Laura Summy, CPC, CRC Aug 23, 2021 11:01:06 AM 6 min read

Understanding Initial, Subsequent and Sequela ICD10 Codes

The codes in Chapter 19 of the ICD10 book are for injury, poisoning, and other consequences of external causes (S00-T88). Many of them require a 7th character to identify the correct ICD10 code for the episode of care: initial, subsequent, or sequela. Below are helpful reminders to ensure you’re selecting the correct code for the patient visit.

Initial Encounter

An initial encounter uses the letter A. This code indicates visits where the injury/condition is diagnosed for the first time and has nothing to do with whether the provider has seen the patient in the past. It also applies to visits by any provider during the “active” treatment of the injury/condition.

Example 1: The use of T21.23XA, burn of 2nd degree of upper back, is correct for the patient’s first visit. The new condition is the reason for the visit. Examples of initial encounters include an Emergency Department or office visit, surgery, or a new course of medication.

The ICD10 guidelines don’t specify when “active treatment” becomes “routine care.” This is a clinical decision by the provider and is based on the patient’s course of treatment. Rhonda Buckholtz, AAPC VP of Strategic Development, explains, “When the doctor sees the patient and develops a plan of care—that is active treatment. When the patient is following the plan—that is subsequent. If the doctor needs to adjust the plan of care—for example, if the patient has a setback or returns to the OR—the care becomes active, again.”

Active treatment can be performed in stages. It may involve multiple episodes of care for fracture/injury or complications of medical/surgical care, and it may involve more than one physician treating the patient. However, in many cases, the patient doesn’t need active treatment after the first visit, such as a laceration that received stitches and the patient returns for suture removal or a fracture that gets treated by surgery or a cast/splint. The patient returning for follow up of the laceration or fracture during the healing stage would support the subsequent code.

Subsequent Encounter

A subsequent encounter uses the letter D and is used appropriately during the recovery phase, no matter how many times the patient has seen the provider for this problem previously.

Example 2: The use of T21.23XD, burn of 2nd degree of upper back, subsequent, is for a patient’s follow-up visit to determine whether the treatment plan is being followed and the patient is healing or recovering as expected. Examples include cast change or removal, medication adjustment, and other follow-up visits for treatment of the injury or condition.

Sequela Encounter

A sequela encounter uses the letter S and indicates a late effect that occurs after the acute phase of the injury or illness has passed. When reporting sequela(e), you usually will need to report two codes. The first describes the condition or nature of the sequela(e), and the second describes the sequela(e) or “late effect.” If a late effect code describes all the relevant details, you should report that one code, only (e.g., I69.191 Dysphagia following nontraumatic intracerebral hemorrhage).

Example 3: Use of T21.23XS, burn of 2nd degree of upper back, sequela, should be billed with the new condition, such as L90.5, scar conditions and fibrosis of skin. A sequela code is for complications or conditions that arise as a direct result of a condition or injury. Examples include joint contracture after a tendon injury, hemiplegia after a stroke or scar formation following a burn. The sequela code should be primary and followed by the injury/condition code.

 There are very few examples of reporting both a code for the acute illness and a code for the late effect at the same encounter, for the same patient. These only occur if both conditions exist, such as a patient who has a current cerebrovascular condition and deficits from an old cerebrovascular condition.

Still have questions about Initial, Subsequent and Sequela ICD10 Codes? Our team is here to help. Please contact Laura Summy at for support.

Laura Summy is Managing of coding of MMG Healthcare Solutions / Medic Management Group. MMG is a national provider of consulting services and back office administrative support to independent and system owned physician practice groups.  Additionally, MMG has been formally recognized as a multi-year Northeast Ohio Top Workplaces award winner.