A perinephric abscess may result due to 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.
On this page:
Images:
Pathology
Perinephric abscesses will usually form as a sequela of pyelonephritis that causes disruption of the renal parenchyma especially in the presence of 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.
Etiology
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.
Radiographic features
Ultrasound
Ultrasound is usually the first imaging investigation performed for assessment of 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.
CT
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 the diagnosis of renal or perinephric abscess 4.
Treatment and prognosis
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 dependent on the visibility and accessibility.1 Only those with unsuccessful or inadequate treatment with percutaneous drainage and antibiotics tend to require surgery.2
Unable to process the form. Check for errors and try again.