Penetrating trauma to the diaphragm: natural history and ultrasonographic characteristics of untreated injury in a pig model.

HYPOTHESIS: Recent use of minimally invasive techniques to evaluate the chest and abdomen in patients with penetrating thoracoabdominal trauma has led to the discovery of many occult diaphragm injuries. Surgical repair of these injuries is relatively straightforward. However, diagnosis can be difficult, and the natural history of these injuries is controversial. By developing a penetrating diaphragm injury model, the ultrasonographic characteristics 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 thoracoscopy.
INTERVENTIONS: Thoracoabdominal x-ray and ultrasonographic examinations were performed preoperatively; at 2, 4, 8, and 12 weeks postoperatively; and when symptoms related to the diaphragm injury occurred. At 12 weeks, or at the time of earlier death, a postmortem thoracoabdominal examination was performed. MAIN OUTCOME MEASURES: x-Ray and ultrasonographic characteristics, and evidence of wound healing, in a penetrating diaphragm injury model.
RESULTS: Perioperative recovery occurred in all pigs. No pigs had radiographic evidence of immediate postoperative herniation. Pigs in the right-sided injury group died early (</=10 days postoperatively). At the time of death, x-ray and ultrasonographic examination revealed hollow viscus herniation into the thorax (n = 2). Pigs in the left-sided injury group remained asymptomatic, without radiographic evidence of herniation, although subtle ultrasonographic signs of diaphragm injury were seen at the 2-week (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 character despite small-bowel herniation. Conversely, the left hemidiaphragm was well protected by the relatively fixed liver, spleen, and large stomach. The 4 left-sided defects (100%) spontaneously healed.
CONCLUSIONS: We developed a penetrating diaphragm injury model with high and low risk of herniation. Ultrasonography may prove to be an important diagnostic adjunct in evaluating diaphragm injuries with and without herniation. Moreover, since the "protected" diaphragm injuries in our model healed spontaneously, a role may exist for the nonoperative treatment of diaphragm injuries in clinical practice. This pig model may prove useful in further defining future management and repair techniques for such injuries.