The diaphragm is an extremely resilient dome-shaped muscle. The fibers of the diaphragm surround the central tendon, which is an aponeurotic sheath that separates the abdominal and thoracic cavities. Arching from the first through third lumbar vertebrae posteriorly, the diaphragm attaches to the ribs laterally and to the posterior aspect of the lower sternum. The crura of the diaphragm decussate to form the aortic and esophageal hiatus through which passes the aorta, thoracic duct, azygos vein, esophagus, and the vagi. The caval hiatus is located laterally to the right and transmits the inferior vena cava (IVC) at approximately the eighth thoracic vertebral level. The liver is adjacent to the undersurface of the diaphragm on the right along with the right kidney, whereas the spleen, stomach, and left kidney border the inferior aspect of the diaphragm on the left. Multiple branches from the aorta, pericardiophrenic arteries, and the intercostals supply the diaphragm. The phrenic nerves innervate the diaphragm arising from the third through the fifth cervical roots and travel along the lateral aspect of the mediastinum on the right and the pericardium on the left.

There is significant variability in the location of the diaphragm during the respiratory cycle. It fluctuates between the fourth and eighth intercostal spaces during inspiration and expiration—a fact of vital importance in trauma. As the diaphragm moves so does the closely associated organs, putting them at risk with trauma to the lower chest. Because of this risk, the space from the costal margin up to thoracic spine 4 (T4) anteriorly, T6 laterally, and T8 posteriorly is considered the thoracoabdominal region. This region requires evaluation for both abdominal and thoracic injury as well as injury to the diaphragm.

Physiologically, the diaphragm is an integral part of the respiratory cycle. By its motion, the diaphragm creates a negative intrathoracic pressure that enhances the tidal volumes generated by the lung. In this function, the diaphragm has more contribution than the rib cage. The creation of negative intrathoracic pressure also allows the diaphragm to play a major role in the venous return to the right heart. The fall in pressure during inspiration decreases right atrial pressure, which enhances both superior vena cava (SVC) and IVC blood flow. Because of the ability of the abdominal venous compartment to be a capacitor when hypervolemic but collapsible when hypovolemic, inspiration does not always result in increased flow to the heart. Increases in abdominal pressures produced by active diaphragmatic descent can increase the total IVC venous return by enhancing the splanchnic IVC
flow under relatively hypervolemic conditions, but decrease the total IVC venous return by impeding the nonsplanchnic IVC flow under hypovolemic conditions.

Injury to the diaphragm can therefore interfere with the normal physiology of this organ. Defects resulting from penetrating trauma may produce hemopneumothoraces, which impairs the ability of the diaphragm to appropriately contract and produce negative pressure. Herniation of abdominal contents into the thoracic cavity after rupture of the diaphragm can increase pressure on the IVC as it traverses the hiatus. Such pressure can lead to impaired venous return to the heart and cardiovascular collapse. Of interest is the observation that in a patient mechanically ventilated with positive pleural pressure, there is no pressure gradient so intra-thoracic migration may not occur and the diaphragmatic rupture may be missed. The remainder of the chapter focuses on the identification of such injuries after both blunt and penetrating trauma and the treatment options.

Blunt trauma accounts for 10% to 30% of traumatic diaphragmatic ruptures in North American urban trauma centers.¹ Overall, its incidence is rather low and ranges substantially depending on the series. It has been reported as low as 0.8% to as high as 7%.²,³ The left side is affected more often than the right side. The reasoning for this is not clear and it may be due to a combination of under diagnosis, underreporting, true congenital weakening, or effective and protective buffering by the liver. In a recent review of 65 patients with traumatic rupture of the diaphragm, Mihos et al. reported left-sided ruptures in 43 patients (66%) with 86% of the ruptures resulting from blunt trauma.⁴ Similar results were seen by Shah et al. in a review of 980 patients, where left-sided rupture was reported in 68.5% of patients.⁵

Motor vehicle collisions and falls from heights are the most common cause of blunt diaphragmatic injuries (BDIs).⁶,⁷ An acute increase in intra-abdominal pressure results in rupture of the diaphragm. Such forces are quite severe, which explains the significant association with other injuries. In a series of 52 patients with blunt diaphragmatic injury, blunt thoracic injuries (multiple rib fractures and pneumothoraces) accounted for the most frequent associated injuries (90%). Long bone fractures and closed head injuries were seen in 75% and 42% of the patients, respectively. Intra-abdominal injuries that were identified included splenic in 60% of patients, hepatic in 35% of patients, and to the kidney, pancreas, and small bowel in 10% to 12% of patients.⁸ Moreover, right side diaphragm injuries were more commonly associated with other injuries compared to the left. In one series, there was a 100% incidence on the right.⁹ All these factors can assist in making the diagnosis of a BDI in these patients.

