Parasternal Line

Parasternal Line (from Greek para- beside, near and Latin sternum- breastbone), or parasternal, parasternal line - a line drawn vertically downward on the anterior wall of the chest midway between the edge of the sternum and the nipple line. The position of the parasternal line, resp. its distance from the adjacent parallel edge of the sternum, can vary considerably in different individuals depending on both the width of the chest and the position of the nipple. Since the position of the latter, especially in women, can in individual cases vary greatly, it is more convenient to use the medial-clavicular line, which runs downward from the middle of the clavicle and is close to it in position, to determine the position of the parasternal line. In clinical practice, the right parasternal line is used to judge the degree of pathological enlargement of the border of the right heart (its relative dullness), as well as when determining the lower border of the right lung (in normal conditions it is located along the parasternal line at the lower edge of the VI rib) and the right lobe of the liver (the upper border of the liver, resp. the right dome of the diaphragm, is located along this line at the level of the IV intercostal space, while the lower border of the liver in normal conditions percutaneously protrudes slightly from under the costal margin). The left parasternal line is used in clinical practice to determine the position of: the left border of the absolute dullness of the heart (in normal conditions it lies approximately along this line or slightly extends outward from it); the lower border of the left lung (located at the level of the IV rib and descends along this line and slightly to the left of it to the VI rib) and finally when determining the degree of pathological enlargement of the left lobe of the liver and in exceptional cases - the spleen. In addition, these lines are used to determine the degree of pathological enlargement of the organs of the anterior mediastinum.