Ureterolithiasis: can clinical outcome be predicted with unenhanced helical CT?

Early versus delayed ureterolithotripsy following obstructive acute pyelonephritis treatment

BACKGROUND AND OBJECTIVES

There is no recommendation on the timing of ureterolithotripsy after the treatment of obstructive acute pyelonephritis (APN). The effect of early and delayed ureterolithotripsy on postoperative urinary tract infection (UTI) and other complications was investigated.

METHODS

Patients who underwent ureterolithotripsy after obstructive APN treatment between February 2017 and August 2021 were divided into two groups, those operated during hospitalization and those operated within 3 months after discharge. Two groups were compared in terms of stone-free status, postoperative complications, postoperative UTI, and urosepsis rates.

RESULTS

Of the 91 patients included in the study, 68 were in the early ureterolithotripsy group, while 23 patients were in the delayed ureterolithotripsy group. The postoperative UTI rate was significantly higher in patients who underwent early ureterolithotripsy (29.4% vs 8.7%, p = 0.045). Patients with postoperative UTI had a higher moderate/severe perinephric fat stranding (PFS) on non-contrast CT at hospital admission (52.2% vs 29.4%, p = 0.048). Among the laboratory parameters, white blood cells were significantly higher in the group with postoperative UTI (21604.5 vs 14728.9, p = 0.042). In the multivariate analysis, early ureterolithotripsy and moderate/severe PFS were independent predictors for postoperative UTI. In the created model, the probability of postoperative UTI after ureterolitripsy after obstructive APN treatment was 3.5% in patients without risk factors, while this rate was 51.9% in patients with both risk factors.

CONCLUSION

There is no consensus on the timing of stone removal after treatment of obstructive APN. Early ureterolithoripsy and moderate/severe perinephric fat stranding on non-contrast CT are risk factors for postoperative UTI.

Development of prediction models of spontaneous ureteral stone passage through machine learning: Comparison with conventional statistical analysis

Objectives

To develop a prediction model of spontaneous ureteral stone passage (SSP) using machine learning and logistic regression and compare the performance of the two models. Indications for management of ureteral stones are unclear, and the clinician determines whether to wait for SSP or perform active treatment, especially in well-controlled patients, to avoid unwanted complications. Therefore, suggesting the possibility of SSP would help make a clinical decision regarding ureteral stones.

Methods

Patients diagnosed with unilateral ureteral stones at our emergency department between August 2014 and September 2018 were included and underwent non-contrast-enhanced computed tomography 4 weeks from the first stone episode. Predictors of SSP were applied to build and validate the prediction model using multilayer perceptron (MLP) with the Keras framework.

Results

Of 833 patients, SSP was observed in 606 (72.7%). SSP rates were 68.2% and 75.6% for stone sizes 5–10 mm and <5 mm, respectively. Stone opacity, location, and whether it was the first ureteral stone episode were significant predictors of SSP. Areas under the curve (AUCs) for receiver operating characteristic (ROC) curves for MLP, and logistic regression were 0.859 and 0.847, respectively, for stones <5 mm, and 0.881 and 0.817, respectively, for 5–10 mm stones.

Conclusion

SSP prediction models were developed in patients with well-controlled unilateral ureteral stones; the performance of the models was good, especially in identifying SSP for 5–10-mm ureteral stones without definite treatment guidelines. To further improve the performance of these models, future studies should focus on using machine learning techniques in image analysis.

The effect of perirenal fat stranding on infectious complications after ureterorenoscopy in patients with ureteral calculi

Objective

Perirenal fat stranding (PFS) is linear areas of soft-tissue attenuation in the perirenal space on non-contrast computed tomography. The present study aimed to investigate whether PFS is associated with infectious complications after ureterorenoscopy (URS) in patients with ureteral calculi in any location.

Methods

The data of 602 patients with ureteral stones who underwent URS were analyzed retrospectively. The patients were divided into two groups as Group 1 (PFS not detected) and Group 2 (PFS detected). Gender, and age of patients, size, side, and location of the stone, operation time, double-J stent insertion status, perioperative ureter injury, postoperative infection after URS and related complications, and duration of hospital stay were compared.

Results

While PFS was not detected in 530 patients, PFS was detected in 72 patients. The mean age, male/female ratio, side and localization of the stones, operation time, and perioperative insertion of the double-J after lithotripsy were statistically similar (p>0.05). The median stone diameter was smaller in Group 2 (9 mm vs. 8 mm) (p=0.033). Fever was observed in 30 and 38 patients in Group 1 and Group 2, respectively (p=0.0001). Urinary tract infection was detected in 24 and 27 patients in Group 1 and Group 2, respectively (p=0.0001). The urosepsis did not occur in any patients in Group 1, whereas 8 (11.1%) patients in Group 2 experienced urosepsis (p=0.0001).

Conclusion

According to the results of the present study, patients with ureteral stones accompanied by PFS are much more prone to ureteral injuries and infectious complications such as urinary tract infection, fever, and sepsis after URS.

Side-by-side evaluation of virtual non-contrast and post-contrast images improves detection of clinically significant urolithiasis on single-phase split bolus dual-energy CT urography

OBJECTIVES

Studies show insufficient sensitivity of virtual non-contrast (VNC) reconstructions for stone detection in dual-energy CT urography (DE-CTU). The aim of this study was to investigate if side-by-side-evaluation of both VNC and post-contrast images could increase the sensitivity of single-phase split bolus DE-CTU.

METHODS

Consecutive patients with haematuria who underwent split bolus DE-CTU on the same dual-source DE-CT scanner were retrospectively enrolled in the study. Intravenous furosemide and oral hydration were employed. Two readers, independently and then jointly in two separate sessions, recorded the location and the longest axial stone diameter on three randomised sets of images: separate VNC and post-contrast images, and side-by-side-reconstructions. True non-contrast (TNC) images served as the standard of reference.

RESULTS

A total of 83 urinary stones were detected on TNC images. Independent reader side-by-side-evaluation of VNC and post-contrast images yielded higher stone detection sensitivity (76 and 84%, respectively) compared to evaluation of only VNC (71 and 81%, respectively) or post-contrast images (64 and 80%, respectively). The sensitivity of joint reader evaluation of side-by-side-images reached almost 86% and was not significantly different from TNC images (p = 0.77). All stones larger than 3 mm were correctly detected by side-by-side-evaluation. Dose reduction of 55% could be achieved by omitting TNC scans.

CONCLUSION

Side-by-side-VNC and post-contrast image evaluation enable detection of clinically significant urolithiasis on single-phase split bolus DE-CTU with significant dose reduction.

ADVANCES IN KNOWLEDGE

This study shows that single-phase DE-CTU is feasible if VNC imaging is simultaneously utilised with post-contrast images.

