Xanthogranulomatous pyelonephritis with perinephric abscess

Case contributed by A.Prof Frank Gaillard

Presentation

Left loin pain and fever.

Patient Data

Age: 70 years
Gender: Female
CT

CT abdomen / pelvis

A thick walled collection measuring 11 x 8 x 11.7cm extends from the perinephric space through the pararenal space and into the abdominal wall. The left kidney is displaced anteriorly and measures 12.2cm. It contains a large staghorn calculus. The parenchyma is thinned with decreased enhancement. Extensive rounded radiolucencies are seen in the parenchyma. Fat stranding is seen throughout the retroperitoneum, however no free fluid collections identified. There is mild dilatation and inflammatory stranding of the left ureter, however, no obstructing lesion is identified. The bladder is hyperdense, thought to relate to previous CT study.

The right kidney measures 12.5cm and contains simple cysts. Splenomegaly measures 17 x 6.5 x 11cm. 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 artefact noted. No CT evidence of osteomyelitis/discitis.

Films obtained following perinephric abscess drainage (ultrasound guided - Proteus mirabilis). 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 faecal 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 nephrectomy.

Histology

MACROSCOPIC DESCRIPTION: A left nephrectomy specimen weighing 862g and measuring 135x82x80mm.  The external surface is pale tan and multinodular.  On cut section, numerous yellow-brown calculi, measuring up to 25mm 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 48mm 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 tumour 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. 

Gross pathology image courtesy of Dr Alpha.Tsui, Royal Melbourne Hospital.

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Case information

rID: 16883
Case created: 27th Feb 2012
Last edited: 18th Nov 2016
System: Urogenital
Tag: kidney
Inclusion in quiz mode: Included

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