Diseases related to the urogenital system in both males and females, are common in clinical routine of small animal and represents important causes of morbidity and mortality in dogs and cats. Pyocolpos is a cystic dilatation of the vagina due to the accumulation of pus resulting from the genital tract obstruction. The main cause of obstruction is imperforate hymen, transverse vaginal membrane, or vaginal atresia.We present a case of a three-year-old female Pinscher with a history of constipation for four days, even after administration of laxatives and enema, and estrus for ten days without a report of cover. Physical examinations were performed, which revealed increased abdominal size. Ultrasound confirmed the presence of large amounts of vaginal fluid. Exploratory laparotomy was performed, which confirmed the diagnosis of pyocolpos. Although pyocolpos is a rare congenital malformation in female domestic animals, this report of its existence underscores the importance of more accurate clinical research when increased abdominal size is noted by veterinarians.