine stones from struvite stones.

Imaging in the diagnosis of pediatric urolithiasis

Pediatric urolithiasis is an important and increasingly prevalent cause of pediatric morbidity and hospital admission. Ultrasound (US) is the recommended primary imaging modality for suspected urolithiasis in children. There is, however, widespread use of CT as a first-line study for abdominal pain in many institutions involved in pediatric care. The objective of this review is to outline state-of-the-art imaging modalities and methods for diagnosing urolithiasis in children. The pediatric radiologist plays a key role in ensuring that the appropriate imaging modality is performed in the setting of suspected pediatric urolithiasis. Our proposed imaging algorithm starts with US, and describes the optimal technique and indications for the use of CT. We emphasize the importance of improved communication with a greater collaborative approach between pediatric and general radiology departments so children undergo the appropriate imaging evaluation.

Ultrasonography Significantly Overestimates Stone Size When Compared to Low-dose, Noncontrast Computed Tomography

OBJECTIVE

To evaluate the differences between low-dose noncontrast computed tomography (NCCT) and renal ultrasound (US) in the identification and measurement of urinary calculi.

MATERIALS AND METHODS

A retrospective review was conducted at 3 institutions of patients evaluated for flank pain with both renal US and NCCT, within 1 day of one another, from 2012 to 2015. Stone presence and size were compared between imaging modalities. Stone size was determined by largest measured diameter. Stones were grouped into size categories (≤5 mm, 5.1-10 mm, and >10 mm) based on NCCT and compared with US. Statistical analysis was performed using 2-sided t tests.

RESULTS

One hundred fifty-five patients received both a renal US and NCCT within 1 day. In 79 patients (51.0%), both US and NCCT identified a stone for size comparison. Fifty-eight patients (37.4%) had a stone visualized on NCCT but not on US, and 2 patients (1.3%) had a stone documented on US but not seen on NCCT. The average NCCT size of the stones missed on US was 4.5 mm. When comparing the average largest stone diameter for US (9.1 mm) vs NCCT (6.9 mm), US overestimated stone size by 2.2 mm (P < .001). US overestimated stone size by 84.6% for stones ≤5 mm, 27.1% for stones 5.1-10 mm, and 3.0% for stones >10 mm.

CONCLUSION

US significantly overestimated stone size and this was most pronounced for small (≤5 mm) stones. The potential for systematic overestimation of stone size with standard US techniques should be taken into consideration when evaluating endourologic treatment options.

Is Hydronephrosis on Ultrasound Predictive of Ureterolithiasis in Patients with Renal Colic?

PURPOSE

Renal ultrasound accurately identifies hydronephrosis but it is less sensitive than computerized tomography for the detection of ureterolithiasis. We investigated whether the presence of hydronephrosis on ultrasound was associated with a ureteral stone in patients who underwent both ultrasound and computerized tomography during the evaluation of acute renal colic.

MATERIALS AND METHODS

We retrospectively reviewed the records of patients from 3 institutions who were evaluated for acute renal colic by both ultrasound and computerized tomography between 2012 and 2015. Patients were included in analysis if ultrasound and computerized tomography were performed on the same day. The presence of ureterolithiasis, stone location and hydronephrosis was reviewed and compared between imaging modalities.

RESULTS

Ureteral stones were present in 85 of 144 patients. Ultrasound identified hydronephrosis in 89.8% of patients and a ureteral stone in 25.9%. Computerized tomography identified hydronephrosis in 91.8% of patients and a ureteral stone in 98.8%. In 75.0% of cases the presence or absence of hydronephrosis on ultrasound correctly predicted the presence or absence of a ureteral stone on computerized tomography. Hydronephrosis on ultrasound had a positive predictive value of 0.77 for the presence of a ureteral stone and a negative predictive value of 0.71 for the absence of a ureteral stone.

CONCLUSIONS

Hydronephrosis on ultrasound did not accurately predict the presence or absence of a ureteral stone on computerized tomography in 25.0% of the patients in this study. Ultrasound is an important tool for evaluating hydronephrosis associated with renal colic but patients may benefit from other studies to confirm the presence or absence of ureteral stones.

Irreversible Renal Function Impairment Due to Silent Ureteral Stones

OBJECTIVE

To evaluate if renal function loss and hydronephrosis due to a silent ureteral stone might be reversed.

