According to a recent study, 158,753 patients

...who had been discharged from a hospital after undergoing one of 10 major surgical procedures were tracked to determine whether they had been readmitted to a hospital within the first 90 days of discharge. The study found:

• 10.4% of the patients were readmitted within the first 30 days of discharge
• 6.5% of the patients were readmitted between 31 and 90 days of discharge
• 38.3% of the readmitted patients were readmitted to a different hospital than the original hospital

Source: "Early Versus Late Readmission After Surgery Among Patients With Employer-provided Health Insurance," Annals of Surgery, abstract only, September 2015, http://journals.lww.com/annalsofsurgery/Abstract/2015/09000/Early_Versus_Late_Readmission_After_Surgery_Among.12.aspx