Renal abscess with perinephric extension

Case contribution: Dr Radhiana Hassan


  • A 58 years old lady
  • Autoimmune hemolytic anemia (AIHA) under follow up
  • NO DM, no HPT
  • Left PUJ stone, laser endopyelorotomy, laser lithotripsy and stenting done one month ago
  • Discharged well
  • Presented with left lumbar pain and fever for 2 days
  • Hb: 6.4, TWBC 20.0
KUB radiograph shows renal calculi with left ureteric stent in-situ
Ultrasound left kidney

Ultrasound findings:

  • A hypoechoic lesion in the left renal cortex (yellow arrow)
  • Irregular outline with internal echoes
  • A collection is seen outside the left renal (white arrow)
  • No other significant finding
CT scan abdomen post contrast in axial plane soft tissue window
CT scan abdomen post contrast reformatted image in coronal plane

CT scan findings:

  • The left kidney is shrunken with bipolar length (BPL) of 7.4cm.
  • Multiple calculi are seen in the upper and lower pole of the left kidney.
  • There are multi-loculated peripherally enhancing lesions within the left renal cortex. The largest loculation is seen within the midpole, peripherally, measuring about 1.6cm x 2.4cm x 3.8cm (APxWxCC).
  • A larger peripherally enhancing collection is seen within the splenorenal region measuring about 7.0cm x 7.9cm x 8.3cm (APxWxCC). Multiple small air pockets noted.
  • ┬áThis collection is seen connected to the left renal collection at the anterolateral aspect of the left kidney.
  • Double – J stent is seen in situ.

Diagnosis: Left renal abscesses with perinephric collection


  • Renal abscess is usually a sequalae of pyelonephritis
  • On ultrasound, it appears as a well-defined hypoechoic area within the cortex or in the corticomedullary parenchyma. It demonstrates internal echoes within and an associated diffusely hypoechoic kidney due to acute pyelonephritis may be seen.
  • Perinephric collection may also be seen.
  • On CT scan it appears as a well-defined mass of low attenuation with a thick, irregular wall or pseudo capsule. Gas within a low attenuation/cystic mass strongly suggests abscess formation.
  • Associated fascial and septal thickening is seen with obliteration of perinephric fat.
Author: radhianahassan