Multidetector CT urography with abdominal compression and three-dimensional reconstruction

The importance of CT Urography in early diagnosis of anatomical variations in urogenital tract: case presentation

Anatomic variations in the urogenital tract have generally been diagnosed through intravenous urography as a modality of choice. In recent years, computerized tomography (CT) urogram has replaced the traditional intravenous imaging of the genitourinary tract. Hematuria, tumoral mass, obstructive uropathy, and congenital collecting system abnormalities are indications for CT imaging. In this report, we present a young woman with intermittent right flank pain and recent urinary tract infection. Her history was also positive for spontaneous abortion. She was referred to the Radiology Clinic for a CT urography. Our aim, in this case report, is to highlight the role of CT urography in the early diagnosis of anatomical variations of the urogenital system and appropriate prevention of clinical progression.

Korean ureter length: A computed tomography-based study

Purpose

We measured ureter length in healthy Koreans using reformatted computed tomography (UL_CT) and found ways to indirectly estimate ureter length by measuring LL_CT, the length between the ureteropelvic junction and the ureterovesical junction, and standing and sitting height.

Materials and Methods

A total of 508 ureters of 254 healthy patients (median age, 55.0 years; 148 males and 106 females) were included in this retrospective study. UL_CT, LL_CT, and sitting and standing body height were measured.

Results

The mean left and right UL_CT were 25.2±2.2 and 25.0±2.2 cm, respectively. The mean left and right LL_CT were 21.1±1.8 and 20.3±1.9 cm, respectively. Standing and sitting body height were 164.1±8.9 and 88.3±4.3 cm, respectively. Height was significantly correlated with UL_CT, but this relation was not linear (r²=0.064 standing height, 0.062 sitting height). However, LL_CT showed a significant linear correlation with UL_CT (r²=0.485). UL_CT can be estimated indirectly by the following equation: UL_CT=0.823×LL_CT+8.093.

Conclusions

We could measure the ureteral length of healthy Koreans by UL_CT. UL_CT could be estimated indirectly by LL_CT and standing and sitting height. Of these variables, LL_CT provided the most accurate estimate of ureteral length.

CT urography: how to optimize the technique

PURPOSE

Computed tomography urography (CTU) has emerged as the modality of choice for imaging the urinary tract within the past few decades. It is a powerful tool that enables detailed anatomic evaluation of the urinary tract in order to identify primary urothelial malignancies, benign urinary tract conditions, and associated abdominopelvic pathologies. As such, there have been extensive efforts to optimize CTU protocol.

METHODS

This article reviews the published literature on CTU protocol optimization, including contrast bolus timing, dose reduction, reconstruction algorithms, and ancillary practices.

CONCLUSION

There have been many advances in CTU techniques, which allow for imaging diagnosis of a wide spectrum of diseases while minimizing radiation dose and maximizing urinary tract distension and opacification.

Bladder cancer diagnosis with CT urography: test characteristics and reasons for false-positive and false-negative results

PURPOSE

To determine test characteristics of CT urography for detecting bladder cancer in patients with hematuria and those undergoing surveillance, and to analyze reasons for false-positive and false-negative results.

METHODS

A HIPAA-compliant, IRB-approved retrospective review of reports from 1623 CT urograms between 10/2010 and 12/31/2013 was performed. 710 examinations for hematuria or bladder cancer history were compared to cystoscopy performed within 6 months. Reference standard was surgical pathology or 1-year minimum clinical follow-up. False-positive and false-negative examinations were reviewed to determine reasons for errors.

RESULTS

Ninety-five bladder cancers were detected. CT urography accuracy: was 91.5% (650/710), sensitivity 86.3% (82/95), specificity 92.4% (568/615), positive predictive value 63.6% (82/129), and negative predictive value was 97.8% (568/581). Of 43 false positives, the majority of interpretation errors were due to benign prostatic hyperplasia (n = 12), trabeculated bladder (n = 9), and treatment changes (n = 8). Other causes include blood clots, mistaken normal anatomy, infectious/inflammatory changes, or had no cystoscopic correlate. Of 13 false negatives, 11 were due to technique, one to a large urinary residual, one to artifact. There were no errors in perception.

