Obstructed renal collecting system containing pus or infected urine

Presence of mobile debris and layering of low-amplitude echoes within dilated collecting system on US

Dilated collecting system containing intermediate- or high-density material on CT

Enlarged kidney with perinephric inflammatory changes on CT

Sterile hydronephrosis

Complex renal cyst

Urothelial carcinoma

Stagnant urine becomes infected, filled with white blood cells, bacteria, debris, and pus

Chronic > acute ureteral obstruction

Etiology

• ○
  

  Young adult: Calculus or ureteropelvic junction obstruction or duplicated collecting system more common

  
  
• ○
  

  Elderly: Malignant ureteral stricture other mechanical obstruction

Urologic emergency: Delay in diagnosis and treatment leads to irreversible renal parenchymal damage and renal failure

• ○
  

  Progress to bacteremia or septic shock and can lead to 25-50% mortality

Symptoms include fever, chills, flank pain

Most common organism: Escherichia Coli

Treatment: Percutaneous nephrostomy

Diabetes is risk factor for worse clinical outcomes

Early diagnosis and drainage are crucial to prevent bacteremia and septic shock

Coronal plane best demonstrates collecting system, renal contour, renal cortex, medulla, and renal vessels

To obtain good coronal view, place probe between iliac crest and lower costal margin; start with midaxillary window then try posterior axillary line where rib spaces are wider

Graded probe pressure may help move bowel gas away