Pyonephrosis

Pyo- (pus), -nephrosis (process of the kidney)

Pyonephrosis is exactly that . It is infection of the kidney where there is purulent material (pus) in the collecting system.

Complications:

• Renal Obstruction
• Renal abscess
• Xanthogranulomatous pyelonephritis
• Sepsis

Radiology

Ultrasound:

• hydronephrosis
• echogenic debris within the collecing system
• fluid-fluid levels within the collecting system
• dirty shadowing (from gas) within the collecting system

CT:

• Signs of infection + hydronephrosis
  • increased density in the collecting system
  • layering material (or excreted contrast) in the collecting system
  • gas in the collecting system
• Don't forget to look for typical signs of infection
  • perinephric stranding
  • heterogeneous renal enhancment (aka lobar nephronia)
  • Urothelial thickening/enhancement

MRI:

• similar findings as CT

Treatment:

Percutaneous nephrostomy + antibiotic therapy is the treatment of choice to drain the pus from the collecting system and relieve the obstruction.

Our Case

On both the axial and sagital images above, you can see the dilated collecting system with urine-pus level. Note the size of the right kidney is much larger than the left (from the obstruction/infection) with right perinephric stranding.
 

Perhaps you also noted the thick walled urinar bladder. Could that be simple redundant thickening of the bladder wall that is non-distended? Or could it be inflammatory thickening from cystitis? Fortunately if it is infection it will be treated by the antibiotics used to treat the upper urinary tract infection.