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ICD-10-CM: Translating Documentation to Codes

ICD-10-CM: Translating Documentation to Codes


A coder has to identify pertinent diagnoses and procedures and translate them into codes. Many beginning coders believe that coding simply involves looking up the term, finding the code number next to that term, and then assigning that code. However, there is much more involved in the coding process. Some coding guidelines are complicated, so the coder must understand how to translate documentation into codes to resolve many common problems. 

Diagnosis versus Procedure

To determine what should be coded, the coder has to identify two main elements: the diagnosis and the procedure. The procedure is "what is done," and the diagnosis is "why it is done." If a patient has a tonsillectomy because of acute tonsillitis, then the coder recognizes that "what is done" is the tonsillectomy, and "why it is done" refers to tonsillitis. There must be at least one diagnosis for each procedure performed, as payers require proof that services are "medically necessary." The diagnosis is usually the determining factor to justify procedures and various services.

What Should be Coded?

Sometimes, physicians and other healthcare providers give numerous diagnoses and information regarding past conditions. This information may not be relevant to the procedure or encounter being coded. The coder has to review medical documentation to find the necessary appropriate code. When a definitive diagnosis is established, the coder should not assign codes for signs and symptoms of that illness. However, additional signs and symptoms, as well as other conditions, should be coded when they are pertinent to the care provided during the encounter. The coder can find guidance about this through the "use additional code" and "code first" directions.

Example of "Code First" and "Use Additional Code"

R65 Symptoms and signs specifically associated with systemic inflammation and infection

 R65.1 Systemic inflammatory response syndrome (SIRS) of non-infectious origin

      Code first underlying condition, such as:

                      heatstroke (T67.0)                  

                      injury and trauma (S00-T88)

 Excludes 1: sepsis- code to infection

                      severe sepsis (R65.2)

 R65.11 Systemic inflammatory response syndrome (SIRS) of non-infections origin with   acute organ dysfunction

     Use additional code to identify specific acute organ dysfunction, such as:

      acute kidney failure (N17.-)

      acute respiratory failure (J96.0-)

If using codes from the subclassification R65.1, the coder should sequence the code for the underlying condition first, either with heatstroke or injury and trauma. If code R65.11 is assigned, then an additional code is needed to identify specific acute organ dysfunction.

Inpatient Coding vs. Outpatient Coding

A definite diagnosis is not always identified by the physician in both inpatient and outpatient settings. For the outpatient setting, a diagnosis could be listed as "probable," "possible," "rule out," or "questionable." It is not appropriate to assign a code of "pneumonia" for the condition listed as "probable pneumonia." Rather, the coder should assign a code related to any signs and symptoms of the condition. For instance, the physician orders a chest x-ray and documents the reason for the test as "dyspnea, rule out pneumonia." The code should be assigned for "dyspnea," not for "pneumonia".

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The opposite of the above rule applies when coding in the inpatient setting. In the inpatient coding environment, the coder has to assign a code for suggested conditions, rather than code the associated signs and symptoms. Therefore an inpatient admission listed as "possible pneumonia" would be assigned the code for pneumonia.

Inpatient Diagnosis Coding

For inpatient diagnosis coding, the principal diagnosis is the established condition responsible for the admission of the patient to the healthcare facility. When there is a definitive diagnosis, the coder does not assign a code for signs and symptoms of the diagnosis. When two conditions meet the definition for a principal diagnosis, then the coder has to sequence one of them. The exception to this rule is when coding guidelines suggest alternate sequencing or the admission situation dictates otherwise.

With contrasting or comparative diagnoses (referred to as differential diagnoses), the coder must document as "either/or" or "diagnosis A versus diagnosis B." These diagnoses are coded as if they are confirmed and sequenced according to the admission situation. For instance, if the physician lists "acute gastritis versus peptic ulcer disease," both conditions must be coded, and the admission circumstances are evaluated to find a reason why one should be sequenced before the other.

Secondary diagnoses extend the length of hospital stay and/or document the need for clinical evaluation, diagnostic procedures, therapeutic treatment, and increased monitoring and care. Reporting these conditions as secondary codes is necessary when they impact care and treatment. For instance, a patient is admitted with a diagnosis of total hip replacement due to osteoarthritis of the right hip, and the physician lists Crohn's disease as a secondary diagnosis. The existence of Crohn's disease has an impact on the care of the patient and potential issues with healing from the hip replacement.

