CASE 9344 Published on 06.07.2011

Xanthogranulomatous pyelonephritis and a perinephric abscess presenting with large paraspinal fluid collection

Section

Uroradiology & genital male imaging

Case Type

Clinical Cases

Authors

Speers CJB, Thompson TJ, Nambirajan T

Patient

82 years, female

Categories
Area of Interest Urinary Tract / Bladder ; Imaging Technique CT
Clinical History
An 82-year-old female patient presented with 2 week history of lethargy, vomiting, suspected fall and a tense firm swelling on her left flank. Bloods showed an inflammatory picture with deranged renal function. Ultrasound showed a large para-spinal collection not typical of traumatic haematoma, suggesting that it originated within the abdomen.
Imaging Findings
The abdominopelvic CT examination showed renal appearances in keeping with bilateral duplex collecting systems, with bilateral staghorn calculi related to both lower renal moieties.

The fluid collection in left flank originated from the upper moiety of the left kidney, with perinephric inflammatory changes extending to form an abscess pointing superficially in the left flank (Fig. 1 & 2).

The right upper renal moiety appeared atrophic, and was associated with a large mixed attenuation mass, at its largest 15 cm in diameter. The images demonstrated that this extensive right sided peri-renal expanse of fatty tissue had caused destruction of renal parenchyma with multiple low-density rounded areas, extension to the psoas muscle inferomedially, and squashing of the inferior vena cava (Fig. 2, 3, 4 & 5). The second staghorn calculus was seen in the right lower renal moiety (Fig. 5).
Discussion
Chronic xanthogranulomatous pyelonephritis is a rare and severe form of chronic renal infection associated with obstructive uropathy, commonly secondary to nephrolithiasis, with staghorn calculi being present in 34 - 48% of cases [1, 2]. The condition is almost exclusively unilateral and is characterised renal parenchymal destruction by lipid-laden macrophages, with definitive diagnosis made by histopathological assessment [1].

Clinical features vary from patient to patient but often include fevers, rigors, loin tenderness, loin mass and weight loss [1, 3, 4]. Our patient presented with vague and non-specific symptoms common in cases of XGP, with the flank swelling initially thought to be a haematoma related to a fall some weeks before.

The common CT characteristics of XGP from the literature include; an enlarged kidney maintaining a reniform shape, the presence of a calculus within renal pelvis/calcies, multiple low-density fluid filled areas representing abscess and necrotic areas, contrast enhancing rims, the bear paw’ sign and spread of the disease beyond the kidney (often to psoas muscle, peri- and pararenal spaces, with further cases documenting spread to lung and spleen) [1, 2, 4].

It was felt that in view of our patient’s other co-morbidities, further investigation for definitive diagnosis by biopsy was not warranted. However, the CT scan showed many of the features of XGP, namely the presence of a calculus within renal calyces with multiple low-density areas spreading extensively through the abdomen to the psoas muscle and compressing the inferior vena cava.

Optimal treatment of XGP involves appropriate antibiotic therapy with surgical intervention in the form of either percutaneous drainage or open drainage, with partial or total nephrectomy [3].

Of course this case XGP was an incidental finding on CT study aimed at identifying the source of our patient’s flank fluid collection. This case illustrates an obstructive uropathy with bilateral staghorn calculi manifesting in two clinical conditions; on the left side with formation of a large peri-renal abscess, and on the right with advanced and extensive chronic XGP.
Differential Diagnosis List
Bilateral duplex collecting systems with staghorn calculi, perinephric abscess and xanthogranulomatous pyelonephritis
Renal cell carcinoma
Haematoma
Tuberculosis
Final Diagnosis
Bilateral duplex collecting systems with staghorn calculi, perinephric abscess and xanthogranulomatous pyelonephritis
Case information
URL: https://www.eurorad.org/case/9344
DOI: 10.1594/EURORAD/CASE.9344
ISSN: 1563-4086