Massachusetts Subscriber
Answer: Complex renal cysts are a problem for coders. Clinically, they make up a large category, ranging from simple cysts to malignant neoplasms (renal carcinomas). If the cyst is benign with a few thin septa, use 593.2 (cyst of kidney, acquired).
If the cyst is indeed complex with multiple internal septa and a thickened wall, this may represent either a true neoplasm (benign or malignant) or a renal dysplasia. For a preoperative diagnosis code, use either 753.15 (renal dysplasia) or 239.5 (neoplasms of unspecified nature; other genitourinary organs). Or you can wait for the postoperative pathology, if the complex cyst is explored or removed, to code the final diagnosis either benign lesions as above or 189.0 (malignant neoplasm of kidney).
The best option is to have the doctor choose the code, especially if no kidney exploration is planned.