Correct!
5. Thoracentesis
Thoracentesis is the most appropriate next step among the choices listed. While pleural effusion can occur in the setting of thromboembolic disease, fluid in the pleural space is a non-specific finding, and if pulmonary embolism is suspected in this setting, CT pulmonary angiography would probably be a better choice for assessment of suspected thromboembolic disease than 99mTc-MAA ventilation-perfusion scintigraphy given that the chest radiograph is abnormal (which often results in a higher likelihood of indeterminate results at 99mTc-MAA ventilation-perfusion scintigraphy compared with patients who have normal chest radiographs). Abdominal MRI has little role in the assessment of a pleural effusion of unknown etiology (although it was performed in this patient and showed the bilateral cystic renal disease and expected post-procedural changes, but with no evidence of hydronephrosis, hemorrhage, or undrained fluid collection). 99mTc-Ga-citrate scintigraphy is sometimes useful when thoracic infection or inflammation is suspected in the setting of diffuse lung opacities, but would be unrewarding in this circumstance. Decubitus chest radiography is useful for detection of pleural effusion and quantification of fluid to determine if enough fluid is present to perform thoracentesis successfully. However, for this patient, decubitus chest radiography should be performed in the right lateral decubitus position, not the left, for pleural fluid quantification.
Further clinical course: Thoracentesis was performed and showed hazy, straw-colored fluid with an increased cell count (chronic inflammatory and mesothelial cells) but no cytological evidence of malignancy. The total pleural fluid protein and LDH were 4.4 and 200, respectively, with these values interpreted as representing an exudative effusion. Chest radiography (Figure 7) obtained less than one week following thoracentesis, performed for shortness of breath, showed re-accumulation of the right pleural effusion.
Figure 7. Frontal and lateral chest radiography performed less than one week following right-sided thoracentesis and just under one month following the percutaneous microwave renal ablation procedure shows right pleural effusion re-accumulation. The right pleural effusion is now large.
Repeat right-sided thoracentesis was performed and yielded nearly 2000 cc of fluid with biochemical analysis suggesting a transudate. Unenhanced thoracic CT (Figure 8) was then performed.
Figure 8. Left panel: selected static view of unenhanced thoracic CT performed following right-sided thoracentesis. Right panel: movie of unenhanced thoracic CT scan following right-sided thoracentesis.
Which of the following statements regarding the unenhanced thoracic CT study is most accurate? (Click on the correct answer to proceed to the sixth of seven panels)