The normal hilar height ratio in Kenyan Africans; a study at Kenyatta National hospital, Nairobi

Abstract

The Hilar Height ratio (HHR) is a numerical expression of the radiographic observation that in the normal state the right hilus is positioned in the lower half of the right hemithorax while the left hilus is situated in the upper half of its hemithorax. It is calculated by dividing the distance from the hilus to the lung apex by the distance from the hilus to the diaphragm. This study was done to establish standard baseline values in the Kenyan African and to compare the figures obtained with studies done previously, mainly in the non-African Caucasian population. Chest radiographs (Posterior anterior view) of Kenyan Africans which are taken for routine screening exams were analysed in this study. These radiographs were used to determine the hilar height ratio. The study was both retrospective and prospective. The left hilar height ratio was found to be 0.857 while the right hilar height ratio was found to be 1.195. In no instance was the left hilar height ratio greater than one or the right hilar height ratio less than one. This compares favourably with a study done by Homer M.J. in 1978 (he found the left HHR to be 0.84 and the right HHR to be r.3!). I suggest therefore that this ratio be adopted in evaluating PA erect chest films to aid in diagnosis of chest and subpulmonic diseases.