Presumptive congenital peritoneal encapsulation in a young mixed-breed dog.

A 9-month-old female mixed-breed dog weighing 3.25 kg was referred for elective ovariohysterectomy. A previous attempt had been aborted when the abdominal organs appeared to be enclosed within an abnormal membranous structure. At surgery, the abdominal viscera visible within the operative field were covered by a thin, translucent membrane that could be bluntly dissected from the organ surfaces without hemorrhage. The excised membrane was submitted for histopathological analysis. Postoperative non-contrast computed tomography did not identify abnormal soft-tissue densities or displacement of abdominal organs. Histopathological analysis revealed coarse, fibro-collagenous tissue composed of interspersed, flattened spindle cells without a mesothelial lining and without inflammation. These findings supported a presumptive diagnosis of congenital peritoneal encapsulation, an extremely rare developmental anomaly. This case highlights the need to recognize this condition as a potential incidental finding during routine abdominal procedures in dogs. Key clinical message: Congenital peritoneal encapsulation should be considered when an unexpected membranous covering of abdominal viscera is encountered during routine abdominal surgery in a young dog. Recognition of this rare developmental anomaly may prevent unnecessary surgical intervention or premature abandonment of the procedure.