According to the Rule of Nines for estimating body surface area (BSA) affected by burns in adults, what percentage of BSA is represented by each lower limb?

Explanation

## Rule of Nines in Adult Burns **Key Point:** The Rule of Nines is the standard rapid assessment tool for estimating total body surface area (TBSA) involved in thermal injuries. Accurate estimation is critical for fluid resuscitation and triage decisions. ### Adult Rule of Nines Distribution | Body Region | Percentage of BSA | |---|---| | Head and neck | 9% | | Each upper limb (arm + forearm + hand) | 9% | | Anterior trunk | 18% | | Posterior trunk | 18% | | **Each lower limb (thigh + leg + foot)** | **18%** | | Genitalia | 1% | | **Total** | **100%** | **High-Yield:** Each lower limb represents **18% of BSA** in adults. This is a frequently tested fact in burn assessment. **Clinical Pearl:** The Rule of Nines is less accurate in children (especially <5 years) because the head is proportionally larger (18%) and lower limbs are smaller (13.5% each). Always use age-appropriate charts for pediatric burns. **Mnemonic:** **9-18-1 Rule** — Head 9%, Each arm 9%, Anterior trunk 18%, Posterior trunk 18%, Each leg 18%, Genitalia 1%. **Warning:** Do not confuse the adult rule with pediatric percentages. A common trap is applying child percentages to adult patients or vice versa.