MATERIALS AND METHODS

We prospectively selected patients with silent ureteral stones between January 2006 and January 2014. A silent case was considered if there were no specific or subjective symptoms related to the ureteral stone. Patient, stone, and kidney characteristics were evaluated preoperatively, 3 and 12 months postoperatively. Renal function was accessed in the same intervals with serum creatinine (SCr), glomerular filtration rate (GFR), and (99m)Tc-dimercaptosuccinic acid. Patients without complete pre- and postoperative evaluation were excluded. Primary end point was midterm progress of global and ipsilateral renal function. Secondary end points included the evaluation of renal and collecting system anatomy from diagnosis to 12 months after treatment. Analysis of variance with repeated measures and marginal homogeneity test were used to evaluate renal function and hydronephrosis progression.

RESULTS

Twenty-six patients met our inclusion criteria. Mean preoperative SCr and GFR were 1.24 mg/dL and 72.5 mL/min, respectively. At initial scintigraphy, mean renal function was 33.4%. Laser ureterolithotripsy was performed in 84.6% of cases and all patients were rendered stone free. Two patients (8%) developed ureteral stenosis. There was no difference regarding SCr (P = .89), GFR (P = .48), and renal function at scintigraphy (P = .19) during follow-up. Hydronephrosis significantly improved from preoperatively to 3 months postoperatively (P < .0001), but not from 3 to 12 months (P = .065).

CONCLUSION

Patients with silent ureteral stones present with significant impairment of ipsilateral renal function and hydronephrosis at diagnosis. On midterm follow-up evaluation, renal function of the affected unit remains stable whereas hydronephrosis improves after treatment.

Comparison of Non-contrast-Enhanced Computed Tomography and Intravenous Pyelogram for Detection of Patients With Urinary Calculi

Purpose

The aim of this study was to investigate the changing pattern in the use of intravenous pyelogram (IVP), conventional computed tomography (CT), and non-contrast-enhanced computed tomography (NECT) for evaluation of patients with acute flank pain.

Materials and Methods

We retrospectively reviewed the medical records of 2,180 patients with acute flank pain who had visited Bundang Jesaeng General Hospital between January 2008 and December 2012 and analyzed the use of IVP, conventional CT, and NECT for these patients.

Results

During the study period there was a significant increase in NECT use (p<0.001) and a significant decrease in IVP use (p<0.001). Conventional CT use was also increased significantly (p=0.001). During this time the proportion of patients with acute flank pain who were diagnosed with urinary calculi did not change significantly (p=0.971).

Conclusions

There was a great shift in the use of imaging study from IVP to NECT between 2008 and 2012 for patients with acute flank pain.

Nationwide emergency department imaging practices for pediatric urolithiasis: room for improvement

PURPOSE

Children are particularly vulnerable to the harmful effects of medical radiation, and children with urolithiasis comprise a group that may undergo repeated radiation intensive imaging tests. We sought to characterize imaging practices for children presenting to the emergency department with suspected urolithiasis and to determine factors associated with the choice of imaging study.

MATERIALS AND METHODS

Using the 2006 to 2010 Nationwide Emergency Department Sample, we conducted a retrospective cohort study of patients younger than 18 years presenting with suspected urolithiasis. We determined imaging practices for visits to emergency departments where billing codes for computerized tomography and ultrasound were reliably reported. Logistic regression was used to delineate patient and hospital level factors associated with the use of computerized tomography vs ultrasound.

RESULTS

We identified 18,096 pediatric visits for suspected urolithiasis in the 1,191 Nationwide Emergency Department Sample emergency departments with reliable imaging codes. A total of 11,215 patients underwent computerized tomography alone, ultrasound alone or both. Of the patients 9,773 (87%) underwent computerized tomography alone. Computerized tomography use peaked in 2007 and declined thereafter. On multivariate analysis several factors were associated with the use of computerized tomography alone, including smaller proportion of pediatric patients treated at the emergency department, older age, location in the Midwest or South, evaluation at a nonteaching hospital and visit on a weekend.

CONCLUSIONS

Computerized tomography use is highly prevalent for children presenting with suspected urolithiasis. The lowest computerized tomography use is in emergency departments that care for more children. Ultrasound is used infrequently regardless of site. Awareness regarding risks of computerized tomography and consideration of alternatives including ultrasound are warranted in caring for these patients.

