Diagnosing and Coding for Chronic Kidney Disease

Diagnosing and Coding for Chronic Kidney Disease

  • 18 Jan 0
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Diagnosing and Coding for Chronic Kidney Disease

By: Angie Hlad, CRN-C, Risk Adjustment and Coding Coordinator

Chronic kidney disease (CKD) is the gradual, and often permanent, loss of kidney function.   It is a progressive condition  that can result in significant morbidity and mortality.  The condition is common in the elderly , and impacts the PACE population.  Nearly 50% of individuals over 70 years old meet the definition of CKD and 38% of this age group has stage 3 or stage 4 CKD.

Two of the most notable causes of CKD are hypertension (HTN) and diabetes mellitus (DM.) Patients with HTN, DM, and family history of kidney failure are at a higher risk for developing CKD and should be monitored closely.

Establishing a diagnosis:

To establish a diagnosis of chronic kidney disease and determine the disease stage, two factors must be evaluated:

  1. Determine the presence  of kidney damage
  2. Determine the level of kidney function (GFR)

Kidney damage can be defined as structural or functional abnormalities of the kidney, evidenced by markers, such as microalbuminuria, polycystic kidneys, hydronephrosis, kidney size, cortical thickness, etc.  Microalbuminuria is a definable marker of kidney damage and can be measured with a spot urine check.  Levels of >30 mg/dl (MA/Cr ratio) are significant for clinical microalbuminuria.  This is a simple test that can be performed in the clinic.

Determining the level of kidney function is generally done by measuring the GFR or Glomerular Filtration Rate.  Typically, the GFR is estimated (known as eGFR) using one of several standard formulas (see Estimating GFR below).  Refer to the table, showing each stage of CKD and its corresponding description

Stage

GFR*

Description

Treatment stage

1

90+

Normal kidney function but urine findings or structural abnormalities or genetic trait point to kidney disease

Observation, control of blood pressure.

2

60-89

Mildly reduced kidney function, and other findings (as for stage 1) point to kidney disease

Observation, control of blood pressure and risk factors.

3A
3B

45-59
30-44

Moderately reduced kidney function, with or without other signs of kidney damage

Observation, control of blood pressure and risk factors.

4

15-29

Severely reduced kidney function

Planning for endstage renal failure.

5

<15 or on dialysis

Very severe, or endstage kidney failure (sometimes call established renal failure)

Treatment choices.

* All GFR values are normalized to an average surface area (size) of 1.73m2

To define kidney disease as chronic, the kidney abnormalities must be chronic, as evidenced by repeated findings over time.  For example, to establish CKD 3, two eGFR values <60, must have occurred at least 90 days apart.   An eGFR < 60 represents a loss of at least half of the normal function of the kidneys, and is presumed to represent kidney damage.  Therefore, all individuals with an eGFR <60 mL/min/1.73 m2 for 3 months are considered CKD with or without kidney damage.

As noted in the above chart, for CKD stages 1 and 2, there must be other evidence of renal disease to properly diagnose, thus supporting the need to first identify if kidney damage exists.  

The eGFR can fluctuate in patients and this is common.  It is not uncommon for these fluctuations to be large and require movement of stages, either up or down.  The main concern is whether the eGFR is progressively worsening.

Many methods have been used to calculate eGFR, and others are still being proposed.  Most commercial and hospital laboratories use the MDRD (Modified Diet in Renal Disease) equation, as this formula requires only age, gender, and other factors readily available to the lab.  The chief problem for PACE participants is that the MDRD method has not been validated in patients over 70 years old and thus risks under-detecting CKD in the aged. 

Another method of measuring kidney function is the Cockcroft-Gault equation.  This method is based on age, ideal weight and creatinine.  It’s widely employed by pharmacists as the equation for creatinine clearance is used to determine renal dosing of many medications.  As such, this method has direct clinical relevance for PACE participants, whose multi-morbid conditions mean they take an average of nine or more medications.

Either of these methods are easily available to the practitioner on smartphone apps.  Capstone recommends the Cockcroft-Gault method, especially for those over 70 years old.

Coding for Chronic Kidney Disease

Once a diagnosis of CKD has been made, it must be coded properly to reflect the accurate stage of kidney disease.  ICD-9 guidelines also follow that you must code to the highest specificity for any disease or condition.  Below is a list of ICD-9 codes and corresponding descriptions of the proper coding for CKD:

  • 585.1     Chronic kidney disease, Stage 1
  • 585.2     Chronic kidney disease, Stage 2 (mild)
  • 585.3     Chronic kidney disease, Stage 3 (moderate)
  • 585.4     Chronic kidney disease, Stage 4 (severe)
  • 585.5     Chronic kidney disease, Stage 5
  • 585.6     End Stage Renal Disease
  • 585.9     Chronic kidney disease, unspecified.   (Using this code is not recommended, as measuring the eGFR to assess kidney disease would show the stage based on the eGFR level)

Other evidence of renal disease must also be coded in addition to CKD, if applicable, and would require adherence to ICD-9 guidelines for proper coding.  For example, diabetic nephropathy (583.81)

The key to proper diagnosis and coding of CKD is to first, establish presence of kidney damage, assess the eGFR, and document, document, document. 

 

*The information presented here complies with accepted coding practices and guidelines as defined in the ICD-9-CM coding book. It is the responsibility of the healthcare provider to produce accurate and complete documentation and clinical rationale, which describes the encounter with the patient and the medical services rendered, to properly support the use of the most appropriate ICD-9-CM code(s) according to the official coding  guidelines.

*The information presented herein is for general informational purposes for clinicians only and is not warranted that the information contained herein is complete, accurate or free from defects.

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