Diaphragmatic Rupture

Traumatic diaphragmatic injuries occur in .8 to 8% of patients with blunt abdominal trauma or it can be rarely caused by penetrating injuries such as gunshot wounds or stab injuries [1]. Mechanisms of injury are lateral impaction and shearing of diaphragm due to distortion of chest wall or direct frontal impaction which leads to increase intra abdominal pressure [1]. Diaphragmatic ruptures commonly originate at the musculotendinous junction. Injuries of left diaphragm are three times commoner than the right side following blunt trauma due to protective effect of liver on right hemidiaphragm or the relative weakness of left hemidiaphragm compared to the left [1, 2]. Associated injuries are seen in 52%- 100% of patients with diaphragms tears and common associated injuries are pelvic fractures (40%-55%), splenic injuries (60%) and renal injuries (2%). Liver injuries are seen in 93% of right side diaphragmatic injuries and 24% of left side tears. Thoracic injuries such as pneumohemothoraces and rib fractures seen in 90% patients and aortic injuries are reported in 5% [1]. Chest radiography is valuable in the acute phase of diaphragmatic injury despite technical difficulties. In acute phase the chest radiograph can be normal in one quarter of the patients [3]. Specific features in diaphragmatic rupture are intrathoracic herniation of hollow viscus (stomach, colon, small bowel) through the defect with or without a constriction of hollow viscera at the site defect (collar sign) and visualization of the nasogastric tube above the left hemidiaphragm. Position of the nasogastric tube indicate the level of gastric fundus and does not show the level of the diaphragm or the tear. Findings which suggest a hemidiaphragmatic injury are elevation of the diaphragm, distortion or obliteration of the outline and contralateral shift of the mediastinum [1, 2]. Contrast studies are helpful in diagnosing in the latent or in obstructive phase as their use is limited in emergency situations. In barium studies intrinsic narrowing is seen in the wall of stomach or bowel at the level they pass through the diaphragmatic defect [2, 3]. On ultrasound scan the normal diaphragm is seen as a curved echogenic band at its interface with the liver and spleen. Sonogram may demonstrate the diaphragmatic defect and herniation of intra abdominal viscera through the defect, although it will be of limited value in the presence of subcutaneous emphysema and air within bowel [4]. Use of helical CT has improved the sensitivity and specificity of diagnosing diaphragmatic rupture. Findings that suggest hemidiaphragmatic tears are direct discontinuity of the diaphragm and Intrathoracic herniation of abdominal contents with a waist like constriction at the site of diaphragmatic tear, which is described as the “collar sign”. The collar sign is 100% specific for diaphragmatic rupture. Dependent viscera sign is demonstrated in majority of patients with ruptured diaphragm as they lie supine at CT scan examination. It is described as the herniated viscera which are no longer supported by ruptured diaphragm posteriorly fall to a dependant positions against posterior ribs [1, 2]. The pitfalls on CT examination which can cause false positive diagnosis are diaphragmatic eventration and diaphragmatic defects that present in 6% of normal individuals. MRI scan is reserved for patients with uncertain CT diagnosis and with delayed signs of diaphragmatic tear. The normal diaphragm appears as continuous hypointense band in both T1W and T2W sequences. Signs of diaphragmatic injury on MRI are similar to findings that are depicted of CT scan [1].