Diagnosis of noncalcareous hydronephrosis: role of magnetic resonance urography and noncontrast computed tomography

doi:10.1016/j.urology.2003.09.086

Urology

Volume 63, Issue 2, February 2004, Pages 225-229

https://doi.org/10.1016/j.urology.2003.09.086 Get rights and content

Abstract

Objectives

To evaluate the role of magnetic resonance urography (MRU) and noncontrast computed tomography (NCCT) in the diagnosis of noncalcareous hydronephrosis when excretory urography (intravenous urography) is either contraindicated or inconclusive.

Methods

A total 108 consecutive patients with noncalcareous hydronephrosis were included in this study. In all patients, intravenous urography was either contraindicated or could not determine the diagnosis. In all patients, calculus obstruction was excluded by NCCT and all underwent heavily T₂-weighted MRU. The final definitive diagnosis was established by retrograde or antegrade ureterography, endoscopy, or open surgery and was considered the reference standard for the diagnosis of obstruction. Normal kidneys in patients with unilateral obstruction were considered the reference standard for the absence of obstruction. The results of MRU were compared with those of NCCT regarding sensitivity, specificity, and overall accuracy.

Results

Of the 108 patients, 5 had bilateral obstruction and the remaining 103 had unilateral obstruction. Of the latter group, 5 had a solitary kidney; therefore, the total number of renal units was 211 (113 obstructed and 98 normal units). Ureteral strictures were identified by NCCT in 15 (28%) of 54 and by MRU in 45 (83%) of 54 patients. Bladder, ureter, or prostate tumors causing ureteral obstruction could be diagnosed in one half of the 54 patients with such tumors by NCCT (27 of 54) and in all but 2 patients by MRU (52 of 54). Both NCCT and MRU could identify all extraurinary causes of obstruction. Overall, of the 113 kidneys with noncalculus obstruction, the cause could be identified by MRU in 102 (sensitivity of 90%) and by NCCT in 47 (sensitivity of 42%), a difference of statistically significant value in favor of MRU (P <0.001). The specificity of T₂-weighted MRU and NCCT was 100% and 99%, respectively (not a statistically significant difference). The overall accuracy of T₂-weighted MRU and NCCT was 95% and 68%, respectively (P <0.001).

Conclusions

In patients with ureteral obstruction in whom intravenous urography is not helpful and after NCCT has excluded stone disease, heavily T₂-weighted MRU is a sensitive and specific method in the identification of the cause of obstruction.

Section snippets

Material and methods

This was a prospective study conducted at our center between September 2000 and February 2003. Patients with obstructive uropathy diagnosed by history, clinical examination, combined abdominal radiography, and ultrasonography underwent routine laboratory investigations. Those with normal serum creatinine and no history of allergy to contrast materials underwent IVU. If IVU was either contraindicated or inconclusive, the patient underwent NCCT to search for stone disease. If NCCT failed to

Results

The study included 108 patients; 5 had bilateral obstruction and the remaining 103 had unilateral obstruction. Of the latter group, the contralateral kidney was absent in 5 and normal in 98. Therefore, the total number of renal units was 211 (113 obstructed and 98 normal). Ureteral obstruction was caused by ureteral strictures in 54 renal units, ureteral, bladder, or prostate tumors in 54, and extrinsic obstruction in 5 (Table II).

Ureteral strictures were identified by NCCT in 15 (28%) of 54

Comment

Traditional IVU remains the investigation of choice in revealing the detailed anatomy of the pelvicaliceal system. When IVU is contraindicated or if the kidney has poor function, gray scale ultrasonography is useful in the diagnosis of obstruction; however, its value is limited in the identification of the cause of obstruction. Recently, the introduction of NCCT has provided a rapid, safe, and noninvasive approach to the diagnosis of calcareous obstruction.1, 2 Nevertheless, its value in the

Conclusions

T₂-weighted MRU is effective in the evaluation of the dilated urinary tract and is useful in the identification of noncalcareous causes of obstruction. MRU is indicated when IVU is not helpful and NCCT excludes a calcareous cause of obstruction. In this situation, MRU can replace the more expensive and invasive retrograde or antegrade ureterography. If ureteral obstruction is caused by a tumor, MRU not only identifies the presence of the tumor but also provides information regarding its stage.

