A 7-year-old, intact, female Siberian husky was presented to the Veterinary Medical Center of Chungbuk National University because of vomiting and diarrhea after a fight with a cohabiting dog. Physical examination, radiography, abdominal ultrasonography, and laboratory examination were performed. The dog was diagnosed with pyometra and 10% dehydration. On electrolyte, Na and Cl ion concentration were lower than normal values and Ca ion concentration was slightly lower than normal values. On blood chemistry, blood urea nitrogen and alkaline phosphatase value were extremely higher than normal values. Neutrophil was observed as hypersegmentation. On ultrasonography, enlarged uterine body was observed. Uterus was enlarged and filled with echogenic fluid that is seemed to be pus. Uterine horn was rubbing the bladder. In bacterial culture, the colony morphology was smooth, mucoid, and hemolytic. Also, on molecular diagnosis test, both samples from uterine and abdominal fluid were confirmed to be E. coli. This case describes that uterine pus was leakage to abdominal cavity through oviduct, and pus leakage from uterus may be cause septic peritonitis and death. Also, this case must be considered that physical event such as fight against cohabiting dog, strenuous exercise and kiss-off can cause uterine rupture or pus leakage through oviduct from uterus in dog with pyometra.