<prompt> Gas reaches colonic end in a newborn by?2-3 hours4-5 hours6-7 hours8-10 hours  <response>: 8-10 hours REF: Basic anatomical and physiological data for use in radiological protection by Jack Valentin, ICRP Page 128 Colonic transit time of different age group is Newborn 1 year 5-15 years Adults Male Female 8 hours 10 hours 11 hours 12 hours 16 hours 