Title

Xanthogranulomatous pyelonephritis: Not Your Average Kidney Infection

Authors

Virginia L. Hoch, Nicholas Jennelly, Ajeetpal Hans. Christiana Care, Newark, DE.

Introduction

Xanthogranulomatous pyelonephritis (XGP) is a rare condition characterized by granulomatous inflammation and diffuse renal parenchymal destruction due to chronic pyelonephritis. It is associated with significant morbidity and mortality, typically requiring surgical nephrectomy for definitive management. We present a case of severe XGP in which the patient received standard of care but suffered severe complications.

Case Presentation

A 67-year-old woman with diabetes and a history of nephrolithiasis (status-post lithotripsy one year ago) presented to the emergency department with two weeks of right flank pain and more recent onset of night sweats and weakness in the setting of a recent urinary tract infection. She was found to be tachycardic, tachypneic, and hypoxic, with labs revealing leukocytosis greater than 22,000, anemia with hemoglobin of 7 (decreased from a baseline of 10), mild hyponatremia to 132, and mildly increased creatinine to 1.36 (from a baseline of 1.1). CT kidney protocol showed right-sided XGP with suspected superimposed perinephric abscess. She was started on IV ceftriaxone and admitted for further management. She was evaluated by urology, interventional radiology, and infectious disease specialists, and initially underwent percutaneous nephrostomy with aspiration growing group B streptococcus (GBS). Repeat CT abdomen several days later showed ongoing evidence of perinephric abscess, so she underwent CT guided drainage of the abscess which grew Proteus mirabilis in addition to GBS. She was discharged to subacute rehab after a two-week admission and returned two months later for total nephrectomy after completing a six-week course of antibiotics. Unfortunately, the procedure was complicated by significant blood loss and hypotension. She went into cardiac arrest and was unable to be resuscitated despite cardiopulmonary resuscitation and multiple blood product transfusions.

Discussion

XGP should be suspected in patients presenting with flank pain, fevers, elevated inflammatory markers, and imaging findings showing destruction of renal parenchyma. CT typically shows a heterogenous renal mass with dilation of the renal calyces, known as the “bear paw sign.” Management varies based on severity, but all patients should be initiated on IV antibiotics on initial presentation. Because more than half of patients present with an obstructed upper urinary tract, decompression with nephrostomy is often also required.[1] After at least four weeks of antibiotics, most patients will then undergo total nephrectomy in order to remove all granulomatous tissue and avoid fistula formation into other tissues. For a small number of patients (<2%),[1] a partial nephrectomy may be pursued instead if the disease is focal with minimal parenchymal destruction. Estimates of perioperative mortality vary but have been cited as high as 10-40% for patients undergoing total nephrectomy,[2,3] with certain factors portending a worse prognosis including extension into the renal pelvis or the peri-renal fascia as well as abscess formation.[4,5] It is important to be aware of these prognostic factors when managing patients with severe XGP.

References

1) Harley F, Wei G, O'Callaghan M, Wong LM, Hennessey D, Kinnear N. Xanthogranulomatous pyelonephritis: a systematic review of treatment and mortality in more than 1000 cases. BJU international. 2023 Apr;131(4):395-407. 2) Gibbons R, Leonard N, Magee M, Zanaboni A, Patterson J, Costantino T. Xanthogranulomatous pyelonephritis: a complicated febrile urinary tract infection detected by point-of-care ultrasound in the emergency department. J Emerg Med 2018; 55: e1–4 3) Leoni FA, Kinleiner P, Revol M, Zaya A, Odicio A. Píelonefritis xantogranulomatosa: revisión de 10 casos [Xanthogranulomatous pyelonephritis: review of 10 cases]. Arch Esp Urol. 2009;62(4):259-271. doi: 10.4321/s0004-06142009000400001 4) León Mar R, Montoya Martínez G, Serrano Brambila EA, Moreno Palacios J, Pardo Belausteguigoitia P. Evaluación de factores pronósticos de morbi-mortalidad de los pacientes tratados por pielonefritis xantogranulomatosa. Boletín del Colegio Mexicano de Urología. 2013;28(2):49-53 5) Montelongo-Rodríguez FA, Pallares-Mendez R, Robles-Torres JI, et al.. Perioperative predictors for complications in patients with xanthogranulomatous pyelonephritis treated with nephrectomy [published online ahead of print, 2022 Jun 28]. Urologia. 2022;3915603221107135. doi: 10.1177/03915603221107135