Factors that disrupt urinary flow such as vesicoureteral reflux, congenital urinary tract anomalies, altered bladder function, pregnancy, renal calculi, or mechanical obstruction increase the risk of developing APN [1,7,8]. In the majority of patients, uncomplicated APN is diagnosed clinically and is responsive to treatment with appropriate antibiotics [1]. In patients who are high risk or when treatment is delayed, microabscesses may coalesce to form an acute renal abscess. The renal parenchymal abscess can at times rupture into the perinephric space and lead to development of a perirenal abscess. In other cases, the infection may be confined to an obstructed collecting system causing pyonephrosis, or accumulation of purulent material in the upper urinary collecting system, that often requires decompression for treatment to be successful. Some patients are at high risk for developing complications from APN. High-risk patients include those with a prior history of pyelonephritis, a lack of response to therapy for lower UTI or for APN, diabetes, anatomic or congenital abnormalities of the urinary system, infections by treatment-resistant organisms, nosocomial infection, urolithiasis, renal obstruction, prior renal surgery, advanced age, and pregnancy; renal transplant recipients; and immunosuppressed or immunocompromised patients [1,8-10]. Pregnant patients and patients with renal transplants on immunosuppression are at elevated risk of severe complications. Imaging studies are often requested to aid with the diagnosis, identify precipitating factors, and differentiate lower UTI from renal parenchymal involvement, aUniversity of Alabama at Birmingham, Birmingham, Alabama. bPanel Chair, Northwestern University, Chicago, Illinois. cPanel Vice-Chair, UT Southwestern Medical Center, Dallas, Texas. dIndiana University, Indianapolis, Indiana; Committee on Emergency Radiology-GSER. eUT Southwestern Medical Center, Dallas, Texas. fThe University of Texas MD Anderson Cancer Center, Houston, Texas.
Acute Pyelonephritis. Factors that disrupt urinary flow such as vesicoureteral reflux, congenital urinary tract anomalies, altered bladder function, pregnancy, renal calculi, or mechanical obstruction increase the risk of developing APN [1,7,8]. In the majority of patients, uncomplicated APN is diagnosed clinically and is responsive to treatment with appropriate antibiotics [1]. In patients who are high risk or when treatment is delayed, microabscesses may coalesce to form an acute renal abscess. The renal parenchymal abscess can at times rupture into the perinephric space and lead to development of a perirenal abscess. In other cases, the infection may be confined to an obstructed collecting system causing pyonephrosis, or accumulation of purulent material in the upper urinary collecting system, that often requires decompression for treatment to be successful. Some patients are at high risk for developing complications from APN. High-risk patients include those with a prior history of pyelonephritis, a lack of response to therapy for lower UTI or for APN, diabetes, anatomic or congenital abnormalities of the urinary system, infections by treatment-resistant organisms, nosocomial infection, urolithiasis, renal obstruction, prior renal surgery, advanced age, and pregnancy; renal transplant recipients; and immunosuppressed or immunocompromised patients [1,8-10]. Pregnant patients and patients with renal transplants on immunosuppression are at elevated risk of severe complications. Imaging studies are often requested to aid with the diagnosis, identify precipitating factors, and differentiate lower UTI from renal parenchymal involvement, aUniversity of Alabama at Birmingham, Birmingham, Alabama. bPanel Chair, Northwestern University, Chicago, Illinois. cPanel Vice-Chair, UT Southwestern Medical Center, Dallas, Texas. dIndiana University, Indianapolis, Indiana; Committee on Emergency Radiology-GSER. eUT Southwestern Medical Center, Dallas, Texas. fThe University of Texas MD Anderson Cancer Center, Houston, Texas.