Chronic Pyelonephritis Workup

Updated: Sep 17, 2019
  • Author: James W Lohr, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Workup

Approach Considerations

The characteristic renal scars of vesicoureteral reflux (VUR) are often present at the time of the initial diagnosis of chronic pyelonephritis. New renal scars may develop in 3-5% of patients after the initial evaluation. The progression of renal scars is inversely related to the promptness with which specific antibiotic therapy is instituted. The presence of new scars often suggests the occurrence of breakthrough infections.

Urinalysis results may reveal pyuria. Obtain a urine culture, which often isolates gram-negative bacteria, such as Escherichia coli or Proteus species. A negative urine culture does not exclude a diagnosis of chronic pyelonephritis. Proteinuria may be present and is a negative prognostic factor for this chronic pyelonephritis. Serum creatinine and blood urea nitrogen (BUN) levels are elevated (azotemia).

Renal biopsy specimens show focal glomerulosclerosis in advanced reflux nephropathy, while xanthogranulomatous pyelonephritis must be distinguished from renal malakoplakia based on the presence of inclusions called Michaelis-Gutmann bodies in the latter.

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Imaging Studies

On an intravenous urogram, caliceal dilatation and blunting with cortical scars helps to establish the diagnosis of pyelonephritis. Ureteral dilatation and reduced renal size also may be evident.

Voiding cystourethrogram (VCUG) findings may document the reflux of urine to the renal pelvis and ureteral dilatation in children with gross reflux. [19]  To strike the balance between obtaining high-quality images and minimizing radiation exposure, radiology departments should observe the “as low as (is) reasonably achievable” (ALARA)  Image Gently guidelines. [20]

Radioisotopic scanning with technetium dimercaptosuccinic acid (DMSA) is the gold standard for detecting renal scars and is more sensitive than intravenous pyelography. [21]  

Cystoscopy findings show evidence of previous reflux at the ureteral orifices, even if VCUG images show no reflux because of the spontaneous cessation of reflux due to puberty.

Computed tomography (CT) scanning is the procedure of choice to help diagnose XPN. [14, 22] Renal ultrasonographic images may show calculi, but ultrasonography is not a sensitive screening procedure for reflux nephropathy. However, many cases of VUR are suggested by prenatal ultrasonographic findings.

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