From the Guidelines
To assess rectal tone, a digital rectal examination is the most appropriate method, as it allows for the evaluation of the resting tone of the anal sphincter and its augmentation by a squeezing effort, providing valuable information for diagnosing and managing various colorectal conditions 1.
Key Steps in Assessing Rectal Tone
- Position the patient in the left lateral decubitus position with knees flexed toward the chest
- Explain the procedure to the patient and obtain consent
- Don a lubricated gloved finger and gently insert it into the rectum
- Evaluate the resting tone of the anal sphincter by noting resistance to insertion
- Ask the patient to squeeze your finger to assess voluntary contraction strength
Normal Findings and Potential Abnormalities
Normal findings include moderate resistance at rest and the ability to contract voluntarily. Decreased tone may indicate neurological issues, spinal cord injury, or pudendal nerve damage, while increased tone might suggest anal fissures or inflammation.
Importance of Digital Rectal Examination
This examination is essential for evaluating bowel control, neurological function, and various colorectal conditions, and should be performed in conjunction with a thorough medical history and other diagnostic tests as needed, such as anorectal manometry, which can provide additional information on anorectal sensorimotor functions 1.
Considerations for Accurate Assessment
Ensure patient comfort throughout the procedure and document your findings promptly, noting both resting and squeeze pressures as normal, decreased, or increased. The use of standardized protocols, such as the International Anorectal Physiology Working Group (IAPWG) protocol, can help improve the accuracy and consistency of rectal tone assessments 1.
From the Research
Assessment of Rectal Tone
To assess rectal tone, several methods can be employed, including digital rectal examination (DRE) and anorectal manometry (ARM).
- Digital Rectal Examination (DRE): DRE is a simple and commonly used method to assess anal sphincter tone. The Digital Rectal Examination Scoring System (DRESS) is a novel scoring system that uses a scale of 0 to 5 to describe anal sphincter tone, with 0 indicating no discernable pressure and 5 indicating extremely tight tone 2.
- Anorectal Manometry (ARM): ARM is a diagnostic test that measures intraluminal anal and rectal pressures, providing an objective evaluation of anorectal functional parameters, including tone, contractility, and relaxation 3.
Comparison of DRE and ARM
Studies have compared the effectiveness of DRE and ARM in assessing rectal tone.
- A study found that DRE showed high sensitivity and positive predictive value in detecting dyssynergia compared to HRAM, and could be used as a bedside screening test for the diagnosis of this disorder 4.
- Another study found that the correlation between DRESS and ARM resting measures was 0.196, and between squeeze measures was 0.247, indicating a weak correlation between the two modalities 5.
Limitations of DRE
The accuracy of DRE in assessing anal tone has been debated.
- A study found that the overall correctness of DRE in assessing anal tone was 64%, with no correlation between perceived level of skill and study result 6.
- The study also found that doctors were not significantly more able than healthcare assistants to detect correct tone, suggesting that DRE may not be a wholly accurate tool 6.
Clinical Utility of ARM
ARM is a useful test for numerous indications, including the assessment and management of functional anorectal disorders, preoperative assessment of anorectal function, and facilitating/assessing response to biofeedback training 3.
- Despite its ability to provide detailed information on anorectal and pelvic floor muscle function and synergy, ARM is still infrequently utilized in clinical practice 3.