CT anatomy of hilar lymphadenopathy.

The normal distribution of lymph nodes in the pulmonary hili is diagrammatically shown, with a typical computed tomographic (CT) demonstration of hilar lymphadenopathy. On the basis of observations in anatomic cross sections of cadaver lungs, the lymph nodes in the right lung can be divided into four principal groups (right upper lobe, interlobar, middle lobe, and lower lobe) and in the left lung into three principal groups (left upper lobe, interlobar, and lower lobe). Most of the hilar lymph nodes are situated along the bronchi in close relation with the pulmonary vascular branches. Because of this close proximity, contrast-enhanced CT images are indispensable for precise CT interpretation of a hilar lymphadenopathy.