CONCLUSION

CT urography is an accurate test for diagnosing bladder cancer; however, in protocols relying predominantly on excretory phase images, overall sensitivity remains insufficient to obviate cystoscopy. Awareness of bladder cancer mimics may reduce false-positive results. Improvements in CTU technique may reduce false-negative results.

Diagnostic value of 64-slice spiral computed tomography imaging of the urinary tract during the excretory phase for urinary tract obstruction

The present study aimed to assess the diagnostic value of 64-slice spiral computed tomography (CT) imaging of the urinary tract during the excretory phase for urinary tract obstruction. CT imaging of the urinary tract during the excretory phase was performed in 46 patients that had been diagnosed with urinary tract obstruction by B-mode ultrasound imaging or clinical manifestations. It was demonstrated that out of the 46 patients, 18 had pelvic and ureteral calculi, 12 cases had congenital malformations, 3 had ureteral stricture caused by urinary tract infection and 13 cases had malignant tumors of the urinary tract. The average X-ray dose planned for the standard CT scan of the urinary tract group 1 was 14.11±5.45 mSv, while the actual X-ray dose administered for the CT scan during the excretory phase group 2 was 9.01±4.56 mSv. The difference between the two groups was statistically significant (t=15.36; P<0.01). The results of the present study indicate that CT scanning of the urinary tract during the excretory phase has a high diagnostic value for urinary tract obstruction.

Split-bolus CT urogram: Is less more?

PURPOSE

To determine the accuracy of split-bolus CT urogram (SB-CTU) without special maneuvers for ureteral distention in diagnosing upper urinary tract urothelial carcinoma (UCA).

MATERIALS AND METHODS

A hospital database was searched from 1/1/10, to 9/1/15, for SB-CTU exams without special maneuvers for ureteral distention. Accuracy of SB-CTU for detecting upper and lower urinary tract UCA was computed by comparing the prospective radiology report with cystoscopy, ureteroscopy, and/or urologic clinical follow-up. Patients with less than 12 months of clinical follow-up were excluded.

RESULTS

339 studies were identified in 334 patients (60% male 40% female, avg. age 64). 119 studies were performed for microhematuria, 150 for gross hematuria, 13 for hematuria not otherwise specified, 57 for history of UCA, and one for a collecting system mass on a prior CT. There were five upper tract and 33 bladder tumors with overall prevalence of 1.5% and 9.7%, respectively. The prevalence varied significantly with patient age and clinical indication for SB-CTU. There were one false negative and four false positives for upper urinary tract UCA. Sensitivity, specificity, positive predictive value, and negative predictive value for detecting upper tract and bladder tumors were 80%, 99%, 44%, and 100%, respectively, and 55%, 98%, 78%, and 95%, respectively.

CONCLUSION

Based on this study, SB-CTU without special maneuvers for ureteral distention is highly sensitive for detecting upper tract UCA, although with a low positive predictive value, false positives do occur. The clinical utility of increasing accuracy in diagnosing this low-prevalence disease through other more complex CT urogram protocols should be weighed against the added cost and radiation dose associated with these protocols.

Bladder cancer diagnosis: the role of CT urography

AIMS AND BACKGROUND

To evaluate the diagnostic performance of computed tomography urography (CTU), we first compared it with cystoscopy and subsequently analyzed which CTU phase of acquisition has the highest diagnostic accuracy in identifying bladder cancer.

METHODS

In 2013, 177 patients underwent both cystoscopy and CTU. For all acquisition phases, we calculated sensitivity, specificity, diagnostic accuracy, and positive and negative predictive value (PPV and NPV, respectively). We also evaluated the Cohen κ coefficient.

RESULTS

Computed tomography urography sensitivity, specificity, diagnostic accuracy, PPV, and NPV were as follows: 96.3%, 86.4%, 92.8%, 92.9%, and 92.7%; concordance calculated with Cohen κ was good: 0.8413. The arterial acquisition phase showed the highest diagnostic accuracy, identifying 93.4% of all lesions.

CONCLUSIONS

Computed tomography urography is an accurate examination for the diagnosis of bladder cancer, and the arterial acquisition phase provides the best diagnostic information.

