Severe abdominal distension associated with a paraovarian cyst in a guinea pig (Cavia porcellus).

Abdominal distension in guinea pigs might be a subtle symptom, not easily attributed to an underlying disease. Progressive abdominal enlargement can be caused by many factors, such as weight gain, intra-abdominal fluid, abdominal neoplasia or enlarged abdominal cyst. A 3-year-old intact female guinea pig (Cavia porcellus) weighing 1.5kg was referred to the University of Padova Veterinary Teaching Hospital after 2 months of progressive abdominal distension, and 2 days of anxiety, dysorexia and reduced faecal output. At physical examination, abdominal distention did not allow palpation. Ultrasound examination revealed the presence of abundant intra-abdominal fluid and cytology was not diagnostic. The animal was sedated with ketamine 10 mg/kg, dexmedetomidine 70 mcg/kg, midazolam 0.6 mg/ kg and buprenorphine 0.05 mg/kg subcutaneously (SQ). Anaesthesia was maintained with isoflurane and an exploratory laparotomy was performed. At the midline abdominal wall incision, a 12 cm fluid- filled cystic mass was found, tightly adhered to spleen, pancreas and left ovarium. The cyst was gently isolated, and ovariohysterectomy was performed. A total of 700g including the cyst and intra-abdominal fluid was removed. Enrofloxacine, meloxicam and prokinetic drugs were administered for 5 days. The animal appeared calm but still dysorexic the day after surgery. From the second day it began to progressively increase its appetite and faecal output. No complications were observed in the following 6 months. Histologically, the cyst was in continuity with the ovary and the uterus and showed a wall covered with cubic or flattened and keratinized epithelium with no atypical features. The cystic wall was composed of a layer of smooth muscle and was externally lined by degenerate mesothelium. These findings support the diagnosis of benign paraovarian cyst most likely pertaining to the mesonephric duct. Paraovarian cysts are the rarest type of cysts affecting reproductive system of guinea pigs.(1) Unlike the more common ovarian follicular cysts, paraovarian cysts are not associated to obvious hormone-related symptoms, such as flank alopecia, and could remain unidentified until they reach a large size. Therefore, changes in the volume and shape of the abdomen in female guinea pigs should be carefully investigated.