Etiology

o   Inflammation of the renal parenchyma and renal pelvis
due to an infectious source 

o       Most often secondary to an ascending lower urinary
tract infection from gram-negative bacteria

§     E. coli

§     Klebsiella

§     Proteus

§     Pseudomonas 

o       Exception is S. aureus, which is spread hematogenously

 

· Pathologic Causes

o       Vesicoureteral reflux

o       Obstruction in the collecting system usually due to a
calculus

 

· Signs and symptoms

o       Fever

o       Chills

o       Flank pain

o       Dysuria

o       Increased frequency of urination.

o       On exam, costovertebral angle tenderness may be present.

 

· Clinical Findings

o       CBC

§         Elevated white blood cell count.

o       Urinalysis

§         Bacteriuria

§         Pyuria

§         White blood cell casts

o       Acute pyelonephritis is clinical diagnosis,

§       Radiographic imaging is used to evaluate underlying
pathology

§       Rule out any complications.

 

· Complications

o       Abscess

o       Emphysematous pyelonephritis

§         Most often occurs in diabetics

·       Can produce gas in the collecting system and renal parenchyma

 

· Imaging Findings

o       Enlarged kidneys  (U/S and CT)

o       Hydronephrosis    (U/S and CT)

o       Wedge shaped areas of low attenuation secondary to
decreased perfusion (CT)

o      Loss of the ability to distinguish the corticomedullary
border  (CT)

o      Perinephric stranding.  (CT)

 

· Treatment

o       Antibiotics for non-complicated pyelonephritis.

o       Radical nephrectomy for emphysematous pyelonephritis.

o       Percutaneous drainage of abscesses

Acute Pyelonephritis. Right kidney is markedly enlarged and has a wedge-shaped area of low attenuation.