CT urography as the first line investigation for haematuria: is it truly indicated? A single centre analysis of the use of CT urography in the haematuria clinic

Introduction:

Computed tomographic urography (CTU) is gaining popularity as the first line investigation for haematuria. It can be used to produce a ‘true’ one-stop clinical assessment. However, a large number of investigations can be negative, exposing patients to a number of risks.

Objective:

We set out to evaluate the use of CTU in our one-stop haematuria clinic to see if it supported the utilisation of CTU as a triage investigation for haematuria.

Methods:

Retrospective analysis of all CT urograms performed (508) in our trust in 2013 took place. CTUs requested from the haematuria clinic were identified and analysed further.

Results:

A total of 1086 patients attended the haematuria clinic in 2013. 168 males and 78 females (median age 64, range 25 to 90) went on to have further CTU investigation after ultrasonography (USS) and cystoscopy. Visible haematuria (VH) was reported in 95% of cases. All 9 confirmed cases of upper tract urothelial carcinoma lesions presented with VH (age > 50); 8 out of 9 had reported hydronephrosis on USS. The overall negative predictive CTU rate was 96%.

Conclusion:

Our results show that a large number of CTUs are negative. The use of risk stratification, with particular emphasis on the ultrasonography result, gives adequate guidance on the cases that require further CTU investigation, supportive of the current European Association of Urology guidelines. Our results do not support the use of CTU as a first line or triage investigation for haematuria.

Diagnostic Performance of Ultrasound for Macroscopic Hematuria in the Era of Multidetector Computed Tomography Urography

Purpose

The objective of this study was to evaluate the diagnostic performance of ultrasound for detecting urinary tract neoplasm in the setting of macroscopic hematuria by using multidetector computed tomography urography (MDCTU) and cystoscopy as the reference standard.

Methods

This retrospective study was approved by our institutional review board. Patients with macroscopic hematuria who were investigated with an abdominal or renal ultrasound, an MDCTU, and a cystoscopy between January 2007 and December 2009, were eligible (95 patients). Exclusion criteria were time interval >12 months between index and reference tests or the absence of histopathologic proof of malignancy. Ultrasound results of the remaining 86 patients were collected and compared with the reference standard test, which was the combination of MDCTU for the assessment of upper urinary tract and cystoscopy for assessment of the lower urinary tract. The final diagnosis of neoplasm was based on pathologic findings.

Results

Urinary tract neoplasm was diagnosed in 20% of the patients (17/86). Sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios of ultrasound for detecting urinary tract neoplasms were 35.3% (6/17), 89.9% (62/69), 46.2% (6/13), 84.9% (62/73), 3.48 (95% confidence interval, 1.34-9.02), and 0.72 (95% confidence interval, 0.5-1.3), respectively.

Conclusion

Sensitivity of ultrasound for the evaluation of macroscopic hematuria in the era of MDCTU is lower than expected. Results of our study suggest that patients with macroscopic hematuria should undergo MDCTU as first-line imaging modality, with little added benefit from ultrasound.

Computed tomography urography 1: techniques and technology

Contrast-enhanced computed tomography urography has become possible because of the development of multidetector technology, which has evolved to try and increase its diagnostic efficacy and reduce the radiation exposure. This review highlights important aspects of computed tomography urography as an imaging technique.

Is computed tomography mandatory for the detection of residual stone fragments after percutaneous nephrolithotomy?

The introduction of minimally invasive endourologic procedures for upper urinary stone disintegration has closed the curtain on the era of open surgery for upper urinary tract stones in which complete stone eradication was the rule. This shift to minimally invasive procedures has led to the introduction of new terminology, such as stone-free rates and residual stone fragments, the presence of which after treatment was considered an acceptable therapeutic end point. Percutaneous nephrolithotomy (PCNL) is currently considered the procedure of choice for large renal stones. Its use has been greatly facilitated by the favorable profile of multidetector CT with regard to its sensitivity in detecting small stones. Despite the fact that CT is considered essential for the diagnosis and exact localization of stones and has been used for the creation of percutaneous tracts in PCNL, however, its routine use for the post-PCNL detection of residual stones has not been established. There is evidence that routine application of post-PCNL CT provides additional advantages compared with other imaging modalities-namely, the identification of the presence and location of even small residual fragments, which has been shown to cause significant trouble and necessitate secondary procedures in a significant cohort of patients after PCNL. On the other hand, the issues of cost, availability of CT scanners, and radiation exposure along with the acceptable sensitivity, cost, and availability of other imaging studies has raised doubts as to whether CT should be the routine imaging study after PCNL. The present review will discuss the concept of clinically significant residual fragments and comment on the advantages and drawbacks of different imaging studies used for the detection of residual stones after PCNL. This review also aims to clarify the indications in which CT should routinely be performed or could be omitted in the follow-up after PCNL.

