A renal necrotic mass in the context of massive dvt

A 68 year old female with a long term history of renal impairment presented to the Emergency Department complaining of left lower limb pain. On physical exam said leg appears to be swollen and cold and pedial pulse seems absent. In order to rule out arterial ischemia CT angiography of the lower extremities was performed demonstrating normal contrast opacification of lower limbs arteries. However, signs that suggested bilateral DVT were observed. On Doppler Ultrasound bilateral DVT with extension to IVC was found and a right renal mass that deformed renal outline was observed incidentally. Thus, an abdominopelvic CT was performed demonstrating the existence of a necrotic mass/collection that caused destructuring of the renal parenchyma with renal hilium adenopathic conglomerate, infiltrative extension to the psoas muscle and associated staghorn calculus. Initially, tumoral etiology and Xantogranulomatous Pyelonephritis conformed the main differential diagnosis. Percutaneous renal puncture was performed and anathomopathological results showed the existence of the characteristic “foamy” macrophages. XP diagnosis was reached and surgical nephrectomy was performed.

XP is the result of a chronic destructive granulomatous process following a subacute / chronic pyelonephritis that results in an atypical immune response in which the renal parenchyma is ultimately replaced with lipid-laden (foamy) macrophages. Clinical presentation is vague and inespecific usually consisting on malaise, weight loss or low grade fever. Therefore, imaging features are crucial for XP diagnosis. Contrast enhanced CT is the diagnositic imaging technique of choice for two main reasons: Firstly, the majority of cases demonstrate a highly specific set of findings that allow a confident diagnosis, Secondly, surgical planning depends on the accurate assessment of the extrarenal extent of disease, if any, since surgical nephrectomy is usually curative generally permitting the avoidance of the otherwise likely abdominal sepsis. Findings on CT include normal renal outline loss, dilated calyces with a paradoxical contracted renal pelvis (bear’s paw sign) and, sometimes, perinephric extension or parenchymal fat deposits. Large staghorn calculus is present in 90% of patients. However, this finding by itself is nonspecific and should be associated with extensive inflammatory process for XP diagnosis.

In conclusion, although the definitive diagnose is ultimately histologic, the combination of a nonfunctioning enlarged kidney, a central calculus within a contracted renal pelvis, expansion of the calices, and inflammatory changes in the perinephric fat is strongly suggestive of XP. In our reported case the search for causal factor of a massive DVT permitted a correct diagnostic approach from early on and a prompt surgical treatment of the XP.

- Craig WD, Wagner BJ, Travis MD. Pyelonephritis: radiologic-pathologic review. Radiographics 2008, 28: 255-77 - Leoni AF,Kinleiner P, Pielonefritis Xantogranulomatosa: Revisión de 10 casos Arch. Esp. Urol. 2009, 62: 259-271