Small Pleural Effusions in Myeloma: Clinical Significance

Introduction to Small Pleural Effusions

The American Thoracic Society recommends that small pleural effusions incidentally detected on MRI in myeloma patients are generally not concerning and do not require immediate intervention unless symptomatic or accompanied by specific high-risk features 1, 2
About 15% of patients with malignancy-related effusions have small effusions that are relatively asymptomatic 1, 2

The American College of Chest Physicians suggests pursuing diagnostic thoracentesis if symptomatic dyspnea, progressive enlargement on serial imaging, unilateral effusion without clear alternative explanation, or bilateral effusions with normal heart size on imaging are present 1, 2, 3, 4, 5, 6
Ultrasound-guided thoracentesis is the preferred initial approach, with a 97% success rate even for small effusions 7, 5
Pleural fluid should be sent for cell count with differential, protein, LDH, glucose, pH, cytology, and flow cytometry, which has 85% sensitivity for detecting myeloma cells 8, 5

The European Respiratory Society recommends watchful waiting with interval imaging for small, asymptomatic effusions detected on MRI 6, 5
Review for alternative causes, such as checking cardiac function, renal function, and albumin levels, and reassess if symptoms develop or effusion enlarges significantly 6, 2
Do not pursue thoracentesis for effusions too small to sample safely (<1 cm thickness on lateral decubitus view) 1, 2