Renal cyst

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Left and right kidneys from a 1-year-old female dog with multicystic dysplastic kidneys[1]

Renal cysts (multicystic dysplastic kidney disease) are a rare benign congenital form of renal neoplasia characterized by intramedullary or intracortical cyst-like lesions.

Renal cysts are thought to arise as a result of underlying infections (e.g. microabscesses) from ascending infections (e.g. cystitis), as a consequence of tubular obstruction[2], or from congenital diseases such as renal dysplasia[3] and nodular dermatofibrosis[4].

Some dogs are asymptomatic and renal cysts may be an incidental finding on ultrasonography or postmortem.

Seriously affected dogs often present with a protracted history of hematuria, polyuria, polydipsia and vomiting. Depending on the cyst size, a palpable mass may be evident in the dorsal abdomen, sometimes with concurrent pain and tenderness in the loin region.

Ultrasonic imaging usually reveals small kidneys with a loss of normal architecture and poor corticomedullary distinction. The cyst often appear as anechoic spaces with sharply demarcated, thin-walled, round structures containing anechoic fluid.

Blood tests may reveal leukopenia, hypercalcemia, hyperphosphatemia and non-regenerative anemia. Chronic renal disease may be concurrently observed in severe cases with hyperkalemia and azotemia.

Diagnosis can be made presumptively on ultrasonographic findings of renal contour distortion and presence of hyperechogenic fluid-filled cysts, which may be present unilaterally or bilaterally[5].

A differential diagnosis would include polycystic kidney disease[6], renal carcinoma[7], nephroblastoma, Echinococcus spp infections, renal hypoplasia (Ask-Upmark kidney)[8], X-linked hereditary nephropathy (in Cocker Spaniels), familial juvenile glomerulonephropathy (autosomal-recessive in French Mastiff and Bull Terrier)[9].

Solitary renal cysts are frequently benign and in the majority of instances asymptomatic and do not require treatment. Nevertheless, treatment may be required if abdominal discomfort or pain, hypertension, infection or renal outflow obstruction occur[10].

Canine renal cysts may be successfully managed in some instances by a single ethanol injection and in severe cases ureteronephrectomy may be considered in unilateral cases where renal tissue is extensively compromised.

References

  1. Kim J et al (2011) Multicystic dysplastic kidney disease in a dog. Can Vet J 52(6):645-649
  2. Sorenson CM et al' (1996) Abnormal postpartum renal development and cystogenesis in the bcl-2(-/-) mouse. Am J Physiol 271:F184–F193
  3. Picut CA & Lewis RM (1987) Microscopic features of canine renal dysplasia. Vet Pathol 24:156–163
  4. Bønsdorff TB et al (2009) Loss of heterozygosity at the FLCN locus in early renal cystic lesions in dogs with renal cystadenocarcinoma and nodular dermatofibrosis. Mamm Genome 20(5):315-320
  5. Kitshoff AM et al (2011) Bilateral multiple cystic kidney disease and renal cortical abscess in a Boerboel. J S Afr Vet Assoc 82(2):120-124
  6. Gharahkhani P et al (2011) A non-synonymous mutation in the canine Pkd1 gene is associated with autosomal dominant polycystic kidney disease in Bull Terriers. PLoS One 6(7):e22455
  7. Petterino C et al (2011) Paraneoplastic leukocytosis in a dog with a renal carcinoma. Vet Clin Pathol 40(1):89-94
  8. Kolbjørnsen O et al (2008) End-stage kidney disease probably due to reflux nephropathy with segmental hypoplasia (Ask-Upmark kidney) in young Boxer dogs in Norway. A retrospective study. Vet Pathol 45(4):467-474
  9. Lavoué R et al (2010) Progressive juvenile glomerulonephropathy in 16 related French Mastiff (Bordeaux) dogs. J Vet Intern Med 24(2):314-322
  10. Agut A et al (2008) Imaging diagnosis - Ultrasound-guided ethanol sclerotherapy for a simple renal cyst. Vet Radiol Ultrasound 49(1):65-67