Type:Scientific Electronic Presentation
Authors: Joao Sakuray Pais, Fernando Chahud, Carlos Augusto Molina, Mirelle Rocha, Heitor Ramos Ruellas, Silvio Tucci Jr, Valdair Francisco Muglia
Keywords:Calculi, Xanthogranulomatous pyelonephritis, Pyelonephritis, Radiology, Pathology

Described in 1916 by Schlagenhaufer, Xanthogranulomatous Pyelonephritis (XPG) is an uncommon type of chronic infectious pyelonephritis that evolves with a suppurative process and severe impairment of the renal function. 

There is progressive destruction of the renal parenchyma, replaced by a diffuse infiltrate of granulomatous tissue with macrophages containing lipids in their cytoplasm, called xanthomatous cells,  amid the purulent secretion. The exact pathogenesis is still unknown, but two hallmarks are urinary tract obstruction and renal infection.

XGP diagnosis is challenging, since clinical presentation, most commonly lumbar pain, fever and recurrent urinary tract infections, can be nonspecific as well as laboratory exams of blood and urine. In imaging exams, the perirenal fat tissue is equally compromised by the inflammatory infiltrate, associated with...

...read more

Material and methods

This was a retrospective, observational, single-centre, non-consecutive case series of XGP diagnosed and treated in a 15 years period (2005-2019). The study was conducted by the Urology (Surgery), Imaging, and Pathology Departments of a tertiary care universitary hospital. The study was approved by the Institutional Review Board.

Inclusion criteria were the diagnostic confirmation after revision of all specimens by a pathologist. Diagnostic criteria included xanthomatous macrophages, granulomatous reaction, necrosis, calcification, cavitation, fibrosis, and perinephric fat involvement. Of the 58 cases initially selected, 1 was excluded due to the absence of all criteria, with the diagnosis of Endodermal Sinus Tumor.

Clinical and laboratory data were obtained from the patient's file records. Data retrieved was clinical presentation, laboratory tests results, therapeutic...

...read more


The age of patients ranged from 6 to 83 years, with mean age of 44,3 ± 16,2. The distribution according to decades was  0 to 10 years: 1 (1,8%); 11 to 20 years: 3 (5,3%); 21 to 30 years: 8 (14%); 31 to 40 years: 7 (12,3%); 41 to 50 years: 18 (31,6%); 51 to 60 years: 12 (21,1%); 61 to 70 years (8,8%); 71 to 80 years: 2 (3,5%); 81 to 90 years: 1 (1,8%). 

Of 57 cases, 16 (28,1%) were male and 41 (71,9%) were female with male-to-female rate of 1:2,56. The mean time from the beginning of the symptoms to the first documented diagnostic suspicion of chronic pyelonephritis was 365,1 days, the median was 120, 25th percentile 30 and 75th percentile 365 days. The median hospitalization period was 11 days.

The right kidney was involved in 32 cases (56,1%), the left one in 23 (40,4%) and there was bilateral involvement in 2 (3,5%) cases. 

The main...

...read more

Figure 1. Gross photograph: (A) Enlarged kidney with suppurative secretion and loss of parenchymal architecture. (B) Enlarged kidney with presence of staghorn calculus occupying the renal pelvis and calyces.
Figure 2. Contrast-enhanced computerized tomographies showing impacted coralliform calculus in the renal pelvis, determining upstream pyelocaliceal dilatation and thinning of the parenchyma (hydronephrosis), compatible with xanthogranulomatous pyelonephritis.


XGP is a worrisome infectious affection of the kidney with important morbidity and non-specific clinical presentation or laboratory findings. The lack of knowledge about the disease’s mechanism and the delay in the diagnosis lead to long periods of symptomatology, which results in long periods of hospitalization and surgical and postoperative complications.

As previously described, our study confirmed the higher prevalence in, female patients (71,9%), fifth or sixth decades of life (52,7%), and unilaterality (98,2%). Moreover, in agreement with previous studies, clinical presentation was nonspecific, with abdominal pain (89,5%), fever (43,9%) and urinary tract infection (43,9%) as most common symptoms. Laboratory data (blood and urine tests) is also nonspecific. Cultures showed predominance of E.coli and P. mirabilis, as seen before.

As expected, and not yet well...

...read more