Purpose or Case Report: Calyceal diverticula (CD) are rare lesions which are difficult to differentiate from renal cysts. Cross sectional examination with excretory imaging facilitates diagnosis in a noninvasive fashion. Functional MR urography (fMRU) provides comprehensive morphological, functional and excretory assessment of the kidney with CD. We aim to describe the findings of CD in fMRU.
Methods & Materials: The fMRU records over a 5-year period were reviewed for patients with CD. The following characteristics of the CD were determined: location, diameter, contour, signal characteristics and timing and pattern of contrast filling. Of the involved kidney the calyceal transit time (CTT), volumetric (vDRF) and Patlak (pDRF) differential renal functions were evaluated. The functional parameters were compared to the contralateral side. Renal ultrasound (US) was utilized to determine the presence of calcifications in the CD or its wall.
Results: A total of 16 patients, 9 males and 7 females (mean age 9y 4m [1y7m-17y8m]) were identified to have 19 CD. 1 patient had 2 CD, 1 patient had 3 CD. Diagnosis was confirmed surgically in 10 patients by retrograde pyelogram. 13 CD were located in the upper pole (7=right, 6=left), 5 were located in the interpolar area, 1 in the lower pole. The average diameter was 3.0 cm (0.8-6.4 cm). 16 were simple, 2 contained a single septa and 1 was a complex lesion. The contour of the CD was smooth in 12, lobulated in 5 and irregular in 2. No calcifications were seen on accompanying US. 15 CD (78.9%) demonstrated filling with contrast (7 complete, 4 partial, 4 minimal). 4 (20.1%) CD never filled. The average time from the injection of contrast to the beginning of opacification was 44.4 min (4.6 min-150.5 min). The 6 CD with complete filling demonstrated very early opacification (average 4.3 min), but one was delayed (150.5 min). The 4 CD that had minimal filling showed it late (mean 96.7 min). 4 CD that never were imaged on average for only 22.8 min (17.1 min-27.0 min) without any delayed images. There were no significant differences in CTT, vDRF and pDRF in affected versus contralateral kidneys.
Conclusions: fMRU is a potent tool for evaluation of CD, differentiating a calyceal diverticulum from a simple cyst. A third of the CD are contrasted within a few minutes. In the absence of early contrast filling of the CD delayed post-contrast images are necessary. Majority of CD are located in the upper poles. The presence of CD does not affect renal functional parameters as calculated from the fMRU.