Coding Guidelines | Kidney Related Illness Codes | AKI & CKD

Global Healthcare Resource's General Manager of Coding Quality, Viba Raghavendran (CPC) and General Manager of Coding Operations Sivashankari Thangavelu (CPC,BCHHC,RCC & CCS) share helpful rule reminders and coding information for specific medical conditions.

What is Kidney Disease? 

Kidney disease can affect your body’s ability to clean your blood, filter extra water out of your blood and help control your blood pressure. It can also affect red blood cell production and vitamin D metabolism needed for bone health.

When damage to your kidneys occurs, waste and fluid can build up in your body causing swelling, nausea, weakness, poor sleep and shortness of breath. Without treatment, ongoing damage can become life-threatening. 

Kidney Disease Types

Acute kidney disease: If your kidneys suddenly stop working, over a very short period of time (usually 48 hours or less), doctors diagnose it as acute kidney injury or acute renal failure. The main causes are:
• Not enough blood flow to the kidneys
• Direct damage to the kidneys
• Build up of urine in the kidneys

Chronic kidney disease: When your kidneys do not work well for longer than 3 months, doctors diagnose it as chronic kidney disease. You may not have any symptoms in the early stages, but that's when it is simpler to treat. Diabetes (types 1 and 2) and high blood pressure are the most common culprits. High blood sugar levels over time can harm your kidneys. High blood pressure creates wear and tear on your blood vessels, including those that go to your kidneys.

ICD-10 Diagnosis Codes for
Acute Kidney Injury (AKI)

• N17-Acute kidney failure.
• N17.0-Acute kidney failure with tubular necrosis.
• N17.1-Acute kidney failure with acute cortical necrosis.
• N17.2-Acute kidney failure with medullary necrosis
• N17.8-Other acute kidney failure.
• N17.9-Acute kidney failure, unspecified.
• N17.0-Acute kidney failure with tubular necrosis. If the AKI has progressed to acute tubular necrosis (ATN), assign code N17.0. The documentation should be checked for terms such as renal tubular necrosis or tubular.
• N17.1-Acute kidney failure with acute cortical necrosis. Report N17.1 if the AKI has progressed to acute cortical necrosis. cortical necrosis and renal cortical necrosis are other terms to describe acute cortical necrosis.
• N17.2-Acute kidney failure with medullary necrosis N17.2 is reported if the AKI has progressed to with medullary necrosis. acute medullary [papillary] necrosis or renal medullary necrosis are other terms to describe acute medullary necrosis.
• N17.8-Other acute kidney failure. N17.8 should be reported when there is a specificity to the diagnosis of AKI (non-traumatic), but not one of the above. Excludes1: posttraumatic renal failure.
• N17.9-Acute kidney failure, unspecified. This code is used when only AKI/ARF is documented without documentation of any further specificity.

Chronic Kidney Disease (CKD)

Chronic Kidney Disease (CKD) has numerous causes with hypertension (HTN) being one of the most common. Diagnosing CKD involves identifying an individual’s glomerular filtration rate (GFR) which is a measure of their kidney function levels. These levels are defined as stages 1 through 5, increasing with severity (stage 5 = kidney failure).

Coding the Stages of CKD | The ICD-10-CM code is assigned to depict the documented severity (stage) of CKD:

• N18 Chronic Kidney Disease.
• N18.1 chronic kidney disease, stage 1.
• N18.2 chronic kidney disease, stage 2 (mild).
• N18.3 chronic kidney disease, stage 3 (moderate).
• N18.4 chronic kidney disease, stage 4 (severe).
• N18.5 chronic kidney disease, stage 5.
• Code N18.6 End stage renal disease is assigned only when the provider has documented end-stage renal disease (ESRD).
• Encounters where both a stage of CKD and ESRD are documented, report N18.6, only.
• N18.9 chronic kidney disease, unspecified.

CKD & Hypertension

ICD-10-CM Coding Guidance:
The ICD-10-CM code book does not have a hypertension table in the index. The reference to terms malignant and benign hypertension were removed as they were considered outdated. All three previous designations in ICD-9 are now reported with just one ICD-10 code for essential hypertension, code I10.

Hypertensive CKD:
Category I12 (hypertensive CKD) applies when both HTN and CKD are stated as diagnoses. If the documentation specifically identifies a different cause, CKD should not be coded as hypertensive.

Hypertensive heart and CKD:
Combination category I13 (hypertensive heart and CKD) applies when both hypertensive heart disease and hypertensive kidney disease are stated as diagnoses.

Category I13 includes the conditions from I11 and I12 categories. If a patient has hypertension, heart disease and CKD, only a code from I13 should be used. Do not use individual codes for hypertension, heart disease and CKD, or codes from I11 or I12.

CKD &
Diabetes Mellitus

In ICD-10-CM, more than one code is required for patients with diabetic CKD. A combination code indicating the type of diabetes with diabetic CKD, along with a code identifying the stage of CKD.

Based on the type of diabetes, a code would be assigned:

• For category N18, CKD, there is an instructional note to code first any associated diabetic CKD (E08.22, E09.22, E10.22, E11.22, E13.22). Category N18 would be reported after the diabetes code, as secondary, to specify the stage of CKD (N18.1-N18.6, N18.9).
• It is also advised to use an additional code to identify dialysis status (Z99.2), if applicable. Code N18.6, end-stage renal disease, is to be reported for CKD that requires chronic dialysis
• In ICD-10-CM, there is an assumed cause and effect relationship between diabetes and CKD when both conditions are documented in the medical record. However, if documentation specifies that diabetes is not the underlying cause of CKD, it should not be coded as a diabetic complication.

Anaemia in CKD
Code D63.1, Anaemia in CKD, is a manifestation code (i.e., not to be reported as a primary/ first listed diagnosis). It is necessary to first identify the underlying stage of CKD from category N18.

CKD &
Kidney Transplant

Patients with a kidney transplant may still suffer some type of CKD as the transplant may not completely reinstate kidney function. Thus, having CKD alone does not mean that there is a transplant complication. Assign a code to establish the stage of CKD (N18 category) and kidney transplant status (Z94.0).

If a complication resulting from the transplant (e.g., failure or rejection) is clearly documented, it would be appropriate to code the complication of kidney transplant from subcategory T86.1-.

Conclusion

Like all medical conditions, chronic kidney disease can be nuanced and challenging to code. We hope our coding tips provide helpful rule reminders for CPCs. 

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