Renal Forniceal Rupture in the Setting of Obstructing Ureteral Stones: An Analysis of Stone Characterization and Urologic Intervention Pattern

Introduction and Objective: Forniceal rupture due to obstructing ureterolithiasis (FROU) is a seldom encountered radiographic finding, but the impact of this diagnosis and influence on stone management has not been well studied in the literature. The purpose of the study is to examine stone characteristics and intervention patterns of patients with radiographic evidence of FROU. Materials and Methods: A retrospective analysis of all patients with radiographic evidence of FROU was compared with patients with obstructing ureteral stones without forniceal ruptures (noFROU). All patients presented to our Emergency Department from January 2015 until December 2018. Data analyzed included patient demographics, clinical presentation, stone characteristics, and management pattern. Primary outcome was need for hospital admission and surgical intervention. Results: Thirty-two patients with FROU (mean age = 45) were compared with 50 patients with noFROU (mean age = 57). Univariate analysis revealed that age, history of diabetes mellitus, history of hypertension, days of symptoms, degree of hydronephrosis, and degree of perinephric stranding were associated with forniceal rupture (p ≤ 0.05). On multivariate analysis, only degree of perinephric stranding remained significant (p ≤ 0.05). Average maximum axial stone diameter in the FROU group was 5.1 mm vs 4.7 mm in the noFROU group (p = 0.66). Overall, 68.8% of stones were located within the distal ureter in the FROU group vs 48.8% in the noFROU group (p = 0.09). There was no difference in hospital admission (FROU 37.5% vs noFROU 44%, p = 0.56) and need for surgical intervention (FROU 50% vs noFROU 48%, p = 0.86). There were no 30-day complications in patients with FROU. Conclusions: Ureteral stone location and size does not seem to impact the presence of FROU. FROU may be an alarming reported finding but its presence does not appear to impact clinical outcomes or affect urological management, including admission or need for urologic intervention.

Primary and secondary diseases of the perinephric space: an approach to imaging diagnosis with emphasis on MRI

The perinephric space is the middle compartment of the retroperitoneum, containing the kidneys and adrenal glands. Differential considerations for diseases involving primarily the perinephric space differ from those arising from the kidney itself, show variant imaging features, and require identification and characterisation by interpreting radiologists-an imaging diagnosis can be suggested in many cases. Lymphangiomas are congenital cystic lesions that may contain lipid-laden chyle, which may be detectable on magnetic resonance imaging (MRI). Retroperitoneal fibrosis, Erdheim-Chester disease, and lymphoma may present as a perinephric soft tissue rind. Osseous findings favour Erdheim-Chester, ureteric obstruction favours retroperitoneal fibrosis, and associated lymphadenopathy with mass-effect, but without invasion of adjacent structures favours lymphoma. Extramedullary haematopoiesis and brown fat stimulation are both characterised by signal drop on opposed-phase T1-weighted (W) images, the former resulting from severe anaemia and the latter in the context of elevated serum catecholamines, especially in the setting of phaeochromocytoma. Liposarcoma is the most common primary sarcoma of the retroperitoneum. Metastases are uncommon; however, they can be seen in melanoma, among other primary malignancies. Increased T1W signal hyperintensity is typical of melanoma metastases and haematomas. Abscesses show non-enhancing fluid centrally with marked diffusion restriction. This article presents a review of the perinephric space, pathological conditions of the perinephric space, and an approach towards imaging and diagnosis using cross-sectional imaging, with emphasis on MRI. MRI provides better tissue characterisation, assessment of enhancement kinetics, and detection of intralesional fat in comparison to CT. Clinical and laboratory correlation or tissue sampling may be required for definitive diagnosis in some cases.

In-vitro comparison of different slice thicknesses and kernel settings for measurement of urinary stone size by computed tomography

Non-contrast enhanced computed tomography (NCCT) is widely used measuring stone size in patients with urolithiasis. We performed an evaluation of the accuracy of stone size measuring via NCCT. In an in-vitro study, we analyzed a total of 38 uric acid and 38 phantom stones. Within NCCT, we used different slice thicknesses (1.5 mm, 2.0 mm, and 3.0 mm) and kernel settings (bone and soft-tissue window). Maximal height, maximal length, and maximal width of each stone were measured on a picture archiving and communication system workstation. Blinded to these results, a second physician measured stone size in the same way using a caliper (real stone size). We used the Bland-Altman method for the analysis of agreement between the two measuring methods. The limit of agreement that was deemed clinical insignificant was ± 1.0 mm. All measurements via NCCT correlated significantly with the real stone size (p < 0.001). This was more pronounced for bone window and smaller slice thickness. Bland-Altman plots showed limits of agreement that exceeded the a priori defined level for all types of measurement with bone window and small slice thickness (1.5 mm) being better than soft-tissue window and large slice thickness (3.0 mm). We conclude that stone size measurement by NCCT with established settings is not exact. Stone size can easily be over- or underestimated by several millimeters. Using bone window and small slice thickness leads to more accurate results.

Evaluation of the clinical significance of sonographic perinephric fluid in patients with renal colic

OBJECTIVE

To evaluate the significance of sonographic perinephric fluid collection on the emergent management of patients with acute urinary stone obstruction.

METHODS

We conducted a prospective study with retrospective analysis. Since January 2016 through July 2017, patients admitted to our tertiary hospital's emergency department (ED) with suspected symptomatic urinary stones underwent ultrasound evaluation. Images were prospectively interpreted by experienced radiologist who analyzed each case for the following imaging features: hydronephrosis, perinephric fluid and urethral stone identification. The presence and measurements of perinephric fluid were re-evaluated by second radiologist who was blinded for the first reader's measurements. Retrospective analysis was conducted to evaluate for an association between perinephric fluid collection and the following outcome variables: need for analgesics, the number of doses of analgesics and the amount of morphine (mg) in the ED, elevation of creatinine levels, hospitalization and need for urological interventions.

RESULTS

The need for analgesics, the number of doses of analgesics and the amount of morphine were significantly associated with the presence of perinephric fluid (p < 0.05). The odds ratio for the need for analgesics was 3.8 in the presence of any perinephric fluid, and 8.9 in the presence of moderate/severe perinephric fluid. No other patient outcome variables were found to be significantly associated with the presence of perinephric fluid (p > 0.05).

CONCLUSIONS

This study shows a correlation between sonographic evidence of perinephric fluid and more severe pain. Therefore, an emergency physician can consider the evidence of perinephric fluid, in acute urethral stone obstruction, a predictor for more severe pain.

Assessment of factors affecting the spontaneous passage of lower ureteric calculus on the basis of lower ureteric calculus diameter, density, and plasma C- reactive protein level

Introduction:

The study aimed to evaluate the factors which affect the spontaneous passage of lower ureteric calculus on the basis of noncontrast computed tomography kidneys, ureters, and bladder (NCCT KUB) stone diameter, stone density, and plasma C-reactive protein (CRP) level.

Materials and Methods:

We conducted a prospective study of 200 patients with lower ureteric calculus 5–10 mm in size, from October 2015 to December 2016. All patients underwent NCCT KUB region with a 5 mm axial and reformatted coronal section. Edema just above the calculus and rim sign at the level of calculus and density of calculus is evaluated. Only scan with isolated, unilateral, solitary ureteric calculus was included in the final analysis and monitored up to 4 weeks, and plasma CRP is estimated in all patients to determine the clinical outcome.

Results:

A total of 200 patients (145 males, 55 females; mean age ± standard deviation, 34.73 ± 10.29) were included in the study. Lower ureteric calculus between 5–7 mm passed in 70% and 7–10 mm passed in 40%. There was 18% underestimation of maximum stone diameter in axial plane as compared to coronal plane. For spontaneous passage of calculus, craniocaudal (CC) diameter is more reliable then axial in NCCT. Rim sign and edema is absent in 64% of those passed spontaneous calculus. CRP level more than 2.45 mg/dl has low spontaneous expulsion rate. The stone with different HU passes through the ureter with same rate.

Conclusion:

Plasma CRP level and CC diameter and absence of rim sign on NCCT KUB are more reliable factors then density for spontaneous passage of ureteric calculus.

