Kidney, acute renal failure NOS

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ICD10 Diagnosis
Dx: Kidney, acute renal failure NOS
ICD10 code: N17.9
Pre-ICD10 counterpart: ARF, ARI
Charlson/ALERT Scale: none
APACHE Como Component: none
APACHE Acute Component: 2019-0: Renal/Metabolic NOS, 2019-0: Metabolic/Renal NOS
Start Date:
Stop Date:
External ICD10 Documentation

This diagnosis is a part of ICD10 collection.

  • SMW
    • 2019-01-01
    • 2999-12-31
    • N17.9
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Additional Info


  • Kidney, acute tubular necrosis (ATN) - This code Kidney, acute renal failure NOS is, by definition, for acute renal failure that is "not otherwise specified" (NOS). ATN is more specific, so if it is right, use it

Terminology related to Acute Kidney Injury

  • Nephrologists want us to use the term Acute Kidney Injury (AKI).
    • The reason is that this entity, whatever it's called, includes the full range of levels of kidney injury from minor all the way up to complete renal shutdown needing dialysis.
  • Some other terms for it are:
    • Acute Renal Failure
    • Acute Renal Insufficiency (ARI)

KDIGO Guidelines for Acute Kidney Injury (AKI)

  • We use the KDIGO criteria for defining Acute Kidney Injury (AKI, Acute Renal Failure and Acute Renal Insufficiency) (starting January 1, 2019)
  • The main thing here is identifying that the observed problem with kidney function is acute, rather than chronic - and THIS is the reason that identifying AKI requires trying to find a past/baseline value of serum creatinine
  • The KDIGO guidelines delineate several different "levels/degrees" of AKI. You'll note that (at its lowest level) AKI is present even with pretty small rises in serum creatinine. While one MIGHT think that such small rises are inconsequential, indeed they are not. As indicated in the paper "Small Acute Increases in Serum Creatinine Are Associated with Decreased Long-Term Survival in the Critically Ill", even rises in creatinine of 27 mcg/L in ICU patients are associated with higher rates of death. Thus in this new schema we are not overcounting those with significant AKI, but before we probably were undercounting them.
    • After a patient first developed AKI (as indicated by a rise in creatinine) it may continue to rise at a highly variable rate. The importance of this is that we should NOT re-code an AKI-related code each time the creatinine rises by 27 mcg/L if the continuing rise is simply part of the original event.
    • It is possible, however, for a patient to have multiple AKI events. While this would be indicated by creatinine rising again after it stabilized or fell (without dialysis), it requires a medical judgement to determine whether the re-rising is really part of the initial episode or represents a new AKI episode. There is no firm rule about how long creatinine should cease rising to say the first AKI episode is completed.
  • These criteria will apply everywhere we need to identify ARF/AKI -- including:
  • But NOT for Kidney, renal failure/insufficiency/uremia, unspecified as acute or chronic - since as stated this code is for kidney failure or insufficiency when you don't know whether it's acute or chronic.
  • In order to reduce the workload for identifying ARF/AKI, we will implement a first stage screening process to try and filter out the majority of people, who will NOT have AKI/ARF.
    • We expect that this screening will misclassify a few people who do have AKI as not having it, but we also expect that most of those who are missed will continue to experience declining renal function and their AKI/ARF will be identified in the following days.

First stage - screening

Second stage - Full assessment

  • Acute Kidney Injury (AKI) is present if ANY ONE OR MORE of the following are true (these are the KDIGO guidelines):
  • (a) Urine output < 0.5 mL/kg/hour for 6 hours
    • so, obviously, you can't make this determination until there has been at least 6 hours of observation of urine output
    • also you need a weight -- if there isn't one already measured you have the following options: Wait for one to be done; Ask the nurse to do one; Do your best to estimate the weight, remembering that if the person appears to be of average size, then you could use default values based on average values in the Canadian population, i.e. 85 kg for men and 70 kg for women
  • (b) Increase in serum creatinine by 27 micromoles/L or more within 48 hours
    • so, while this may happen quickly and thus this criterion be met before 48 hrs, you cannot make a full determination that it is NOT true until you have at least 2 serum creatinine values separated by at least 48 hours
    • in the case that the creatinine rises by >27, say in the first 12 hours, but then declines back down so that at the end of 48 hrs the net rise is <27, THEN THIS DOES QUALIFY AS AKI
  • (c) Increase in serum creatinine to 1.5 times baseline or more within the last 7 days
    • this criterion is important because since many people have some degree of CHRONIC renal insufficiency or failure, a solitary serum creatinine can't tell you if the high value is acute or chronic
    • thus, to evaluate this criterion, seek a serum creatinine value at least 7 days old -- use whatever is the most recent value more than 7 days old that is available, even if it's years old
    • if there ARE NO values >7 days old, then you can use the sex-specific normal value as follows:
      • Men: 100 micromoles/L
      • Women: 85 micromoles/L

ESRD vs Acute Renal Failure

  • UNLESS the patient has had a renal transplant and the transplanted kidney was functioning (and thus can experience acute renal failure)

About "Acute on Chronic renal failure"

  • Our definition for CRF includes two things, as above. If you are on dialysis then it is technically not possible to also have acute renal failure. And while our threshold of creatinine clearance < 15 ml/min USUALLY gets people on dialysis, that's not always the case. In other words, there are some people who don't need to start dialysis until their clearance is <10 or even 8 ml/min. THOSE people who by our definition have Stage 5 CKD cannot have ARF but rather this is considered a progression of their underlying disease. Instead of coding ARF, code the reason for dialysis ie. Fluid overload, Hyperkalemia, severe or symptomatic etc combined with Chronic kidney disease (end-stage renal/kidney disease, ESRD), Stage 5, GFR LT 15
  • And of course, if you previously had Stage 5, were on dialysis, then got a successful renal transplant, then you CAN get acute renal failure in your graft.

Alternate ICD10s to consider coding instead or in addition

Renal failure codes:
Chronic kidney disease codes:

Candidate Combined ICD10 codes

  • Also code the cause, if known.

Related CCI Codes

Data Integrity Checks

There are a number of coding rules related to renal diagnoses, centralized info about them is in ICD10 Guideline for Renal Coding.

Data Integrity Checks (automatic list)

Can't check ICD10 ARF vs APACHE ARFCCMDB.accdbdeclined
Query check CCI ICD10 Dialysis no DxCCMDB.accdbimplemented
Query check ICD10 ESRD vs ARFCCMDB.accdbnot feasible
Check CRF vs ARF across multiple encountersCentralized data front end.accdbdeclined

Legacy Info

Legacy only   

We understand that the definition in the ICD10 codes is different than the definition in ARF (Diagnosis) and ARI and CRF - Chronic Renal Failure was. We are OK with that and will use the new definitions for the new codes, and the old ones for the old codes. Hopefully we can limit the amount of time where we consider both.

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