Papillary Renal Cell Carcinoma With Widespread Metastases in an Arabian Mare

This report describes a case of massive renal cell carcinoma (RCC) causing mild chronic colic in a 20-day-postpartum Arabian mare. The mare presented with deteriorating abdominal pain following normal parturition. Clinical examination revealed tachycardia, tachypnoea, weak intestinal motility and pale mucosal membranes. Rectal examination identified a very large mass in the caudal part of the abdominal cavity, and abdominal ultrasound examination revealed a huge space-occupying mass with renal architecture. During midline exploratory laparotomy, a massive tumour was observed in the anatomical location of the left kidney, with numerous adhesions to abdominal organs. Due to the severity of the condition and intra-abdominal spread of the neoplasm, the horse was euthanized intraoperatively. Upon necropsy, a 23-kg mass was found in the left kidney, along with widespread metastases to the liver, diaphragm and lungs. Histopathological examination confirmed primary and metastatic papillary RCC. This case highlights that colic should be considered a potential symptom of neoplastic lesions within the abdomen.