RARE-MR-urography (Rapid Acquisition with Relaxation Enhancement) is a fast MR imaging technique (6.4 s/acquisition) that selectively depicts fluid by heavy T2-weighting. From 9/1989 to 11/1990, RARE-MR urograms were prospectively evaluated in the diagnosis of upper urinary tract abnormalities in 55 children. The method is performed in several planes and combined with a coronal, T1-weighted spin-echo sequence. Forty out of 42 kidneys with dilated renal pelvis, and 21 out of 24 dilated ureters were identified, only the mildly dilated ones were missed. Even in non-functioning kidneys the urinary tract was clearly depicted by RARE-MR-urography. However, no differentiation could be made with this technique between vesicoureteral reflux and non-refluxing dilatation of ureter and/or renal pelvis. All 19 pelviureteric obstructions and all eight renal duplications with a dilated segment were identified. RARE-MR-urography is a new tool for diagnosing urinary tract abnormalities in children without having to employ ionizing radiation, contrast media, or general anesthesia. A dilated urinary tract can be shown in one image displaying the entire urinary system, similar to excretory urography. The technique is presently not able to provide the information of voiding cystourethrography or renal scintigraphy, nor is it as easy to perform as ultrasound. However, in certain cases it may replace excretory urography.

From September 1989 to November 1990, 55 consecutive children (35 boys, 20 girls) with suspected morphologic pathology of kidneys and urinary tract were prospectively examined by magnetic resonance imaging (MRI). No other patient selection criteria were applied. In 25 of the cases suspicion had been aroused by an abnormal finding on an ultrasound screening examination. Twenty-two patients were examined due to a pathologic finding on ultrasound (US), which had been performed because of urinary tract infection, and/or due to other reasons like multiple malformations with expected kidney involvement (8 cases). Four children were evaluated twice — yielding a total of 59 examinations. These four repeated examinations were scheduled for control of therapy and are not included in this presentation. The patients were between 2 days and 13.2 years old, half of them were under 6 months old.