Perinephric stranding

A CT finding of increased attenuation within the perinephric fat, reflecting edema, inflammation, hemorrhage, or infiltration within the perirenal space surrounding the kidney.

Causes

• Renal infection with surrounding inflammatory changes

  • Acute pyelonephritis

  • Perinephric abscess

  • Xanthogranulomatous pyelonephritis

• Post-renal obstruction --> Hydronephrosis --> secondary perirenal inflammation

  • Ureterolithiasis

  • Bladder outlet obstruction

  • Urinary tract obstruction

• Traumatic and hemorrhagic causes

  • Renal trauma

  • Perinephric hematoma

  • Renal biopsy complications

  • Anticoagulation-related perirenal bleeding

• Fibrotic and infiltrative causes

  • Retroperitoneal fibrosis

  • Infiltrative malignancy

  • Lymphoma involving the perirenal space

  • Metastatic disease affecting perinephric tissues

• Vascular and renal causes

  • Renal infarction with inflammatory response

  • Renal vein thrombosis

• Age-related: Perinephric fat stranding as a normal anatomical variant in older adults

• Other causes

  • Postoperative changes after renal or retroperitoneal surgery

  • Radiation-related inflammation