Interstitial Pattern, Pleural Thickening and Effusion

Christopher M. Walker, MD

DIFFERENTIAL DIAGNOSIS

Common

Pulmonary Edema

Less Common

Lymphangitic Carcinomatosis
Asbestosis
Systemic Lupus Erythematosus
Rheumatoid Arthritis

Rare but Important

Lymphangiomyomatosis
Diffuse Pulmonary Lymphangiomatosis
Pulmonary Venoocclusive Disease
Pulmonary Capillary Hemangiomatosis
Erdheim Chester Disease

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Chronicity of process and response to diuretics helps guide differential

Helpful Clues for Common Diagnoses

Pulmonary Edema
- Caused by increased capillary hydrostatic pressure
- New onset edema in outpatient without apparent cause may be secondary to myocardial infarction
- Radiographic and CT findings
  - Cardiomegaly
  - Right ≥ left pleural effusions
  - Smooth interlobular septal thickening or Kerley B lines
  - Dependent lung distribution (posterior lung in supine patient and lower lung in upright patient)
  - ± lobular or centrilobular ground-glass opacity with fissural thickening
  - Spared lobules among affected lobules secondary to differing lobular perfusion
  - Crazy-paving; intralobular interstitial thickening superimposed on ground-glass opacity
  - Mild lymph node enlargement secondary to increased lymphatic drainage

Helpful Clues for Less Common Diagnoses

Lymphangitic Carcinomatosis
- Metastatic disease to lymphatics from
  - Breast, lung, stomach, colon, cervix, prostate, pancreas, and thyroid carcinoma among others
- Smooth or nodular or “beaded” thickening of interlobular septa and peribronchovascular interstitium
- Preserves underlying lung architecture
- No change with diuretics
- ± hilar/mediastinal lymphadenopathy
- ± pleural effusions
- Unilateral disease more common in lung carcinoma
- Look for other sites of metastatic disease (liver or bone)
Asbestosis
- Prone imaging important in diagnosis
- HRCT findings
  - Posterior and basal subpleural lung
  - Subpleural reticular or dot-like opacities indicates early fibrosis
  - Subpleural lines parallel pleural surface
  - Short or long parenchymal bands extend inward from abnormal pleural surfaces
  - Pleural plaques
  - Late fibrosis shows honeycombing and thickening of interlobular septa
Systemic Lupus Erythematosus
- Elevated antinuclear antibodies in young women
- HRCT shows
  - Ground-glass and reticular opacities in a basal, posterior, and subpleural distribution
  - Traction bronchiectasis or bronchiolectasis
  - Pleural thickening or effusion seen in 50% of patients
  - ± anterior upper lobe involvement
  - Honeycombing is rare
- Ground-glass opacity
  - Represents lupus pneumonitis, pneumonia, or hemorrhage
Rheumatoid Arthritis
- Subpleural basal predominant fibrosis in UIP, NSIP, or OP patterns
- ± unilateral pleural effusion or pleural thickening
- Bronchiectasis in 30% of patients secondary to chronic infection
- Rheumatoid nodules in ≤ 5% of patients
- ± distal clavicular erosions or high-riding humeral head

Helpful Clues for Rare Diagnoses

Lymphangiomyomatosis
- Women of childbearing age
- Large lungs with pleural effusions and associated pneumothoraces
- Diffuse distribution of round lung cysts
- ± renal angiomyolipomas
- ± mediastinal and retroperitoneal lymphadenopathy
Diffuse Pulmonary Lymphangiomatosis
- Congenital lymphatic disorder with proliferation and dilatation of lymphatics
- Findings confined to thorax
  - Smooth thickening of interlobular septa and bronchovascular bundles
  - ± pleural and pericardial effusions
  - Mediastinal lymphadenopathy with effacement of mediastinal fat
  - ± centrilobular nodules
Pulmonary Venoocclusive Disease
- Occlusion of small pulmonary veins and venules leading to pulmonary hypertension
- Fatal pulmonary edema can follow standard vasodilator therapy
- CT shows
  - Pulmonary arterial diameter ≥ 29 mm
  - ± pleural effusions
  - Smooth or nodular interlobular septal thickening
  - Diffuse, geographic, perihilar or centrilobular ground-glass opacity
Pulmonary Capillary Hemangiomatosis
- Proliferation of thin-walled capillaries leading to obstruction of pulmonary venules
- Fatal pulmonary edema can follow standard vasodilator therapy
- Overlap with imaging findings of venoocclusive disease
- CT shows
  - Pulmonary arterial diameter ≥ 29 mm
  - Diffuse ill-defined centrilobular nodules of ground-glass opacity
  - ± pleural effusions
  - Sparse interlobular septal thickening
Erdheim Chester Disease
- Non-Langerhans cell histiocytosis
- 1/3 have pulmonary involvement
  - Visceral pleural thickening with effusions
  - Smooth interlobular septal and fissural thickening
- Extrapulmonary findings
  - Symmetric osteosclerosis of metadiaphysis of long bones
  - ± circumferential long segment aortic wall thickening
  - ± soft tissue encasement of kidneys
  - ± pericardial thickening
  - ± nodular thickening of dura
  - ± T2/FLAIR hyperintensity within brainstem