Perinephric abscess

Background

Renal anatomy.

Perinephric space with exaggerated pararenal space to show retroperitoneal structures. Perinephric bridging septa are seen between the left kidney and the adjacent renal fascia.

• An abscess of the perinephric fat that abuts the renal cortex
• Can arise as a complication either a pre-existing pyelonephritis (majority) or from hematogenous seeding

Causative Organisms

• E. coli (51.4%)
• S. aureus (10%)

Perinephric vs renal abscess

	Perinephric	Renal
Necrotic Area	Perinephric fat between the renal cortex and Gerota's fascia	Renal parenchyma
Cause	Pyelonephritis (majority)	Pyelonephritis (vast majority)
Risk of morbidity	Higher	Lower

Genitourinary infection

(1) Human urinary system: (2) kidney; (3) renal pelvis; (4) ureter; (5) urinary bladder (6) urethra.
Additional structures: (7) adrenal gland; (8) renal artery and vein; (9) inferior vena cava; (10) abdominal aorta; (11) common iliac artery and vein; (12) liver; (13) large intestine; (14) pelvis.

"UTI" frequently refers specifically to acute cystitis, but may also be used as a general term for all urinary infections; use location-specific diagnosis.

• Renal/perirenal
  • Pyelonephritis
    • Emphysematous pyelonephritis
  • Renal abscess
  • Perinephric abscess
• Ureteral
  • Infected urolithiasis
• Bladder
  • Acute cystitis ("UTI")
  • Chronic cystitis
• Urethra/periurethra
  • Urethritis
  • Prostatitis

Clinical Features

• Sign/symptoms similar to pyelo (fever, CVAT, dysuria)
• Occurs in setting of ascending infection with obstructed pyelo

Differential Diagnosis

Dysuria

• Genitourinary infection
  • Acute cystitis ("UTI")
  • Pyelonephritis
  • Urethritis
  • Chronic cystitis
  • Infected nephrolithiasis
  • Prostatitis
  • Epididymitis
  • Renal abscess/perinephric abscess
  • Emphysematous pyelonephritis
• Nephrolithiasis
• Urethral issue
  • Urethritis
  • Urolithiasis
  • Urethral foreign body
  • Urethral diverticulum
  • Allergic reaction (contact dermatitis)
  • Chemical irritation
  • Urethral stricture or obstruction
  • Trauma to vagina, urethra, or bladder
• Gynecologic
  • Vaginitis/cervicitis
  • PID
  • Genital herpes
  • Pelvic organ prolapse
  • Fistula
  • Cystocele
• Other
  • Diverticulitis
  • Interstitial cystitis
  • Behavioral symptom without detectable pathology

Evaluation

Laboratory Testing

• CBC - Although it is a non-specific finding, a leukocytosis is typically seen.
• Chemistry Panel - Lactic acidosis is a common finding and is seen earlier in the disease course in diabetic patients. Renal insufficiency is also commonly seen as well.
• Urinalysis - Will often show evidence of pyelonephritis, however if the perinephric abscess is secondary to hematogenous spread, the urine could be sterile. Therefore a negative U/A does NOT rule out a perinephric abscess.
• Blood and urine cultures

Imaging

• CT
  • Imaging modality of choice
  • Sensitivity ~90%.
• Renal ultrasound - A fluid filled mass extending from the renal cortex into the perinephric fat can be seen.

Management

• Antibiotic therapy depends on the suspected cause
  • Pyelonephritis (enterobacteriaceae): third generation cephalosporin + quinolone
  • Hematogenous (staphylococcus)): vancomycin
  • Known to be colonized by ESBL: carbapenem
• Abscess drainage
  • Abscess of ANY size requires IR for percutaneous drainage
  • If any urological obstruction is suspected (nephrolithiasis, ureterolithiasis, external compression from abdominal cavity, presence of pre-existing ureteral stent), emergent urological consultation should be obtained

Disposition

• Admission

See Also

• pyelonephritis
• Emphysematous pyelonephritis
• Renal abscess
• Urolithiasis