Predicting calyceal access for percutaneous nephrolithotomy with computed tomography multiplanar reconstruction

OBJECTIVES

Objective parameters in computed tomography (CT) scans that could predict calyceal access during percutaneous nephrolithotomy have not been evaluated. These parameters could improve access planning for percutaneous nephrolithotomy. We aimed to determine which parameters extracted from a preoperative multiplanar reconstructed CT could predict renal calyceal access during a percutaneous nephrolithotomy.

METHODS

From January 2009 through April 2011, 230 patients underwent 284 percutaneous nephrolithotomies at our institution. Sixteen patients presented with complete staghorn calculi, and 11 patients (13 renal units) were analyzed. Five parameters were extracted from a preoperative reconstructed CT and compared with the surgical results of percutaneous nephrolithotomy.

RESULTS

Fifty-eight calyces were studied, with an average of 4.4 calyces per procedure. A rigid nephroscope was used to access a particular calyx, and a univariate analysis showed that the entrance calyx had a smaller length (2.7 vs. 3.98 cm, p=0.018). The particular calyx to be accessed should have a smaller length (2.22 vs. 3.19 cm, p=0.012), larger angles (117.6 vs. 67.96, p<0.001) and larger infundibula (0.86 vs. 0.61 cm, p=0.002). In the multivariate analysis, the only independent predictive factor for accessing a particular calyx was the angle between the entrance calyx and the calyx to be reached (OR 1.15, 95% confidence interval [CI], 1.053-1.256, p=0.002).

CONCLUSION

The angle between calyces obtained by multiplanar CT reconstruction is the only predictor of calyx access.

Detection of urothelial tumors: comparison of urothelial phase with excretory phase CT urography--a prospective study

PURPOSE

To compare contrast material-enhanced computed tomographic (CT) urography 60 seconds after injection of contrast material (urothelial phase [UP]) after intravenous administration of a diuretic with the standard 5-minute delayed excretory phase (EP) in a high-risk population for upper tract tumors.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Eighty CT urographic examinations in 77 patients known to have or at high risk for urothelial malignancy were included. After intravenous administration of a diuretic, dual-phase CT urography was performed at 60 seconds (UP) and 5 minutes (EP) after intravenous administration of contrast material. Two experienced abdominal radiologists independently interpreted each phase more than 1 month apart to minimize recall bias. Urinary tract distention and location and size of all lesions suspected of being urothelial tumors were recorded. Standard of reference was obtained from prospective study interpretation and surgical histopathologic findings. Generalized estimating equations for logistic regression were used to compare performance measures and adjust for the correlation of repeated measures within patients.

RESULTS

There were 23 upper and 61 lower urinary tract tumors confirmed in 15 and 32 patients, respectively. For detection of bladder tumors, there was higher sensitivity for the UP than the EP (89.3% [109 of 122] vs 70.5% [86 of 122], respectively; P<.0001). For detection of upper tract tumors, there was higher sensitivity for the UP than the EP (82.6% [38 of 46] vs 69.6% [32 of 46], respectively; P=.0194). Distention of all upper urinary tract segments was better during the EP than the UP (P<.0001).

CONCLUSION

UP CT urography after injection of a diuretic has a higher lesion detection rate than the EP for both upper and lower urinary tract tumors, which suggests its possible use as a single-phase protocol for evaluation of the entire urinary tract in patients at high risk for urothelial tumors.

