The guidelines state:
HYPERTENSION
The classification presumes a causal relationship between hypertension and heart involvement and between hypertension and kidney involvement, as the two conditions are linked by the term “with” in the Alphabetic Index. 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.
For hypertension and conditions not specifically linked by relational terms such as “ with,” “associated with” or “due to” in the classification, provider documentation must link the conditions in order to code them as related.
1) Hypertension with Heart Disease
Hypertension with heart conditions classified to I50.- or I51.4- I51.9, are assigned to a code from category I11, Hypertensive heart disease. Use an additional code from category I50, Heart failure, to identify the type of heart failure in those patients with heart failure.
The same heart conditions (I50.-, I51.4-I51.9) with hypertension are coded separately if the provider has specifically documented a different cause. Sequence according to the circumstances of the admission/encounter.
2) Hypertensive Chronic Kidney Disease
Assign codes from category I12, Hypertensive chronic kidney disease, when both hypertension and a condition classifiable to category N18, Chronic kidney disease (CKD), are present. CKD should not be coded as hypertensive if the physician has specifically documented a different cause.
The appropriate code from category N18 should be used as a secondary code with a code from category I12 to identify the stage of chronic kidney disease.
See Section I.C.14. Chronic kidney disease.
If a patient has hypertensive chronic kidney disease and acute renal failure, an additional code for the acute renal failure is required.
3) Hypertensive Heart and Chronic Kidney Disease
Assign codes from combination category I13, Hypertensive heart and chronic kidney disease, when there is hypertension with both heart and kidney involvement. If heart failure is present, assign an additional code from category I50 to identify the type of heart failure. The appropriate code from category N18, Chronic kidney disease, should be used as a secondary code with a code from category I13 to identify the stage of chronic kidney disease.
See Section I.C.14. Chronic kidney disease.
The codes in category I13, Hypertensive heart and chronic kidney disease, are combination codes that include hypertension, heart disease and chronic kidney disease. The Includes note at I13 specifies that the conditions included at I11 and I12 are included together in I13. If a patient has hypertension, heart disease and chronic kidney disease, then a code from I13 should be used, not individual codes for hypertension, heart disease and chronic kidney disease, or codes from I11 or I12.
For patients with both acute renal failure and chronic kidney disease, an additional code for acute renal failure is required.
If the patient has CKD and HTN, they are considered to have a causal relationship, even if it's not outright stated in the documentation. However, it the provider specifically documents they are NOT related, then the causal relationship would not apply.
