Digital rectal examination had a highly positive predictive value for diagnosing dyssynergia in patients with chronic functional constipation, wrote Dr. Satish S.C. Rao and colleagues in the November issue of Clinical Gastroenterology and Hepatology.
In what they called the first study to examine the use of digital rectal exam (DRE) in identifying dyssynergia, the authors looked at 209 patients (191 men) referred to a specialized defecation disorders clinic who fulfilled Rome III criteria for functional constipation (Clin. Gastroenterol. Hepatol. 2010 November [doi:10.1016/j.cgh.2010.06.031]).
The Rome III criteria, developed in 2006, define functional constipation as involving at least two of the following symptoms occurring with 25% of defecations: straining, lumpy or hard stools, feeling of incomplete defecation, feeling of blockage, or use of manual maneuvers. Having fewer than three defecations per week is also a symptom.
The criteria also stipulate that for functional constipation to be present, loose stools must be rare without laxative use, and irritable bowel syndrome must be ruled out.
Patients who met these criteria underwent both a DRE and anorectal manometry, with the latter considered the gold standard for the diagnosis of dyssynergia. The same experienced examiner performed all of the digital exams in the study.
Overall, 183 of the patients received a diagnosis of dyssynergia based on manometry. Of these, 134 (73%) also had "features of dyssynergia" according to digital exam. Four patients who had no dyssynergia on manometry were misidentified as dyssynergic on digital exam.
That translated to an overall sensitivity of DRE for dyssynergia diagnosis of 75% and a specificity of 87%, with a positive predictive value of 97%.
Dr. Rao, of the University of Iowa, Iowa City, and his colleagues, also found "good" agreement for normal resting anal sphincter tone between DRE and manometry (87 and 101, respectively, or 86%) and "fair" agreement for increased resting sphincter tone (12 and 28, or 43%). There was low agreement between the two modalities for decreased resting sphincter tone (12 and 80, or 15%).
Despite the value of DRE shown in this study – including its low cost and ease of use – the authors commented that previous studies have shown that medical students are not being trained to use the technique.
"It is imperative that serious efforts are made by faculty mentors during medical school and residency training to improve and facilitate the acquisition of this clinical skill," wrote the authors. "This is particularly relevant as sophisticated tests such as anorectal manometry and balloon expulsion test, although useful and diagnostic, are not widely available."
The authors pointed out several limitations, including the fact that anorectal manometry "may be falsely positive for dyssynergia in 15% of asymptomatic subjects," according to one study cited by the authors.
In addition, "even when performed meticulously, several subjects had low resting and low squeeze sphincter pressure on [anorectal manometry], but were felt to have normal resting sphincter tone and normal squeeze tone during digital rectal examination," they wrote. "This may be due to an apprehension or fear of DRE on the part of a subject that may have temporarily and falsely increased resting tone."
The authors reported having no conflicts of interest related to this study. Dr. Rao disclosed support from the National Institutes of Health. Another researcher was supported by Chulalongkorn University, Bangkok.