CT urography for hematuria

Hematuria can signify serious disease such as bladder cancer, upper urinary tract urothelial cell carcinoma (UUT-UCC), renal cell cancer or urinary tract stones. CT urography is a rapidly evolving technique made possible by recent advances in CT technology. CT urography is defined as CT examination of the kidneys, ureters and bladder with at least one series of images acquired during the excretory phase after intravenous contrast administration. The reasoning for using CT urography to investigate hematuria is based on its high diagnostic accuracy for urothelial cell carcinoma (UCC) and favorable comparison with other imaging techniques. The optimum diagnostic imaging strategy for patients with hematuria at high-risk for UCC involves the use of CT urography as a replacement for other imaging tests (ultrasonography, intravenous urography, or retrograde ureteropyelography) and as a triage test for cystoscopy, resulting in earlier diagnosis and improved prognosis of bladder cancer, UUT-UCC, renal cell cancer and stones. Current problems with CT urography for investigating hematuria might be solved with a formative educational program simulating clinical reporting to reduce reader error, and a new technique for image-guided biopsy of UUT-UCC detected by CT urography for histopathological confirmation of diagnosis and elimination of false-positive results. CT urography is recommended as the initial imaging test for hematuria in patients at high-risk for UCC.

Hematuria evaluation with MDCT urography: is a contrast-enhanced phase needed when calculi are detected in the unenhanced phase?

OBJECTIVE

The purpose of this study was to assess the added utility of the contrast-enhanced phase of MDCT urography (MDCTU) when urinary tract calculi are detected in the preliminary unenhanced phase.

MATERIALS AND METHODS

A computer search of CT reports with the term "hematuria" yielded the records of 1209 patients who had undergone MDCTU. The reports of 286 MDCTU examinations in which urinary tract calculi were detected were identified, and two blinded abdominal radiologists reviewed the images to find a second source of hematuria. The unenhanced images were reviewed first, and the findings were compared with those on the subsequent contrast-enhanced images. The aggregate findings of the 286 examinations in which calculi were present were compared with those of the 923 examinations in which calculi were absent. The follow-up diagnosis was based on histopathologic findings, findings at urologic procedures, or the imaging diagnosis.

RESULTS

In 119 of the 1209 patients (10%), 127 lesions other than urinary tract calculi were identified as possible sources of hematuria. Eighty-two lesions were diagnosed in 77 patients (6%) at follow-up evaluation. A second source of hematuria was found in 19 of the 286 examinations (7%) with calculi compared with 58 of the 923 examinations (6%) without calculi (p = 0.828), and contrast was needed to make a specific diagnosis in 16 of the 19 examinations (84%).

CONCLUSION

When urinary tract calculi are identified at MDCTU, the rate of detection of other potential causes of hematuria is not different from that in MDCTU examinations without calculi. The contrast-enhanced portion of the MDCTU examination is needed even if calculi are seen because important pathologic changes are diagnosed only after the contrast-enhanced phase.

Accuracy and factors affecting the outcome of multi-detector computerized tomography urography for bladder tumors in the clinical setting

Purpose

The objective of this study was to investigate the diagnostic accuracy of multi-detector computerized tomography urography (MDCTU) for the detection of bladder tumors.

Materials and Methods

We retrospectively reviewed the medical records of 143 patients who were scanned by use of 64-channel MDCTU and who underwent cystoscopy due to painless hematuria or a clinical suspicion of bladder tumor. We examined the accuracy of MDCTU for the detection of bladder tumors by comparing the results obtained by MDCTU with those obtained by cystoscopy. The associations between tumor characteristics, frequency of transurethral resection (TUR), and bladder volume and detectability of bladder tumors on MDCTU were also analyzed.

Results

Of 143 patients, 50 patients had a history of urothelial carcinomas. In these patients, the sensitivity and specificity of MDCTU were 60.0% and 80.0%, respectively. In 93 patients without previous urothelial carcinomas, the sensitivity and specificity of MDCTU were 86.7% and 96.8%, respectively. Falsely diagnosed cases had a smaller distended bladder volume (p=0.014) and a smaller tumor size (p=0.022) than did true diagnosed cases. The false-negative rate increased when the bladder tumor was located at the bladder neck. In the univariate analysis, the tumor location, size, frequency of TUR, bladder volume, and initial hematuria were associated with detectability by MDCTU (p<0.05).

