The Evaluation of Digital Rectal Examination for Assessment of Anal Tone in Suspected Cauda Equina Syndrome.
Methods: Seventy-five doctors completed a questionnaire documenting their grade, specialty, and experience in performing digital rectal examination (DRE). A model anus, using a pressure transducer surrounding an artificial canal, was assembled and calibrated. Participants performed 4 DREs on the model (with a break between attempts) and predicted tone as "reduced" or "normal" (35 and 60 mm Hg, respectively), followed by a "squeeze" test. Thirty health care assistants partook as a control group with no training in DRE. Objective: Our main objective was to investigate the validity of digital rectal examination (DRE) for assessment of anal tone.
Background: Cauda equina syndrome represents the constellation of symptoms and signs resulting from compression of lumbrosacral nerve routes. Combined with subjective neurological findings, a reduction in anal tone is an important sign, deeming further imaging necessary. DRE is an invasive procedure used to assess anal tone despite debated accuracy.
Methods: A total of 75 doctors from various specialties were asked to fill in a questionnaire detailing their grade, age, and area of expertise. In addition, information was gathered with regard to prior training in performing DRE to assess anal tone and the importance placed on any findings. Thirty hospital health care assistants (HCAs) were used as a control group. HCAs were selected as a control group because they receive no training on the technique and would never be required to perform it in their clinical practice. A model anus was assembled using a modified pediatric sphygmomanometer cuff to act as a sphincter. The cuff could be inflated to simulate a full range of anal tone. The cuff was incorporated into an artificial anal canal, which was, in turn, placed into a model buttock created from plaster of Paris. The apparatus was calibrated across a range of pressures.
Results: In each attempt, 60%, 61%, 63%, and 67% of doctors correctly identified the anal tone, respectively (average accuracy: 64%). HCAs had an identical average accuracy of 64%. All participants (100%) were able to correctly identify the squeeze test. For doctors, no correlation was found between confidence in assessing anal tone using DRE and a correct result. Seventy-one percent had received previous training in DRE, with 64% of these taught how to assess anal tone. Forty-three percent of doctors thought that further training would be beneficial.
Conclusions: The results demonstrate that accuracy in assessing anal tone using DRE is limited, with overall correctness of 64%. Poor correlation exists between perceived level of skill and study result. Doctors were not significantly more able than HCAs to detect correct tone. Therefore, DRE for the assessment of anal tone is not a wholly accurate tool. A squeeze test may be of greater value if interpreted correctly. Methods: 4.