During a teaching round on foreign body aspiration, a senior resident is asked: 'In children with aspirated foreign bodies that lodge in the tracheobronchial tree, what is the most common site of impaction?' What is the correct answer?

Explanation

## Most Common Site of Foreign Body Lodgment in the Tracheobronchial Tree **Key Point:** The right main bronchus is the most common site of foreign body impaction, accounting for 60–70% of cases. This is due to anatomical factors, not chance. ### Anatomical Basis for Right-Sided Predominance | Feature | Right Main Bronchus | Left Main Bronchus | | --- | --- | --- | | **Angle of divergence** | ~20–25° (more vertical) | ~40–45° (more horizontal) | | **Diameter** | Wider | Narrower | | **Length** | Shorter (~2–3 cm) | Longer (~4–5 cm) | | **Frequency of FB lodgment** | 60–70% | 20–30% | **High-Yield:** The right main bronchus is a direct continuation of the trachea, making it the "path of least resistance" for aspirated objects. Gravity and airflow dynamics favor right-sided impaction. **Clinical Pearl:** When examining a child with suspected foreign body aspiration: - Unilateral decreased air entry on the **right** is the most common finding - Right-sided hyperinflation may develop if the FB acts as a ball valve - Chest X-ray (inspiratory and expiratory) shows asymmetrical aeration with right-sided findings ### Mechanism of Right-Sided Predilection 1. **Anatomical alignment:** The right main bronchus is more in line with the trachea (straighter path) 2. **Gravity:** In supine or semi-recumbent position, objects preferentially travel rightward 3. **Airflow dynamics:** Higher airflow velocity on the right during inspiration 4. **Diameter:** Wider right main bronchus accommodates larger objects **Mnemonic: RIGHT SIDE** — **R**ight is straighter, **I**mpaction is common, **G**ravity favors right, **H**igher frequency 60–70%, **T**rachea aligns with right, **S**ite of lodgment, **I**nspection shows asymmetry, **D**ecreased air entry right, **E**xpiratory films show hyperinflation **Warning:** Do NOT assume left-sided lodgment is impossible. Left main bronchus impaction occurs in 20–30% of cases, especially if the child is in a left lateral decubitus position during aspiration or if the FB is very small. **Clinical Pearl:** Rigid bronchoscopy findings often show: - Right main bronchus: FB directly visible at the carina or in the right bronchus - Granulation tissue and edema around the FB (especially if delayed presentation) - Possible ball-valve mechanism with air trapping [cite:Dhingra 7e Ch 8]