Gastrointestinal Imaging

What Is the Best Initial Imaging for a Suspected Traumatic or Congenital Diaphragmatic Hernia?

·
What Is the Best Initial Imaging for a Suspected Traumatic or Congenital Diaphragmatic Hernia?

A 34-year-old restrained driver arrives in the trauma bay following a high-speed motor vehicle collision. They are tachycardic with decreased breath sounds over the left hemithorax. A portable chest radiograph is equivocal but suggests an elevated left hemidiaphragm with a suspicious air-fluid level above it. You are concerned for a traumatic diaphragmatic injury with herniation of abdominal contents. The next imaging study you order is critical for definitive diagnosis and surgical planning. This article details the American College of Radiology (ACR) recommended workflow for suspected diaphragmatic hernia, whether traumatic, Bochdalek, or Morgagni. For this specific clinical scenario, the ACR designates CT chest and abdomen with IV contrast as Usually Appropriate.

Who Fits This Clinical Scenario for a Suspected Diaphragmatic Hernia?

This guidance applies to patients where there is a clinical suspicion of a defect in the diaphragm allowing abdominal contents to enter the thoracic cavity. This suspicion may arise in several distinct contexts:

  • Acute Trauma: Patients who have sustained significant blunt or penetrating trauma to the chest or abdomen, particularly from motor vehicle collisions or falls from height. Clinical signs may include respiratory distress, decreased breath sounds, or scaphoid abdomen.
  • Incidental Radiographic Findings: Patients who have an abnormal chest radiograph, often obtained for other reasons, that shows bowel gas, a soft tissue mass, or an air-fluid level in the chest, raising suspicion for a chronic or congenital hernia.
  • Vague or Chronic Symptoms: Patients presenting with nonspecific, often postprandial, chest pain, shortness of breath, or gastrointestinal symptoms like nausea and vomiting, where a diaphragmatic hernia is on the differential.

This workflow is specifically for evaluating the diaphragm itself. It is crucial to distinguish this scenario from other types of hernias that have entirely different imaging pathways. This guidance does not apply to:

  • Suspected abdominal wall hernias (e.g., umbilical, ventral, incisional, or Spigelian).
  • Suspected groin hernias (e.g., inguinal or femoral).
  • Suspected deep pelvic hernias (e.g., obturator or sciatic).

These other hernia types are evaluated with different imaging protocols, often involving focused ultrasound or CT of the abdomen and pelvis without chest imaging.

What Diagnoses Are You Working Up with Imaging for a Suspected Diaphragmatic Hernia?

The primary goal of imaging in this scenario is to confirm or exclude a diaphragmatic defect and characterize any herniated contents. The differential diagnosis is narrow but includes conditions with significantly different etiologies and management urgency.

Traumatic Diaphragmatic Injury (TDI): This is the most urgent consideration in the setting of trauma. Blunt force can cause a sudden increase in intra-abdominal pressure that tears the diaphragm, most commonly on the left side. Penetrating injuries can also directly violate the diaphragm. Herniation of the stomach, spleen, colon, or small bowel can lead to strangulation and ischemia, a surgical emergency.

Bochdalek Hernia: This is the most common type of congenital diaphragmatic hernia, resulting from a failure of the posterolateral diaphragmatic foramina to close during fetal development. While many are diagnosed in neonates, a small percentage present for the first time in adulthood, often as an incidental finding or with the onset of vague respiratory or gastrointestinal symptoms. They are far more common on the left side.

Morgagni Hernia: A less common congenital defect, this hernia occurs through an anteromedial defect just posterior to the xiphoid process. These are more often right-sided and typically contain omentum or a portion of the transverse colon. Like Bochdalek hernias, they can be discovered incidentally in adults.

Diaphragmatic Eventration: This is not a true hernia but can mimic one on imaging. It involves an abnormal elevation of a portion of the diaphragm due to congenital muscular weakness, without a true defect or tear. The diaphragm remains intact, which is a key distinguishing feature that imaging aims to clarify.

Why Is CT of the Chest and Abdomen with IV Contrast Usually Appropriate for This Presentation?

The ACR rates CT chest and abdomen with IV contrast as Usually Appropriate because it provides the most comprehensive and definitive evaluation for this clinical question. Its high spatial resolution and multiplanar reformatting capabilities are essential for directly visualizing the diaphragm and identifying defects.

CT excels at identifying the key diagnostic signs of diaphragmatic hernia. The “collar sign,” where herniated viscera are constricted at the level of the diaphragmatic defect, is a classic finding. CT can also show the herniated organ “falling” against the posterior chest wall when the patient is supine (the “dependent viscera” sign). Most importantly, CT definitively identifies which organs have herniated (stomach, colon, spleen, liver, omentum) and, with the use of intravenous contrast, can assess for signs of strangulation, such as bowel wall thickening, poor organ enhancement, or surrounding fluid and fat stranding. This information is critical for determining the urgency of surgical intervention.

Alternative studies are rated lower for specific reasons in this initial workup:

  • Radiography chest is rated May be appropriate. While it is often the first test performed and can be highly suggestive (e.g., showing a nasogastric tube tip coiled in the chest), it has low sensitivity. A normal chest radiograph does not exclude a diaphragmatic injury, especially a small or right-sided one where the liver can obscure the finding.
  • US abdomen is rated Usually not appropriate. While ultrasound can sometimes visualize the diaphragm, its utility is severely limited by overlying ribs and air-filled lungs and bowel, making it an unreliable tool for excluding a defect in adults.

The recommended CT study carries a radiation dose of ☢☢☢☢ (10-30 mSv). While significant, this risk is justified by the need for a rapid and accurate diagnosis in a potentially life-threatening condition. The use of IV contrast is crucial for evaluating organ perfusion and detecting ischemia. A non-contrast CT is also rated Usually Appropriate and can be used if there is a severe contrast allergy or renal contraindication, but it provides less information about visceral viability.

