The reproducibility of measuring the anorectal angle in defecography

Dynamic proctography is a radiographic procedure that has become widely used in the evaluation of pelvic floor function. The anorectal angle (ARA) is one parameter which is usually quantified during this examination. To determine the accuracy with which this measurement can be made, three physicians independently measured the resting and squeezing ARAs of 22 women. The coefficient of variation and the kappa statistic were used to describe the degree of agreement among the three examiners. These analyses revealed poor agreement among examiners for all 22 patients taken as individuals, (kappa less than or equal to 0.40; mean coefficient of variation at rest = 18 percent; mean coefficient during squeezing = 21 percent). These results suggest that measurements of ARAs will vary among examiners for any particular patient, even though individual examiners may demonstrate consistency in recording ARA data. There is wide interobserver variation in the measurement of the ARA from lateral radiographs, making quantification an exercise of only limited clinical value.