Computed tomography of pyonephrosis

Abstract

Computed tomographic (CT) findings of 17 pyonephrotic and 20 uninfected hydronephrotic kidneys were reviewed. Parameters evaluated included: renal pelvic wall thickness (none; grade 1, < or = 2 mm; grade 2, 3-5 mm; and grade 3, > 5 mm), renal pelvic contents, parenchymal, and perirenal findings. All patients underwent subsequent percutaneous nephrostomy within 1 week of CT. Common CT findings suggesting pyonephrosis include increased pelvic wall thickness and more severe perirenal fat changes than are seen in uninfected hydronephrosis. However, for any one patient, these findings are often not diagnostic. The presence of clinical signs of infection with hydronephrosis on CT is a more sensitive indicator of pyonephrosis than most CT findings.

Computerized tomography attenuation values can be used to differentiate hydronephrosis from pyonephrosis

“…Therefore, the radiologic investigations gain more importance to establish the diagnosis in a quick and appropriate manner. Of the commonly applied modalities, while sonography of the affected kidney demonstrates hydronephrosis accompanied with fluid-debris levels within the dilated collecting system [2,5], CT evaluation is often associated with nonspecific findings such as thickening of the renal pelvis and stranding of the perirenal fat [1,9,10]. As a result of these suspicious but not indicative of radiologic findings, most of the patients are diagnosed during the percutaneous drainage of the collecting system either during nephrostomy tube placement or percutaneous nephrolithotomy procedure.…”

“…However, despite the presence of more pronounced contrast-enhanced CT findings like pelvic and ureteral wall thickness, perinephric fat stranding, striated nephrogram in the renal parenchyma that could be indicative of pyonephrosis [1,9], it is difficult to distinguish it from uninfected hydronephrosis [1,9,10].…”

Acute Urinary Tract Disorders

“…Similar findings are seen on MR imaging. 54,61 When infection causes liquefactive necrosis of the renal parenchyma, microabscesses coalesce and a renal abscess forms (Fig. 14).…”

Computed Tomographic Imaging of Renal and Ureteral Emergencies

“…Distinguishing between uncomplicated hydronephrosis and pyonephrosis on CT is difficult, 16,26 although features suggestive of pyonephrosis include more severe perinephric inflammatory changes and increased pelvic wall thickness. 27 Urgent drainage is needed in cases of pyonephrosis, 28 and definitive diagnosis is made by fluid analysis following decompression. 17 …”