US singer Selena Gomez, 25, finally announced why she had a quiet summer. According to a post by the singer on social media platform Instagram on Sept 14, she was keeping a low profile (低调) while she recovered from a kidney transplant (肾移植). Gomez, who limited her public appearances (露面) over the summer despite the release of new tracks, said the surgery was a result of her longtime battle with lupus (红斑狼疮).