Non-contrast CT at comparable dose to an abdominal radiograph in patients with acute renal colic; impact of iterative reconstruction on image quality and diagnostic performance

OBJECTIVES

The aim was to assess the performance of low-dose non-contrast CT of the urinary tract (LD-CT) acquired at radiation exposures close to that of abdominal radiography using adaptive statistical iterative reconstruction (ASiR).

METHODS

Thirty-three patients with clinically suspected renal colic were prospectively included. Conventional dose (CD-CT) and LD-CT data sets were contemporaneously acquired. LD-CT images were reconstructed with 40 %, 70 % and 90 % ASiR. Image quality was subjectively and objectively measured. Images were also clinically interpreted.

RESULTS

Mean ED was 0.48 ± 0.07 mSv for LD-CT compared with 4.43 ± 3.14 mSv for CD-CT. Increasing the percentage ASiR resulted in a step-wise reduction in mean objective noise (p < 0.001 for all comparisons). Seventy % ASiR LD-CT images had higher diagnostic acceptability and spatial resolution than 90 % ASiR LD-CT images (p < 0.001). Twenty-seven calculi (diameter = 5.5 ± 1.7 mm), including all ureteric stones, were correctly identified using 70 % ASiR LD-CT with two false positives and 16 false negatives (diameter = 2.3 ± 0.7 mm) equating to a sensitivity and specificity of 72 % and 94 %. Seventy % ASiR LD-CT had a sensitivity and specificity of 87 % and 100 % for detection of calculi >3 mm.

CONCLUSION

Reconstruction of LD-CT images with 70 % ASiR resulted in superior image quality than FBP, 40 % ASIR and 90 % ASIR. LD-CT with ASIR demonstrates high sensitivity and specificity for detection of calculi >3 mm.

TEACHING POINTS

• Low-dose CT studies for urinary calculus detection were performed with a mean dose of 0.48 ± 0.07 mSv • Low-dose CT with 70 % ASiR detected calculi >3 mm with a sensitivity and specificity of 87 % and 100 % • Reconstruction with 70 % ASiR was superior to filtered back projection, 40 % ASiR and 90 % ASiR images.

As low as reasonably achievable: Methods for reducing radiation exposure during the management of renal and ureteral stones

Imaging for urolithiasis has evolved over the past 30 years. Currently, non-contrast computed tomography (NCCT) remains the first line imaging modality for the evaluation of patients with suspected urolithiasis. NCCT is a dominant source of ionizing radiation for patients and one of its major limitation. However, new low dose NCCT protocols may help to reduce the risk. Fluoroscopy use during operating room (OR) surgical procedures can be a substantial source of radiation for patients, OR staff and surgeons. It is important to consider the amount of radiation patients are exposed to from fluoroscopy during operative interventions for stones. Radiation reduction can be accomplished by appropriate selection of imaging studies and multiple techniques, which minimize the use of fluoroscopy whenever possible. The purpose of this manuscript is to review common imaging modalities used for diagnosing and management of renal and ureteral stones associated with radiation exposure. We also review alternatives and techniques to reduce radiation exposure.

Renal scintigraphy in the acute care setting

Renal scintigraphy is a powerful imaging method that provides both functional and anatomic information, which is particularly useful in the acute care setting. In our institution, for the past 2 decades, we have used a 25-minute renal diuretic protocol, technetium-99m ((99m)Tc) mercaptoacetyltriglycine with simultaneous intravenous injection of furosemide, for all ages and indications, including both native and transplant kidneys. As such, this protocol has been widely used in the workup of acutely ill patients. In this setting, there are common clinical entities which affect patients with native and transplant kidneys. In adult patients with native kidneys one of the most frequent reasons for emergency room visits is renal colic due to urolithiasis. Although unenhanced computed tomography is useful to assess the anatomy in cases of renal colic, it does not provide functional information. Time zero furosemide renal scintigraphy can do both and we have shown that it can effectively stratify patients with renal colic. To this end, 4 characteristic patterns of scintirenography have been identified, standardized, and consistently applied: no obstruction, partial obstruction (mild vs high grade), complete obstruction, and stunned (postdecompressed) kidney. With the extensive use of this protocol over the past 2 decades, a pattern of "regional parenchymal dysfunction" indicative of acute pyelonephritis has also been delineated. This information has proved to be useful for patients presenting with urinary tract infection and suspected pyelonephritis, as well as for patients who were referred for workup of renal colic but were found to have acute pyelonephritis instead. In instances of abdominal trauma, renal scintigraphy is uniquely suited to identify urine leaks. This is also true in cases of suspected leak following renal transplant or from other iatrogenic/postsurgical causes. Patients presenting with acute renal failure can be evaluated with renal scintigraphy. A scintigraphic pattern of "relative preservation of flow as compared to function" has been identified as indicative of acute tubular necrosis, which is distinct from other potential causes of acute renal failure, such as nephrotoxicity and in the case of renal transplants, rejection.

