The word diaphragm is the term for the large muscle dividing the thorax from the abdomen in mammals. It draws on the term’s Latin and Greek origins and encompasses its true definition as a barricade.
The diaphragm performs an important function in the human body—regulating breathing via its contraction. The diaphragm consists of peripheral muscles that attach to the rib cage, extending to the lumbar vertebra posteriorly, giving it a domed shape. As we inhale, the diaphragm contracts and is drawn into the abdominal cavity while pulling the pleura of the thoracic cavity inferiorly. This movement causes the pleural pressure and alveolar pressure to drop, allowing air to inflate the lungs. As we exhale, the diaphragm relaxes and returns to its resting dome-shaped position.1
Disorders of the diaphragm
Anatomic disorders of the diaphragm can be classified as congenital or acquired/traumatic. Congenital disorders are secondary to failure of proper embryologic development. They often are diagnosed in the neonatal period and carry a mortality rate of 45 to 50 percent, secondary to hypoplasia of the lung of the affected side.2
Traumatic diaphragm injuries can be caused by either penetrating or blunt mechanisms. Blunt traumatic injury of the diaphragm has an incidence ranging from 1 to 7 percent and is considered a marker of severe injury with other concomitant injuries (thoracic aorta, lung, spleen, hollow viscus, bladder, and pelvis).3,4 Shearing of the stretched membrane, avulsion of the diaphragm from its attachment points, and sudden transmission of forces through the viscera are postulated mechanisms of traumatic diaphragm rupture in the setting of blunt trauma.2
In 1974, Orville Grimes, MD, described three clinical phases of diaphragmatic injuries: the acute phase at time of injury; a latent phase that may be asymptomatic but evolve into a gradual process of herniation of abdominal contents; and an obstructive phase as a result of visceral or bowel herniation, incarceration, obstruction, strangulation, and possible rupture.5
Unfortunately, there is not a pathognomonic sign for diaphragm injury. In general, symptoms are dependent on the size of the muscle defect and the organs herniated into the chest cavity. Computed tomography is the imaging modality of choice with findings of diaphragm discontinuity, intrathoracic herniation of abdominal viscera, and collar sign (constriction of herniated abdominal viscera) to suggest diaphragm injury.6
Prevalence of diaphragm injuries
To examine the occurrence of blunt diaphragm injuries in the National Trauma Data Bank® (NTDB®) research admission year 2016, medical records were searched using mechanism of injury and International Classification of Diseases, 10th Revision Clinical Modification codes. Specifically searched were records that contained a mechanism of injury as blunt along with a diagnosis code of S27.80 (injury of the diaphragm). A total of 1,266 records were found, of which 1,033 records contained a discharge status, including 408 patients discharged to home, 296 to acute care/rehab, and 107 to skilled nursing facilities; 222 died. Of these patients, 67 percent were male, on average 45.1 years of age, had an average hospital length of stay of 13.8 days, an intensive care unit length of stay of 11.7 days, an average injury severity score of 32.2, and were on the ventilator for an average of 8.9 days (see Figure 1). Of those patients tested, 23 percent (176 out of 755) were over the legal limit for alcohol. This group of patients had some of the highest injury severity scores, lengths of stay, and mortality rates as compared with patients with other injuries described in previous Bulletin articles.
Figure 1. Hospital Discharge Status