Once you’ve decided on this study, our protocol guide covers the technique, contrast, and reading principles: CT Chest/Abdomen/Pelvis with IV Contrast.

What Is the Downstream Workflow After a CT Scan for a Diaphragmatic Hernia?

The results of the CT scan directly guide the subsequent clinical pathway. The workflow branches based on the key findings of presence, type, and complication of the hernia.

  • Positive for Traumatic Diaphragmatic Injury: This finding necessitates an immediate surgical consultation. The presence of herniated viscera, especially with any signs of strangulation or ischemia on the contrast-enhanced CT, constitutes a surgical emergency requiring prompt repair to prevent irreversible organ damage.
  • Positive for Incidental Bochdalek or Morgagni Hernia: If an asymptomatic congenital hernia is found, the next step is typically a consultation with a thoracic or general surgeon for elective repair. While the risk of future strangulation in asymptomatic adult cases is debated, many surgeons recommend repair, particularly for larger defects or in younger patients.
  • Negative for Diaphragmatic Hernia: If the CT scan is definitively negative and the diaphragm is intact, the workup should pivot to other causes of the patient’s symptoms. In a trauma patient, this means carefully evaluating for other thoracic and abdominal injuries. In a patient with chronic symptoms, this may involve endoscopy, manometry, or further cardiac or pulmonary evaluation.
  • Indeterminate or Equivocal Findings: In rare cases, such as severe diaphragmatic eventration that is difficult to distinguish from a true hernia, further imaging may be considered. An MRI chest and abdomen, rated May be appropriate, can be a valuable problem-solving tool. Its superior soft-tissue contrast can sometimes better delineate the diaphragmatic muscle and differentiate a thinned but intact diaphragm from a true defect, without using ionizing radiation.

What Are the Common Pitfalls to Avoid in This Imaging Workflow?

Navigating the workup for a suspected diaphragmatic hernia requires vigilance to avoid several common pitfalls that can delay diagnosis or lead to misinterpretation.

  • Over-reliance on Chest Radiography: A normal or nonspecific chest x-ray can provide false reassurance. Small traumatic tears or hernias obscured by the liver on the right side can be easily missed. Maintain a high index of suspicion based on the clinical mechanism and exam, proceeding to CT even if the radiograph is unimpressive.
  • Omitting IV Contrast: In the absence of a strong contraindication, ordering a non-contrast CT can be a critical error. The key question in a symptomatic hernia is not just its presence, but its perfusion. IV contrast is essential to assess for strangulation, which dictates the urgency of surgery.
  • Misinterpreting Diaphragmatic Eventration: Mistaking a focal eventration for a true hernia can lead to an unnecessary surgical referral. Careful review of multiplanar CT images to trace the continuity of the thinned diaphragmatic muscle is key to making this distinction.
  • The Right-Sided Injury Blind Spot: Left-sided traumatic injuries are more common and often more obvious. Right-sided injuries are less frequent because the liver provides a protective buffer, but they can be more subtle on imaging. Scrutinize the right hemidiaphragm carefully in any major thoracoabdominal trauma.

If the CT findings are complex or the clinical picture does not match the imaging, escalation to a subspecialty radiologist or a multidisciplinary discussion with the surgical team is the appropriate next step.

Related ACR Topics and Tools

This article focuses on one specific clinical scenario. For a comprehensive overview of imaging for all types of hernias, from the abdominal wall to the groin, please see our parent guide. For tools to help with ordering, protocoling, and explaining studies to patients, see the resources below.

Frequently Asked Questions

Why not just start with a chest x-ray for every patient with suspected diaphragmatic hernia?

A chest x-ray is often the very first image obtained, especially in trauma, and it is rated as *May be appropriate*. It can sometimes show classic signs like bowel gas in the chest. However, its sensitivity is low. A normal chest x-ray does not rule out a diaphragmatic injury, particularly smaller tears or those on the right side. Therefore, in cases of high clinical suspicion, CT is required for a definitive diagnosis.

Is MRI a good alternative to CT for diagnosing a diaphragmatic hernia?

MRI is rated *May be appropriate* and is generally considered a second-line or problem-solving tool in this scenario. It avoids ionizing radiation and offers excellent soft tissue contrast, which can be helpful for distinguishing a true hernia from a severe diaphragmatic eventration. However, CT is typically faster, more widely available in emergency settings, and superior for evaluating acute traumatic injuries, making it the preferred initial advanced imaging modality.

What is the imaging difference between a Bochdalek and a Morgagni hernia?

The key difference is their location. A Bochdalek hernia is a posterolateral defect, meaning it occurs in the back and to the side of the diaphragm. It is much more common on the left side. A Morgagni hernia is an anteromedial defect, located in the front and middle, just behind the sternum, and is more common on the right side. CT can easily distinguish between these two locations.

If a CT shows a traumatic diaphragmatic tear, does the patient always need surgery?

Yes, a diagnosed traumatic diaphragmatic rupture is considered an indication for surgical repair. Unlike some solid organ injuries that can be managed non-operatively, a tear in the diaphragm will not heal on its own and creates a permanent risk for herniation and strangulation of abdominal organs, which can occur days, months, or even years after the initial injury.

Is oral contrast necessary in addition to IV contrast for the CT scan?

The ACR guidelines do not specify the need for oral contrast. While it can sometimes help delineate the bowel, it is often omitted in the acute trauma setting because it delays the scan and poses an aspiration risk. IV contrast is the critical component for assessing organ viability and is almost always sufficient for identifying herniated bowel loops.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026