Spontaneous pelvic rupture as a result of renal colic in a patient with klinefelter syndrome

We present the case of a young man with Klinefelter syndrome, who was admitted to our clinic with renal colic. Shortly after admittance, spontaneous decrease in pain has occurred. Ultrasound and intravenous contrast computed tomography were performed, which showed the evidence of urine extravasation at the level of left renal pelvis and a 4 mm stone in the lower third of the left ureter. The management with a double-J ureteric stent for three weeks was successful. Then, the stent was removed and computed tomography confirmed the absence of urine extravasation. We also analyze the literature related to this case and discuss the main mechanisms of collecting system rupture.

Longitudinal stone diameter on coronal reconstruction of computed tomography as a predictor of ureteral stone expulsion in medical expulsive therapy

OBJECTIVE

To evaluate stone diameter and ureteral dilation using computerized tomography as a predictor of ureteral stone expulsion after medical expulsive therapy.

MATERIALS AND METHODS

We retrospectively reviewed the records of 328 patients with symptomatic ureteral stones <10 mm on axial computerized tomography images, who were treated with alpha blockers for 2 weeks. Computerized tomography scans were also performed 2 weeks after medical expulsive therapy to confirm ureteral stone expulsion. Patients were divided into upper ureteral stones and lower ureteral stones above and below the iliac vessels, respectively. Transverse stone diameter and longitudinal stone diameter were defined as the largest stone diameter determined on the axial and coronal computerized tomography images, respectively. Ureteral diameter was determined on one computerized tomography slice proximal to each ureteral stone on axial computerized tomography images, and the ratio of ureter-to-stone diameter was defined as ureteral diameter divided by transverse stone diameter.

RESULTS

Among 328 patients, the stone expulsion rate was 44.1% in 145 upper ureteral stones and 69.4% in 183 lower ureteral stones. Transverse stone diameter, longitudinal stone diameter, ureteral diameter, and the ratio of ureter-to-stone diameter were significantly lower in patients with ureteral stone expulsion in upper ureteral stones and lower ureteral stones (P < .001 for all parameters). Logistic regression analysis revealed that only longitudinal stone diameter was a significant predictor of stone expulsion in patients with upper ureteral stones (odds ratio 0.580, P = .040) and lower ureteral stones (odds ratio 0.415, P = .012).

CONCLUSION

Longitudinal stone diameter was a significant predictor of stone expulsion in patients with upper ureteral stones and lower ureteral stones after medical expulsive therapy. Measurement of stone diameters in coronal reconstruction may help to better choose a patient who is suitable for medical expulsive therapy.

Analyzing the effect of distance from skin to stone by computed tomography scan on the extracorporeal shock wave lithotripsy stone-free rate of renal stones

Purpose

To determine whether the distance from skin to stone, as measured by computed tomography (CT) scans, could affect the stone-free rate achieved via extracorporeal shock wave lithotripsy (ESWL) in renal stone patients.

Materials and Methods

We retrospectively reviewed the records 573 patients who had undergone ESWL at our institution between January 2006 and January 2010 for urinary stones sized from about 5 mm to 20 mm and who had no evidence of stone movement. We excluded patients with ureteral catheters and percutaneous nephrostomy patients; ultimately, only 43 patients fulfilled our inclusion criteria. We classified the success group as those patients whose stones had disappeared on a CT scan or simple X-ray within 6 weeks after ESWL and the failure group as those patients in whom residual stone fragments remained on a CT scan or simple X-ray after 6 weeks. We analyzed the differences between the two groups in age, sex, size of stone, skin-to-stone distance (SSD), stone location, density (Hounsfield unit: HU), voltage (kV), and the number of shocks delivered.

