Q&A: Relationship between hypertension and CKD

Q: I’ve been told that if there are clinical indicators to support that chronic kidney disease (CKD) is the etiology of a patient’s hypertension, a code from category I15 would be assigned. Code I12 is for hypertensive CKD, isn’t it? So why do we have to use I15 codes instead? What’s the main difference between I12 and I15?  

A: The relationship between CKD and hypertension is a complicated one. Hypertension is the second leading cause of renal failure. The kidneys are highly vascularized as their purpose is to filter the blood of wastes and fluid. Hypertension leads to stiff and damaged arteries (narrow, stiff, and weak) which are less efficient in delivering the blood to the kidneys. When the blood vessels become damaged, the nephrons that filter blood don’t receive the oxygen and nutrients they need to function well. This is hypertensive kidney disease which is coded using I12.0.

The converse of this is that renal disease can also cause hypertension. The I15 code grouping classifies secondary hypertension. Secondary hypertension is hypertension caused by another condition or disease. There are many different conditions or diseases that can cause secondary hypertension, including diseases of the kidney. Diseases such as diabetic nephropathy, polycystic kidney disease, and glomerular disease can lead to hypertension. I15.0, Renovascular hypertension, or I15.1, Hypertension secondary to other renal disorders, would be assigned depending on the condition. A code for the contributing condition should be assigned as well.

If you are unsure as to the relationship between the hypertension and the kidney disease, you should query the provider.

Editor’s Note: Laurie Prescott, RN, MSN, CCDS, CCDS-O, CDIP, CRC, CDI education director at HCPro, answered this question. For information regarding CDI Boot Camps, click here. This article originally ran in September 2019 and has been updated according to all new coding and documentation guidelines.