Diaphragm

Kevin M. Schuster and Kimberly A. Davis

INTRODUCTION

The diaphragm, the most important muscle of respiration, separates the thorax and the abdomen. It can be injured in isolation or involved with injury in either body cavity, and the most challenging concern is the identification of injury. Initially the injury may be asymptomatic with later development of herniation and strangulation of the stomach or other viscera.

HISTORY

Traumatic diaphragmatic rupture was first reported by Sennertus in 1541, and Ambroise Paré was the first to report a series of diaphragmatic perforations found at autopsy.¹ Paré also described gastric and colonic incarceration in a ruptured diaphragm and the consequences.² The diagnosis was made in an antemortem fashion for the first time by Bowditch in 1853,³ and it was not until 1886 that Riolfi was credited with the first successful repair.⁴ The first acute repair by Walker in 1899 was in a patient who had been struck by a falling tree.⁵ The largest early review of 378 diaphragmatic hernias was by Hedblom in 1925.⁴

ANATOMY

The diaphragm is a dome-shaped musculofibrous septum separating the abdomen and thorax. It is bounded above by both pleural spaces and the pericardium, which is attached to the central tendon. Structures immediately adjacent to the inferior side of the diaphragm include the liver, spleen, stomach, and to varying degrees the colon, omentum, and small bowel. The origin of the diaphragm includes the lower sternum, lower six costal cartilages and adjacent ribs, and medial and lateral lumbocostal arches. The crura, two tendinous pillars, arise from the lumbar vertebrae. The insertion of the diaphragm is into the central tendon, an aponeurosis, located at the top of the dome, oriented transversely, and separated into three segments. At rest the diaphragm rises to the level of the fourth intercostal space on the right and the fifth intercostal space on the left. At maximal contraction the diaphragm descends two rib spaces bilaterally. The aorta passes behind the diaphragm and between the crura where it has no attachments. Along with the aorta the thoracic duct and azygous vein pass through this opening. The esophagus traverses the esophageal hiatus mostly composed of the right crus along with the vagus nerves. The inferior vena cava passes through its hiatus at the junction of the right and middle leaflets of the central tendon to which it may be adherent (Fig. 28-1).

FIGURE 28-1 View of the diaphragm from the abdomen including the aortic, esophageal, and caval hiatuses. IVC = inferior vena cava.

The blood supply to the diaphragm is multiply redundant making necrosis extremely rare.⁶ The major source of blood supply to the abdominal side of the diaphragm is the inferior phrenic arteries, which are branches of the abdominal aorta or celiac trunk. Additional blood supply is from the superior phrenic, pericardiophrenic, musculophrenic, and the intercostal arteries. Lymphatic drainage is rich on both sides of the diaphragm with the peritoneal surface the major contributor to peritoneal lymphatic drainage. Innervation is principally through the phrenic nerves with some contribution of the sixth or seventh intercostal nerves to the costal region of the diaphragm. Both phrenic nerves enter the diaphragm near the anterior border of the central tendon. These nerves give branches along the thoracic surface of the diaphragm before penetrating it to spread branches in anterior, posterior, and lateral directions. The nerves are often buried deep in the muscle, and one should not rely on visualizing the nerves in order to choose incisions in the diaphragm. Safe diaphragm incisions that protect the phrenic nerves are depicted in Fig. 28-2.

FIGURE 28-2 Surgical incisions on the diaphragm. (A) An incision with a risk of total paralysis of the diaphragm. (B) A preferred incision with minimal risk of nerve injury. (C, D) Incisions in safe areas, but with small risk of nerve injury. (Reprinted from Anraku M, Shargall Y. Thoracic Surgical Clinics Vol. 19 Surgical conditions of the diaphragm: anatomy and physiology, Page 422., Copyright 2009, with permission from Elsevier.)