Results

The success group included 33 patients and the failure group included 10. In the univariate and multivariate analysis, age, sex, size of stone, stone location, HU, kV and the number of shocks delivered did not differ significantly between the two groups. Only SSD was a factor influencing success: the success group clearly had a shorter SSD (78.25±12.15 mm) than did the failure group (92.03±14.51 mm). The results of the multivariate logistic regression analysis showed SSD to be the only significant independent predictor of the ESWL stone-free rate.

Conclusions

SSD can be readily measured by CT scan; the ESWL stone-free rate was inversely proportional to SSD in renal stone patients. SSD may therefore be a useful clinical predictive factor of the success of ESWL on renal stones.

Management of urinary tract infections associated with nephrolithiasis

Nephrolithiasis is a common clinical entity, and the incidence of renal stones appears to be increasing in the United States. Infection with uropathogens that produce urease can lead to the development of stones (infection stones), which serve as a continued source of recurrent infection and can lead to chronic kidney disease. Other than treating infection, medical management has little role in the treatment of infection stones; complete eradication of the stones with percutaneous nephrolithotomy or extracorporeal shock wave lithotripsy is required. Stones of metabolic origin can cause obstruction in the ureter and predispose to the development of urinary tract infection (UTI). Recognizing obstruction and initiating prompt drainage of the collecting system is important in the successful management of nephrolithiasis complicated by UTI. These patients are often at high risk of infection with an antimicrobial-resistant pathogen, so careful consideration of antimicrobial therapy is required, especially for patients who present with severe sepsis.

Nephrolithiasis: evaluation and management

Nephrolithiasis is a major cause of morbidity involving the urinary tract. The prevalence of this disease in the United States has increased from 3.8% in the 1970s to 5.2% in the 1990s. There were nearly two million physician-office visits for nephrolithiasis in the year 2000, with estimated annual costs totaling $2 billion. New information has become available on the clinical presentation, epidemiologic risk factors, evaluative approach, and outcome of various therapeutic strategies. In this report, we will review the epidemiology and mechanisms of kidney-stone formation and outline management aimed at preventing recurrences. Improved awareness and education in both the general population and among health-care providers about these modifiable risk factors has the potential to improve general health and decrease morbidity and mortality secondary to renal-stone disease.

Acute abdominal pain: is there a potential role for MRI in the setting of the emergency department in a patient with renal calculi?

Acute flank pain is a frequent clinical presentation encountered in emergency departments, and a work-up for obstructive urolithiasis in this setting is a common indication for computed tomography (CT). However, imaging alternatives to CT for the evaluation of renal colic are warranted in some clinical situations, such as younger patients, pregnancy, patients that have undergone multiple prior CT exams and also patients with vague clinical presentations. MRI, although relatively insensitive for the direct detection of urinary calculi, has the ability to detect the secondary effects of obstructive urolithiasis. Using rapid, single shot T2-weighted sequences without and with fat saturation provides an abdominopelvic MR examination that can detect the sequelae of clinically active stone disease, in addition to alternate inflammatory processes that may mimic the symptoms of renal colic. In addition, MR nephro-urography (MRNU) has the ability to provide quantitative analysis of renal function that has the potential to direct clinical management in the setting of obstructing calculi. This review describes the potential utility and limitations of MRI in the emergency setting for diagnosing causes of flank pain and renal colic, particularly in patients with unusual presentations or when an alternative to CT may be warranted.

Genitourinary applications of dual-energy CT

OBJECTIVE

Recent advances in CT technology provide improved diagnostic characterization of materials using dual-energy CT methods. Application of these methods improves lesion conspicuity and detection. In addition, improved material characterization and creation of virtual unenhanced techniques potentially result in decreased radiation dose. We will review the role of dual-energy CT as applied to the genitourinary system.

CONCLUSION

Dual-energy CT is beginning to play an important role in patients with genitourinary diseases by providing unique characterization tools for calculi and masses.

Unexpected changes in clinical diagnosis: early abdomino-pelvic computed tomography compared with clinical evaluation

BACKGROUND

To evaluate the value of early computed tomography (CT) on identifying clinically "unexpected" diagnosis in patients presenting with "non specific" acute abdominal pain.

