Acute Kidney Injury: A Codable Condition?

The third quarter 2011 issue of the AHA Coding Clinic for ICD-9-CM has clarified the issues surrounding the code of “acute kidney injury.” There has been much discussion in the medical community about the differentiation and coding of acute kidney injury (AKI), acute kidney disease (AKD) and how they relate and interact with chronic kidney disease (CKD).

Acute kidney injury (AKI) is a non-traumatic disease that is a subset of acute kidney disease but the exact definitions and differences between the two are not completely agreed upon in the provider community. The conventionally used term acute renal failure (ARF) is often used in reference to the subset of patients who are often admitted in the ICU with a need for acute dialysis support. Evidence from recent studies has demonstrated that even minimal increases in serum creatinine are associated with a dramatic impact on the risk of mortality. For this reason, the term ARF was replaced by “acute kidney injury” (AKI), as defined by criteria defined by risk, injury, failure, loss, and end-stage kidney disease. AKI is not just ARF; it also incorporates the entire spectrum of the syndrome, from minor changes in renal function to the requirement for renal replacement therapy. Stages of AKI were developed, based on rate of change of kidney function or magnitude of urine output, but have not been accepted in the medical community at the same level that those related to chronic kidney disease (represented by codes 585.1 – 585.9) were.

The current indexed entry for acute kidney injury in ICD-9-CM is as follows:



acute (nontraumatic) 584.9

This assignment to code 584.9 for acute kidney injury encompasses all stages (as documented in the medical record), and that due to all underlying conditions. Several questions have been submitted to the Central Office on ICD-9-CM concerning several different conditions, such as AKI with diabetic nephropathy and CKD, or AKI due to lupus nephritis. The questions revolved around whether diagnosis code 584.8 Acute kidney failure with other specified pathological lesion in kidney, wouldn’t be a more appropriate assignment. The Coding Clinic Advisory Board and the Cooperating Parties have had multiple extensive conversations with subject matter experts in the field of nephrology concerning these issues. Although a restructuring of category 584 is generally supported and seen as useful, there is no consensus in the medical community about the designation of AKI stages or how the category should be restructured. As a result, official coding guidance instructs the coder to assign any case documented as “acute kidney injury” to code 584.9.

The Central Office on ICD-9-CM sited the partial code-set freeze and the limited remaining years for ICD-9-CM as reasons for declining to make major revisions at this time. Stay tuned though . it appears that the ICD-10-CM system is structured similarly with one code (N17.9) indexed to AKI.

Whether they can agree or not on the classification of AKI, clinicians agree that it’s a major condition that needs to be specifically tracked. The mortality with AKI in the ICU setting can be extraordinarily high and the condition is often accompanied by multiple organ failure. Determining actual incidence of the disease and differentiating it from the other renal diseases depends to a certain extent on being able to classify it appropriately from an ICD classification point of view. Look for more information to follow on AKI during the next several years.

Refer to Coding Clinic, 3rd quarter 2011, and 2nd quarter 2003 for guidance related to coding AKI. Then test yourself with the following quiz:


1. The term AKI is an abbreviation for:

a. acute knee injury

b. acute kidney intervention

c. acute kidney injury

d. antiplastic kidney indicator

2. The most appropriate ICD-9-CM diagnosis code for AKI is:

a. 584.8

b. 584.9

c. N17.9

d. 585.9

3. AKI is defined as a subset of:

a. CKD (chronic kidney disease)

b. AKD (acute kidney disease)

c. diabetic nephropathy

d. ARF (acute renal failure)

e. congenital kidney disease

This month’s column has been prepared by Cheryl D’Amato, RHIT, CCS, director of HIM, hospital solutions, and Melinda Stegman, MBA, CCS, clinical technical editor, OptumInsight (formerly Ingenix).

Coding Clinic is published quarterly by the American Hospital Association.
CPT is a registered trademark of the American Medical Association.


1. c. AKI is an abbreviation for acute kidney injury, a disease process relation to acute kidney failure.

2. b. AKI is indexed only to code 584.9, regardless of the stage documented or the underlying cause.

3. d. AKI is a severe condition and is a subset of acute renal failure.

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