If a physician relates abnormal findings from a diagnostic test to additional treatment or testing or to an additional diagnoses, then the coder must code that information. For example, a patient has a Pap smear, and the physician finds symptoms that require ordering a test for infections. It would be appropriate to report the abnormal findings to support the additional testing.

Outpatient Diagnosis Coding

In the outpatient setting, there is less documentation than in the inpatient setting. This is due to limited time and less contact with physicians. An "encounter" is when a patient presents in the outpatient setting for care. Also, in the outpatient setting, the term "first-listed diagnosis" is used instead of "principal diagnosis," which is used in the inpatient setting. The first-listed code is the ICD-10-CM code for the problem, illness, or condition for the encounter. Additional codes are used to report coexisting conditions. If the physician has not made an initial diagnosis, the coder must use a symptom code for the first-listed diagnosis.

If a chronic condition coexists with the condition being treated in the outpatient setting, that illness should be reported if it is treated or if it impacts management of care. If the chronic condition does not meet these specifications, it is not coded. However, a history code can be used as a secondary code when a "history of" a condition impacts treatment or care for the current first-listed code.

Special Rules of Outpatient Coding

  • Routine and preventive testing – Routine testing or preventive care is coded with Z01.80, which represents "Encounter for other specified special examinations."

  • Diagnostic testing – Results of diagnostic testing should be reported rather than related signs and symptoms if the final results are documented by the physician.

  • Therapeutic services – With therapeutic services, the first-listed code represents the reason for the services, and additional codes are used to report pertinent chronic conditions.

  • Chemotherapy and radiation – For these services, an appropriate Z code is used as first-listed code, followed by the diagnosis/reason for the service.

  • Preprocedural testing – The first-listed code for preprocedural testing should be a code from the subcategory Z01.81. Also, to report the reason for the testing, a secondary code should be assigned.

  • Ambulatory surgery – When coding for ambulatory surgical procedures, the reason for the procedure must be reported. When preoperative and postoperative diagnoses are different, then the postoperative diagnosis is reported only.

How to Look up Codes

The main term is the word or phrase used to search for and locate the necessary corresponding code. The subterm is a term used to modify the main term when searching for codes. The first step for the coder is to search the main term in the Alphabetic Index. Once that term is found, the coder has to determine if subterms exist. The subterms are listed below the main term, and they are used to modify the main term. To verify that the code selection is appropriate, the coder then must cross-reference the Tabular List, which allows for identification of additional characters that have to be reported.


Hernia, hernia (acquired) (recurrent) K46.9


     gangrene – see Hernia, by site, with, gangrene

     incarceration – see Hernia, by site, with, obstruction

     irreducible – see Hernia, by site, with, obstruction

     strangulation – see Hernia, by site, with, obstruction

 Abdomen, abdominal K46.9


       gangrene (and obstruction) K46.1

       obstruction K46.0

The main term is "Hernia," and the subterms are indented below the main term, such as "abdomen" and "with gangrene."

After finding the code in the Tabular List, the coder must look for any instructional terms, which are listed in several locations. They can be found at the start of a section range, at the beginning of a category, or at the start of a chapter. If the main term is located and has a code next to it, this is considered the default code for that main term. A default code is used when no further specific documentation exists


Conjunctivitis (staphylococcal) (streptococcal) NOS H10.9

    acute H10.3-

    atopic H10.1-

If the physician only documents "conjunctivitis," then the code assigned will be H10.9. However, if the physician documents "acute conjunctivitis," the correct code to use is H10.3 with the appropriate additional character found when cross-referencing the Tabular List.

If documentation reflects that both acute and chronic forms of a particular condition are present, the coder must use the Alphabetic Index to find entries for both terms and assign both codes. The code for the acute condition is usually sequenced before the chronic code.


Cystitis (exudative) (hemorrhagic) (septic) (suppurative) N30.90

 acute N30.00

 chronic N30.20

The correct code sequence will be N30.00 followed by N30.20.

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