MATERIALS AND METHODS

All patients presenting to on-call surgeons with acute abdominal pain were eligible study participants. Patients were randomised to CT within one hour of admission or supine abdominal and erect chest radiography. Ninety-nine patients randomized to CT arm were reviewed for the purpose of this study. The number and severity of unexpected and/or incidental diagnoses detected on the CT were assessed.

RESULTS

In 20 of the 99 patients CT revealed primary or secondary diagnoses, which were unexpected following the initial clinical examination and led to completely different therapeutic options. In 15 of those 20 patients CT revealed clinically unexpected conditions, whereas in two patients severe complications of the clinically suspected diagnosis were detected on CT. Five patients had significant incidental findings in addition to their primary diagnosis on CT. In two of these patient CT also revealed clinically unexpected diagnoses.

CONCLUSION

Early CT has the advantage of detecting unexpected clinically significant primary and secondary diagnoses in patients presenting with acute abdominal pain and best guides the surgeon to the appropriate patient management.

Pancreatic tail cancer with sole manifestation of left flank pain: a very rare presentation

Pancreatic cancer is sometimes called a "silent disease" because it often causes no symptoms in the early stage. The symptoms can be quite vague and various depending on the location of cancer in the pancreas. The anatomic site distribution is 78% in the head of the pancreas, 11% in the body, and 11% in the tail. Pancreatic cancer is rarely detected in the early stage, and it is very uncommon to diagnose pancreatic tail cancer during an emergency department visit. The manifestation of pancreatic tail cancer as left flank pain is very rare and has seldom been identified in the literature. We present a case of pancreatic tail cancer with the sole manifestation of dull left flank pain. Having negative findings on an ultrasound study initially, this female patient was misdiagnosed as having possible acute gastritis, urolithiasis or muscle strain after she received gastroendoscopy and colonofiberscopy. Her symptoms persisted for several months and she visited our emergency department due to an acute exacerbation of a persistent dull pain in the left flank area. Radiographic evaluation with computed tomography was performed, and pancreatic tail tumor with multiple metastases was found unexpectedly. We review the literature and discuss this rare presentation of pancreatic tail cancer.

Is the KUB radiograph redundant for investigating acute ureteric colic in the non-contrast enhanced computed tomography era?

AIM

To establish whether non-contrast enhanced computed tomography (NCCT) renders the kidneys-ureters-bladder (KUB) radiograph redundant as the initial imaging investigation for suspected acute ureteric colic.

MATERIALS AND METHODS

The imaging investigations for 120 patients consecutively admitted to an emergency department-led clinical decisions unit (CDU) with suspected acute ureteric colic were retrospectively reviewed. A multidisciplinary meeting reviewed the findings and recommended that KUB radiographs should not be routinely performed prior to NCCT. Prospective assessment of 116 consecutive patients admitted over a comparable period was then undertaken.

RESULTS

In the retrospective group, 61 (50.8%) patients had calculi to account for symptoms (positive NCCT) and 59 (49.2%) patients did not have stone disease (negative NCCT). Ninety (75%) patients had a KUB radiograph prior to NCCT. However, in 46 (38% of total) of these patients the NCCT was negative for stones, and therefore, they had been subjected to an unnecessary radiographic examination. These results prompted a change in practice. In the subsequent and prospectively studied group, preliminary KUB radiographs were performed in only 6% of the patients, with no significant change in the positive NCCT rate (50.8 versus 51.7%) or the total number of examinations performed (120 versus 116).

CONCLUSION

NCCT should be the initial imaging examination for acute ureteric colic. Up to 50% of patients with clinical suspicion do not have stone disease, and therefore, preliminary KUB radiographs with attendant radiation and cost implications are unjustified. Preliminary KUB radiographs can be omitted from the imaging pathway with no resultant indication creep or increase in demand for NCCT examinations.

Characterization of human renal stones with MDCT: advantage of dual energy and limitations due to respiratory motion

OBJECTIVE

Our aim was to determine, using CT attenuation values, the chemical composition of 241 human renal stones placed in a jelly phantom and to analyze the influence of respiratory motion on the classification.

MATERIALS AND METHODS

The stones were placed in a jelly simulating the X-ray attenuation of the kidneys. A dynamic platform was used to apply to the phantom free-breathing motion (sinusoidal motion in z-axis) and motion due to lack of maintenance of a breath-hold (5 mm x s(-1) in z-axis). Determination of the chemical composition was performed with mean CT attenuation values obtained at 80 and 120 kV and with dual-energy CT attenuation values.

