Baby Was Coughing Before.baby Spitting Up Brown Mucus. On 3

baby was coughing before.baby spitting up brown mucus. on 3 bibs,it had streaks and blobs, the colour was light brown and dark brown. He had one feed and took him hospital, they sed it could be colic. After his feed when he was doing sickness the colour was brown mixing with white mucus.His left kidney is dilated before born and has gone worse, he recently had a mag3 scan for his kidneys.I am waiting for his kidney results as wel. I am worried is it to do with his kidney?.