Presentation
Left loin pain and fever.
Patient Data
A thick walled collection measuring 11 x 8 x 11.7 cm extends from the perinephric space through the pararenal space and into the abdominal wall. The left kidney is displaced anteriorly and measures 12.2 cm. It contains a large staghorn calculus. The parenchyma is thinned with decreased enhancement and extensive rounded radiolucencies. Fat stranding throughout the retroperitoneum. There is mild dilatation and inflammatory stranding of the left ureter; however, no obstructing lesion is identified. Bladder content is hyperdense, thought to relate to previous CT study.
The right kidney measures 12.5 cm and contains simple cysts. Splenomegaly - the spleen measures 17 x 6.5 x 11 cm. No focal lesion. What appear to be loops of small bowel are seen in the pouch of Douglas.
The pancreatic duct is dilated (5 mm), however, no intra- or extra-hepatic biliary dilatation is seen. Pancreatic duct dilatation appears to extend to the ampulla without an obstructing lesion identified.
Gallbladder and adrenals are unremarkable. No free intraperitoneal gas or fluid. Lung bases are clear.
No aggressive bony lesions. Right hip prosthesis with associated artifact noted. No CT evidence of osteomyelitis/discitis.
Films obtained following perinephric abscess drainage. Large staghorn calculus with several noncontiguous large calculi filling dilated renal calyces in the left kidney. The left renal shadow is enlarged. Pigtail drainage catheter projects over the left inferior pole, compatible with abscess drainage catheter. No right-sided renal tract or ureteric calculi. Hyperdense fecal material in the left-sided colon and rectum compatible with mixed enteric contrast.
Once the acute infection had subsided, with drainage and antibiotics, the patient went on to have a nephrectomy.
The patient went on to have a left nephrectomy.
Histology
MACROSCOPIC DESCRIPTION:
A left nephrectomy specimen weighing 862 g and measuring 135 x 82 x 80 mm. The external surface is pale tan and multinodular. On cut section, numerous yellow-brown calculi, measuring up to 25 mm in maximum dimension, are identified within the dilated pelvicalyceal system. Other calyces contain green-yellow fibrinous material and pus. The overlying cortex is thinned and there is loss of cortico-medullary differentiation. At the posterior surface, there is an extrarenal collection of pus measuring up to 48 mm in maximum dimension. Hilar vascular and ureteric resection margins are obscured by fibrinous material but appear otherwise unremarkable. No perinephric lymph nodes are identified.
MICROSCOPIC DESCRIPTION:
Sections of the kidney show active chronic xanthogranulomatous inflammation. There are scattered areas of necrosis, being surrounded by palisaded histiocytes. Multinucleated giant cells are occasionally seen. There are many neutrophils, lymphocytes, plasma cells and foamy macrophages. The inflammation extends into the surrounding perinephric fat. Some of the glomeruli are sclerosed. There is dilatation and thyroidisation of the tubules, containing eosinophilic secretion and inflammatory cells. The interstitium is markedly inflamed, along with fibrosis. Some of the blood vessels show moderate to severe thickening. No tumor is identified. The vascular resection margins are unremarkable. The Gram stain shows no bacteria. The Grocott stain shows no fungi. The Ziehl-Neelsen stain shows no acid fast bacilli.
FINAL DIAGNOSIS:
Left kidney: nephrolithiasis with secondary active xanthogranulomatous pyelonephritis and hydronephrosis.
Case Discussion
This case demonstrates typical appearances of xanthogranulomatous pyelonephritis complicated by a large perinephric abscess. The abscess was drained before nephrectomy and yielded Proteus mirabilis.
Gross pathology image courtesy of Dr Alpha.Tsui, Royal Melbourne Hospital.
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