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Functional and Morphologic Evaluation of Congenital Urinary Tract Dilatation by Using Combined Static-Dynamic MR Urography: Findings in Kidneys with a Single Collecting System¹

¹ From the Dept of Pediatric Radiology, Radiological Clinic, Univ of Heidelberg, Im Neuenheimer Feld 153, D-69120 Heidelberg, Germany (W.K.R., R.W., K.D., J.T.); Dept of Nuclear Medicine, Radiological Univ Clinic Heidelberg, Germany (S.H.); Div of Pediatric Urology, Dept of Urology, Univ Hospital Heidelberg, Germany (M.W.); Div of Pediatric Nephrology, Univ Children’s Hospital Heidelberg, Germany (B.T.); and Dept of Nuclear Medicine, German Cancer Research Center Heidelberg, Germany (J.H.C.). From the 2000 RSNA scientific assembly. Received Jul 16, 2001; revision requested Sept 10; final revision received Mar 7, 2002; accepted Mar 25. Address correspondence to W.K.R. (e-mail: wiltrud_rohrschneider@med.uni-heidelberg.de).

View larger version (78K): [in a new window]   Figure 1. 3D volume maximum intensity projection images, reformatted from the static T2-weighted 3D inversion-recovery fast spin-echo (3,500/600/250 [inversion time msec], 90° flip angle) images obtained in a 1-year-old girl with right-sided hydroureteronephrosis due to ureterovesical junction stenosis, are displayed in three projections (left oblique, posteroanterior, and right oblique), rotated around the longitudinal axis. Bilateral orthotopic ureteral insertions are demonstrated with the oblique projections. Note depiction of the entire normal left side of the urinary tract. The medullary pyramids are also shown (arrowheads) because of their high water content.

View larger version (108K): [in a new window]   Figure 2. Images obtained in an 8-month-old female infant. A, US image might suggest the presence of a duplex kidney with dilated upper collecting system. A dilated ureter is not depicted, however, and morphology remains unclear. B, MR urographic image shows fluid collection without evidence of calyces within the upper pole tissue, seen as an area of high signal intensity (arrows) in the maximum intensity projection image from the static T2-weighted 3D inversion-recovery fast spin-echo (3,500/600/250, 90° flip angle) sequence. C, Fluid collection is also seen without contrast material enhancement on a dynamic coronal T1-weighted fast field-echo (17/4.2, 90° flip angle) image. The lower portion of the fluid is surrounded by normal parenchyma belonging to the well-depicted normal collecting system. Neither any separate upper pole parenchyma nor a second ureter is demonstrated. These MR urographic findings disprove duplication but suggest a cyst. L = left.

View larger version (132K): [in a new window]   Figure 3. Left-sided hydroureteronephrosis in a 5-year-old girl. Nine MR images selected from the dynamic T1-weighted fast field-echo (17/4.2, 90° flip angle) sequence demonstrate the characteristic phases. On the normal right side, a peripheral cortical rim with high signal intensity (arrowheads in top middle image) is seen initially (glomerular arrival of the contrast material bolus). Note the subsequent homogenous signal intensity increase and decrease in the tissue, enhancement of the collecting system and ureter, and final washout. Conversely, the tissue on the left side is narrow and shows faint enhancement. Contrast material transport is delayed into the dilated collecting system and ureter, but furosemide application (two images on bottom right) leads to timely washout.

View larger version (112K): [in a new window]   Figure 4. Time-intensity curves generated from the dynamic T1-weighted fast field-echo (17/4.2, 90° flip angle) sequence used to obtain the images in Figure 3. A, Parenchymal renograms show three typical segments (steep increase, reflecting perfusion; slower increase to a peak maximum, reflecting kidney function; and prompt decline, reflecting contrast material elimination). To improve differentiation of the first and second curve segments, the horizontal axis is spread to 600 msec. The right-to-left-ratio of the product of the area under the second curve segment (in square millimeters) and the tissue area (in pixels) represents the relative distribution of renal function. B, Renograms obtained from ROIs placed over the whole kidney. Urinary excretion is assessed from the decline of the third curve segment. On the normal right side, this decreases quickly and concavely to baseline, from which the second segment starts (P level), indicating good washout. On the left side, the decline is delayed. After furosemide (F) administration, excretion is prompt and complete, while the third segment is concave, indicating that there is no relevant obstruction.

View larger version (28K): [in a new window]   Figure 5. Plot shows correlation of single-kidney function of the abnormal kidney in 62 corresponding dynamic MR urographic and DRS examinations (symbols vary according to the number of kidneys with identical values).

View larger version (130K): [in a new window]   Figure 6. Right-sided hydronephrosis due to ureteropelvic junction stenosis in a 12-month-old boy. A, Dynamic T1-weighted fast field-echo (17/4.2, 90° flip angle) MR urographic images depict an area of irregular tissue narrowing and reduced enhancement at the right upper pole, indicative of scarring (arrows), and reduction of single-kidney function. B, DRS images confirm the zone of functional compromise at the right upper pole (arrows), as well as the distribution of single-kidney function. The morphology is poorly visualized when compared with the MR urographic images.

View larger version (54K): [in a new window]   Figure 7. Right-sided hydroureteronephrosis due to ureterovesical junction stenosis in a 6-month-old female infant. A, 3D volume image processed from the static T2-weighted 3D inversion-recovery fast spin-echo (3,500/600/250, 90° flip angle) MR sequence, which also depicts a cyst in the normal left kidney (arrow). B, Renograms generated from the dynamic T1-weighted fast field-echo (17/4.2, 90° flip angle) MR urographic images with ROIs placed over the whole kidney demonstrate accumulation curves for the right kidney with MR urography and scintigraphy, the latter showing minimal convex curve decrease after furosemide application. This was judged as relevant obstruction with both modalities. The left kidney has prompt and complete washout.