The Hilar Height Ratio in Normal Chest Radiographs of Adults Seen at Selected Tertiary Hospitals in Kampala, Uganda; A Forgotten Parameter in Pulmonary Medicine

Abstract

Background: The hilar height ratio (HHR) is a numerical expression of the hila position. Displacement of the pulmonary hilum is the most reliable indirect sign, in conditions that result in pulmonary volume changes. Despite the high utility of the chest radiograph, it has a relatively low diagnostic accuracy, high interobserver disagreement and numerous errors following interpretation. Routine use of the HHR with knowledge of the normal ranges would, therefore, help improve the overall chest radiograph sensitivity, reduce on errors and the interobserver disagreement in the interpretation of pulmonary volume changes. This study aims to determine the HHR in our study population, compare it with previous studies, and to relate it with sex, stratified age groups, height and body mass index (BMI).Methods: A consecutive cross-sectional study with purposive sampling were used to filter out a total of 384 normal chest radiographs of adults seen from three tertiary hospitals in Kampala, Uganda. The right and left HHRs were evaluated for each chest radiograph, along with the age, sex weight, height and BMI.Results: The median right HHR for the participants was 1.42 (IQR = 1.31- 1.57), and the median left HHR was 0.92 (IQR = 0.86- 0.98). There was a significant mean difference in the right HHR between the sex groups (p = 0.017) and age groups (p = 0.001). The mean difference in the left HHR was not affected by sex (p = 0.178) or age (p = 0.198). The right and left HHRs showed a very weak correlation to height (r = - 0.10 and r = 0.08, respectively). The right and left HHRs were not significantly different among the BMI groups (p = 0.254 and 0.20 respectively).Conclusion: The median left HHR was not affected by sex, age, weight and height while the right HHR varied with sex and age in our study population. Weight and height do not affect HHRs. The females in our study population had a higher positioned right hilum, whereas the position of the right hilum progressively lowered with increasing age.