Conclusions

To improve the accuracy of MDCTU for diagnosing bladder tumors, bladder filling is recommended. Thus, cystoscopy should be considered as a standard diagnostic tool for bladder tumors even in patients with normal MDCTU results, especially in the evaluation of recurrent, bladder neck-located, small, or sessile bladder tumors.

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.

Kidney and urinary tract imaging: triple-bolus multidetector CT urography as a one-stop shop--protocol design, opacification, and image quality analysis

PURPOSE

To retrospectively evaluate renal, vascular, and urinary tract visualization following a single postcontrast multidetector computed tomographic (CT) urographic sequence performed with three limited-volume bolus injections.

MATERIALS AND METHODS

The institutional review board approved this retrospective study. Patient informed consent was waived. Triple-bolus multidetector CT urography was performed in 110 patients. Triple-bolus protocol consisted of 30 mL of contrast material at 2 mL/sec at 0 seconds, 50 mL at 1.5 mL/sec at 435 seconds, 65 mL at 3 mL/sec at 488 seconds, with total abdominal scanning time of 510 seconds. Two independent readers rated urinary tract opacification and qualitatively and quantitatively assessed renal parenchymal and vascular contrast enhancement. Upper urinary tract (UUT) distention was measured by one reader. Interobserver agreement was assessed by using kappa statistics.

RESULTS

Complete opacification of the intrarenal collecting system and proximal ureter was achieved in 91% (184 of 202) (kappa = 0.62) and 82% (166 of 202) (kappa = 0.94) of segments, respectively. The distal ureter was not opacified in 21% of the cases (kappa = 0.92), and the bladder was not opacified in 20% of the cases. Mean distention was higher for proximal (3.9 mm) than for distal (3.7 mm) segments. Image quality of renal parenchymal enhancement was excellent in 76% of cases. Arteries showed better contrast enhancement than veins (excellent rating in 89% vs 59% of the cases). Radiation dose calculated for triple-bolus acquisition was 9.8 mSv.

CONCLUSION

Triple-bolus multidetector CT urography is a dose-efficient protocol acquiring corticomedullary-nephrographic-excretory and vascular enhancement phases in a single acquisition and provides sufficient opacification and distention of the UUT. Simultaneously, adequate image quality of renal parenchyma and vascular anatomy is achieved.

Computed tomography for percutaneous renal access

Abstract Successful percutaneous nephrolithotomy (PCNL) relies on appropriate preoperative planning and optimal percutaneous access. CT has now become the standard imaging tool for PCNL. For percutaneous renal access, CT may be used for planning access, guiding access, and in the follow-up after access. In this review, we discuss the role of each aspect for percutaneous access in PCNL. In particular, we describe the technique for gaining access using CT, a valuable method in the difficult collecting system.

MDCT Urography: Exploring a new paradigm for imaging of bladder cancer

OBJECTIVE

The purpose of this article is to review the epidemiology, staging, and treatment of bladder cancer; to discuss the role of MDCT urography for the evaluation of patients with known or suspected bladder cancer; and to address the role of MDCT urography in patients who require follow-up imaging after a diagnosis of bladder cancer has been made.

CONCLUSION

MDCT urography now has a large role in the evaluation of patients with known and suspected bladder cancer. However, its precise role has not been established. Because many bladder neoplasms will not be detected by MDCT urography and more research is needed to determine the optimal technique for diagnosing bladder cancer, we think that MDCT urography cannot replace cystoscopy at present.

Current use of computed tomographic urography: survey of the society of uroradiology

OBJECTIVE

To determine uroradiologists' opinions and practices regarding computed tomographic (CT) urography.

METHODS

A Web-based survey was sent via e-mail to all 259 members of the Society of Uroradiology. Of the 229 successfully delivered e-mails, 90 (39%) members responded.

RESULTS

Of 90 uroradiologists, 87% perform CT urography. Compared with intravenous (IV) urography, 69% of uroradiologists use CT urography more than 75% of the time urinary tract imaging is requested; 27% stated that CT urography has completely replaced IV urography. Most uroradiologists perform CT urography using multidetector-row CT alone (79%) and use a 3-phase technique (52%) using a single injection (76%) of contrast material at 3 mL/s (52%) without a compression device (81%) and with the patient in supine position (80%).

