Specificity Coding of Acute Kidney Injury (AKI) and Sequencing

There are several different codes that can be used to report the diagnosis of acute kidney injury and/or acute renal failure. This is one example of why diagnoses should not be coded by the use of only the Alphabetic Index within ICD-10-CM. It is imperative that coders also use the tabular before final determination of the code is made. If the coder only looks in the Alphabetic Index under injury | kidney | acute, the index goes to N17.9 (acute renal kidney failure, unspecified). If the type or cause of the AKI/ARF is further specified then N17.9 would not be appropriate. However, if the coder begins the search with the term “failure” there will be several selections for further specificity under failure | renal | acute.

When coding AKI/ARF, there are instructional notes within the ICD-10-CM Index for coders to follow as well as Exclude1 and Excludes2 notes. When a cause for the AKI/ARF has been identified the underlying condition/cause should be reported also. Traumatic kidney injuries are reported with codes from S37.0-.

• N17.0—Acute kidney failure with tubular necrosis. Coders see ATN (acute tubular necrosis) documented in patient records often. This is a common diagnosis that a query is necessary for clarification. If the AKI has progressed to ATN then the code N17.0 is reported and not the code default in the Alphabetic Index for AKI. Other terms that may be used to describe ATN could be renal tubular necrosis or tubular necrosis. These are terms that should be searched for when AKI is documented to see if there could be further specificity in code assignment. ATN occurs when there is damage to the kidney tubule cells. These are the cells that reabsorb fluid and minerals in the kidney from urine as it is forming. When this occurs, there is a lack of oxygen reaching the cells of your kidneys.
• N17.1—Acute kidney failure with acute cortical necrosis. This isn’t as commonly documented as ATN but coders will see this. If the AKI has progressed to acute cortical necrosis then N17.1 is reported and not the code default in the Alphabetic Index for AKI. Other terms that may be used to describe acute cortical necrosis can be cortical necrosis and renal cortical necrosis. This is a rare cause of AKI and is due to ischemic necrosis of the renal cortex. This is typically caused by diminished/reduced renal arterial perfusion. Intravascular coagulation, vascular spasm and microvascular injury are the main causes of this type of AKI.
• N17.2—Acute kidney failure with medullary necrosis This isn’t as commonly documented as ATN but coders will see this. if the AKI has progressed to with medullary necrosis then N17.2 is reported and not the code default in the Alphabetic Index for AKI. Other terms that may be used to describe acute medullary necrosis can be acute medullary [papillary] necrosis or renal medullary necrosis. This is caused by infarction involving the medulla and referred to as necrotizing papillitis.
• N17.8—Other acute kidney failure. This code is reported when there is a specificity to the diagnosis of AKI (non-traumatic) but is not one of the ones above.
• N17.9—Acute kidney failure, unspecified. This code is reported when only AKI/ARF is documented without any further specificity documented.

Sequencing of AKI

There are many different scenarios that would dictate the sequencing of AKI/ARF. The definition of PDX should always be used when determining the PDX. Remember that just because the condition may be present on admission does not necessarily mean that it is appropriate as PDX. Chapter specific guideline must be followed as well as other coding guidance that your record may require. Some of the most common specific guidelines that come to mind are sepsis, OB/delivery records and transplant complications.

To see examples of each of these, purchase our Acute Kidney Injury eBook.

More AKI Blogs

• What is Acute Kidney Injury? 
• Clinical Indicators for Acute Kidney Injury
• Is Documentation Present to Report Acute Kidney Injury?
• Reasons for Acute Kidney Injury Denials and Prevention

Authored by Kim Boy, RHIT, CDIP, CCS, CCS-P

References
cdc.gov/mmwr/volumes/67/wr/mm6710a2.htm
emedicine.medscape.com/article/1925597
americannursetoday.com/acute-kidney-injury
kidney.org/atoz/content/AcuteKidneyInjury#
mayoclinic.org/diseases-conditions/kidney-failure/symptoms-causes/syc-20369048
uofmhealth.org/health-library/aa115361
ICD-10-CM Alphabetic and Tabular Indexes
ICD-10-CM/PCS Coding Clinic, First Quarter 2019 Page: 12
ICD-10-CM/PCS Coding Clinic, Second Quarter 2019 Page: 7
ICD-10-CM Official Guidelines for Coding and Reporting FY 2020

The information contained in this coding advice is valid at the time of posting. Viewers are encouraged to research subsequent official guidance in the areas associated with the topic as they can change rapidly.