Solitary exophytic renal cysts in dogs: A retrospective case series of nine dogs with clinicopathological, diagnostic imaging and 12-month outcome data following unilateral nephrectomy

Abstract Solitary exophytic renal cysts are uncommon in dogs, and information regarding their clinical characteristics, diagnostic imaging findings, and outcomes following surgical treatment is limited. This retrospective case series describes the clinicopathological, imaging, and histopathological findings and 12-month outcomes of nine dogs with solitary exophytic renal cysts treated by unilateral nephrectomy. Medical records from May 2023 to December 2024 were reviewed. Clinical examination, hematology, serum biochemistry, serum symmetric dimethylarginine (SDMA), urinalysis, urine culture, ultrasonography, contrast-enhanced computed tomography (CT), histopathology, and postoperative follow-up data were evaluated. Six cysts involved the right kidney, and three the left, with dimensions ranging from 32 × 30 to 61 × 56 mm. Seven cysts originated from the cranial pole and two from the mid-pole. Ultrasonography and CT demonstrated well-circumscribed, thin-walled, fluid-filled exophytic lesions without septations, mural nodules, mineralization, or contrast-enhancing solid components. Four cysts compressed the adjacent renal cortex. Urine cultures were positive in three dogs. Histopathology confirmed benign renal cystic lesions with variable tubular ectasia, fibrosis, and chronic inflammatory changes. During 12 months of follow-up, urinary erythrocyte and leukocyte counts and serum creatinine and SDMA concentrations decreased significantly. No recurrence or clinically apparent renal insufficiency was identified. In this selected population, unilateral nephrectomy was associated with favorable clinical and clinicopathological outcomes; however, these findings do not establish nephrectomy as routine treatment for uncomplicated renal cysts, and renal-sparing approaches should remain a consideration in appropriately selected cases.