CT of Acute Pyelonephritis

Etiology:
* Inflammation of the renal parenchyma and renal pelvis due to an infectious source

* Most often secondary to an ascending lower urinary tract infection from gram-negative bacteria
- E. coli
- Klebsiella
- Proteus
- Pseudomonas.

* 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:
- Fever
- Chills
- Flank pain
- Dysuria
- Increased frequency of urination.
- On exam, costovertebral angle tenderness may be present.

Clinical Findings:

1- CBC
- Elevated white blood cell count.

2- Urinalysis
- Bacteriuria
- Pyuria
- White blood cell casts

3- Acute pyelonephritis is clinical diagnosis,
- Radiographic imaging is used to evaluate underlying pathology
- Rule out any complications as:

-Abscess
-Emphysematous pyelonephritis.....Most often occurs in diabetics Can produce gas in the collecting system and renal parenchyma.

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

Radiographic Imaging Findings:
$ Enlarged kidneys (U/S and CT)
$ Hydronephrosis (U/S and CT)
$ Wedge shaped areas of low attenuation secondary to decreased perfusion (CT)
$ Loss of the ability to distinguish the corticomedullary border (CT)
$ Perinephric stranding (CT)


Treatment

o Antibiotics for non-complicated pyelonephritis.
o Radical nephrectomy for emphysematous pyelonephritis.
o Percutaneous drainage of abscesses