ICD 10 Coding Alert

Specialty Spotlight:

Beware These Sequela Myths

Published on Mon Jun 05, 2023

Hint: Know when the character ‘S’ applies.

Providers don’t always see patients during active illness or injury, so coders have to know how to account for the aftereffects. Coders need to know how to use sequelae.

Know how to identify an aftereffect as a sequela and know when to add the 7th character “S” to a diagnosis code.

Myth 1: Aftereffect and Sequela Are Synonymous

This is a common myth, and it’s easy to understand why. First, let’s look at how ICD-10-CM guideline I.B.10 describes sequela: “A sequela is the residual effect (condition produced) after the acute phase of an illness or injury has terminated. There is no time limit on when a sequela code can be used. The residual may be apparent early, such as in cerebral infarction, or it may occur months or years later, such as that due to a previous injury.” In other words, sequela is a new issue that has developed as a result of a previous issue, such as a scar caused by a previous burn. On the surface, this can appear identical to an aftereffect, but it’s not exactly the same

Even though most medical conditions are the result of a cause-and-effect relationship, it is important to note that causality does not always mean sequela. Complications from a medical procedure, for example, are not regarded as sequela, and neither are symptoms of illnesses and conditions caused by organisms.

For example, even though you would code a urinary tract infection (UTI) caused by a staph infection with two codes, such as N39.0 (Urinary tract infection, site not specified) and B95.- (Streptococcus, Staphylococcus, and Enterococcus as the cause of diseases classified elsewhere), the UTI in this example is not regarded as a sequela of the infection but a result of it.

Myth 2: Adding the 7th Character ‘S’ Is Appropriate for All Sequela

This is a common misconception. Even though “S” stands for “sequela,” you add the “S” as the 7th character to identify sequela from the initial injury, not the actual sequela. This is because sequelae that occur in relation to an injury or accident do not have their own codes. For codes in the S00-T88 and V00-Y99 sections, for example, ICD-10 guideline I.C.19.a notes: “the 7th character ‘S’, sequela, is for use for complications or conditions that arise as a direct result of a condition. ... The ‘S’ is added only to the injury code, not the sequela code. The 7th character ‘S’ identifies the injury responsible for the sequela. The specific type of sequela … is sequenced first, followed by the injury code.”

“So, using the example to which the guidelines allude, if one were coding scar formation as a sequela to a burn, you would code the scar first and then the burn injury code second and add ‘S’ in the seventh position on the burn injury code only,” says Kent Moore, senior strategist for physician payment at the American Academy of Family Physicians.

Example: Let’s say a patient comes in complaining that a scar on the back of her left hand has recently become painful. The provider notes that five years ago, she suffered a third-degree burn to that location and notes that the scar is a sequela to the burn. In this situation, the injury (the burn) has healed, and the patient is experiencing no further issues from the injury itself. However, the injury has created a scar, which is a sequela of the injury and the reason for the encounter.

In this case, you would code both the scar and the injury that caused it, using the 7th character “S” for the injury code like this:

L90.5 (Scar conditions and fibrosis of skin)
T23.362S (Burn of third degree of back of left hand, sequela)

Remember: Before using “S” as a 7th character, you should “make sure that the original or previous illness or injury is completely resolved. Oftentimes, I see providers using the 7th character ‘S’ without a clear understanding of sequela,” cautions Chelle Johnson, CPMA, CPC, CPCO, CPPM, CEMC, AAPC Fellow, billing/credentialing/ auditing/coding coordinator at County of Stanislaus Health Services Agency in Modesto, California.

Myth 3: Never Make Sequelae the Primary Code

Proper ICD-10-CM sequencing is often confusing, but with sequelae, things can get even trickier. When in doubt, check the guidelines.

Take the above burn example. The primary issue at the encounter is the painful scar. Even though the burn is technically a sequela, you will follow ICD-10-CM guideline I.B.10, which states: “the condition or nature of the sequela is sequenced first. The sequela code is sequenced second.” Remember that when coding with the 7th character “S,” the sequela code identifies the injury. Also, as we mentioned earlier, guideline I.C.19.a explains that in situations such as this, “the specific type of sequela (eg, scar) is sequenced first, followed by the injury code.” In other words, in this example, the sequela of the injury, the scar, is reported as the first-listed condition.

However, some sequelae have their own code or code group, such as:

B94.- (Sequelae of other and unspecified infectious and parasitic diseases)
I69.- (Sequelae of cerebrovascular disease)

In these cases, you don’t need to identify the injury with the “S,” so you would therefore report the code for the specific sequela after the condition code, as in the following example:

Let’s say a patient suffered a COVID-19 infection in the past and presented with multisystem inflammatory syndrome as a result. “Section 1.C.1.g.1.l of the ICD-10 guidelines states, in part, that if MIS [multisystem inflammatory syndrome] develops as a result of a previous COVID-19 infection, assign codes M35.81 [Multisystem inflammatory syndrome] and B94.8 [Sequelae of other specified infectious and parasitic diseases],” notes Moore.