Cystinuria

This code represents an inherited metabolic disorder characterized by defective transport of dibasic amino acids (cystine, ornithine, lysine, and arginine) in the renal tubules and gastrointestinal tract. The primary clinical manifestation is the formation of cystine stones in the urinary tract due to the insolubility of cystine.

Assign this code for patients diagnosed with cystinuria, typically identified through urinalysis showing cystine crystals or amino acid chromatography. Documentation should confirm the diagnosis of this specific aminoacidopathy, often following recurrent urolithiasis or family history.

• Do not confuse with other amino acid metabolism disorders; ensure documentation specifically states "cystinuria."
• Code any associated urinary tract calculi separately, such as N20.0 for calculus of kidney.
• This code is a primary diagnosis when the patient is being treated for or evaluated for cystinuria itself.