Perinephric Fat Stranding Is Associated with Elevated Creatinine Among Patients with Acutely Obstructing Ureterolithiasis

INTRODUCTION

Pyelovenous/pyelolymphatic backflow from acute ureteral obstruction, manifesting radiologically as perinephric fat stranding (PFS), may result in elevated serum creatinine. Among patients with acutely obstructing ureterolithiasis, we evaluated the relationship between degree of PFS and changes in serum creatinine from baseline.

METHODS

Our tertiary care center's radiology dictation system (Fluency Discovery, M Modal) was queried for noncontrast abdominopelvic CT studies obtained in the Emergency Department for patients with obstructing ureteral calculi from 7/2015 to 4/2016. A single radiologist blinded to clinical data reviewed all CT scans and coded stone size, location, severity of hydronephrosis, and degree of PFS (none, mild, moderate, severe). For patients who met imaging criteria, a retrospective chart review was performed.

RESULTS

We evaluated 148 patients with mean age of 46 years (SD 14.6), 56.0% (n = 83) were male. On univariate analysis, moderate-severe perinephric stranding was associated with elevated creatinine from baseline (OR 2.93, p = 0.03). Mean creatinine increased as the severity of stranding increased (none Cr = 0.978 mg/dL, mild Cr = 0.983 mg/dL, moderate Cr = 1.165 mg/dL, severe Cr = 1.370 mg/dL; p < 0.01). An increase in creatinine from baseline was not associated with greater severity of hydronephrosis (OR 0.504, p = 0.189). There was no association between degree of PFS and severity of hydronephrosis, positive urine culture, stone location, or symptom duration (p > 0.05). On regression analysis controlling for positive urine culture and degree of hydronephrosis, there remained an association between elevated serum creatinine from baseline and moderate-severe PFS (OR 9.0, p = 0.01).

CONCLUSIONS

Among patients with acute obstructive ureterolithiasis, moderate-severe PFS was associated with elevated serum creatinine from baseline. This elevated creatinine was not explained by the obstructed kidney alone, as there was no association between the severity of hydronephrosis and increased creatinine. Pyelovenous/pyelolymphatic backflow resulting in PFS may be a contributing factor to elevated serum creatinine in this setting.

Factors associated with absent microhematuria in symptomatic urinary stone patients

INTRODUCTION

The aim of this study was to identify factors associated with absent hematuria in patients with symptomatic urinary stones.

METHODS

This retrospective study analyzed the clinical and imaging findings of emergency department patients who underwent computed tomography (CT) for suspected ureteral colic over the past 2years. All patients also underwent a microscopic urinalysis, and the presence of 4 or more red blood cells/high-power field was defined as microhematuria.

RESULTS

A total of 798 patients were included in this study. Of these patients, 750 (94.0%) presented with hematuria, while 48 (6.0%) urine samples did not have evidence of hematuria. The group with an absence of hematuria was more likely to have a lower stone location (located in an area from the distal ureter to the bladder) and perinephric stranding on CT than the hematuria group (75.0% vs. 54.3%, p=0.005; 47.9% vs. 30.5%, p=0.012, respectively). The degree of hematuria at each stone location was significantly different (p=0.001). In multivariate analysis, perinephric stranding (odds ratios (OR) 1.87 [95% confidence interval (CI) 1.01-3.46], p=0.047), a lower stone location (OR 2.72 [95% CI 1.37-5.36], p=0.004), and elevated serum blood urea nitrogen (BUN) levels (OR 1.06 [95% CI 1.01-1.12], p=0.026) were associated with absent hematuria.

CONCLUSIONS

In this large cohort of patients with renal colic, 6% had no microhematuria. Although some CT findings and elevated BUN were independently associated with hematuria absence, there was no difference in the demographics, time of presentation and degree and location of pain between the groups.

Significance of Neutrophil-to-Lymphocyte Ratio as a Novel Indicator of Spontaneous Ureter Stone Passage

PURPOSE

Stone size and location are generally considered the most important factors associated with spontaneous ureter stone passage (SSP). Several parameters related to inflammatory changes have been identified as predictors associated with SSP. Our aim was to investigate the predictive role of neutrophil-to-lymphocyte ratio (NLR) for SSP.

MATERIALS AND METHODS

A retrospective review was performed on 131 patients who were referred to the urology outpatient clinic and diagnosed with unilateral ureteral stones at our emergency department between July 2016 and December 2016. The presence of ureteral stones was confirmed with non-contrast-enhanced computed tomography (NCCT) for all patients. SSP was confirmed with either the patient collecting the stone during urination or by NCCT performed at 3 weeks from the first stone episode. Physical examination, urinalysis, complete blood count, serum chemistry and inflammatory markers, plain radiographs, and NCCT at initial presentation were reviewed to analyze predictors of future SSP.

RESULTS

Of 113 patients included for analysis, 90 (79.6%) passed their stones spontaneously. The SSP rates within 3 weeks according to the stone's size (5-10 mm and ≤5 mm) were 62.2% and 88.2%, respectively. A lower stone location [odds ratio (OR), 11.54; p=0.001], smaller stone size (≤5 mm) (OR, 8.16; p=0.001), and NLR (<2.3) (OR, 9.03; p=0.003) were independent predictors of SSP.

CONCLUSION

Low NLR (<2.3) may predict SSP in patients with ureter stones ×1.0 cm in size. Our results suggest that ureteral inflammation plays an important role in SSP. Early intervention may be considered for patients presenting with high NLR (≥2.3).

Radiological noninvasive assessment of ureteral stone impaction into the ureteric wall: A critical evaluation with objective radiological parameters

PURPOSE

To determine the predictive value of certain radiological parameters for an objective asssessment of the presence of ureteral stone impaction.

MATERIALS AND METHODS

Seventy-nine patients with a single proximal ureteral stones were retrieved from the departmental database. Both clinical and particularly radiological data of all cases were well evaluated on this aspect. In addition to the time period between the first colic attack and definitive management; diameter of proximal ureter and renal pelvis, longitudinal and transverse stone size, Hounsfied unit (HU) of the stone and lastly ureteral wall thickness at the impacted stone site were all carefully evaluated and noted.

RESULTS

Patients had a single proximal ureteral stone. While mean age of the cases was ranged 20 to 78 years; mean stone size was 15.62±4.26 mm. Evaluation of our data demonstrated that although there was a statistically significant correlation between ureteral wall thickness and patients age, transverse diameter of the stone, ureteral diameter just proximal to the stone, renal pelvic diameter and the duration of renal colic attacks; no correlation could be demonstrated between patients sex and the HU of the stone.

CONCLUSIONS

Prediction of the presence and degree of proximal ureteral stone impaction is a challenging issue and our data indicated a highly significant correlation between ureteral wall thickness and the some certain radiological as well as clinical parameters evaluated which will give an objective information about the presence of impaction which may in turn be helpful in the follow-up and also management plans of such calculi.

Is computed tomography-defined obstruction a predictor of urological intervention in emergency department patients presenting with renal colic?

INTRODUCTION

Our objective was to determine whether unilateral calculus-induced ureteric obstruction on computed tomography (CT) was independently associated with the need for urological intervention and 30-day return to the emergency department (ED).

METHODS

We performed a retrospective cohort study of patients with symptomatic urinary calculi diagnosed by unenhanced helical CT. Stepwise regression analysis was used to determine the predictors of urological intervention and 30-day return to the ED. Potential predictors assessed included: patient demographics, calculus size, calculus location, degree of obstruction, analgesic doses, signs and symptoms of infection, serum creatinine, cumulative intravenous fluid administered, and the prescription of medical expulsive therapy.

