Substance P in rectal mucosa of children with chronic constipation.

Substance P content was determined by radioimmunoassay in rectal mucosa of 17 children with idiopathic constipation and 9 with normal bowel movements who were used as controls. In children with chronic idiopathic constipation, rectal mucosa substance P levels were lower than levels in the control group: 47.6 +/- 11 vs. 79.4 +/- 11 pg/mg net weight respectively (differences not statistically significant). Substance P levels in rectal mucosa of children with soiling (11/17) did not differ from those of chronically constipated children without soiling (46.0 +/- 16 vs. 50.5 +/- 19 pg/mg net weight). In children with constipation, substance P levels did not correlate either with age or duration of symptoms. Substance P levels in normal controls were similar to levels previously observed in non-constipated adults, whereas levels in constipated children were intermediate between levels observed in healthy subjects and levels in adults with chronic constipation. These findings may point to a motility derangement as a possible factor in the pathogenesis of chronic constipation in childhood.