RESULTS

Two hundred forty-one human urinary stones were classified into six groups: uric acid, cystine, struvite, weddellite (calcium oxalate dihydrate), whewellite (calcium oxalate monohydrate), and brushite. With no motion, the use of dual energy enabled differentiation of all of the types of stones with statistically significant differences. Uric acid (-20 +/- 22 H), cystine (106 +/- 19 H), struvite (271 +/- 16 H), weddellite (323 +/- 5 H), brushite (415 +/- 30 H), and whewellite (510 +/- 17 H) were identified as distinct groups. Motion-induced mean CT attenuation values were significantly different from those obtained with no motion. With motion, dual-energy CT attenuation values did not allow differentiation of all stone types.

CONCLUSION

Dual-energy CT attenuation values can be used to predict the chemical composition of stones in vitro. However, when slight motion is applied to renal stones during image acquisition, the values become significantly different from those obtained with no motion. Consequently, confusion arises in differentiating stone types. A perfect breath-hold has to be performed for in vivo use of attenuation value to discern stone type.

Non-Enhanced Spiral CT Versus Excretory Urography in Acute Renal Colic

Objective: To evaluate the usefulness of non-enhanced spiral CT (NECT) and compare it with that of excretory urography (EU) in patients with acute flank pain.

Methods: Ninety five patients presenting with acute flank pain underwent both NECT and EU. Both techniques were used to determine the presence, size, and location of urinary stone, and the presence or absence of secondary signs was also evaluated. The existence of ureteral stone was confirmed by its removal or spontaneous passage during follow-up. The absence of a stone was determined on the basis of the clinical and radiological evidence.

Result: Seventy eight of the 95 patients had one or more ureteral stones and 17 had no stones. CT depicted 79 of 83 calculi in the 78 patients with a stone and no calculus in all seventeen without a stone. The sensitivity and specificity of NECT were 95% and 100%, respectively. EU disclosed 73 calculi in the 78patients with a stone and no calculus in fifteen of the seventeen without a stone, with sensitivity and specificity 89% and 88% respectively.

Conclusion: For the evaluation of patients with acute flank pain, NECT is an excellent modality with high sensitivity and specificity. In near future it may replace EU.

Split-bolus MDCT urography with synchronous nephrographic and excretory phase enhancement

OBJECTIVE

Our purpose was to evaluate the utility of CT urography performed using a split contrast bolus that yields synchronous nephrographic and excretory phase enhancement.

MATERIALS AND METHODS

Five hundred consecutive patients referred for evaluation of possible urinary tract abnormalities (327 for painless hematuria) underwent CT urography with unenhanced scanning of the abdomen and pelvis and scanning during concurrent nephrographic and excretory phase enhancement produced by administration of a split contrast bolus. The enhanced abdomen scan was obtained with abdominal compression; the enhanced pelvis scan was obtained after release of compression. Findings from axial sections and coronal maximum intensity projections were correlated with clinical follow-up and, as available, with laboratory and other imaging studies including cystoscopy, ureteroscopy, urine cytology, surgery, and pathology. Follow-up management for each patient was determined by the clinical judgment of the referring physician.

RESULTS

CT urography identified 100% of pathologically confirmed renal cell carcinomas (n = 10) and uroepithelial malignancies involving the renal collecting system or ureter (n = 8). An additional nine renal masses were identified for which no pathologic proof has yet been obtained, including eight subcentimeter solid renal masses and one multiloculated lesion. Fourteen of 19 confirmed cases of uroepithelial neoplasm involving the bladder were identified. CT urography yielded one false-positive for bladder tumor, two false-positives for ureteral tumor, and one patient with a bladder mass who refused further evaluation. CT urography yielded sensitivity and specificity of 100% and 99% and 74% and 99% and positive predictive value and negative predictive value of 80% and 100% and 93% and 99% for the renal collecting system and ureter and bladder, respectively. CT urography was ineffective in identifying 11 cases of noninfectious cystitis. CT urography also depicted numerous other congenital and acquired abnormalities of the urinary tract.

CONCLUSION

Split-bolus MDCT urography detected all proven cases of tumors of the upper urinary tract, yielding high sensitivity and specificity. The split-bolus technique has the potential to reduce both radiation dose and the number of images generated by MDCT urography.