Normal Pulmonary Vessels

Axial and supernumerary vessels: Axial vessels, either veins or arteries, branch dichotomously at acute angles into equal-sized vessels. Supernumerary vessels, either veins or arteries, arise at right angles to axial vessels and are much smaller than the parent vessel. On the arterial side, they arise most frequently from vessels <1 mm in diameter. In this region the supernumerary arteries are 4 times as frequent as axial branches and have 1/4 the diameter of the parent vessel [1]. These vessels supply the capillary bed directly.

Plexiform lesions occur at branch points. In the photo, the parent artery wall is thickened and has increased bluish matrix, indicating remodeling. Note the relatively thin wall of the supernumerary vessel. It is believed that normally the mouths of the supernumerary arteries are closed.

Supernumerary arteries may play a role in the acute pulmonary edema of high altitude or crack cocaine smoking. In these conditions, the acute increase in blood pressure and flow may open the supernumerary channels that lead directly to the capillary bed and produce capillary leakage [2,3].

References

1. Elliott F, Reid L. Some new facts about the pulmonary artery and its branching pattern. Clin Radiol 1965; 16:193-198.

2. Goetz A, Kuebler W, Peter K. High-altitude pulmonary edema. N Engl J Med 1996; 335:206-207.

3. Fadil A, Lodato R. Cocaine intoxication presenting as hypotension with high cardiac index, simulating septic shock. Am J Resp Crit Care Med 1997; 155:A707.

Discussion

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