Complete androgen insensitivity syndrome (CAIS) is a rare disorder; however, surgeons have noted a higher rate in girls with inguinal hernias. A few retrospective studies have estimated the incidence of CAIS to be 0.8%to 2.4%in girls with inguinal hernias. An inexpensive, quick screening method for this population has not been established. Because CAIS is associated with a short vagina, measuring vaginal length could serve this purpose if normal standards were known. The authors endeavored to (1) prospectively confirm the incidence of CAIS, (2) identify normal standards of vaginal length, and (3) assess the usefulness of measuring vaginal length to screen for CAIS in girlswith inguinal hernias. Vaginal lengths were measured in 270 girls with inguinal hernias at a university hospital from 1991 to 2003. A fallopian tube was identified to exclude CAIS. If CAIS was suspected, gonadal tissue was sampled and karyotyping was performed. Linear regression analysis was performed, and 95%confidence intervals were calculated for individual values. Normal vaginal length for age was established. Three patients were found to have significantly short vaginas: 2 were confirmed to have CAIS, 1 did not (false-positive). One other infant was proved to have CAIS despite having a normal vaginal length (false-negative). The incidence of CAIS in our study was 1.1%(3/270). This is the largest prospective study of the incidence of CAIS in girls with hernias. The authors found that 1.1%of premenstrual girls with inguinal hernias have this syndrome. The authors also provide standards for normal vaginal length in the pediatric population. Vaginal length increases predictably with age, and some patients with CAIS have significantly shorter vaginas. Vaginal length is not a perfect predictor of this disorder, but can be a useful adjunctive screening tool.
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