What are the ICD-10 2018 Coding Guidelines for Chronic Kidney Disease?

More than 660,000 Americans have kidney failure, according to the National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK). People with CKD face a very high risk of cardiovascular disease, with renal impairment progressing to loss in renal function over time. Once the physician makes a diagnosis of CKD, it should be coded appropriately to reflect the correct stage of the kidney disease. Physicians can ensure proper ICD-10 code assignment by partnering with a medical coding service provider that understands CKD, its causes and risk factors, and treatment options.

Causes of CKD

Diabetes and high blood pressure are the two main causes of CKD. Diabetes causes damage to many organs, including the kidneys and heart, as well as blood vessels, nerves and eyes. High blood pressure, or hypertension, if poorly controlled, is a leading cause of heart attacks, strokes and CKD. Also, CKD can cause high blood pressure.

Other conditions that affect the kidneys are:

• Glomerulonephritis, a group of diseases that cause inflammation and damage to the kidney’s filtering units.
• Polycystic kidney disease, an inherited disease which causes large cysts to form in the kidneys and damage the surrounding tissue.
• Malformations that occur as a baby develops in its mother’s womb and affect the kidneys.
• Lupus and other diseases that damage the body’s immune system.
• Kidney stones, tumors or an enlarged prostate gland in men.
• Repeated urinary infections

Acute Kidney Disease (AKF) and CKD

The rising incidence of CKD is attributable to factors such as aging population and the higher prevalence of co-morbidities, such as, hypertension, diabetes, and obesity. Patients with CKD may also experience acute kidney failure (AKF), which is abrupt loss of the ability of the kidneys to remove waste and concentrate urine and/or excrete electrolytes. AKF is potentially reversible, but CKD gets worse over time and can lead to permanent kidney failure.  If the physician clearly documents both AKF and CKD, both conditions must be coded.

ICD-10 Codes for Reporting CKD

In ICD-10, coding of CKD comes under the section of Diseases of Genitourinary System (N00-N99). The ICD-10 codes for acute kidney failure and chronic kidney disease come under N17-N19:

• N17 Acute kidney failure
• N18 Chronic kidney disease (CKD)
• N19 Unspecified kidney failure

CKD classified based on Severity

Based on severity, CKD is designated by Stages 1-5.

• N18, Stage 2 – mild CKD
• N18.3, Stage 3 – moderate CKD
• N18.4, Stage 4 – severe CKD
• N18.6 Stage 5 – End-stage renal disease (ESRD) or end-stage renal failure
  Typically, ESRD patients will have kidney function in the area of 10-15% or so. If the provider documents both a stage of CKD and ESRD, only code N18.6 should be assigned.

If a patient has CKD stage 5 and requires chronic dialysis, ESRD code E18.6 should be reported.

CKD Coding for Patients who have had a Kidney Transplant

In the case of patients who have undergone kidney transplant, the provider must document the status of the transplant. As the kidney transplant may not fully restore kidney function, the patient may still have some form of CKD. ICD-10 coding guidelines state that the presence of CKD alone does not constitute a transplant complication. Therefore, the documentation must specify whether:

• CKD is evidence of continued impairment of the kidney function, or
• CKD it is a complication of the transplant

For patients who have received a kidney transplant, the coder should assign the appropriate N18 code for the patient’s stage of CKD and code Z94.0, Kidney transplant status.

Coding Kidney Transplant Complications

A transplant complication code is only assigned if the complication affects the function of the transplanted organ.

• Code T86.1 should be used to report complications of a kidney transplant, such as transplant failure or rejection or other transplant complications. Code T86.1 should not be assigned for post kidney transplant patients who have chronic kidney (CKD) unless a transplant complication such as transplant failure or rejection is documented.
• Two codes are required to fully describe a transplant complication. To report conditions that affect the function of the transplanted kidney, other than CKD, use a code from subcategory T86.1 Complications of transplanted organ, Kidney, and a secondary code that identifies the complication.
• Pre-existing conditions or conditions that develop after the transplant are not coded as complications unless they affect the function of the transplanted organs.

If the documentation is unclear as to whether the patient has a complication of the transplant, the medical coding company should clarify the matter with the provider.

Coding CKD along with Other Conditions

Patients with CKD may also suffer from diabetes mellitus, hypertension and other serious conditions. In this case, the coding guidelines are as follows:

Hypertensive CKD:

• Codes from category I12, Hypertensive chronic kidney disease, should be assigned when both hypertension and a condition that come under category N18, Chronic kidney disease (CKD), are present. ICD-10 presumes a cause-and-effect relationship and classifies CKD with hypertension as hypertensive chronic kidney disease.
• If both hypertension and CKD are present, hypertensive CKD (I12, I13) should be coded first and a secondary code from category N18 should be assigned to identify the stage of the CKD.
• If both hypertensive chronic kidney disease and acute renal failure are present, an additional code should be used to indicate the acute renal failure.

Hypertensive Heart and CKD:

• When there is hypertension, heart disease and CKD, codes from combination category I13 should be reported (not individual codes for hypertension, heart disease and CKD, or codes from I11 or I12).
• If heart failure is present, an additional code from category I50 should be assigned to identify the type of heart failure.
• The appropriate code from category N18, CKD, should be used as a secondary code with a code from category I13 to identify the stage of chronic kidney disease.

Pre-existing hypertension in pregnancy:

• Category O10, Pre-existing hypertension complicating pregnancy, childbirth and the puerperium, includes codes for hypertensive heart and hypertensive CKD. When assigning one of the O10 codes, a secondary code from the appropriate hypertension category should be included to specify the type of heart failure or chronic kidney disease.

Chronic kidney disease (CKD) affects 1 in 7 people in the United States and is the 9^th leading cause of death in the country. Early detection can help prevent the progression of kidney disease to kidney failure. In fact, kidney disease is considered a public health concern and is a top priority due to its increasing and widespread prevalence and morbidity. Physicians can ensure correct code assignment and reimbursement by providing consistent, complete documentation in the medical record and working with an experienced medical coding service provider to report CKD.