Derm Dx: Blisters on the buttock after surgery

An 8-year-old boy is admitted to the hospital with acute appendicitis. He is brought to the operating room for a laparoscopic appendectomy. During the procedure he is placed in a supine position, and his skin is prepped with povidone-iodine solution (Betadine) and draped in a sterile fashion. The procedure lasted two hours.

Immediately upon awaking from anesthesia, the patient ...