RESULTS

Of 195 patients, 81 (41.5%) underwent urological intervention. The size of the calculus, its location, and the cumulative opioid dose were all independent predictors for urological intervention. Every 1 mm increase in calculus size increased the likelihood of intervention 2.2 times (odds ratio [OR] 2.17; 95% confidence interval [CI] 1.67-2.85). Proximal stones were 4.7 times more likely to require intervention than distal calculi (OR 0.21; 95% CI 0.09-0.49). Every 10 mg increase in morphine was associated with a 30% increase in the odds of intervention (OR 1.30; 95% CI 1.07-1.58). Degree of obstruction was not associated with the need for urological intervention. Finally, none of the variables were predictors for 30-day return to the ED.

CONCLUSIONS

Although stone size, proximal location, and severe pain, as indicated by higher opioid doses, were associated with the need for intervention, the degree of obstruction did not influence the management of patients with CT-defined urinary calculi.

Body mass index predicts outcome of ureteroscopy-assisted retrograde nephrostomy for percutaneous nephrolithotomy

INTRODUCTION

Several clinical series of retrograde nephrostomy for percutaneous nephrolithotomy (PCNL) have been published over the past 30 years demonstrating good outcomes and safety. We previously reported our adaptation of the Lawson technique, wherein we deploy the puncture wire through a flexible ureteroscope. We herein aim to clarify the performance characteristics of this nephrostomy creation technique.

MATERIALS AND METHODS

Institutional Review Board approval and informed consent were obtained. A ureteroscopy-assisted retrograde nephrostomy (UARN) procedure was performed as described previously. Data were collected prospectively. Multiple patient and operative factors were evaluated for association with UARN success and nephrostomy creation time: body mass index (BMI), skin-to-stone distance, Guy's score, Clinical Research of the Endourological Society nephrolithometric score, hydronephrosis, stone burden, location of nephrostomy, exit from a stone-bearing calix, and use of holmium laser to access calix.

RESULTS

Nephrostomy was successful in 49/52 UARN procedures (94%). Only single access was placed: upper-18, mid-27, and lower-7. Median BMI was 29 kg/m(2) and median time for nephrostomy creation was 39 minutes. Fluoroscopy time for the entire PCNL including nephrostomy creation was 84 and 16 seconds for case numbers 1-25 and 26-52, respectively. By stepwise linear regression, variables correlating with nephrostomy creation time were BMI (r(2)=0.219), stone burden (r(2)=0.094), use of holmium laser to access calix (r(2)=0.104), and total r(2) linear=0.416.

CONCLUSIONS

UARN is an intuitive safe procedure that offers dramatic reductions in fluoroscopy times. UARN is best suited to cases requiring only one nephrostomy tract. Upper pole access is commonly performed with a subcostal technique to navigate the puncture wire below the ribs. Increasing BMI best predicts longer nephrostomy creation times; procedure failure was associated with BMI exceeding 40 kg/m(2). UARN is a robust technique for nephrostomy creation in appropriately selected patients.

Functional aspects of silent ureteral stones investigated with MAG-3 renal scintigraphy

Background

To investigate functional aspects of silent ureteral stones with special focus on obstruction and its relationship to renal anatomy. The present study is the first investigation of renal excretory function in patients with silent ureteral stones.

Methods

Patients with primarily asymptomatic ureteral stones underwent a mercapto-acetyltriglycine (MAG-3) renal scintigraphy prior to treatment, in addition to anatomic evaluation of renal units and serum creatinine levels. The primary outcome measure was the presence or absence of obstruction. Secondary outcome measures were kidney anatomy, grade of hydronephrosis, location of stones, stone size, and serum creatinine levels.

Results

During a ten-year period, 14 patients (median age 52.6 years; range 37.3 to 80.7 years) were included in the study. The relative frequency of primarily asymptomatic ureteral stones among all patients treated for ureteral stones in the study period was 0.7%. Eleven renal units showed some degree of hydronephrosis while 3 kidneys were not dilated. On the MAG-3 scan, 7 patients had an obstruction of the ureter, 5 had no obstruction, and 2 had dysfunction of the kidney. A statistically significant correlation was established between the grade of obstruction and stone size (p = 0.02).

Conclusions

At the time of presentation, only 64.3% of the patients revealed an obstruction in the stone-bearing renal unit. The degree of hydronephrosis and renal function were very diverse in this subgroup of patients with ureteral stones. The onset of ureterolithiasis and the chronological sequence of obstruction remain unclear in patients who have never experienced symptoms due to their stones.

Computed tomography-based novel prediction model for the stone-free rate of ureteroscopic lithotripsy

The purpose of this study was to evaluate whether computed tomography (CT) parameters can predict the success of ureteroscopic lithotripsy (URSL) and establish a model for predicting the success rates of a single URSL procedure for the treatment of a single ureteral stone. We retrospectively reviewed the records of 237 patients who underwent URSL for ureteral stones diagnosed by CT between January 2009 and June 2012. Stone-free status was defined as the absence of stones or residual stone fragments <2 mm by ureteroscopy and plain abdominal radiography. We analyzed the correlations between the outcome of URSL and the patients' sex, age, height, body weight, body mass index, and history of ureteral stone. Stone factors such as the diameter (D), stone height (H), volumetric stone burden (VSB; D(2) × H × 5 mm × π × 1/6), estimated stone location (ESL; number of axial cut images between the stone and uretero-vesical junction), tissue rim sign (RS; 0-3), perinephric edema (0-3), hydronephrosis (0-3), and Hounsfield unit (HU) were also analyzed. We then developed a model to predict the probability of successful URSL by applying a logistic model to our data. The success rate of URSL was 85.7% (203/237). Univariate analysis found that stone diameter, length, VSB, ESL, HU and RS significantly affected the stone-free rate. Multivariate analysis indicated that stone diameter, ESL and RS independently influenced the stone-free rate. The logistic model indicated that success rates = 1/[1 + exp{-6.146 + 0.071(D) + 0.153(ESL) + 1.534(RS)}] with an area under the receiver operating characteristic curve of 0.825. Stone diameter, ESL, and RS were independent predictors of the outcome of a single URSL for a single ureteral stone.

Predictive factors of the outcome of extracorporeal shockwave lithotripsy for ureteral stones

Purpose

Extracorporeal Shock Wave Lithotripsy (ESWL) has shown successful outcomes for ureteral stones. We investigated predictive factors for failure of ESWL for treating ureteral stones.

Materials and Methods

A total of 153 patients who underwent ESWL between July 2006 and July 2009 for ureteral stones diagnosed by non-enhanced spiral computed tomography were divided into two groups: (group A, stone size ≤10 mm; and group B, stone size >10 mm). The failure was defined as remnant stones >4 mm. We assessed age, sex, body mass index, stone size, laterality, location, skin-to-stone distance (SSD), Hounsfield unit, and the presence of secondary signs (hydronephrosis, renal enlargement, perinephric fat stranding, and tissue rim sign). We analyzed predictive factors by using logistic regression in each group.

