The Pelicans said medical imaging taken Sunday morning revealed a small "pneumothorax" -- where air leaks into the space between the lung and chest wall to collapse the lung.
Additional examinations will be performed in the next 48 hours to determine the progress of healing, the Pelicans said, with more information to follow those results.
The 32-year-old American shooting guard also was diagnosed with a pneumothorax in December 2021 while he was playing for the Portland Trail Blazers. He was sidelined for about six weeks.
So far this season, McCollum has averaged 21.7 points, 5.7 assists and 4.8 rebounds a game for the Pelicans.
McCollum was the 10th overall pick of the 2013 NBA Draft by Portland and in 2016 was named the NBA's Most Improved Player.
McCollum was traded to the Pelicans in February 2022 in a deal involving seven players and three draft picks. He agreed on a two-year contract extension in September 2022 worth $64 million.
Last year marked the first season in his career that McCollum missed the NBA playoffs.
