Renal and perinephric abscess are complications of urinary tract infection that usually occur in the setting of ascending infection with obstructed pyelonephritis (usually due to gram-negative enteric bacilli or polymicrobial infection) [1,2]. The major predisposing conditions for renal and perinephric suppuration are diabetes mellitus and renal stones. However, they also occur in the setting of bacteremia with hematogenous seeding, usually due to Staphylococcus aureus [3-7]. Infections in these sites are sometimes referred to as renal (or kidney) carbuncles and perirenal abscesses, respectively.
Renal abscess occurs more frequently than perinephric abscess. Both start with tissue necrosis (lobar necrosis in renal abscess; perirenal fat necrosis in perinephric abscess). Renal abscess forms a walled-off cavity; perinephric abscess consists of a more diffuse liquefaction.
Predisposing factors include diabetes mellitus and urinary tract abnormality (such as renal stone--especially large staghorn stones, vesicoureteral reflux, neurogenic bladder, obstructive tumor, benign cyst, or polycystic kidney disease) [1,2,8].
The clinical manifestations, diagnosis and management of renal and perinephric abscesses will be reviewed here. Pyelonephritis, emphysematous pyelonephritis and xanthogranulomatous pyelonephritis are discussed in detail separately (see "Emphysematous urinary tract infections" and "Xanthogranulomatous pyelonephritis" and "Acute complicated cystitis and pyelonephritis").
Clinical manifestations of renal and perinephric abscess are similar to those of a severe, acute pyelonephritis. These include fever, flank pain, abdominal pain, dysuria and/or frequency. A palpable mass may or may not be present . In the setting of perirenal suppuration, the overlying skin may demonstrate an inflammatory reaction . The diagnosis should be considered in patients with signs and symptoms of acute renal infection that fail to improve after five days of appropriate antimicrobial therapy [10,11]. (See "Acute complicated cystitis and pyelonephritis".)