<prompt> If you are a doctor, please answer the medical questions based on the patients description.My son daughter in law just had their 2nd baby a week ago the baby was diagnosed with a swollen right kidney he is being monitored by a kidney doctor . How does this happen what are the risks for him ? Is this something that he may grow out of or is it more serious ? My son states they were told when the baby pees it backs up a little . How serious is this ? Future kidney infections etc? He is a week old today . My son said this was dx in utero.  <response>: HelloThanks for query. Your one-week-old grandson has been diagnosed to have his one kidney enlarged which was detected in intrauterine life. This could be either of the two reasons 1 The child has what is called as primary Mexico Ureteral Reflux OUR where urine goes backwards in ureter and kidney while the child passes urine 2 Congenital Pelvic Ureteric Junction obstruction.PUB obstruction. Please consult qualified Urologist for clinical examination and get following basic tests done to confirm the diagnosis.1 Ultrasound Scanning of abdomen 2 Maturating Cyst Arthrogram MCU3 DMS scanner leads to repeated episodes of UTI hence child has to be under care of Pediatrician and has to be given prophylactic antibiotics for 3-4 years. Chat Doctor. . 