The diagnosis of BDI is very difficult even with the highest index of suspicion. Previously, these injuries were diagnosed intraoperatively or at postmortem. Up to two thirds of conservatively managed patients had a missed diaphragm injury. In the largest reported series (160 patients) of blunt diaphragmatic ruptures from six university centers in Canada, the rupture was diagnosed preoperatively in only 37.1% of patients operated for other indications.⁶ The goal of early diagnosis is to avoid the significant morbidity and mortality from visceral herniation and strangulation.

When possible, a thorough history and physical examination can assist with this challenging diagnosis. It is useful to recall that most ruptures are associated with crush, falls, and particularly side impact motor vehicle collisions. This history of the trauma along with patient complaints of upper abdominal pain and possibly shortness of breath should stimulate one to consider the diagnosis of BDI. It is also important to remember that these patients may have no complaints at all or may be in shock. Physical findings of decreased breath sounds or decreased chest expansion or the detection of bowel sounds in the chest should heighten one’s concern. Once the diagnosis is entertained, then further radiographic studies and interventions can assist to confirm the diagnosis.

Currently, there is no ideal radiologic tool for the diagnosis of the occult diaphragmatic insult. The diagnosis relies on the demonstration of visceral herniation rather than the actual visualization of the diaphragmatic tear. Options that are currently available to evaluate for diaphragm injuries include chest x-rays, upper and lower gastrointestinal contrast studies, thoracoabdominal computed tomography (CT), sonography, diagnostic peritoneal lavage, liver scintigraphy, contrast or air peritoneography, and magnetic resonance imaging (MRI). Other than the first three modalities, there is little evidence to support the use of any of the latter interventions. Sonography is operator dependent and therefore, unreliable, and MRI tends to be impractical in the acute trauma setting. The focus of this chapter is on the plain film, contrast studies, and CTs.

The radiographic workup for a blunt diaphragm injury should always begin with a plain chest x-ray because this is quick and easily obtained in the trauma bay. The initial chest x-ray may show visceral herniation, elevation of the diaphragm, loss of the diaphragmatic shadow, irregularity of the apparent contour of the diaphragm, or a pleural effusion. A nasogastric tube should be placed because its presence in the left chest cavity is pathognomonic for left diaphragmatic rupture and gastric eventration into the left thorax. Unfortunately, up to half the number of
the patients with this injury will have a normal chest x-ray. Those patients with abnormal chest radiographs may have other chest pathology such as pulmonary contusions and hemothoraces that can mimic a diaphragm injury. Therefore, if there continues to be suspicion for a BDI then further evaluation should be pursued.

Contrast studies may be helpful in both the acute and chronic situations. Both the upper gastrointestinal series and barium enema can identify visceral herniation through a diaphragm injury. Unfortunately, injuries may be missed if the bowel contents remain intraperitoneal. Consequently, CT has found a role in the diagnosis, given its overall increased sensitivity after blunt trauma.

CT scan is currently the diagnostic modality of choice in stable patients with blunt thoracoabdominal injuries. It has the benefit of evaluating for other chest or abdominal pathology that may require surgical intervention. Its specific accuracy in identifying BDI, however, is variable and often disappointing especially when typical chest x-ray findings are absent.¹⁰,¹¹ The sensitivity suffers on the right side because the liver obscures the view and often precludes visceral herniation. It remains to be seen whether the advent of helical (spiral) CT with three-dimensional reconstruction can enhance its diagnostic utility for blunt diaphragmatic injury. Until studies are performed to determine the reliability of the helical CT, further interventions must be pursued if the diagnosis of diaphragm injury is still being entertained.

Currently, either thoracoscopy or laparoscopy remains the diagnostic tool of choice for diaphragmatic injuries, both being much more reliable than nonoperative modalities.⁴,¹² Thorocoscopy is mainly helpful in the chronic situation or when abdominal injuries have been ruled out. If any question remains about intra-abdominal pathology, then laparoscopy is more appropriate. Tension pneumothorax remains the main potential complication in the use of laparoscopy in patients with diaphragmatic injuries. Fundamentally, the comfort level of the surgeon should dictate which approach is taken.