The nation spends billions of dollars a year on patients' return visits to the hospital—many of which are readmissions that could be prevented with better follow-up care, according to a study published in the New England Journal of Medicine. As many as a fifth of all Medicare patients are readmitted within a month of being discharged and a third are rehospitalized within 90 days, according to the study. Half the patients who returned to the hospital within 30 days of undergoing treatment other than surgery apparently did not see a doctor before they went back.