Try this rewrite which is based on JOINs and see if the error persists
SELECT p.LastName, p.FirstName, p.Phone , pr.ProcDescription
FROM Patient p
INNER JOIN Visit v ON p.MedicalRecNum = v.MedicalRecNum
INNER JOIN Visit_proc vp ON v.VisitID = vp.VisitID
INNER JOIN [PROCEDURE] pr ON vp.ProcID = pr.ProcID
WHERE pr.ProcDescription LIKE '%tomy'
ORDER BY pr.ProcDescription ASC, p.LastName ASC, p.FirstName DESC;