42 CFR §417.423

1. (a)ESRD patients.
   1. (1)A Medicare beneficiary who has been medically determined to have end-stage renal disease is not eligible to enroll in an HMO or CMP.
   2. (2)However, if a beneficiary is already enrolled in an HMO or CMP when he or she is determined to have end-stage renal disease, the HMO or CMP—
      1. (i)Must reenroll the beneficiary as required by § 417.434; and
      2. (ii)May not disenroll the beneficiary except as provided in § 417.460.
2. (b)Hospice patients. A Medicare beneficiary who elects hospice care under § 418.24 of this chapter is not eligible to enroll in an HMO or CMP as long as the hospice election remains in effect.