What causes an elevated left diaphragm?

Causes of Elevated Left Diaphragm

An elevated left diaphragm results from four primary mechanisms: phrenic nerve injury causing paralysis, congenital eventration from incomplete muscle development, traumatic diaphragmatic rupture with herniation, or acquired diaphragmatic hernias (most commonly hiatal hernias). 1, 2, 3

Primary Etiologic Categories

Phrenic Nerve Injury and Paralysis

• Acquired phrenic nerve injury is the most common cause of diaphragmatic paralysis, resulting in loss of muscle contractility, progressive atrophy, and subsequent elevation of the diaphragmatic dome 2, 4
• Iatrogenic injury during thoracic surgery (including mediastinal tumor resection, cardiac surgery, or intentional phrenicectomy) accounts for the majority of cases 5
• The paralyzed diaphragm demonstrates paradoxical motion on fluoroscopy (upward movement during inspiration), which distinguishes it from eventration 6, 3
• Symptoms develop gradually as atrophy progresses, with dyspnea on exertion and reduced exercise tolerance being the primary manifestations 4, 5

Congenital Eventration

• Congenital eventration represents incomplete diaphragmatic muscle development during the eighth week of gestation, specifically a failure of mesenchymal development in the posterolateral region 1
• Left-sided eventration predominates in 81.5-85% of cases, with right-sided involvement occurring in only 15-19% 1
• Genetic mutations in FOG2, GATA4, or COUP-TFII genes interrupt critical molecular pathways for diaphragmatic development 1
• Adult presentation occurs at a mean age of 40-44 years, often discovered incidentally on chest imaging 1
• Unlike paralysis, eventration shows no paradoxical motion on fluoroscopy because the thin diaphragmatic tissue moves normally, just from an elevated baseline position 6, 3

Traumatic Diaphragmatic Rupture with Herniation

• Left-sided diaphragmatic injuries occur in 50-80% of traumatic cases after blunt or penetrating trauma, compared to 12-40% on the right side, due to the protective effect of the liver 7
• Road traffic collisions are the most common cause of blunt diaphragmatic rupture, occurring in 1-5% of vehicle crash victims 7
• Penetrating injuries (particularly knife wounds) to the lower chest cause diaphragmatic herniation in 10-15% of cases 7
• The natural history follows three phases: acute (often missed due to associated injuries), latent (intermittent herniation with nonspecific symptoms), and obstructive (bowel strangulation requiring emergency surgery) 7
• Dyspnea (86%) and abdominal pain (17%) are the predominant symptoms, with a 25-50% decrease in pulmonary function from herniated organs occupying thoracic space 7, 8

Acquired Diaphragmatic Hernias

• Type I sliding hiatal hernias (90% of hiatal hernias) cause left hemidiaphragm elevation when the gastric cardia and gastroesophageal junction migrate above the diaphragm through a widened esophageal hiatus 9
• Type II paraesophageal hernias (10% of cases) involve gastric fundus herniation through a phrenoesophageal membrane defect while the gastroesophageal junction remains in normal position 9
• Large Type IV hernias can accommodate multiple viscera (stomach, colon, spleen) and create substantial diaphragmatic elevation 9

Critical Diagnostic Considerations

Imaging Approach

• Chest X-ray is the initial screening tool but misses 25-62% of diaphragmatic pathology, showing nonspecific findings like hemidiaphragm elevation, abnormal bowel gas patterns, or air-fluid levels 7
• CT scan is the gold standard with 82% sensitivity and 87% specificity, identifying diaphragmatic discontinuity, the "collar sign" (organ constriction at rupture site), and the "dependent viscera sign" (herniated organs abutting the chest wall) 7
• Fluoroscopy definitively distinguishes paralysis (paradoxical motion) from eventration (no paradoxical motion), guiding treatment decisions 6, 3

High-Risk Features Requiring Urgent Evaluation

• Acute onset dyspnea with history of recent trauma mandates immediate CT imaging to exclude diaphragmatic rupture with visceral herniation 7, 8
• Bowel sounds in the chest, acute abdominal pain with respiratory distress, or mediastinal shift indicate potential strangulation requiring emergency surgery 7, 8
• Delayed diagnosis occurs in 5-45% of cases, with right-sided ruptures particularly prone to being missed (50% of delayed diagnoses) 7

Common Pitfalls to Avoid

• Do not dismiss an elevated hemidiaphragm as "incidental" without functional assessment, as even asymptomatic elevation may progress to disabling dyspnea requiring surgical intervention 6, 4
• Avoid misdiagnosing traumatic diaphragmatic hernias as pneumonia or pleural effusion on initial chest X-ray, particularly in the acute trauma setting where 33-66% are initially missed 7
• Do not assume congenital eventration is benign—symptoms can develop decades after birth, requiring surgical plication when lung compression causes disabling dyspnea 1, 4
• In trauma patients, small diaphragmatic tears may be asymptomatic initially but progress over years to large hernias with bowel strangulation, sepsis, and multi-organ failure 7