Results

The success rates were 90.2% and 68.6% in group A and B, respectively. In the univariate analysis of each group, stone size, SSD, and all secondary signs showed statistically significant differences in terms of the outcome of ESWL (p<0.05). In the multivariate logistic regression, stone size (odds ratio [OR], 50.005; 95% confidence interval [CI], 6.207 to 402.852) was an independent predictive factor in group A. The presence of perinephric fat standing (OR, 77.634; 95% CI, 1.349 to 446.558) and stone size (OR, 19.718; 95% CI, 1.600 to 243.005) were independent predictive factors in group B.

Conclusions

Stone size is an independent predictive factor influencing failure of ESWL for treating ureteral stones. In larger ureteral stones (>10 mm), the presence of perinephric fat stranding is also an independent predictive factor.

The relationship between ureteral stone characteristics and secondary signs in renal colic

PURPOSE

To assess correlations between stone size/location and severity of secondary signs for ureteral obstruction.

METHODS

Unenhanced multi-detector computed tomography examinations of 150 patients with acute renal colic were reviewed. Stone size, location in the ureter, kidney size and Hounsfield unit values, perinephric edema, and degree of hydronephrosis were assessed.

RESULTS

Pale kidney sign was detected in 36%. Hydronephrosis was mild in 63% and severe in 21%; severe hydronephrosis was associated with larger stones. Mid-ureter and ureteropelvic junction stones were more likely to cause hydronephrosis. Perinephric edema (56%) was not correlated with stone size/location.

CONCLUSION

Only severe hydronephrosis was significantly associated with larger stone size.

Factors that predict the spontaneous passage of ureteric stones in children

Objective

To study the natural history of stone passage in children with ureterolithiasis and to define factors predictive of spontaneous passage.

Patients and methods

In all, 72 children with ureteric stones were evaluated; patients with ureteric calculi of >10 mm were excluded, as were those with absolute indications for surgical stone removal. Stone size, location, side, presence of hydronephrosis, perinephric stranding and degree of the tissue-rim sign were estimated by unenhanced helical computed tomography (UHCT). All patients were sent home with no administration of an α-blocker. The stone status was evaluated by a plain abdominal film or CT at ≈6 weeks after the initial diagnostic evaluation. The time from the initial complaint to the passage of the stone was recorded for each patient.

Results

In all, 54 (75%) children with ureteric stones of ⩽6 mm eventually passed their stones spontaneously. However, stones of <4 mm and those in the distal ureter had a significantly higher spontaneous passage rate and shorter time to stone passage (P < 0.05). The UHCT findings of a higher degree of the tissue-rim sign, hydronephrosis and perinephric fat stranding were associated with a lower likelihood of stone passage.

Conclusions

The rate of spontaneous passage of ureteric stones in children varies with stone location, and perinephric stranding on UHCT seems to be useful for predicting the possibility of spontaneous passage. In cases with unfavourable signs an early intervention might have better outcomes than conservative therapy.

CT-based determination of maximum ureteral stone area: a predictor of spontaneous passage

OBJECTIVE

The purpose of this study was to test the hypothesis that the maximum axial area of ureteral stones is a more accurate predictor of spontaneous passage than the maximum axial diameter.

MATERIALS AND METHODS

This study retrospectively reviewed 211 consecutive emergency department patients (mean age, 48.8 years; age range, 18-88 years) with acute flank pain due to ureteral stones diagnosed using unenhanced CT. Measurements of maximum atrial area were obtained using fixed (FTM) and variable (VTM) threshold methods. For the FTM, stones were segmented using an attenuation threshold of 130 HU. For the VTM, stones were segmented using an attenuation threshold determined by one half of individual stone attenuation. Measurements of maximum atrial diameter were obtained using soft-tissue and bone window settings. Receiver operating characteristic (ROC) analysis was used to compare the accuracy of maximum atrial area with maximum atrial diameter measurements for predicting spontaneous passage.

RESULTS

Fifty-seven patients (27%) required urologic intervention. The areas under the ROC curve (AUC) of maximum atrial area using FTM (0.83, p = 0.013) and VTM (0.84, p = 0.004) were larger than the AUC (0.8, p = 0.4) for maximum atrial diameter using bone window settings or AUC (0.79) for maximum atrial iameter using soft-tissue window settings. For stones with maximum atrial diameter (in soft-tissue window settings) > 5 mm and ≤ 10 mm, the accuracy of maximum atrial area using VTM (AUC = 0.75) and FTM (AUC = 0.74) was superior to the accuracy of maximum atrial diameter in soft-tissue (AUC = 0.67) and bone (AUC = 0.69) window settings (p < 0.05) in predicting spontaneous passage.

CONCLUSION

Determination of the maximum axial area may improve the accuracy in predicting spontaneous passage of ureteral stones, particularly those between 5 and 10 mm.

Predictors for spontaneous stone passage in patients with renal colic secondary to ureteral calculi

OBJECTIVES

To determine the clinical, laboratory, and imaging variables that can predict spontaneous stone passage in patients with renal colic secondary to ureteral calculi.

METHODS

We prospectively analyzed the medical records of 114 patients who admitted to the emergency department for renal colic from June until November of 2010. Forty-six of them were excluded. The presence of ureteral calculi was confirmed by either a kidney-ureter-bladder plain film or an ultrasound or a computer tomography. In all patients, a second visit after 1 month was planned and the stone status was checked by the same imaging techniques.

RESULTS

From the 68 patients, 16 had a calculus in the upper ureter, 10 in the mid ureter, and 42 in lower part. Stone size was ranged from 2.3 to 15 mm, 52.9% of them were located in the left ureter and 51.5% were radiopaque. Stones passed spontaneously in 36 patients. In multivariate analysis, serum white blood cell count found to be the most significant predictor (P = 0.028) for spontaneous passage followed by stone size (P = 0.037). In analysis of patients with stone size <10 mm, left side (P = 0.017) and serum white blood cell count (P= 0.032) found to be significant predictors.

CONCLUSIONS

Serum white blood cell count is an easy to assay variable in everyday practice. This study showed that its value, at the acute phase of a renal colic, is a significant predictor for stone spontaneous passage and should be considered. Stone size remains a valuable predictor. Stones <10 mm on the left ureter have a higher likelihood to pass spontaneously.

Detectability of urinary stones on virtual nonenhanced images generated at pyelographic-phase dual-energy CT

PURPOSE

To evaluate the detectability of urinary stones on virtual nonenhanced images generated at pyelographic-phase dual-energy computed tomography (CT).

MATERIALS AND METHODS

This retrospective HIPAA-compliant study was institutional review board approved. All included patients had previously consented to the use of their medical records for research. Sixty-two patients (38 men, 24 women; age range, 35-91 years) had undergone CT urography, which consisted of nonenhanced and pyelographic-phase dual-energy CT performed by using a dual-source scanner. Commercial software was used to create virtual nonenhanced images by suppressing the iodine signal from the pyelographic-phase dual-energy CT scans. Two radiologists, in consensus, evaluated the virtual nonenhanced images for the presence of stones. Sensitivity for detecting stones was calculated on a per-stone basis. Sensitivity, specificity, and accuracy were also calculated on a per-renal unit (defined as the intrarenal collecting system and ureter of one kidney) basis. The true nonenhanced scan was considered the reference standard. A jackknife method was used because any patient may have multiple stones.