PHYSIOLOGY

The diaphragm is a vital muscle involved in the function of both the digestive and respiratory systems. It participates in breathing, swallowing, coughing, defecation, emesis, micturition, parturition, sneezing, and vocalization.⁷ In humans it is the most important muscle of inspiration and can independently generate negative intrapleural pressure sufficient for respiration.⁸ The innervation of the diaphragm is centrally unified in the spinal cord, and the entire diaphragm from the crura to the lateral margins has motor neuron origins intermingled within the spinal cord.⁹ The crural components, however, may have their function overridden through peripheral or central mechanisms related to function of the gastrointestinal tract.

Perforation of the diaphragm can lead to acute changes in physiology. The displacement of intra-abdominal viscera into the chest under the influence of the pressure gradient between the abdomen and the chest may compromise both cardiac and respiratory function. Cardiac function can become deranged due to reduced ventricular filling leading to decreased cardiac output. Significant compression of the pulmonary parenchyma can lead to impaired ventilation on the ipsilateral side, and, if more severe, mediastinal shift and compression of the contralateral lung. As with any herniation of portions of the gastrointestinal tract, sequelae such as ischemia, necrosis, and perforation may develop. Unfortunately, there are no long-term outcome data that describe diaphragmatic function after repair for trauma. There are many reports of delayed repairs of diaphragmatic injuries, and this suggests that repair is durable and has little impact on either pulmonary or gastrointestinal tract function.

INCIDENCE

The reported incidence of injuries to the diaphragm after blunt trauma ranges from less than 1 to 7% and from 10 to 15% in victims of penetrating trauma.^10–12 This wide range stems from an inability to identify injuries treated at nontrauma centers, death prior to hospital admission, and missed injuries after admission to a trauma center despite complete evaluation. A query of the National Trauma Data Bank (NTDB) for the years 2002–2007 demonstrated an incidence of 0.43% or 10,128 injuries among 2,349,554 patients (Table 28-1).¹² In a study at one center that included data from the medical examiner, survival to hospital admission was 87% indicating a relatively small fraction of patients are missed due to death.¹³ The highest rate of injury occurs in patients sustaining penetrating trauma to the thoracoabdominal region where the incidence of diaphragm injury has been reported to range as high as 42%.¹⁴ In one study of asymptomatic patients with penetrating thoracoabdominal trauma an injury rate of 24% was documented when mandatory laparoscopy was performed.¹⁵

TABLE 28-1 Diaphragm Injury Statistics from the National Trauma Data Bank Years 2002 to 2007

MECHANISM OF INJURY AND PATHOPHYSIOLOGY

Approximately 75% of diaphragmatic hernias occur on the left side.¹⁰ It has been postulated that this is secondary to a congenital weakness of the left side of the diaphragm.¹¹ Many authors, however, have found no evidence for a congenital weakness of one side of the diaphragm and attribute the tendency for blunt rupture to occur on the left to protection of the right side by the liver.¹⁶ Others have reported no difference in incidence between the left and right sides in autopsy studies.¹⁷ Although less common, right-sided injuries are often associated with ipsilateral high energy impacts. Similarly the most common mechanism on the left is a left-sided impact though it is often of much lower energy.¹⁸ The higher energy impact necessary to cause right-sided rupture may explain the difference between the autopsy study and the clinical studies because high energy right-sided impacts would more commonly cause death. Similarly, penetrating injury to the diaphragm has a left-sided predilection secondary to prevalence of right-handed assailants.^19,20 Penetrating wounds typically result in a smaller injury, but these injuries may enlarge over time and eventually cause acute incarceration and/or strangulation.^19–21

PRESENTATION

Grimes classified diaphragmatic injuries into the following three phases of presentation: acute, or during the period of recovery from injury; latent, an asymptomatic period; and obstructive, during which time herniation leads to cardiovascular compromise or gastrointestinal obstruction or perforation.²² Presentation in the acute phase is often dominated by symptoms from concomitant injuries. Patients may have minimal signs of external injury or be experiencing severe shock and respiratory compromise that may or may not be directly related to the diaphragmatic injury. In the less severely injured, possible signs and symptoms include shoulder pain, epigastric pain, vomiting, dyspnea, absent breath sounds, or bowel sounds heard during auscultation of the chest.²³ It is likely that the advent of routine helical computed tomography (CT) scanning has decreased the incidence of missed injuries after blunt trauma.²⁴ Several case series have reported 3–15% of cases presenting in the late or obstructive phase.^25,28

