CTRL and necrotizing enterocolitis: The mean fecal K8 level in the NEC group (day at onset) was 221.64 μg/ml (range 65.64–413.7 μg/ml), which was significantly higher compared to the GA-matched Ctrl1 group (221.64 ± 156.97 vs. 13.36 ± 7.96 μg/ml, p = 0.041) (Figure 2(a)).