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However, in the past decade, computed tomography urography has rapidly replaced IVU and RU in the initial evaluation of the urothelial disease largely due to the ability of mutlidetector computed tomography (CT) to allow understanding of complex anatomic relationships and provide high spatial resolution, multiplanar, or three-dimensional images during a short single breath-hold [1,4,5]. Magnetic resonance (MR) urography combined with conventional MR sequences is extremely useful for investigating the causes of urinary tract dilatation and diagnosing urinary tract obstruction due to causes other than urolithiasis [6–10]. However, because of the excellent diagnostic performance of CT for many urinary tract pathologies, MR urography has been reserved for patients who cannot receive iodinated contrast or for whom exposure to radiation is undesirable [1].
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Many imaging modalities are used to evaluate the obstructive uropathy such as plain X-ray of the urinary tract combined with abdominal gray-scale ultrasonography and excretory urography, other methods of visualizing the ureteric obstruction e.g. retrograde or antegrade pyelography or ureteropyeloscopy, are invasive (1). In the last decades some recent noninvasive investigations have been introduced for the diagnosis of ureteral obstruction, e.g. the renal resistive index, (2) non-contrast MDCT (3–5) and magnetic resonance urography with their ability to image the urinary tract in ways that exceed the excretory urography (6). With the revolution of multidetector technology, multidetector CT urography has become the imaging modality of choice for many urologic problems (7).
To evaluate the usefulness of MDCT using a curved planar reformation technique for the noninvasive assessment of the causes and level of ureteral obstruction in patients with compromised renal function.
Between January 2012 and February 2013, 50 patients with clinical and sonographic manifestations of ureteral obstruction underwent non-contrast multidetector CT (MDCT) using a 16-slice machine. A total of 65 ureters were examined. Curved planar reformation images were performed to display the entire course of ureters in the same image. All patients had renal impairment with serum creatinine greater than 2.0 mg/dl. The gold standard for diagnosis of the cause of obstruction was ureteroscopy and/or open surgery. The sensitivity, specificity and overall accuracy of MDCT using curved planar reformation in the diagnosis of ureteral obstruction were calculated in comparison with the gold standard.
A total of 65 ureters were examined (35 unilateral, 15 bilateral). The most common cause of ureteric obstruction was ureteric stone representing 27/65 (41.5%), followed by ureteric stricture representing 23/65 (35.4%). The lower third was the most affected in our study, it was encountered in 38/65 ureters (58.46%). The total sensitivity, specificity and accuracy of CPR for the cause of the ureteric obstruction were 98.5%, 98.5% and 97.8%, respectively (P value >0.05). CPR also was more sensitive and accurate for the level of ureteral obstruction with a total sensitivity of 100% and accuracy of 100% (P value >0.001).
Curved planar reformation MDCT is a useful noninvasive technique which is accurate in diagnosing the cause and level of ureteral obstruction in patients with compromised renal functions and is helpful for planning the therapeutic management of such patients.
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Alternative methods of visualizing the upper urinary tract, such as retrograde or antegrade pyelography or ureteropyeloscopy, are invasive. In the last few years some recent noninvasive investigations have been introduced for the diagnosis of ureteral obstruction as the renal resistive index (3), non-contrast helical computerized tomography (NCCT) (4–9) and magnetic resonance urography (MRU) (10–12). Low-molecular-weight Gd-chelates, as Gd-DOTA are considered as glomerular tracers because freely filtered by the glomeruli without any tubular secretion or reabsorption (13).
