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Conventions and General Coding Guidelines - PART 3

Continuation of PART 2

Etiology/Manifestation Convention

Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the  ICD-10-CM  has a  coding convention that requires the underlying condition to be sequenced first, if applicable, followed by the manifestation. 

Wherever such a  combination exists,  there is a “use additional code” note at the etiology code,  and a “code first” note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes,  etiology followed by manifestation. 

In  most cases, the manifestation codes will have in  the code  title,  “in  diseases classified elsewhere.”  Codes with this title are components of the etiology/ manifestation convention. 

There are manifestation codes that do not have  “in diseases classified elsewhere” in the title. For such codes,  there is a  “use additional code” note at the etiology code and a “code first” note at the manifestation code,  and the rules for sequencing apply.

“Code first”  and  “Use additional code” notes are also used as sequencing rules in the classification for certain codes that are not part of an etiology/ manifestation combination. 


The word “and” should be interpreted to mean either “and” or “or” when it appears in a title. For example, cases of  “tuberculosis of bones”, “tuberculosis of joints”  and “tuberculosis of bones and joints” are classified to subcategory  A18.0, Tuberculosis of bones and joints.


The word “with” or “in” should be interpreted to mean “associated with” or “due to” when it appears in a code title,  the Alphabetic Index  (either under the main term or subterm),  or an instructional note in the Tabular  List.  

The classification presumes a causal relationship between the two conditions linked by these terms in the  Alphabetic Index or  Tabular  List.  

These conditions should be coded as related even in the absence of provider documentation explicitly linking them unless the documentation clearly states the conditions are unrelated or when another guideline exists that specifically requires a  documented linkage between two conditions  

(e.g.,  sepsis guideline for  “acute organ dysfunction that is not clearly associated with the sepsis”). 

Code Also Note

A “code also” note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.  The sequencing depends on the circumstances of the encounter.

Default Codes 

A code listed next to a main term in the ICD-10-CM Alphabetic  Index is referred to as a default code The default code represents that condition that is most commonly associated with the main term or is the unspecified code for the condition. If a condition is documented in a  medical record  (for example, appendicitis) without any additional information,  such as acute or chronic, the default code should be assigned. 

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