The University of the Incarnate Word has sued the owner of Texas Vista Medical Center, the South Side hospital slated to close on Monday, accusing it of not paying millions to students completing residencies there. Texas Vista owner Steward Health Care Systems owes $4.5 million in unpaid salaries to students doing post-graduate training contracted by the hospital, according a suit filed April 5 by UIW’s Texas Institute for Medical Education and Research. Steward spokesperson Josephine Martin told the Current her employer is aware of the lawsuit filed in Bexar County district court but doesn’t comment on pending litigation.