Uroradiology & genital male imaging
Case TypeClinical Cases
Authors
Michela Antonucci1, Lidia Rabiolo2, Giorgia Moro2, Emma Lot2, Claudio Leto2, Andrea Bruscagnin2, Giuseppe Brancatelli1
Patient63 years, male
A 63-year-old man, with no relevant medical history and in good clinical condition, presented to a urologist with right-side flank pain and tenderness; laboratory investigation did not reveal elevated creatinine values or inflammation markers.
The patient underwent a non-contrast Computed Tomography (CT) due to suspected urolithiasis. CT showed an extensive right-side peri-renal expanse (Fig. 1, red arrow) with a heterogeneous pattern characterized by large mixed attenuation, predominantly fat content, with a central dystrophic calcification (Fig 1, yellow arrow) and dense “radial” streaks. There was no infiltration of the psoas and flank muscle, but a thickening of perirenal fascias. The right kidney was dislocated upper and appeared enlarge with mild ectasia of the upper calyces collecting system.
Later, the patient underwent a Contrast Magnetic Resonance Imaging (MRI) due to malignancy suspicion. MRI showed similar findings as on CT (Fig. 2 and 3), with dystrophic calcification inside the ureteral lumen (“staghorn” lithiasis), responsible for mild prominence of the ureteral calibre upstream. It was detected thickening and enhancement of the right ureter wall, and bright enhancement of perirenal fascia, reflecting true perirenal inflammatory extension
Xanthogranulomatous pyelonephritis (XPN) is an unusual variant of chronic pyelonephritis. Most cases occur in the setting of obstruction due to infected renal stones [1-5].
Affected patients usually have massive destruction of the kidney due to granulomatous tissue containing lipid-laden macrophages; the appearance may be confused with renal malignancy.
XPN is seen essentially in all age groups, but most frequently presents in middle-aged to elderly patients [6,7].
There is a 2:1 female predilection, presumably relating to an increased incidence of urinary tract infections and thus struvite (staghorn) calculi.
The diagnosis of XPN is confirmed by radiologic testing and pathology. The CT scan has several advantages [8]:
- It shows the characteristic replacement of the renal tissue by several rounded, low-density (15 to 18
Hounsfield units) areas that are surrounded by an enhanced rim of contrast medium.
- It can determine the extent of the lesion and any extension into the perirenal area.
- The extent of the lesion can be classified into three stages:
• Stage 1 – Localized disease confined to renal parenchyma.
• Stage 2 – Extent of inflammation involves the perinephric fat.
• Stage 3 – Extent of inflammation involves the perinephric spaces and/or abdominal wall. In the most advanced forms, the mass of xanthogranulomatous tissue can involve the adjacent gastrointestinal tract, and fistulas may be created into the colon or duodenum [1].
- Renal stones which, as noted above are a frequent cause of XPN, are visible on CT scan films.
XPN is due to inflammation which may occur as a result of a defect in the macrophage processing of bacteria. The factors responsible for the accumulation of lipids and cholesterol in the lesion are not well understood.
XPN is usually unilateral and is associated with the virtually destruction of the kidney. Treatment is therefore surgical (after an initial course of antimicrobials to control the local infection) and consists of en-bloc nephrectomy, in which all the involved tissue is removed and any fistulas closed. Patients with a localized form (usually children) or with bilateral disease can be treated with partial nephrectomy [9].
The laparoscopic nephrectomy is a potential approach, depending on the extent of the lesions and the urologist's expertise [10].
Teaching Points
XPN is an unusual variant of chronic pyelonephritis in which there is massive destruction of the kidney by granulomatous tissue containing lipid-laden macrophages. It is thought to be due to aberrant inflammation as a result of a macrophage defect in microbial processing.
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URL: | https://www.eurorad.org/case/17779 |
DOI: | 10.35100/eurorad/case.17779 |
ISSN: | 1563-4086 |
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