To present the role of MR renography in diagnosis of upper urinary tract obstruction (UTO) with evaluation of diagnostic criteria for acute obstruction.
Thirty consecutive patients with obstructive anuria were included in our study. For identification of the cause of obstruction, all patients were subjected to plain abdominal X-ray (KUB), gray scale ultrasonography, non-contrast CT for the abdomen and pelvis (NCCT). There were five patients with bilateral obstruction and 25 with obstructed solitary functioning kidney, so the study included 35 units. All patients were subjected to radioisotope diuretic renography and magnetic resonance renography (MRR) before relief of obstruction and 3 days after drainage. Of the 30 patients included, 20 were men and 10 women.
Among our patients the mean serum creatinine at time of presentation was 7 ± 4.5 mg/dl (range 2.4–12) and GFR ranged from 33 to 48 ml/min (mean ± SD; 38 ± 4.2). All the renal units have hydronephrosis. The mean pre drainage SI values 133 ± 22 (range 120–180). The mean time to peak (TP) for each unit was 171.6 ± 78 s and at isotope renography it was 320 ± 66 s. There was good corticomedullary differentiation (CMD) in 31 units and the remaining 4 showed loss of CMD differentiation. The CMD crossing time was 163.6 ± 70.4 s. Post kidney drainage the parenchymal SI was increased in 30 units, in 3 units there was drop and no change in 2 (r = 0.29). There is relative reduction in the time to peak, it becomes 67 ± 79 s after drainage (r = 0.76).
MR renography is a clinically valuable technique that provides diagnostic criteria to diagnose the acute urinary obstruction and allows follow up of renal function.
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We retrospectively evaluated the accuracy of gadolinium enhanced magnetic resonance urography to detect upper urinary tract tumors.
A total of 91 magnetic resonance urography studies for suspected upper tract malignancy were done in 70 males and 18 females with a mean age of 71.7 years. Breath hold coronal T2-weighted single shot fast spin-echo and breath-hold coronal 3-dimensional T1-weighted spoiled gradient-recalled echo images with fat suppression were obtained during the nephrographic and excretory phases after intravenous injection of gadolinium based contrast material. Two radiologists independently reviewed magnetic resonance images for a tumor by 4 regions (right/left and renal collecting system/ureter). Sensitivity, specificity and accuracy were calculated.
A total of 35 urinary tract regions in 18 males and 7 females with a mean age of 70.4 years were confirmed to have an upper tract malignant tumor and 219 urinary tract regions were confirmed to be tumor-free. Sensitivity, specificity and accuracy to detect upper urinary tract malignancy were 74.3%, 96.8% and 93.7% for reviewer 1, and 62.9%, 96.3% and 91.7% for reviewer 2, respectively. When patients with a ureteral stent or nephrostomy tube were excluded from analysis, sensitivity, specificity and accuracy were 86.2%, 99.5% and 97.7% for reviewer 1, and 72.4%, 97.9% and 94.6% for reviewer 2, respectively.
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Adult urologyDiagnosis of noncalcareous hydronephrosis: role of magnetic resonance urography and noncontrast computed tomography

Abstract

Objectives

Methods

Results

Conclusions

Section snippets

Material and methods

Results

Comment

Conclusions

J Urol

J Urol

Magn Reson Imaging Clin North Am

Urology

Clin Radiol

Acute flank paincomparison of noncontrast enhanced CT and intravenous urography

Radiology

Magnetic resonance urography enhanced by gadolinium and diureticsa comparison with conventional urography in diagnosing the cause of ureteric obstruction

BJU Int

MR urography in evaluation of acute flank painT2-weighted sequences and gadolinium-enhanced three-dimensional FLASH compared with urography

AJR Am J Roentgenol

Adult urology
Diagnosis of noncalcareous hydronephrosis: role of magnetic resonance urography and noncontrast computed tomography

MR urography in evaluation of acute flank painT₂-weighted sequences and gadolinium-enhanced three-dimensional FLASH compared with urography