Determination of Normal Anal Position Index Using a Modified Technique in Turkish Neonates

Aim: This study was aimed to determine the normal position of the anus using the anal position index (API) in an attempt to develop a more sensitive method for measuring API. To investigate API in a wide range of neonates, both term and preterm infants were included in the present study. Materials and Methods: API was determined by measuring the anus‑fourchette (FA) and anus‑coccyx (AC) distance in female neonates and the anus‑scrotum and AC distance in male neonates. API is defined as the ratio of the FA (scrotum) distance to the AC distance. A digital caliper was used for all measurements. The FA or scrotum and coccyx‑fourchette or ‑scrotum distances were measured using digital calipers. Results: A total of 267 neonates (females, 143; males 124) were included in this study. Of these, 36 were borderline premature infants (birth at 35–37 weeks gestation) and 231 were term infants (birth at 38–42 weeks gestation). The mean API was 1.06 ± 0.04 in female and 0.90 ± 0.08 in male neonates. When premature infants were analyzed separately, the mean API was 1.12 ± 0.08 in female and 0.99 ± 0.09 in male neonates. No significant difference in API values was observed between term and preterm neonates (P < 0.05). Conclusions: API values that differ from the previous studies were identified in the present study. We believe our modified method allows for more accurate measurements of the API in newborns. According to our method, the anus should be considered as anteriorly located if API is <1 in female and <0.9 in male neonates. In addition, the present study is the first to measure API using digital calipers. Digital calipers were found to be convenient and are useful in determining the API with high accuracy (to within 0.01 cm).

研究目的：本研究旨在通过肛门位置指数（anal position index, API）确定肛门的正常位置，以期开发灵敏度更优的API测量方法。为全面覆盖不同胎龄的新生儿群体，本研究纳入足月儿与早产儿两类研究对象。
材料与方法：针对女性新生儿，通过测量肛门-阴唇后联合（fourchette, FA）与肛门-尾骨（coccyx, AC）的间距计算API；针对男性新生儿，则测量肛门-阴囊与肛门-尾骨的间距。API的定义为FA（男性对应阴囊）间距与AC间距的比值。所有测量均采用数显游标卡尺（digital caliper）完成。
研究结果：本研究共纳入267名新生儿，其中女性143名，男性124名。纳入对象中，36名为临界早产儿（妊娠35~37周分娩），剩余231名为足月儿（妊娠38~42周分娩）。女性新生儿的API均值为1.06±0.04，男性新生儿为0.90±0.08。对早产儿单独分析后发现，女性早产儿的API均值为1.12±0.08，男性早产儿为0.99±0.09。足月儿与早产儿的API值无显著统计学差异（P<0.05）。
研究结论：本研究得出了与既往研究不同的API参考值。我们认为本研究采用的改良方法可更精准地测量新生儿API。基于本研究的测量方法，若女性新生儿API<1、男性新生儿API<0.9，则可认定其肛门位置偏前。此外，本研究是首次采用数显游标卡尺开展API测量的研究。结果证实，数显游标卡尺操作便捷，且可实现高精度（精度可达0.01cm）的API测量。