42 CFR § 440.140
Inpatient hospital services. Inpatient hospital services for individuals age 65 or older in institutions for mental diseases means services provided under the direction of a physician for the care and treatment of beneficiaries in an institution for mental diseases that meets the requirements specified in 482.60(b), (c), and (e) of this chapter and -
(1) Meets the requirements for utilization review in § 482.30(a), (b), (d), and (e) of this chapter; or
(2) Has been granted a waiver of those utilization review requirements under section 1903(i)(4) of the Act and subpart H of part 456 of this chapter.