Uncategorized
  • Perilymphatic distribution refers to
    • a pattern of lung involvement in which pulmonary abnormalities, such as
      • lymphatic congestion
      • lymphatic infiltration
      • or nodules,
    • align with the lymphatic vessels surrounding specific regions of the lung.
    • This distribution pattern is often indicative of diseases that affect the lymphatic system.
  • For the purpose of this definition, the
    • lymphatic distribution can be visualized in the following regions:
      • bronchovascular
      • interlobular septa of the secondary lobule
      • intralobular regions of the secondary lobule
      • pleura
      • fissures
      • pulmonary veins

AKA:

  • Lymphangitic Distribution

Abbreviation:

  • PLD (Perilymphatic Distribution)

How does it appear on each relevant imaging modality?:

Chest X-ray:

  • Parts: The pattern may show up as
      • fine, linear or reticular markings
      • nodular densities
    • along the
      • bronchovascular bundle
      • interlobular septa of the secondary lobule
      • intralobular regions of the secondary lobule
      • pleura
      • fissures
      • pulmonary veins

CT Scan:

With higher contrast resolution the CT scan is far better to identify the anatomic location of the lymphatic or peri lymphatic involvement and similarly

the pattern may as

      • fine, linear or reticular markings
      • nodular densities
    • along the
      • bronchovascular bundle
      • interlobular septa of the secondary lobule
      • intralobular regions of the secondary lobule
      • pleura
      • fissures
      • pulmonary veins

MRI:

  • Parts: MRI is not typically used for evaluating perilymphatic distribution .

PET-CT:

  • Role: PET-CT is  not typically used for evaluating perilymphatic distribution .

Differential diagnosis:

Infection:

  • Tuberculosis (TB):
    • Character: Perilymphatic distribution of nodules or infiltrates in the lungs, often with associated hilar lymphadenopathy.
    • Imaging Findings: Small nodules or linear opacities located in a lymphatic distribution, often in the upper lobes.
  • Fungal Infections (e.g., Histoplasmosis, Coccidioidomycosis):
    • Character: Granulomatous infection causing nodules in a perilymphatic distribution, sometimes with calcification.
    • Imaging Findings: Nodular infiltrates, often with a fine reticular pattern along the bronchovascular structures.

Inflammation:

  • Sarcoidosis:
    • Character: Granulomatous disease causing nodular infiltrates along the bronchovascular bundles.
    • Imaging Findings: Hilar and mediastinal lymphadenopathy with a perilymphatic pattern, often associated with fine reticular opacities.
  • Rheumatoid Arthritis (RA):
    • Character: Perilymphatic involvement due to inflammation associated with interstitial lung disease in RA.
    • Imaging Findings: Reticular or nodular infiltrates in the subpleural regions of the lungs.

Neoplasm (Benign or Malignant):

  • Lymphangitic Carcinomatosis:
    • Character: Malignant spread via the lymphatic vessels, leading to a perilymphatic distribution of nodular infiltrates.
    • Imaging Findings: Fine nodular patterns around the bronchovascular bundles, often with pleural effusions.
  • Metastatic Disease:
    • Character: Malignant cells can spread through the lymphatic vessels, leading to a perilymphatic distribution.
    • Imaging Findings: Nodules along the bronchovascular structures or at the pleural surface, associated with mediastinal or hilar lymphadenopathy.

Metabolic:

  • Pulmonary Langerhans Cell Histiocytosis (PLCH):
    • Character: A rare disease that may present with perilymphatic distribution of nodules or cysts.
    • Imaging Findings: Peripherally distributed nodules that may evolve into cystic changes over time.

Recommendations:

Next diagnostic steps:

  • Further imaging with CT or MRI to evaluate the extent, distribution, and characteristics of the perilymphatic distribution.
  • Biopsy or fine needle aspiration (FNA) may be necessary for histological examination if malignancy or infection is suspected.
  • Laboratory testing: Blood tests to evaluate for infections (e.g., tuberculin skin test), autoimmune markers (e.g., sarcoidosis), or cancer screening.