how many hours have passed since patient 52898 stayed in the careunit csru for the last time in their current hospital visit?
select 24 * ( strftime('%j',current_time) - strftime('%j',transfers.intime) ) from transfers where transfers.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 52898 and admissions.dischtime is null ) and transfers.careunit = 'csru' order by transfers.intime desc limit 1