RESULTS

Of 62 patients with 122 renal units, 21 patients with 25 renal units had a total of 43 stones (maximal transverse diameter range, 1-24 mm; median, 3 mm). The overall sensitivity for detecting stones was 63% (27 of 43 stones) per stone. Sensitivities were 29% (four of 14 stones) for 1-2-mm stones, 64% (nine of 14 stones) for 3-4-mm stones, 83% (five of six stones) for 5-6-mm stones, and 100% (nine of nine stones) for 7-mm or larger (7, 7, 7, 8, 8, 9, 11, 15, and 24 mm) stones. All three ureteral stones (3, 4, and 8 mm) were correctly identified. The sensitivity, specificity, and accuracy for detecting stones on a per-renal unit basis were 65% (17 of 26 renal units), 92% (88 of 96 renal units), and 86% (105 of 122 renal units), respectively.

CONCLUSION

Virtual nonenhanced images generated at pyelographic-phase dual-energy CT enabled the detection of urinary stones with moderate accuracy. The detection of small (1-2-mm) stones was limited.

Thick curved planar reformation of unenhanced multislice computed tomography demonstrating urolithiasis

OBJECTIVES

To determine what slice thickness provides optimal curved planar reformation (CPR) images of the urinary tract.

METHODS

A total of 75 consecutive patients with acute flank pain were included in a retrospective pilot study and underwent unenhanced multislice computed tomography (MSCT) (collimation 3.75 mm, pitch 6, reconstruction increment 3 mm, working voltage 120 kV, and tube current 100 mA) with CPR reconstruction of the urinary tract. CPRs with differing slice thicknesses of 3-20 mm at 1-mm increments to reformat each ureter were assessed in each patient separately. Two radiologists and a urologist evaluated the quality of the reformatted images by judging each ureter in terms of the delineation of all its parts using a 5-point scale (insufficient, poor, moderate, good, and excellent).

RESULTS

Of the 75 patients in our cohort, 52 (69%) had urolithiasis. CPR images could be made of all ureters in all patients. Good to excellent image quality was found in the CPRs performed with a slice thickness of 8-12 mm: 27.7% at 8 mm, 14.3% at 9 mm, 26.9% at 10 mm, 12.6% at 11 mm, and 18.5% at 12 mm. Thus, a slice thickness of 8-12 mm determined a cumulative likelihood of 96.7% to demonstrate the ureter totally.

CONCLUSIONS

The results of our study have shown that CPR is a feasible and quick useful tool. CPRs of the urinary tract with a slice thickness of 8-12 mm are best for good delineation of the whole ureter.

Dual-energy CT iodine-subtraction virtual unenhanced technique to detect urinary stones in an iodine-filled collecting system: a phantom study

OBJECTIVE

The objective of our study was to evaluate the feasibility of virtual unenhanced images reconstructed from a dual-energy CT scan to depict urinary stones in an iodine solution in a phantom study.

MATERIALS AND METHODS

Twenty urinary stones of different sizes (1.4-4.2 mm in short-axis diameter) were placed in plastic containers. The containers were consecutively filled with different concentrations of iodine solution (21, 43, 64, 85, and 107 mg/dL; CT attenuation value range, 510-2,310 H at 120 kVp). Dual-energy CT was repeated with 80-140 and 100-140 kVp pairs, two collimation-slice thickness combinations, and the presence or absence of a 4-cm-thick oil gel around the phantom. The iodine-subtraction virtual unenhanced images were reconstructed using commercial software. The images were evaluated by three radiologists in consensus for the visibility of the stones and the presence of residual nonsubtracted iodine. Stone visibility rates were compared between the 80-140 and 100-140 kVp pairs and the five different iodine concentrations.

RESULTS

Stone visibility rates with the 80-140 kVp pair were 99%, 93%, 96%, 94%, and 3% and those with the 100-140 kVp pair were 98%, 95%, 99%, 94%, and 99% for an iodine concentration of 21, 43, 64, 85, and 107 mg/dL, respectively. The poor visibility rate with 80-140 kVp and 107 mg/dL iodine concentration was due to the failure of iodine subtraction.

CONCLUSION

Dual-energy CT iodine-subtraction virtual unenhanced technique is capable of depicting urinary stones in iodine solutions of a diverse range of concentrations in a phantom study.

Acute Flank Pain Secondary to Urolithiasis: Radiologic Evaluation and Alternate Diagnoses

This article discusses the radiologic management of the patient who has acute flank pain. It describes the evolution of radiologic imaging in patients who present with acute symptoms caused by suspected urolithiasis, the advantages of unenhanced helical CT and the limitations of abdominal radiography, intravenous urography, and ultrasonography in this setting, and the alternative diagnoses encountered within the urinary tract, abdomen, and pelvis.

External Validation of Outcome Prediction Model for Ureteral/Renal Calculi

PURPOSE

We externally validated a previously designed neural network model to predict outcome and duration of passage for ureteral/renal calculi. The model was also evaluated using a 6 mm largest stone dimension cutoff in predicting stone outcome.

MATERIALS AND METHODS

The model was previously designed on 301 patients at Albany Medical Center (free shareware from www.uroengineering.com). The model had a prediction accuracy of 86% for passage outcome and 87% for passage duration. In this study we tested the model on a separate 384 patients from 6 different external institutions to assess the prediction accuracy. All patients had a single renal/ureteral calculus by evaluation in an emergency room setting or by primary physicians and were then referred for further treatment. Model accuracy was also compared to using a 6 mm largest stone dimension cutoff in predicting the need for intervention.

RESULTS

Testing on the 384 patients from all 6 external institutions revealed an outcome prediction accuracy of 88%. The area under the ROC curve was 0.9. Using a 6 mm stone size cutoff provided 79% (ROC 0.8) accuracy. The model duration of passage prediction accuracy was 80% (133 patients passed the stone, area under ROC of 0.8).

CONCLUSIONS

The model provided high stone outcome prediction accuracy (ROC of 0.9 and 0.8) at the 6 external institutions, comparable to that of the design institution. The model provided higher accuracy than using only the largest stone dimension as a cutoff. Increasing experience will further assess the model's accuracy.

[Imaging techniques and their impact in treatment management of patients with acute flank pain]

The purpose of this overview is to provide a general summary of the imaging techniques applied at the Vienna Hospital for the investigation of acute flank pain and the diagnosis of stone disease and the evaluation of their efficacy and impact on therapy management. The number of publications on the issue of "intravenous urography (IVU) vs computed tomography (CT)" is abundant; in recent years, advocates of CT make up the majority. In the Department of Urology at the Vienna Hospital, conventional techniques such as ultrasound and IVU besides UHCT still play an important role. This overview presents the advantages and disadvantages of the various imaging techniques for diagnosis of stone disease and evaluates their significance regarding therapy management of patients with acute flank pain.

Quantitation of stone burden: imaging advances

The accurate diagnosis and quantitation of nephrolithiasis in patients with primary hyperoxaluria (PH) often directly impacts the medical and surgical management for individuals with both symptomatic and asymptomatic calculi. Traditionally, depiction of the size, location and appearance of urinary calculi has been provided by kidney, ureter and bladder plain film radiographs with or without tomography. Given advances in imaging technology there is a shift from conventional radiographs to cross-sectional imaging technology, namely unenhanced computed tomography (CT), CT urography, ultrasound and magnetic resonance imaging. These diagnostic techniques provide differing advantages and disadvantages for imaging stone disease. This review outlines imaging advances in the accurate diagnosis and quantitation of patients with metabolically active stone disease such as PH.