CONCLUSIONS

Most uroradiologists use CT urography in their practice today; some no longer perform IV urography. Variability in multidetector-row CT technique suggests that more research is needed to determine the optimal protocol.

Bladder cancer detection with CT urography in an Academic Medical Center

PURPOSE

To evaluate the performance characteristics of computed tomographic (CT) urography for the detection of bladder cancer in patients at risk for the disease.

MATERIALS AND METHODS

Institutional review board approval was obtained for this retrospective HIPAA-compliant review of medical records of 2600 consecutive patients undergoing CT urography. Of these, 838 CT urograms in 779 patients (449 men, mean age of 62 years, range of 27-92 years; 330 women, mean age of 56 years, range of 18-86 years) evaluated for hematuria or a history of urothelial cancer, who had undergone cystoscopy within 6 months of the CT urogram, were included in the study. Clinical reports of CT urograms containing a bladder lesion interpreted as suspicious for malignancy were classified as positive. All others were classified as negative. Cystoscopy reports were classified as positive if a lesion underwent biopsy or was resected or negative if no lesion was detected. Performance characteristics for both CT urography and cystoscopy were determined by using pathologic findings or clinical follow-up as the reference standard. Ninety-five percent confidence intervals were estimated for each test characteristic.

RESULTS

The overall sensitivity, specificity, accuracy, positive predictive value, and negative predictive value (NPV) for bladder cancer detection were 79% (117 of 149), 94% (649 of 689), 91% (766 of 838), 75% (117 of 157), and 95% (649 of 681) for CT urography and 95% (142 of 149), 92% (634 of 689), 93% (776 of 838), 72% (142 of 197), and 99% (634 of 641) for cystoscopy. The NPV of CT urography was higher in patients evaluated for hematuria alone (98%, 589 of 603). However, the accuracy of CT urography was considerably lower in patients with a prior urothelial malignancy (78%, 123 of 158).

CONCLUSION

CT urography is an accurate noninvasive test for detecting bladder cancer in patients at risk for the disease. The high NPV of CT urography in patients with hematuria may obviate cystoscopy in selected patients.

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.

Vascular renal anatomy and the ureteropelvic junction: preoperative multidetector CT scanning with split-bolus injection as a predictor of laparoscopic findings

PURPOSE

To compare multidetector CT scan (MDCT) results with intraoperative findings in the detection of an inferior-pole pedicle crossing the ureteropelvic junction.

PATIENTS AND METHODS

Over the 2-year study period, 35 patients receiving laparoscopic pyeloplasty underwent preoperative investigation with a novel MDCT protocol in order to detect crossing vessels. Postprocessing, including maximum intensity projection, volume-rendering technique, and multiplanar reconstruction, was used in addition to standard axial views.

RESULTS

All the arteries found during laparoscopic surgery were detected by MDCT, but one radiologic false-positive was noted at the beginning of the series. Seven veins were not detected with MDCT. In the only case featuring an isolated inferior-pole vein, the aberrant vessel was identified by MDCT.

CONCLUSION

Multidetector CT scanning is a highly accurate way of providing all the information necessary preoperatively concerning renal parenchymal anomalies, urinary stones, and collecting system and vessel anatomy. It helps physicians make appropriate therapeutic decisions and gives surgeons information about what they can expect during laparoscopic procedures.

Imaging of hematuria

Hematuria may have a number of causes, of which the more common are urinary tract calculi, urinary tract infection, urinary tract neoplasms (including renal cell carcinoma and urothelial tumors), trauma to the urinary tract, and renal parenchymal disease. This article discusses the current status of imaging of patients suspected of having urologic causes of hematuria. The role of all modalities, including plain radiography, intravenous urography or excretory urography, retrograde pyelography, ultrasonography, and multidetector computed tomography (MDCT) in evaluation of these patients is discussed. The article highlights the current status of MDCT urography in imaging of patients with hematuria, and discusses various-often controversial-issues, such as optimal protocol design, accuracy of the technique in imaging of the urothelium, and the significant issue of radiation dose associated with MDCT urography.