Renal abscesses

Case contribution: Dr Radhiana Hassan


  • A 65 years old man
  • Underlying DM, HPT
  • Also had bilateral staghorn calculi. PCNL done for the left renal calculus.
  • Presented with fever, dysuria and suprapubic pain for 3 days.
  • Associated with chills and rigor. No hematuria.
  • Noted low BP and started on medication
KUB radiograph AP supine view

Radiographic findings:

  • Faint opacities seen overlying both renal shadows (yellow arrows)
  • The renal outline is partially obscured by bowel gas  and fecal material
  • Obliteration of both psoas outline
  • Degenerative change of the spine
Ultrasound KUB

Ultrasound findings:

  •  There is a fairly well-defined multiseptated lesion at upper pole of right kidney measuring about 4.0 cm x 4.7 cm (AP x W). No intralesional debris, calcification or increased vascularity seen within.
  • Another small well-defined anechoic lesion is seen at lower pole of right kidney which measures about 1.5 cm x 1.5 cm (AP x W). No intralesional septation or increased in vascularity seen.
  • There is echogenic calculus with posterior shadowing seen occupying the right renal pelvis likely represents staghorn calculus.
  • No focal lesion  within the left kidney. No hydronephrosis or hydroureter seen bilaterally.
CT urography in axial planes, soft tissue window: non-contrast (upper row) and nephrographic phase (lower row)

CT scan findings:

  • There are several rim-enhancing hypodense lesions seen in both kidneys.
  • The largest of these lesions is seen in the right kidney interpolar region measuring 3.5 x 3.9 x 3.9 cm (AP x W x CC). This particular lesion can be seen to contain multiple septations. This lesion causes a focal bulge on the renal outline.
  • No calcification or air pocket is seen within all of these lesions.
  • Minimal fat streakiness is observed in both perinephric fat, more apparent on the right side. Both Gerota and Zuckerkandl fascias are intact bilaterally.
  • Multiple calculi are again seen occupying the right renal pelvis, forming a staghorn calculi.

Diagnosis: Renal abscesses.

Progress of patient:

  • Patient had an episode of atrial flutter secondary to sepsis during admission
  • Percutaneous US guided drainage done.
  • About 20mls of thick haemopurulent fluid was aspirated and sent for laboratory investigations (no growth).
  • Post aspiration shows significant reduction in abscess size.
  • Patient recovered well.


  • Renal abscess is a collection of infective fluid in the kidney.
  • It is usually develop as a sequelae of acute pyelopnephritis
  • It can affect all ages with no sex predilection
  • Predisposing factors include: DM, renal calculi or ureteral obstuction
  • On ultrasound, a renal abscess appears as a well-defined hypoechoic area within the cortex. It demonstrate internal echoes within. Associated diffusely hypoechoic kidney due to acute pyelonephritis has been reported. Perinephric collection may also be seen.
  • CT scan is the most accurate modality for diagnosis and follow-up of renal abscesses.
  • An abscess appears as a well-defined mass of low attenuation with a thick, irregular wall or pseudo capsule, which is better visualized on contrast enhanced scans.
  • 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