HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ko, J. P. Articles by Primack, S. L. Search for Related Content PubMed Articles by Ko, J. P. Articles by Primack, S. L.

Invited Commentary

Department of Radiology, New York University Medical Center, New York, New York

Steven L. Primack, MD

Department of Radiology, Oregon Health Sciences University, Portland, Oregon

	Commentary

Top Commentary References

 
The diagnosis of traumatic diaphragmatic injuries is challenging. Chest radiographs are usually abnormal but are nonspecific in the majority of cases. CT scans are obtained in most patients with major trauma by using single–detector row and more recently multi–detector row spiral CT scanners. While diaphragmatic injury can be diagnosed or excluded with CT, the specific findings may be difficult to confidently detect. MR imaging, although accurate, is difficult to perform in patients who are potentially clinically unstable and therefore is practical for evaluating only a small percentage of patients who have acutely sustained major trauma.

Diaphragmatic injuries can be overlooked when there are concomitant injuries to the viscera such as the spleen, liver, or kidneys and bony structures. In addition, acute diaphragmatic lacerations may or may not be accompanied by herniation of the abdominal viscera into the thorax. While the CT diagnosis of visceral herniation is usually straightforward, diaphragmatic laceration without herniation is frequently more difficult to detect but is still essential to diagnose because of the risk of delayed herniation and incarceration of abdominal viscera. For this reason, diaphragmatic laceration, with or without abdominal visceral herniation, is surgically repaired.

A practical approach for imaging of diaphragmatic injury is essential. In the preceding article, Iochum et al (1) have summarized the important radiographic, CT, and MR imaging findings for diagnosing traumatic diaphragmatic injuries. Prior to discussing specific imaging findings, they provide a concise review of the anatomy of the diaphragm. A large portion of the diaphragm is well depicted at CT, but the anterior or costal portions of the diaphragm are difficult to identify on axial images. It is also important to realize that only portions of the diaphragm outlined by fat will be evident on axial images. Therefore, areas of the diaphragm that abut the liver or spleen may not be visible, particularly if intravenous contrast material is not administered.

Although usually nonspecific, chest radiographs can be useful for the diagnosis of diaphragmatic rupture with herniation. A specific diagnosis can be made if herniation of the stomach or colon, possibly with an associated waistlike constriction of the herniated organs at the site of diaphragmatic injury (collar sign), or the presence of a nasogastric tube above the left hemidiaphragm is identified. However, associated findings such as atelectasis, pleural fluid, and pulmonary contusion often obscure visualization of the diaphragm.

Since CT is used to evaluate trauma patients with increasing frequency, knowledge of the CT appearance of diaphragmatic injury is essential. Diagnostic findings include abrupt discontinuity of the diaphragm and herniation of abdominal viscera or organs into the thorax with a collar sign (2). Another recently described finding termed the dependent viscera sign is also discussed by Iochum et al (1). A limitation of axial CT is that many tears may be axially oriented and difficult to detect. Sagittal and coronal reformation images often depict the outline of the diaphragm better than axial sections and may increase sensitivity, particularly for the collar sign in right-sided diaphragmatic injuries (3,4). However, it is unclear at this time if the overall accuracy for diaphragmatic rupture will significantly improve, although the use of multi–detector row spiral CT may increase sensitivity and specificity.

Multi–detector row CT technology enables improved spatial and temporal resolution secondary to the multiple-row detector array and faster gantry rotation times (5,6). Imaging of the entire thorax can be performed in a single breath hold by using a technique that makes possible data reconstruction into axial sections with thicknesses on the order of 1.0–2.5 mm. These thin axial sections reconstructed at overlapping intervals improve the quality of multiplanar reformation images. Secondary to their speed and flexibility, multi–detector row CT scanners are being used in the evaluation of the emergency room trauma patient (7).

The accuracy of CT has varied in reported studies, with sensitivities and specificities of approximately 70%–80% and 80%–90%, respectively (8). False-negative results occur because of obscuration of the diaphragm by adjacent hemothorax or intraabdominal blood or because the location of the diaphragmatic injury prevents adequate visualization. False-positive interpretation may result from misinterpretation of incidentally detected small congenital Bochdalek hernias or acquired posterior diaphragmatic defects, which have been described particularly in older patients.

