Renal Dysplasia in a Maltese dog

Background: Renal dysplasia (RD) is a common cause of renal failure in young dogs. It is defined as a disorganization in renal parenchymal development, with abnormal differentiation. In all domestic animal species, RD may be hereditary or acquired. The affected animals show clinical signs of early chronic kidney disease, usually between 3 months to 3 years of age. The alterations include persistent metanephric ducts surrounded by primitive mesenchyme, glomeruli and fetal tubules, and abnormal interstitial fibrous tissue. We aimed to report the case of a 1-year-old canine with renal dysplasia.Case: A 1-year-old male Maltese dog experiencing polyuria, polydipsia, recurrent episodic vomiting, bloody diarrhea, weight loss, apathy, and anorexia was referred to a private clinic in the municipality of Itabuna-Bahia. Physical examination revealed hypochromic mucosa, dehydration estimated at 8%, rectal temperature of 37.5º C, halitosis, and a body score of 3 out of 9. Laboratory abnormalities included hematocrit of 18%, with hypochromic normocytic aregenerative anemia, azotemia (urea - 530 mg/dL, creatinine - 10.5 mg/dL), hyperglobulinemia (4.7 g/dL), low urinary density (1005), proteinuria (300 mg/dL), and urinary pH - 7.0. Ultrasonography revealed bilateral small kidneys with loss of cortico-medullary definition, cystic formations of different sizes on the renal surface, and hyperechoic areas in the parenchyma; these alterations were suggestive of bilateral chronic nephropathy. Considering the clinical, hematological, biochemical, and ultrasonographic presentation associated with the age of the patient, renal dysplasia was suspected. The patient's clinical condition progressed to loss of consciousness and convulsions, followed by death. Necropsy revealed pale, hypotrophic kidneys with firm consistency, irregular capsular surface containing multiple cortical cysts of different sizes, and altered cortico-medullar proportion. . Kidney fragments were sent to the Laboratory of Histopathology of the State University of Santa Cruz.  Histopathological analysis revealed a marked alteration of renal architecture with glomeruli and immature tubules (adenomatous aspect), persistent primitive mesenchyme, and remnants of the metanephric ducts, as well as tubular dilatation associated with marked interstitial fibrosis, discrete lymphohistiocytic interstitial nephritis, and multifocal areas of mineralization.Discussion: The clinical changes observed in the present case occurred as a consequence of chronic kidney failure caused by RD and included anorexia, apathy, vomiting, bloody diarrhea, polyuria, polydipsia, and dehydration. These alterations were also found in other reported cases. The macroscopic findings were similar to those described in the literature and are characteristic of chronic kidney disease: small, firm, pale-colored kidneys. Microscopic changes of renal dysplasia include persistent metanephric ducts surrounded by primitive mesenchyme, glomeruli and fetal tubules, and abnormal interstitial fibrous tissue. In the histopathological renal evaluation in the present report, morphological alterations compatible with the described alterations in the literature were observed, thus allowing the diagnosis of renal dysplasia. Renal dysplasia can affect young dogs of different breeds, causing clinical manifestations of chronic kidney disease. In view of this, this disease should be included as a differential diagnosis in patients under 3 years old who present signs of chronic nephropathy.