Association between stool consistency and clinical variables among infants with cystic fibrosis: Findings from the BONUS study.

Background: Concerns related to stool consistency are common in the first year of life among children with cystic fibrosis (CF). However, normal stool patterns for infants with CF have not been described.

Methods: Secondary analysis was completed from the previously described BONUS cohort which followed 231 infants with CF through the first 12 months of life. Pain, stool category, stool frequency, feeding type, PERT dose, acid suppression medication, antibiotics usage, stool softener usage and fecal calprotectin were described at 3, 6, and 12 months. Repeated measure ANOVA was used to test the difference in mean stool number. Generalized linear mixed models were used to investigate the relationship between stool characteristics and various factors.

Results: The frequency of constipation was stable throughout the first year of life (10-13%) while watery stool significantly decreased from 21.3% at 3 months to 5.8% at 12 months (p=<0.001). The number of stools at months 6 (mean=2.40) and 12 (mean=2.50) are significantly lower than in month 3 (mean=2.83), p<0.025. Exclusive breast feeding was associated with an increased risk for constipation (OR=2.64  [1.60-4.37], p = 0.002) while exclusive formula feeding and acid suppression was associated with decreased risk for constipation (OR=0.40  [0.26-0.61], p=<0.0001 and OR=0.59  [0.39-0.89], p = 0.01 respectively). Pain was not significantly associated with stool consistency.

Conclusion: Stool frequency and consistency evolves in infant with CF in a fashion similar to that reported in non-CF infants over the first year. Constipation was not associated with pain and was less common among infants receiving acid suppression or exclusively formula feeding.