Emperor Naruhito underwent a prostate examination at the University of Tokyo Hospital on Sunday after a rise in a tumor marker, the Imperial Household Agency said.
The 62-year-old arrived at the hospital at around 9:30 a.m., underwent an MRI scan and left at around 1 p.m., the agency said. The result of the scan will be learned in a few days, it added.
The emperor has no symptoms. When the agency announced in early October that the emperor would undergo an examination, it said his prostate specific antigen level was slightly higher than normal and "showing a slightly worrying movement."
The doctors at the hospital will study the result and determine whether a biopsy is required, the agency said.
The emperor has been engaged in official duties since the announcement regarding the medical examination and visited Okinawa with Empress Masako late last month.
In 2007, the emperor had endoscopic surgery to remove a benign duodenal polyp, but he has not had any other medical problems.