Renal abscess
Renal abscess is a focal, pus-filled collection in the renal parenchyma (intrarenal) or perinephric space, most often complicating unresolved ascending pyelonephritis with gram-negative organisms or hematogenous staphylococcal seeding. Persistent fever and pyuria despite 5-7 days of appropriate antibiotics should prompt CT or ultrasound imaging, with percutaneous or surgical drainage required for perinephric collections and intrarenal abscesses larger than 5 cm.
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What this article covers
- Overview
A focal, pus-filled collection of the kidney or its surrounding space: a renal (intrarenal, cortical or corticomedullary) abscess forms within the renal parenchyma, while a perinephric abscess forms…
- Epidemiology
Complicates a minority of pyelonephritis cases: a rare complication occurring when infection is not adequately controlled by initial antibiotic therapy.
- Risk factors
Unresolved or inadequately treated pyelonephritis: the leading pathway to an ascending intrarenal or perinephric abscess.
- Pathophysiology
Ascending route: gram-negative bacilli (predominantly Escherichia coli, as in uncomplicated pyelonephritis) ascend from the bladder, establish pyelonephritis, and, when infection is inadequately…
- Clinical features
Persistent fever despite antibiotic therapy for pyelonephritis: the hallmark presentation is a patient being treated for pyelonephritis who remains febrile and continues to show white cells on urinalysis after 5 to 7 days.
- Differential diagnosis
Uncomplicated (resolving) pyelonephritis: defervescence and resolving pyuria within 5 to 7 days of appropriate antibiotics, without a discrete fluid collection on imaging, excludes abscess.
- Diagnosis
The diagnosis is confirmed by imaging demonstrating a fluid collection, with the clinching microbiologic diagnosis made by image-guided aspiration: there is no formal severity-grading system; the…
- Management
First, obtain source control by drainage: all perinephric abscesses require drainage, as do intrarenal abscesses larger than 5 cm; image-guided percutaneous catheter drainage is preferred, with…
- Complications
Sepsis and septic shock: an undrained abscess is a persistent source of bacteremia and can progress to systemic sepsis.
- Prognosis
Outcome depends on prompt drainage and source control: abscesses that are drained early, with correction of any underlying obstruction, generally resolve without permanent kidney damage.
- Prevention
Treat pyelonephritis promptly and completely: obtain urine culture with susceptibility testing before empiric therapy, and use an effective empiric regimen (ciprofloxacin 500 mg PO twice daily for 7…
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