Intravenous Contrast-Enhanced Dynamic Mr Urography: Diagnosis of Vesicoureteral Reflux During Bladder Filling With Time-Signal Intensity Curves

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Abstract

Purpose:

To evaluate the time-signal intensity (SI) curves generated from intravenous (IV) gadodiamide-enhanced dynamic magnetic resonance (MR) urographic scans for identifying vesicoureteral reflux (VUR) during bladder filling.

Materials and Methods:

MR urographic studies of children were retrospectively reviewed, and 52 ureterorenal units of 26 patients (15 females and 11 males, mean age = 5.5 years) who had also undergone voiding cystourethrographic (VCUG) examination were included in this study. The patients were examined on a 1.5T scanner. For functional MR urography and to generate time-SI curves, we used a post IV contrast-enhanced two-dimensional (2D) fast field echo (FFE) sequence (TR = 17 msec, TE = 3.2 msec, flip angle (FA) = 90°) in the coronal plane. MR urographic time-SI curves that demonstrated a prompt and concave fall of the initial third phase followed by intermittent or constantly increasing SI peaks above the baseline from which the second phase starts were considered to have VUR. We compared the differences in time-SI curves between the control group and patients with VUR during bladder filling.

Results:

Twelve ureterorenal units of eight patients (four bilateral and four unilateral) had VUR during bladder filling on VCUG. The time-SI curves of these patients showed intermittent (N = 8 ureterorenal units), and constantly increasing (N = 4 ureterorenal units) SI peaks consistent with VUR. One patient also had bilateral abnormal time-SI curves suggesting VUR despite the normal VCUG study. In the control group, 25 units had normal triphase time-SI curves, six renal units had urinary dilatation with good washout after diuretic injection, and four renal units had upper urinary dilatation without contrast washout, while five renal units did not show any function. None of the patients in the control group revealed distortion in the time-SI curve. The differences in time-SI curves patterns between the control group and patients with VUR during bladder filling were statistically significant (P < 0.001).

Conclusion:

After a prompt and concave decrease of the initial third phase of the time-SI curve, intermittent spikes or a constant rise in SI above the baseline suggest the existence of VUR.

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