Value of rectoanal pressure gradient in seated position in evaluation of anorectal motility disorder in patients with constipation

Objective To investigate the differences of anorectal manometry (ARM) parameters in different position (left lateral position and seated position) in patients with functional constipation (FC), and the value of rectoanal pressure gradient (RAPG) was assessed in seated position in the evaluation of anorectal motility disorder in patients with FC. Methods From March 2015 to July 2016, at Clinical Gastrointestinal Motility Center of Ningbo Yinzhou People′s Hospital, 66 consecutive patients with FC aged 18 to 75 who met Rome Ⅲ criteria were recruited. The questionnaires of patient assessment of constipation symptom (PAC-SYM) and patient assessment of constipation quality of life (PAC-QoL) were recorded. Patients randomly underwent ARM examination in left lateral or seated positions, and then followed by a balloon expulsion test (BET) in seated position. The differences of ARM parameters in different positions were compared. The correlation between ARM parameters and BET results, constipation symptoms and quality of life scores were analyzed. T-test, Spearman correlation analysis and Kappa coefficient were performed for statistical analysis. Results ARM parameters including rectal resting pressure, rectal defecation pressure and RAPG in seated position were both higher than those of left lateral position ((30.83±7.89) mmHg (1 mmHg=0.133 kPa) vs. (10.53±3.94) mmHg, (78.86±22.25) mmHg vs. (54.92±21.26) mmHg, (17.53±27.40) mmHg vs. (-7.80±26.88) mmHg), and the differences were statistically significant (t=-21.10, -12.35 and -8.84, all P 0.05). The RAPG in seated position was highly consistent with BET, with a maximum Kappa-value of 0.643, which was higher than the maxium Kappa-value of 0.349 in left lateral position. The optimal RAPG threshold of seated position was 10 mmHg, the sensitivity of RAPG in the prediction of BET was 85.71% and the specificity was 79.17%. According to the optimal RAPG threshold in seated position, the patients were divided into high RAPG group and low RAPG group. The frequency of weekly spontaneous defecation of high RAPG group was higher than that of low RAPG group (2.88±2.16 vs. 1.66±0.96), and the difference was statistically significant (t=2.65, P=0.01). The satisfaction score of PAC-QoL questionnaire of high RAPG group was lower than that of low RAPG group (2.05±0.55 vs.2.83±0.78), and the difference was statistically significant (t=-4.72, P<0.01). Conclusion It may be more reasonable to perform ARM in the seated position in FC patients, especially for the RAPG in seated position is better correlated with BET results, constipation symptoms and quality of life scores which may have more clinical value in the evaluation of anorectal motility disorder in FC patients. Key words: Functional constipation; Anorectal manometry; Balloon expulsion test; Rectoanal pressure gradient