Kidney: perinephric/perirenal pseudocysts in Cats (Felis) | Vetlexicon
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Kidney: perinephric/perirenal pseudocysts

ISSN 2398-2950

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  • 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.

Presenting signs

  • Abdominal distension.

Age predisposition

  • Middle-aged (median 11-13.5 years - although may occur at any age).

Breed/Species predisposition

  • Long haired breeds?



  • 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.


Presenting problems

  • Abdominal distension.
  • Renomegaly Abdominal organomegaly.
  • Signs consistent with chronic kidney disease (polydipsia/polyuria, weight loss, inappetence).

Client history

  • Signs consistent with chronic kidney disease.
  • Abdominal swelling.
  • Anorexia.
  • Weight loss.

Clinical signs

  • Apparent renomegaly.
  • Abdominal distension (may be only presenting sign).
  • Signs of chronic kidney disease or systemic disease.
  • Abdominal discomfort.
  • Vomiting.

Diagnostic investigation


  • May show large soft tissue densities in the region of the kidneys Radiography: abdomen.
  • Contrast radiography (eg intravenous urography Radiography: intravenous urography) may help distinguish the kidney from surrounding fluid.
  • Fluid surrounds nephrogram phase on intravenous radiography (no contrast leaks into cyst).
  • For urinoma - excretory urography shows communication between urinary tract and the pseudocyst.

2-D Ultrasonography

  • More useful that radiography to distinguish the cause of the renomegaly Ultrasonography: kidney
  • Anechoic fluid accumulation between renal capsule and parenchyma.
    Mixed echogenicity fluid may suggest renal abscessation or hemorrhage.
  • Altered size, margination, echogenicity and demarcation between cortex and medulla consistent with diffuse (but non-specific) parenchymal diseases.





  • Biopsy Kidney: surgical approach:
    • If renal neoplasia or reversible renal disease suspected.
      Biopsy is not routinely indicated due to risks of hemorrhage and deterioriation of renal function.


Confirmation of diagnosis

Discriminatory diagnostic features

  • Signs.
  • Radiography.

Definitive diagnostic features

  • Ultrasonography.
  • Cystic fluid analysis.

Gross autopsy findings

  • Enlarged renal capsule containing serous fluid.
  • Underlying kidney may be shrunken and pitted if chronic kidney disease.

Histopathology findings

  • Fibrous capsule surrounding cyst.
  • Differentiated from true cyst as no epithelial lining.
  • May be evidence of chronic interstitial fibrosis in kidney.

Differential diagnosis

Other causes of renomegaly


Initial symptomatic treatment

Standard treatment

  • Ultrasound guided drainage repeated as necessary.
  • Consider concurrent IV fluids Fluid therapy: for electrolyte abnormality, especially if chronic kidney disease present.
  • In some cats cystic fluid does not re-accumulate.
  • Surgical drainage:
    • Resection of pseudocyst lining.
    • May be curative but will not reverse chronic kidney disease if present.
    • Ventral midline celiotomy and dissection of pseudocyst lining from retroperitoneal fascia. Open and drain (collect fluid for cytology and biochemistry).
    • Resect renal capsule where it has detached from renal parenchyma - leave a collar of capsule around the hilus and use this to perform a nephropexy at two sites on the abdominal wall.
    • Indicated for cats with little or no azotemia Azotemia that are likely to develop signs as a result of enlargement of the pseudocysts.
      Resection of the capsule probably does not stop transudation but may improve absorption by a larger part of the peritoneal cavity.
    • Fenestration has been suggested as an alternative to resection.
  • Omentalization of the cyst has been reported.
  • Laparoscopic pseudocyst resection may be successful and result in fewer surgical complications.
    Consult an experience surgeon and consider referral before attempting resection or omentalization if the technique is unfamiliar.Nephrectomy should be avoided because underlying renal pathology may already be present in remaining kidney

Subsequent management


  • Reassess cyst size 4-6 weeks after drainage.
  • Monitor chronic kidney disease if present and for the development of CKD if cat non-azotemic at diagnosis.




  • Good: if no underlying renal disease.
  • Guarded: if chronic kidney disease present Kidney: chronic kidney disease.
  • Degree of azotemia correlates with prognosis; median survival time following surgery in 8 cases was 9 months; recurrence follows percutaneous drainage within days to weeks.
  • Individual case reports describe complete resolution without development of chronic kidney disease.

Expected response to treatment

  • Resolution of abdominal distension.

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.