Nephrology ICD-10-CM codes

CKD is staged in category N18, and the stage must match the documented GFR: N18.31 (stage 3a) and N18.32 (stage 3b) replaced the old undivided stage 3 for most reporting, with N18.30 only when 3a versus 3b is not documented. N18.6 (ESRD) is assigned only on provider documentation of end stage disease and takes precedence over a stage code; dialysis patients add Z99.2 (dependence on renal dialysis), and transplant recipients carry Z94.0.

The guidelines presume causal links that nephrology claims must reflect. Hypertension with CKD is coded to I12 (I12.9 for stages 1 to 4, I12.0 for stage 5 or ESRD) followed by the N18 stage; when heart failure is also present the I13 series applies (I13.0, I13.2). Diabetic CKD uses the combination code E11.22 first, then the stage. Reporting N18 codes alone for a hypertensive or diabetic patient understates the clinical picture and fails payer edits.

The metabolic complications of renal failure are separately reportable and affect risk adjustment: anemia in CKD (D63.1, coded after the CKD stage), secondary hyperparathyroidism of renal origin (N25.81), hyperkalemia (E87.5), acidosis (E87.20), and hyponatremia (E87.1). Acute kidney injury (N17.9) can be coded with CKD when acute-on-chronic injury is documented. Proteinuria workups use R80.9 or R80.1 (persistent) until a glomerular diagnosis like N04.9 is established.