Perinephric abscess

Last revised by Mohammad Taghi Niknejad on 9 Jan 2024

A perinephric abscess may result due to the rupture of a renal abscess into the perirenal space, but usually, it develops directly from acute pyelonephritis. However, any inflammatory process outside the Gerota's fascia may also result in a perinephric abscess. Perinephric abscesses are associated with diabetic patients with calculi and in patients with septic emboli.

Perinephric abscesses usually form as a sequela of pyelonephritis that disrupts the renal parenchyma, especially in an obstructing stone 3. Less commonly, rupture of an abscess within the corticomedullary region of the kidney secondary to gram-negative urosepsis or metastatic infection can also occur. Perforation of the ureter or calyceal fornix is an uncommon cause 3.

Implicated organisms include 3

  • Escherichia coli (most common) 

  • Klebsiella spp.

  • Proteus spp.

  • Enterobacter spp.

  • Pseudomonas aeruginosa

  • Serratia spp.

  • Citrobacter sp.

Hematological seeding from a primary infected site outside the kidney is most commonly associated with Staphylococcus aureus 4

Ultrasound is usually the first imaging investigation to assess a renal abscess, perinephric collection, or pyelonephritis. As elsewhere, the collection is usually hypoechoic or mixed echogenicity, depending on the content. Ultrasound may also aid treatment in offering percutaneous drainage of the collection.

It often shows areas of soft tissue or fluid attenuation within the perirenal space. It may extend to involve the psoas muscle and down to the pelvis. Gas may be present within the abscess. CT has been quoted to be superior to ultrasound in diagnosing renal or perinephric abscess 4

Perinephric and mixed perinephric/renal abscesses are typically treated with imaged guided percutaneous drainage. This may be with either ultrasound-guided percutaneous abscess drainage or CT-guided, depending on the visibility and accessibility.1  Only those with unsuccessful or inadequate treatment with percutaneous drainage and antibiotics tend to require surgery.2

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