PMC6159247_01
(a-c) Plain CT images axial and coronal reformats (a) showing disproportionately dilated upper pole calyces with perinephric fat stranding; (b,c) showing papillary calcifications in the lower pole.
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Significant perinephric and periureteric fat stranding with locoregional lymphadenopathy was noted (Figure 1).
(a-d) Coronal reformats of CT urogram images showing (a,b) papillary cavities with distorted calyces in the upper and lower poles without opacification by contrast. Infundibular stenosis with a dilated triangular-shaped calyx is seen suggesting a papillary cavity with excreting calyces or a papillary cavity showing communication with the calyceal system. (c) Also seen is the narrowed lumen of the renal pelvis with wall thickening suggesting a renal pelvic stricture. A necrotic hilar lymph node is also seen in these images. (d) Coronal reformat showing irregularly thickened enhancing walls of the ureter. (e) - -, The terminal ureter and the vesicoureteral junction shows wall thickening.
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Also, the ureter showed thickened and enhancing walls (Figure 2).
(a-c) Axial and coronal CT sections showing different signs of papillary necrosis: (a) blunt-tipped calyces in the right lower pole; (b) a ring sign, where a ring-like contrast opacification is noted around centrally non-opacified sloughed off papilla within the interpolar calyx. (c) Clefting in the middle interpolar calyx. In this coronal section pooling of contrast in dilated upper pole calyces is seen.
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Other signs of papillary necrosis such as blunt-tipped calyces and a ring sign:where contrast is seen surrounding a centrally non-opacified calyx:are seen (Figure 3).
(a-c) showing coronal slices of a 3D magnetic resonance cholangiopancreatography sequence and (d) showing the maximum intensity projection of the 3D magnetic resonance cholangiopancreatography sequence of the left kidney. Seen in (a) is the infundibular stenosis with the triangular papillary cavity corresponding to the CT urogram in Figure 2a. (b) shows a ring sign corresponding to the CT urogram image in Figure 3b with distorted and irregular lower pole calyces. (c) shows a cleft in the interpolar calyx. Also seen in this image is the renal hilar lymph node. (d) shows the renal pelvic and interpolar infundibular stricture with disproportionately dilated upper and lower pole calyces, with irregular contour of the lower pole calyces. 
 (e) shows T2 hyperintensity of the renal parenchyma.
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MR urogram showed the filling defects within the calyces including the signs of papillary necrosis found on the CT urogram such as calyceal filling defects, blunt-tipped calyces, the ring sign and clefts (Figure 4).
(a,b) Thick slab magnetic resonance cholangiopancreatography and maximum intensity projection of thin slab (3 mm) 3D magnetic resonance cholangiopancreatography sequence show irregular dilation of the- - lower ureter, with abrupt narrowing at its insertion into the vesicoureteral junction.
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The distal ureteric stricture was seen better on MRI (Figure 5).