Felis ISSN 2398-2950

Kidney: perinephric/perirenal pseudocysts

Synonym(s): Perinephric pseudocysts, Renal capsular cysts, Retroperitoneal perirenal cysts

Contributor(s): Samantha Taylor


  • Rare condition associated with accumulation of fluid around one or both kidneys. The fluid is usually a transudate between the renal capsule and the renal parenchyma.
  • Cause: unknown; associated with renal disease or, more rarely, trauma.
  • Signs: asymptomatic, uni- or bilateral renomegaly, abdominal swelling or chronic kidney disease.
  • Diagnosis: radiography, ultrasonography.
  • Treatment: surgery (omentalization, pseudocyst resection).
  • Prognosis: depends on degree of underlying renal disease, some cases recur after drainage.



  • A number of etiologies have been proposed for pseudocyst development in man:
    • Resolving perirenal hematoma.
    • Inflammatory reaction due to extravasated urine (trauma or obstruction).
    • Hypertension Hypertension.
    • Idiopathic.
  • In cats:


  • Structural renal disease.


  • A pseudocyst is a fluid-filled cavity with no epithelial lining.
  • Three types of peri-renal pseudocysts have been described (maybe uni- or bi-lateral):
    • Intracapsular (most common) - transudate accumulates between the capsule and parenchyma.
    • Extracapsular - transudate accumulates between the renal capsule and the lining of the retroperitoneum.
    • Peri-renal urinoma - leakage of urine from the urinary tract causing an inflammatory response and formation of a fibrous wall around the site of leakage.
  • Poorly understood:
    • Transudate may originate from the capsule or the parenchyma.
    • A transudate occurs due to changes in hydrostatic or oncotic pressure in the vasculature or interstitium.
    • Impaired capsular lymphatic drainage has been hypothesized as a cause of transudation from the capsule.
    • Interstitial fibrosis may obstruct lymphatic or venous drainage   →   transudation from parenchyma (a more likely source of transudate).
  • Pseudocysts progressively enlarge.


  • Insidious onset over months.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Mouat E E, Mayhew P D, Weh J L et al (2009) Bilateral laparoscopic subtotal perinephric pseudocyst resection in a cat. J Feline Med Surg 11 (12), 1015-1018 PubMed.
  • Beck J A, Bellenger C R, Lamb W A et al (2000) Perirenal pseudocysts in 26 cats. Aust Vet J 78 (3), 166-171 PubMed.
  • Hill T P, Odensnik B J (2000) Omentalisation of perinephric pseudocysts in a cat. JSAP 41 (3), 115-118 PubMed.
  • Ochoa V B, DiBartola S P, Chew D J et al (1999) Perinephric pseudocysts in the cat - a retrospective study and review of the literature. JVIM 13 (1), 47-55 PubMed.

Other sources of information

  • Dibartola S P & Westropp J (1997) Perinephric pseudocysts. In: Consultations in feline internal medicine 3. Ed. J R August. Philadelphia: W B Saunders CO. pp 341-344.