Penetrating trauma to the diaphragm - Natural history and ultrasonographiccharacteristics of untreated injury in a pig model

Hypothesis: Recent use of minimally invasive techniques to evaluate the che st and abdomen in patients with penetrating thoracoabdominal trauma has led to the discovery of many occult diaphragm injuries. Surgical repair of the se injuries is relatively straightforward. However, diagnosis can be diffic ult, and the natural history of these injuries is controversial. By develop ing a penetrating diaphragm injury model, the ultrasonographic characterist ics and natural history of this injury can be better understood. Setting: Surgical laboratory of a tertiary care hospital. Subjects: Seven pigs (Sus scrofa), weighing between 55 and 80 kg, received a 3-cm right-sided (n=3) or left-sided (n=4) diaphragm injury via thoracosc opy. Interventions: Thoracoabdominal x-ray and ultrasonographic examinations wer e performed preoperatively; at 2, 4, 8, and 12 weeks postoperatively; and w hen symptoms related to the diaphragm injury occurred. At 12 weeks, or at t he time of earlier death, a postmortem thoracoabdominal examination was per formed. Main Outcome Measures: x-Ray and ultrasonographic characteristics, and evid ence of wound healing, in a penetrating diaphragm injury model. Results: Perioperative recovery occurred in all pigs. No pigs had radiograp hic evidence of immediate postoperative herniation. Pigs in the right-sided injury group died early (less than or equal to 10 days postoperatively). A t the time of death, x-ray and ultrasonographic examination revealed hollow viscus herniation into the thorax (n=2). Pigs in the left-sided injury gro up remained asymptomatic, without radiographic evidence of herniation, alth ough subtle ultrasonographic signs of diaphragm injury were seen at the 2-w eek (n=2), 4-week (n=2), and 8-week (n=3) intervals. Postmortem examination of the right-sided injury group revealed the liver afforded no protection against herniation. Right-sided defects (n=3) did not change size or charac ter despite small-bowel herniation. Conversely, the left hemidiaphragm was well protected by the relatively fixed liver, spleen, and large stomach. Th e 4 left-sided defects (100%) spontaneously healed. Conclusions: We developed a penetrating diaphragm injury model with high an d low risk of herniation.:Ultrasonography may prove to be an important diag nostic adjunct in evaluating diaphragm injuries with and without herniation . Moreover, since the "protected" diaphragm injuries in our model healed sp ontaneously, a role may exist for the nonoperative treatment of diaphragm i njuries in clinical practice. This pig model may prove useful in further de fining future management and repair techniques for such injuries.