Question: Wisconsin Subscriber Answer: Reason: You'll employ the "Rule of Nines" to select the fourth and fifth digits. The Rule matches percentages and body areas thusly: • head and neck, the right arm, and the left arm each equal 9 percent • the back trunk, front trunk, left leg, and right leg each equal 18 percent (the front and back trunk are divided into upper and lower segments, and each leg is divided into back and front segments, each equaling 9 percent) • genitalia equal 1 percent. Let's say a patient has a severely burned right leg: he has multiple second-degree burns on his front right leg and additional third-degree burns to his back right leg, but no loss of body part. In this instance, you would list the following in this order • 945.39 (Burn of lower limb[s]; full-thickness skin loss [third-degree NOS]; multiple sites of lower limb[s]) for the third-degree burn • 945.29 (... blisters, epidermal loss [second degree]; multiple sites of lower limb[s]) for the second-degree burn • 948.10 (... 10-19 percent of body surface; less than 10 percent or unspecified) to represent TBSA burned. -- Reader Questions and You Be the Coder reviewed by Michael A. Granovsky, MD, CPC, FACEP, president of MRSI, an ED coding and billing company in Woburn, Mass.