The use of MR imaging in the evaluation of diaphragmatic rupture will be enhanced with improvements in physiologic patient monitoring devices and faster imaging sequences that will decrease respiratory motion (9). The contrast resolution of MR imaging is superior to that of CT, and the high signal intensity of abdominal and mediastinal fat on T1-weighted images enables demonstration of the low-signal-intensity hemidiaphragm. The multiplanar capabilities of MR imaging facilitate visualization of the diaphragmatic contour.

In summary, the diagnosis of traumatic diaphragmatic injury can be difficult. Diaphragmatic lacerations without herniation may be subtle, but detection is important because of the risk of delayed herniation and incarceration of viscera. One obstacle to the diagnosis of diaphragmatic injuries is that most radiographs and CT scans in trauma patients are not obtained specifically for evaluation of the diaphragm. Therefore, since most patients have accompanying injuries, the technique of the imaging studies and clinical attention may be focused on other thoracic and abdominal organs or body regions. However, the evaluation of the diaphragm has improved with spiral CT and should continue to improve with the flexibility provided by multi–detector row spiral CT technology. Volumetric data obtained from a multi–detector row CT study for routine evaluation of the thorax or abdomen in a trauma situation may be reconstructed into high-resolution sections and subsequently used to create high-quality multiplanar reformations. It is imperative to carefully assess the diaphragm in multiple planes in all chest and abdominal CT studies of patients who have sustained major trauma. This in combination with laparoscopic investigation in high-risk patients (10) will likely decrease the number of patients with missed diaphragmatic lacerations.

	References

Top Commentary References

 

1. Iochum S, Ludig T, Walter F, Sebbag H, Grosdidier G, Blum AG. Imaging of diaphragmatic injury: a diagnostic challenge? RadioGraphics 2002; 22:S103-S118.
2. Worthy SA, Kang EY, Hartman TE, Kwong JS, Mayo JR, Müller NL. Diaphragmatic rupture: CT findings in 11 patients. Radiology 1995; 194:885-888.[Abstract/Free Full Text]
3. Killeen KL, Mirvis SE, Shanmuganathan K. Helical CT of diaphragmatic rupture caused by blunt trauma. AJR Am J Roentgenol 1999; 173:1611-1616.[Abstract]
4. Israel RS, McDaniel PA, Primack SL, Salmon CJ, Fountain RL, Koslin DB. Diagnosis of diaphragmatic trauma with helical CT in a swine model. AJR Am J Roentgenol 1996; 167:637-641.[Abstract/Free Full Text]
5. Klingenbeck-Regn K, Schaller S, Flohr T, Ohnesorge B, Kopp AF, Baum U. Subsecond multi-slice computed tomography: basics and applications. Eur J Radiol 1999; 31:110-124.[CrossRef][Medline]
6. Hu H. Multi-slice helical CT: scan and reconstruction. Med Phys 1999; 26:5-18.[CrossRef][Medline]
7. Weishaupt D, Grozaj AM, Willmann JK, Roos JE, Hilfiker PR, Marincek B. Traumatic injuries: imaging of abdominal and pelvic injuries. Eur Radiol 2002; 12:1295-1311.[CrossRef][Medline]
8. Shanmuganathan K, Killeen K, Mirvis SE, White CS. Imaging of diaphragmatic injuries. J Thorac Imaging 2000; 15:104-111.[CrossRef][Medline]
9. Mirvis SE, Shanmuganathan K. MR imaging of thoracic trauma. Magn Reson Imaging Clin N Am 2000; 8:91-104.[Medline]
10. Murray JA, Demetriades D, Asensio JA, et al. Occult injuries to the diaphragm: prospective evaluation of laparoscopy in penetrating injuries to the left lower chest. J Am Coll Surg 1998; 187:626-630.[CrossRef][Medline]

This Article Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ko, J. P. Articles by Primack, S. L. Search for Related Content PubMed Articles by Ko, J. P. Articles by Primack, S. L.