instruction: how many people have had replace nephrostomy tube done?
response: SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT procedures_icd.hadm_id FROM procedures_icd WHERE procedures_icd.icd9_code = (SELECT d_icd_procedures.icd9_code FROM d_icd_procedures WHERE d_icd_procedures.short_title = 'replace nephrostomy tube'))