Urinary calculi: improved detection and characterization with thin-slice multidetector CT

The aim of this study was to assess the effect of reconstructed slice thickness on the detection and characterization of human urinary calculi on a multidetector helical CT scanner. Nineteen human urinary calculi of various chemical composition measuring 1.0-3.7 mm were embedded into agar in a chamber of a nylon body phantom. The phantom was imaged with a four detector-row CT scanner. The number of detected calculi increased as the reconstructed slice thickness decreased. Measured diameters and density of the visible calculi decreased as the slice thickness increased. The results of the present study support the use of thin reconstructed slices to detect and characterize urinary calculi.

Avaliação dos métodos de imagem no diagnóstico da urolitíase: revisão da literatura

O objetivo deste trabalho foi comparar a tomografia computadorizada helicoidal com os métodos imaginológicos atualmente disponíveis para a abordagem dos pacientes com dor lombar aguda e revisar brevemente as características fisiopatológicas da urolitíase e a evolução da sua abordagem diagnóstica. Foi revista a literatura publicada nos últimos 30 anos, comparando os seguintes métodos: radiografia simples de abdome, urografia excretora, ultra-sonografia e tomografia computadorizada helicoidal. Esta última se mostrou método de alta sensibilidade e especificidade para o diagnóstico de urolitíase, sendo que, virtualmente, todos os cálculos são identificados por este método, exceto em pacientes em uso de indinavir. A radiografia simples de abdome associada à ultra-sonografia têm acurácia semelhante à tomografia computadorizada helicoidal, contudo, esta foi superior como método de avaliação isolado. A literatura sugere que a tomografia computadorizada helicoidal é útil na avaliação de pacientes com dor lombar aguda quando disponível, possibilitando também o diagnóstico diferencial entre as várias doenças que simulam os sintomas de urolitíase.

Diagnostic value of renal parenchymal density difference on unenhanced helical computed tomography scan in acutely obstructing ureteral stone disease

OBJECTIVES

To evaluate the diagnostic value of the renal parenchymal density difference, detected using unenhanced helical computed tomography, as a secondary sign of acute obstruction due to a ureteral stone.

METHODS

Fifty-five patients with acute flank pain, in whom a ureteral stone was detected on the symptomatic side using unenhanced helical computed tomography, and 22 control subjects with no urinary stone disease were included in this prospective study. Computed tomography was performed, starting from the upper poles of the kidneys down to the base of the urinary bladder. The renal parenchymal density was measured in the upper, middle, and lower portions of each kidney, and a mean value was calculated. The difference between the mean values of the two kidneys was used to predict the presence of an acutely obstructing ureteral stone.

RESULTS

In 49 patients with a ureteral stone (89.1%), the difference between the parenchymal densities of the obstructed and nonobstructed kidneys was 5 Hounsfield units (HU) or greater and was lower on the obstructed side. In the remaining 6 patients (10.9%), the density difference was less than 5 HU but was still lower on the obstructed side. All subjects in the control group had a density difference of less than 5 HU. A renal parenchymal density difference of 5.0 HU or greater had 89.1% sensitivity, 100% specificity, 100% positive predictive value, 85.7% negative predictive value, and 93.4% accuracy in predicting the presence of an acute obstructing ureteral stone.

CONCLUSIONS

These data suggest that the renal parenchymal density difference may be a valuable secondary sign of acute obstructing ureteral stone disease.

A COMPUTER MODEL TO PREDICT THE OUTCOME AND DURATION OF URETERAL OR RENAL CALCULOUS PASSAGE

PURPOSE

We developed a computer model to predict the outcome and the duration until passage of ureteral/renal calculi.

MATERIALS AND METHODS

A retrospective, randomized study was performed of the outcome in 301 patients presenting to the emergency room for renal colic. Presenting characteristics of those diagnosed with a single calculus by computerized tomography were recorded for analysis. Predictors of stone passage and passage duration were identified and then used to create a logistic regression model. The algorithm was trained on 141 randomly selected patients and then tested on a separate 160 patients. Model accuracy was compared to predictions from 10 experienced urologists and 9 urology residents in 77 randomly selected patients. The model was tested further in 30 randomly selected patients at a private hospital to assess its general applicability.

RESULTS

The model prediction accuracy in 160 patients was 86.3% for passage and 87.3% for duration (less or greater than 2 weeks). In the comparison group the model, the 10 experienced urologists and the 9 urology residents had an overall prediction accuracy of 88.3%, 70.5% (p = 0.006) and 72% (p = 0.007) for passage, and 87.1%, 71.6% (p = 0.007) and 81% (p = 0.075) for duration, respectively. Prediction accuracy was 93.3% for passage and 90.3% for duration when tested at a private hospital.

CONCLUSIONS

Our model provides outcome and duration of passage predictions for patients presenting acutely in the emergency room with a single ureteral/renal calculus. It performs better than experienced urologists and urology residents. It can be applied to a private practice setting with equal accuracy.

[Imaging of acute urinary obstruction: non-enhanced CT or KUB and US]

The use of non-enhanced CT as a primary imaging technique for acute lumbar pain is now widely accepted in many centers instead of the traditional association of KUB and ultrasound. This review will present the different features of the disease according to each technique, emphasising on respective performances, advantages and disadvantages. Finally, a strategy will be proposed based on clinical presentation.

Combined magnetic resonance urography and targeted helical CT in patients with renal colic: A new approach to reduce delivered dose

PURPOSE

To determine whether magnetic resonance urography (MRU), obtained before helical computed tomography (CT) in patients with acute renal colic, can help delimit the obstructed area to be subsequently examined by a targeted CT scan, thus reducing the dose of radiation.

MATERIALS AND METHODS

Patients (51) with symptoms of acute renal colic underwent MRU and a total urinary tract helical CT. CT images from the 5 cm below the level of ureteral obstruction as demonstrated by MRU were selected out. Combined interpretation of MRU and selected CT images constituted protocol A. Protocol B consisted of the entire unenhanced helical CT of the urinary tract. The two protocols were compared regarding the following points: 1) sensitivity in diagnosing the presence of obstructing urinary stones, and 2) the delivered radiation dose.

RESULTS

Protocol A and protocol B had, respectively, 98% and 100% sensitivity in demonstrating ureteral stone as a cause of renal colic. Estimated average dose calculated from phantom study was 0.52 mSv for protocol A and 2.83 mSv for protocol B. Therefore, the effective radiation dose was 5.4 times lower in protocol A compared to protocol B.

CONCLUSION

Combined MRU and short helical CT has a high sensitivity in detecting ureteral calculi with a reduced radiation dose.

Acute Ureterolithiasis: Incidence of Secondary Signs on Unenhanced Helical CT and Influence on Patient Management

AIM

The purpose of this study was to determine the incidence of secondary signs associated with ureteral stones on unenhanced helical computed tomography (CT) of patients with acute renal colic, and to correlate these with patient management and outcome.

MATERIALS AND METHODS

One hundred and ten patients with ureterolithiasis were evaluated prospectively for the secondary signs of obstruction on unenhanced helical CT. Our attention was focused primarily on the presence or absence of seven secondary signs on unenhanced helical CT, including hydronephrosis, unilateral renal enlargement, perinephric oedema, unilateral absence of the white pyramid, hydroureter, periureteral oedema and lateroconal fascial thickening.

RESULTS

Of the 110 patients, 91 (82.7%) had hydroureter, 88 (80%) had hydronephrosis, 65 (59%) had periureteric oedema and 63 (57.2%) had unilateral renal enlargement. Ninety stones passed spontaneously and 21 required intervention.

