Repair of a Large Congenital Peritoneopericardial Diaphragmatic Hernia with Canine Small Intestinal Submucosa Patch Reinforcement in a Dog: A Case Report

Peritoneopericardial diaphragmatic hernia (PPDH) is a congenital anomaly allowing communication between the peritoneal and pericardial cavities. Surgical repair of large diaphragmatic defects can be challenging due to insufficient tissue for primary closure. A 2-year-old intact female White Miniature Schnauzer weighing 6.23 kg presented with a 1-month history of panting and exercise intolerance. Thoracic radiography, ultrasonography, echocardiography, and CT confirmed PPDH with herniation of the left medial and quadrate liver lobes into the pericardial sac. Surgical repair via midline celiotomy revealed a large defect (4.5 × 5 cm) involving approximately 70% of the central tendon. Primary closure was incomplete because only two simple interrupted sutures could be placed at the dorsal margin due to excessive tension, leaving a triangular residual defect larger than 3 × 3 cm at the ventral aspect, which was closed with a two-layer canine small intestinal submucosa (cSIS) patch applied over the residual defect. Reherniation occurred 42 days postoperatively at the margin between the diaphragm and the cSIS patch. At the second surgery, grossly observed tissue presumed to be newly formed self-tissue at the cSIS site enabled direct suture repair. No recurrence was observed during a 5-month follow-up, and a telephone interview with the owner 3 years after the second surgery confirmed that the dog remained free of clinical signs. This case suggests that cSIS may serve as a feasible reinforcement biomaterial for large diaphragmatic defects where primary closure alone is insufficient, although conclusions drawn from a single case remain preliminary, and surveillance for marginal reherniation is warranted.