In the latent phase herniation may be discovered as an incidental finding on radiographic studies performed for other reasons. Symptomatic patients presenting in the obstructive phase often experience nausea, vomiting, early satiety, pain, dyspnea, postprandial pain, or generalized chest and abdominal pain. These symptoms may be intermittent or progressive. Patients may also present in extremis with signs and symptoms of septic shock due to ischemia or perforation related to strangulation of the stomach or colon or with cardiovascular collapse due to compression similar to a tension pneumothorax.^21,26

ASSOCIATED INJURIES

Blunt diaphragmatic injury typically involves high energy compression-type mechanisms, and associated injuries are common. Traumatic brain injury is present in half of the patients and is predictive of mortality.²³ Other associated injuries include pelvic fractures, long bone fractures, and rib fractures. Intrathoracic injuries have included pneumothorax, pulmonary contusion, lung lacerations, blunt myocardial injury, and aortic rupture.^16,23,27 Solid organ injuries are the most common associated intra-abdominal injuries.^16,27,28

Penetrating injuries also have high rates of associated injuries, especially to intra-abdominal viscera, but including a hemothorax or pneumothorax, as well. Specific intra-abdominal organs typically injured with penetrating diaphragmatic injury include the upper abdominal organs.^14,19,23,28 A list of associated injuries identified in patients with diaphragm injury in the NTDB is presented in Table 28-2.

TABLE 28-2 Injuries Associated with Diaphragmatic Injury from the National Trauma Data Bank Years 2002 to 2007

DIAGNOSIS AND DIAGNOSTIC TESTS

Diaphragmatic rupture is often asymptomatic, or the presentation is dominated by concomitant injury making an immediate diagnosis difficult. Information about the mechanism of injury should be obtained from prehospital personnel. In patients involved in motor vehicle crashes, information about the velocity and direction of impact, the severity of vehicular damage, the presence of passenger-compartment intrusion, and the presence or absence of deformity of the steering wheel will be helpful to indicate the severity of the crash. Injuries are graded according to the American Association for the Surgery of Trauma-Organ Injury Scale for Diaphragmatic Injuries (Table 28-3).²⁹

TABLE 28-3 Grading of Diaphragmatic Injuries

In penetrating trauma any injury to the thoracoabdominal area should raise suspicion for a potential diaphragmatic injury. Although most stab wounds that result in diaphragmatic injury will be in this region, gunshot wounds that injure the diaphragm may occur anywhere on the trunk.²⁶

The initial diagnostic study for any patient where there is suspicion for injury to the diaphragm is a plain chest x-ray. Sensitivity of a chest x-ray for diaphragmatic injury has been reported to be in the range of 27–62% for left-sided injuries and 18–33% for right-sided injuries.³⁰ The finding pathognomonic for blunt and some penetrating injuries of the hemidiaphragm is visualization of a hollow viscus above it with or without an area of constriction at the level of the diaphragm. Identification of the stomach above the diaphragm is often facilitated by the abnormal position of a nasogastric or orogastric tube (Fig. 28-3). Loss of a smooth contour, ipsilateral pleural effusion, ipsilateral elevated hemidiaphragm, and mediastinal shift represent nonspecific findings associated with diaphragmatic herniation. Contrast swallow studies and enemas as well as fluoroscopy have been used in the past and are potentially helpful (Fig. 28-4); however, their use has been largely supplanted by cross-sectional imaging techniques.

FIGURE 28-3 Chest radiograph demonstrating herniated stomach with gastric catheter in place.

FIGURE 28-4 Contrast enema with splenic flexure identified above the diaphragm.

Helical CT for the detection of blunt diaphragmatic disruption has a reported sensitivity of 71–100% and specificity of 75–100%, and sensitivity improves to 78–100% if only left-sided injuries are included.³¹

Stay updated, free articles. Join our Telegram channel

Join