CONCLUSION

Secondary signs of urinary tract obstruction are useful and supportive findings in interpretation of the CT examination. In our experience, the most reliable signs indicating ureteral obstruction are hydroureter, hydronephrosis, periureteral oedema and unilateral renal enlargement, respectively. In addition, stones larger than 6 mm, located within the proximal two thirds of the ureter, and seen associated with five or more the secondary signs of obstruction, are more likely to require endoscopic removal and/or lithotripsy.

CT evaluation of urinary lithiasis

Unenhanced CT has been demonstrated to be the most accurate and efficient diagnostic imaging means to evaluate urinary lithiasis, with capability of directing management, and has become well accepted by radiologists, urologists, and emergency department physicians such that it is now the standard of practice. It is the duty of the radiologist to be aware of proper technique and the details of interpretation. The radiologist also has a duty to be aware of the limitations of unenhanced CT for detection and evaluation of various nonstone disorders, particularly with poor patient selection, and to extend the examination if appropriate. Controversies and future developments include cost containment with care for the selection of patients. Further attempts to reduce radiation exposure should be made. Optimal CT technique is not needed in general merely to detect urinary lithiasis. A consensus should be developed regarding use of CT in pregnant patients. Further improvements in the digital scout view would be useful for following patients.

Evaluation of the patient with flank pain and possible ureteral calculus

Flank pain due to urolithiasis is a common problem in patients presenting to emergency departments. Radiology plays a vital role in the work-up of these patients. Many modalities can be used, including ultrasonography, nuclear medicine, and the traditionally used techniques of intravenous urography and conventional radiography. The development of nonenhanced computed tomography (CT) (single- or multi-detector row helical) has provided a means to enable detection and characterization of urolithiasis with unprecedented sensitivity, specificity, and accuracy while yielding important information for treatment planning, including the size and location of calculi. This technique can also help detect causes for flank pain outside the genitourinary tract. However, close attention must be paid to all aspects of the CT study to prevent misdiagnoses.

Unenhanced helical CT in the investigation of acute flank pain

Unenhanced helical CT has emerged as the imaging technique of choice for the investigation of patients presenting with acute flank pain and suspected nephroureteric stone disease. There are several signs identifiable on unenhanced CT that support a diagnosis of stone disease. However, there are many pitfalls, that may confound a correct diagnosis. Some of the common pitfalls, together with methods to avoid such occurrences, will be discussed. A review of some of the common alternative diagnoses that may mimic the symptoms of nephroureteric stone disease is illustrated.

Suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography

OBJECTIVE

The purpose of this study was to compare the accuracy of unenhanced helical CT with combined sonography and unenhanced radiography in patients with acute flank pain suggestive of ureteral colic.

SUBJECTS AND METHODS

From January 1997 to December 1999, 181 consecutive patients with acute flank pain underwent unenhanced radiography, sonography, and unenhanced helical CT (protocol A). From January 2000 to December 2000, 96 consecutive patients arriving at the emergency department with acute flank pain were alternately submitted either to primary unenhanced helical CT (protocol B, 48 patients) or to unenhanced radiography and sonography with the addition of helical CT in unclear cases (protocol C, 48 patients).

RESULTS

When compared with the diagnostic accuracy for ureterolithiasis of the combined sonography and radiography in the same group of subjects (protocol A), CT had a greater sensitivity (92% vs 77%), negative predictive value (87% vs 68%), and overall accuracy (94% vs 83%). Among patients who underwent primary CT (protocol B), we found three false-negatives (all with spontaneous stone passage) and no false-positives. Among patients initially examined with unenhanced radiography and sonography (protocol C), we found one false-positive (leading to patient admission and needless repeated radiographic and sonographic studies) and six false-negatives (all followed by an uncomplicated course and spontaneous passage); CT depicted four of these stones but did not result in change in treatment. Fourteen percent of the patients in protocol C required invasive treatment, but combined sonography and radiography showed stones and hydronephrosis in all these patients.

CONCLUSION

Unenhanced CT was the most accurate modality for determining the presence of ureterolithiasis. The combination of abdominal radiography and sonography, however, yielded comparable results with no clinically important misdiagnoses and thus can be used as an alternative when CT resources are limited.

Assessment of the clinical utility of the rim and comet-tail signs in differentiating ureteral stones from phleboliths

OBJECTIVE

This study was designed to assess interobserver variability in identifying the rim and comet-tail signs and to determine the clinical utility of these signs in determining whether or not the calcifications with which they are associated represent ureteral calculi.

MATERIALS AND METHODS

Two radiologists and a radiology resident, unaware of the final diagnosis, reviewed preselected helical CT images from renal stone examinations in patients with 65 indeterminate pelvic calcifications. Assessment of calcifications for rim or comet-tail signs was performed independently of an assessment for the following five secondary signs of urinary tract obstruction: caliectasis, pelviectasis, ureterectasis, perinephric stranding, and renal enlargement. Agreement in identifying rim and comet-tail signs was assessed by obtaining kappa statistics. The utility the of rim or comet-tail signs in determining whether ureterolithiasis was present in patients in whom perinephric stranding and ureterectasis were present or absent was determined. The frequency with which one or more of each of the five assessed secondary signs was identified ipsilateral to a calcification having rim or comet-tail signs was also tabulated.

RESULTS

Kappa values for interobserver agreement ranged from 0.49 to 0.73. In only one patient was a rim sign detected in the absence of ureterectasis and perinephric stranding. Reviewers identified at least three of the five assessed secondary signs ipsilateral to calcifications showing a rim sign in all but one patient (by each radiologist) and four patients (by the resident). When three or more secondary signs of obstruction were seen ipsilateral to a calcification having a comet-tail sign, in all but one instance, this was because the calcification was a ureteral calculus or because there was a separate ipsilateral ureteral calculus.

CONCLUSION

In many instances, observers did not agree about whether the rim and comet-tail signs were present. The rim sign was observed in the absence of any secondary signs of urinary tract obstruction in only one (1.5%) of the 65 patients in our series (95% confidence interval, 0-5.3%). The comet-tail sign, when accompanied by secondary signs of obstruction, should indicate that an ipsilateral ureteral stone is present and not the reverse.

Randomized prospective comparison of non-contrast enhanced helical computed tomography and intravenous urography in the diagnosis of acute ureteric colic

Non-contrast enhanced helical CT has become an accepted technique for evaluating acute ureteric colic. The results of a randomized prospective comparison of the accuracy, cost and radiation dose of CT and intravenous urography (IVU) are presented. All patients presenting to the Emergency Department with symptoms and signs suggestive of ureteric colic over a 16-month period (n = 242) were randomized to CT or IVU. Follow up was obtained for 228 patients (94%), with 14 patients (6%) lost to follow up. One hundred and twenty-three patients (54%) underwent CT and 105 (46%) had an IVU. At follow up the sensitivity and specificity of CT were each 100%, while those of IVU were 99% and 100%, respectively. Computed tomography demonstrated seven of 26 (27%) potential alternative diagnoses, whereas IVU suggested one of 23 (4%). Estimates of the average effective dose were calculated for CT (4.95 mSv) and IVU (1.48 mSv, 95% confidence interval (CI) 0.7-2.27). Radiation dose and intravenous contrast material safety are discussed and the relative costs are considered. Computed tomography is as accurate as IVU in the diagnosis of acute ureteric colic. It confers certain major diagnostic benefits, and is a fast, well-tolerated technique. Its accompanying higher effective radiation dose is recognized.