PMC9109271_01
A plain abdominal radiograph shows scattered right kidney stones. Note the small right kidney shadow (arrowhead) compared to the left side and the presence of a left kidney stone.
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Plain abdominal radiography demonstrated a small right kidney shadow with compacted stones (Figure 1).
Computed tomographic urography, non-contrast images. (a) Atrophic change and loss of reniform shape of the right kidney compared to the contralateral side. Scattered caliceal and pelvic stones and perinephric fat stranding are appreciated. (b) Parenchymal calcification (black arrow). (c) Focal fat deposit with an average density of -73.5 HU (measurement, white arrow).
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Pre-contrast images revealed an atrophic and deformed right kidney with multiple nephrolithiasis, parenchymal calcification, multifocal fat deposits throughout the renal parenchyma, and perirenal fat stranding (Figure 2).
Computed tomographic urography, serial contrast images. (a) and (b) Poor enhancement of the right renal parenchyma without corticomedullary differentiation on the corticomedullary phase (a) and nephrogenic phase (b) images. Note the close contact between the renal parenchyma and the D2 duodenum (long arrow) suggesting a fistula. (c) Delayed excretory phase image obtained at 60 min after contrast administration, prone position, demonstrates a dilated, pus-filled right ureter (short arrow). The ureteral wall is thickened and enhanced with surrounding fat stranding. These findings are consistent with chronic pyelonephritis and severely impaired renal function. (d) Sagittal reconstruction image reveals an intramuscular abscess formation with a cutaneous opening (black arrow).
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The right ureter was dilated (# 10 mm) with wall thickening and intraluminal hyper-attenuation compared to the contralateral normal counterpart (Figure 3).
Computed tomographic fistulography. (a) Direct communication between the right renal pelvis and the D2 duodenum is clearly visualized (long arrow). Note the presence of contrast media in the distal D3 duodenum (arrowhead). (b) Coronal reconstruction with maximum intensity project image delineates a connection (short arrow) between the intramuscular abscess (asterisk), the right ureter, and the right renal pelvis. (c) A follow-up abdominal radiograph confirms a complex pyeloduodenal and ureteromuscular fistula. The distal ureter and the bladder were not visible.
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A CT fistulography was consequently performed which demonstrated a complex fistula from the intramuscular collection, connecting with the distal ureter upward to the right pyelocalyceal system and communicating with the adjacent duodenum (Figure 4), corresponding to stage III according to Malek and Elder   classification.
Pathological examination of the resected kidney. (a) The inner zone of lesion: The inflammatory infiltrates is composed of neutrophils, lymphocytes, and necrosis. (b) The outer zone of lesion: Proliferation of fibrous tissues. (c) Renal tubular atrophy, tubular dilatation at various degrees. (d) and (e) Granulation tissue with the presence of foamy macrophages and calcification (arrowhead). (f) Highest magnification shows foamy macrophages (xanthoma cells) with clear cytoplasm, eccentric nuclei at the cell periphery (arrow).
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In addition, various degrees of renal tubular atrophy and tubular dilatation were also observed (Figure 5).
Immunohistochemistry examination showed positive for CD68 (a and b) and vimentin (c) while negative for SMA (d and e) and AE1/3 (f).
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At immunohistochemistry, the lesion was positive for CD68 and vimentin, and negative for smooth muscle actin (SMA), desmin, and epithelial markers (Figure 6).