Renal neoplasia in horses - a retrospective study

Being confronted with a case series of renal neoplasia in several horses which was in striking divergence to literature data, we recognized the need of a retrospective study to assess the presence of renal neoplasms in horses.

Anamnestic animal data, necropsy findings and results of histological and immunohistochemical examinations from 2010 through 2015 were collected and evaluated regarding renal neoplasia.

Data from postmortem examinations of 1069 horses revealed 20 horses with renal tumors constituting a prevalence of 1.87 %. Primary renal neoplasms built the majority of cases (n = 15; 75 % of total renal neoplasms) and comprised nine renal carcinomas, four renal adenomas, one renal neuroendocrine tumor and a single nephroblastoma. Among the five secondary renal neoplasms lymphosarcoma was most common (3/5). Remaining metastatic tumors comprised one melanoma and one hemangiosarcoma. No breed or sex predilections were noticeable. Except for the case of nephroblastoma in a stillborn foal, all horses presenting with renal tumors were more than 10 years of age, often older than 20 years. Anamnestic data and clinical symptoms were inconclusive and not assigned to renal disease in most cases. Merely one horse with renal carcinoma presented with renal insufficiency and two horses showed signs of shock due to severe bleeding after tumor capsule rupture in renal carcinoma.

Renal tumors occur more often than anticipated, especially in older horses. Contradictorily to the literature, primary renal tumors significantly outnumbered secondary neoplasms in this study.