What does the detection of lymphatic channels on standard chest radiographs indicate?

a. Abnormally low pressures in the lymphatic channels
b. Anastomoses with the pulmonary circula-tion
c. Normal fibrotic changes that occur with aging
d. System that is overwhelmed by excessive fluid

ANS: D
Lymphatic channels are usually not visible on chest radiographs. They may be detected if they are distended or thickened by disease. The "butterfly" pattern that radiates from the hilar region of both lungs during acute development of pulmonary edema is thought to largely be the result of interstitial and lymph vessel distension with fluid. In this situation, the lymphatic drainage sys-tem has been overwhelmed by a sudden and excessive surge of fluid from the circulation. The development of a pleural effusion is also evidence that the lymphatic system is unable to remove excess fluid in the lung.