Granulomatous metritis caused by suspected Dirofilaria immitis in a dog: a case report

Here we describe a unique uterine mass in a dog with granulomatous lesions caused by filarial larvae from the family Onchocercidae. An 8-year-old female Maltese was presented to a local animal hospital with anorexia, depression, and vaginal discharge. A markedly distended uterus was observed on lateral abdominal radiographs, leading to a clinical diagnosis of pyometra or uterine mass of an unknown origin. During surgery, the left uterine horn contained a 5 cm diameter mass adhered to adjacent soft tissue. On gross inspection, the mass contained numerous white nematodes. Microscopically, this mass was characterised by a granulomatous inflammation of the myometrium and endometrium. Because all of the nematodes were dead, definitive species identification was not possible. However, based on the histologic appearance, these nematodes were tentatively identified as Dirofilaria immitis larvae.