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Xanthogranulomatous Pyelonephritis Workup

  • Author: Samuel G Deem, DO; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
Updated: Nov 09, 2014

Approach Considerations

A complete blood count (CBC) with differential may reveal leukocytosis and anemia. Expect these conditions to gradually resolve after nephrectomy. The erythrocyte sedimentation rate (ESR) is frequently elevated.

Liver function findings are abnormal in up to 50% of patients with xanthogranulomatous pyelonephritis (XGP).

Serum chemistries are used to determine the presence of any baseline electrolyte abnormalities, although none is pathognomonic of XGP. Creatinine levels before nephrectomy may be abnormal, but removal of the nonfunctioning xanthogranulomatous kidney should not be expected to alter baseline renal function.[3]

Urine typically contains leukocytes and bacteria. Urinalysis often demonstrates proteinuria. The pH is often basic because Proteus mirabilis is a urease-producing organism. Urine cultures are important in determining the offending organism involved in the XGP process and in assisting in the appropriate selection of antibiotics.

Histologic findings

The pathognomonic microscopic feature of XGP (see the image below) is the lipid-laden foamy macrophage. These cells can be difficult to distinguish from clear cell carcinoma on frozen section.

Xanthogranulomatous pyelonephritis. Xanthogranulomatous pyelonephritis.

Imaging studies

Renal ultrasonography usually reveals an enlarged kidney with multiple hypoechoic masses; irregular, thinned parenchyma; and a dilated collecting system.

Mercaptotriglycine (MAG-3) or technetium-99m dimercaptosuccinic acid (99m Tc-DMSA) renal scanning may be used to evaluate or confirm differential renal function.

Magnetic resonance imaging (MRI) is being studied selectively, but reports have not shown MRI to provide any diagnostic benefit beyond that which is achievable with traditional computed tomography (CT) scanning. However, MRI is frequently used in patients with renal insufficiency in whom contrasted images are required, in order to avoid the nephrotoxic intravenous (IV) contrast used for CT imaging.


Computed Tomography

CT scanning is the most useful radiographic technique in evaluating xanthogranulomatous pyelonephritis (XGP), although XGP cannot be diagnosed solely on the basis of radiographic findings. A CT scan demonstrates a heterogenous, nonenhancing mass on a hydronephrotic, nonfunctioning kidney with a central stone. In higher-stage disease, the mass may appear to involve adjacent organs. CT scans may also reveal a large staghorn calculus within the collecting system. (See the images below.)[12]

Xanthogranulomatous pyelonephritis appearing as no Xanthogranulomatous pyelonephritis appearing as nonenhancing, low-attenuation areas of the dilated collecting system surrounded by enhancing, high-attenuation parenchyma (known as the "bear paw" sign).
Xanthogranulomatous pyelonephritis with obstructio Xanthogranulomatous pyelonephritis with obstruction and staghorn calculus.
Contributor Information and Disclosures

Samuel G Deem, DO Faculty, Department of Urology, Charleston Area Medical Center

Samuel G Deem, DO is a member of the following medical societies: American College of Surgeons, American Osteopathic Association, American Urological Association, Endourological Society, Society of Urologic Oncology, American Society of Clinical Oncology, American College of Osteopathic Surgeons

Disclosure: Nothing to disclose.


Joe D Mobley, III, MD, MPH Urologist, Kentucky Lake Urology Clinic

Joe D Mobley, III, MD, MPH is a member of the following medical societies: American College of Surgeons, American Medical Association, American Urological Association, Endourological Society, Tennessee Medical Association

Disclosure: Nothing to disclose.

Chief Editor

Bradley Fields Schwartz, DO, FACS Professor of Urology, Director, Center for Laparoscopy and Endourology, Department of Surgery, Southern Illinois University School of Medicine

Bradley Fields Schwartz, DO, FACS is a member of the following medical societies: American College of Surgeons, Society of Laparoendoscopic Surgeons, Society of University Urologists, Association of Military Osteopathic Physicians and Surgeons, American Urological Association, Endourological Society

Disclosure: Nothing to disclose.


Gamal Mostafa Ghoniem, MD, FACS Professor of Urology, Chief, Division of Female Urology, Pelvic Reconstructive Surgery, and Voiding Dysfunction, Department of Urology, University of California, Irvine, School of Medicine

Gamal Mostafa Ghoniem, MD, FACS is a member of the following medical societies: American College of Surgeons, American Urogynecologic Society, American Urological Association, International Continence Society, International Urogynaecology Association, and Society of Urodynamics and Female Urology

Disclosure: Astellas Honoraria Speaking and teaching; Coloplasty Consulting fee Board membership; Uroplasty Consulting fee Consulting

Scott Rutchik, MD Assistant Professor, Department of Surgery, Division of Urology, University of Connecticut School of Medicine

Scott Rutchik, MD is a member of the following medical societies: American Urological Association

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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Xanthogranulomatous pyelonephritis.
Xanthogranulomatous pyelonephritis with obstruction and staghorn calculus.
Xanthogranulomatous pyelonephritis appearing as nonenhancing, low-attenuation areas of the dilated collecting system surrounded by enhancing, high-attenuation parenchyma (known as the "bear paw" sign).
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