A perinephric abscess is a suppuration (i.e. abscess) of the perinephric fat that abuts the renal cortex. Perinephric abscesses can arise as a complication either a pre-existing pyelonephritis or from hematogenous seeding from bacteremia of any kind. A 10-year retrospective study in 2016 identifying the causative agent of perinephric abscesses found that about 51.4% of perinephric abscesses were caused by E. coli, and that about 10% were caused by S. aureus, thus suggesting that the majority of perinephric abscesses arise as a complication of pyelonephritis. Perinephric abscesses are a distinct entity from renal abscesses in that renal abscesses arise from necrosis of the renal parenchyma and typically arise from pyelonephritis (although hematogenous seeding does occur), whereas perinephric abscess involves a diffuse liquefactive necrosis of the perinephric fat between the renal cortex and Gerota's fascia. Perinephric abscesses have a higher theoretical risk of morbidity because of the fact that the infection can easily spread to the lubosacral area posterioriy and abdominal cavity anteriorly. For this and other reasons, perinephric abscesses of ANY size should prompt a discussion with urology and/or interventional radiology about the possibility of drainage, in addition to parenteral antibiotics. On the other hand, drainage of nephric abscesses is typically only indicated if the size of the abscess exceeds 5 cm.
- Sign/symptoms similar to pyelo (fever, CVAT, dysuria)
- Occurs in setting of ascending infection with obstructed pyelo
- Genitourinary infection
- Urethral issue
- Behavioral symptom without detectable pathology