Evaluation of the anal position in newborns and children with chronic constipation. Incidence of anterior ectopic anus

INTRODUCTION: Anterior ectopic anus (AEA), continues to be a controversial issue. The objective is to determine the normal position of the anus or anal ano-genital index (AGI) in newborns (NB) and in a group of infants with chronic constipation, know the incidence of AEA in both groups, and its relationship with constipation. METHODS: A prospective aleatory study is performed in where the AGI is determined in 529 NB and 64 older patients with chronic constipation. The AGI is obtained by dividing the distances (cm): vulvar fornix-anus/fornix-coccyx in females and scrotum-anus/scrotum-coccyx in males. The NB group is further studied for gestational age, weight, number of meconium discharges and anal calibration. The newborns with AEA are then controlled to exclude constipation. In patients with chronic constipation, their age, sex and AGI are evaluated. The statistical comparisons are made by a Student's t test and Welch's t test for independent samples. RESULTS: 49.5% of NB are male. The average gestational age is 38.95 +/- 2.08/w in NB females and 38.54 +/- 2.26/w in NB males. The average weight is 3101.91 +/- 511.41/g in newborn females and 3145.14 +/- 573.36/g in newborn males. The average AGI of NB females is 0.40 +/- 0.05 and NB males 0.53 +/- 0.06. AEA is considered with AGI < 0.30 in females and < 0.41 in males. 2.2% of NB females (6/267) and 1.1% of NB males (3/262) have AEA. There is a significant difference between the AGI of NB females and NB males (p < 0.0001). 98% of NB discharge meconium in the first 24 hours. 2 NB females with AGI 0,21 and 0,26 had severe constipation in the first months of life. In group with chronic constipation (64 pacients), 59.4% are female. The AGI is 0.36 +/- 0.1 in females and 0.47 +/- 0.1 in males (p < 0.0001). Concerning of AEA in the NB group (AGI < 0.30 in females and 0.41 in males) incidence of AEA in group with chronic constipation is 35% in males and 47% in females. CONCLUSIONS: The position of the anus in the perineal floor is anterior in females, with significant differences (p < 0.0001) to the AGI in males. AEA has more incidence in females (2.2%). In the constipated group 47% of females had AEA and it is considered the probable reason for this disorder in these patients. To conclude, each NB evaluation protocol should include determination of the AGI in the neonatal period to exclude AEA and to prevent clinical consequences.