First author Dr. Chandy Ellimoottil and senior author Dr. Ahmer Farooq of the Loyola University Medical Center near Chicago said the study involved 500 randomly selected urologists of the nation's 9,940 urologists.
The researchers found 79.6 percent of physicians were rated by at least one of the 10 free physician-review websites, the researchers said. Eighty-six percent of physicians had positive ratings, with 36 percent receiving highly positive ratings. The Healthgrades website had the most physician ratings.
The study, published online ahead of the print edition of the Journal of Urology, found websites such as Healthgrades.com might be based on scores per physician ranging from zero to 64 -- with the average 2.4 reviews.
Ellimoottil said because physicians typically received so few ratings, a highly negative or highly positive score from just one or two patients could skew the physician's rating.
"These sites have potential to help inform consumers," Ellimoottil said in a statement. "But the sites need more reviews to make them more reliable."