Dyssynergic defecation is a functional pelvic floor disorder characterized by improper coordination of the pelvic muscles during defecation. Anorectal sensitivity, assessed through high-resolution anorectal manometry (HR-ARM), may be impaired in patients with functional defecation disorders. According to current literature, reduced rectal sensitivity is frequently observed across subtypes of these disorders. Factors such as older age, higher constipation symptom scores, and diabetes have been identified as independent risk factors for rectal hyposensitivity. 1
High-resolution anorectal manometry (HR-ARM) is a valuable tool for assessing both motor function and rectal sensory responses in these patients. Combined with complementary tests such as the balloon expulsion test, HR-ARM confirm the diagnosis of defecatory disorders by identifying dyssynergic patterns and abnormal sensory thresholds. 2,3
Objective: To evaluate rectal sensory thresholds in patients with dyssynergic defecation using high-resolution anorectal manometry (HR-ARM), and to explore the association between sensory alterations (hyposensitivity and hypersensitivity) and dyssynergia.

Patients with a diagnosis of constipation who underwent high-resolution anorectal manometry with a report of defecatory dyssynergia were evaluated; all were older than 20 years of age. Manometry was performed following the standardized IAPWG manometry protocol. A statistical analysis of the sensitivity test values was performed associating them with the type of defecatory dyssynergia. Data were obtained with IBM SPSS Statistics version 30.0.

Forty patients were evaluated, the age ranged from 20 to 84, with a mean of 56 (SD 14.86), 35 were women and 5 men. An association was made between each type of dyssynergia and the presence or absence of alterations in sensitivity (Table 1).
The most frequent type of dyssynergia was type 1 with 35% of the cases. The second most frequent was type 2, and the one that presented more cases with hyposensitivity (25%). Type 1 and Type 2 dyssynergia showed a significant association with hyposensitivity (0.047 and 0.018, respectively).

Dyssynergic defecation is the most prevalent type of defecation disorder, accounting for approximately 40% of individuals with chronic constipation. 4
Physiological evaluations may reveal one or more dysfunctions during defecation attempts, such as: paradoxical contraction of the anal muscles, insufficient relaxation of the anal sphincter, weak pushing effort, or a higher-than-normal threshold for perceiving the need to defecate (rectal hyposensitivity). 4
Zhang et al (2023), conducted a similar study in which no significant differences were found in the volume of the first constant sensation, the volume of defecatory urge and the maximum tolerable volume among the different subtypes of functional defecation disorder. 2

Patients with defecatory dyssynergia exhibit a reduced threshold for urgency to defecate, indicating altered anorectal sensory function. The volumes required to elicit defecatory urgency have potential implications for optimizing therapeutic strategies, particularly in tailoring biofeedback and behavioral interventions. Therefore, future studies with larger patient cohorts are recommended to validate these findings and better understand the sensory alterations associated with each dyssynergia subtype.

Wald A, Bharucha AE, Limketkai B, et al. ACG Clinical Guidelines: Management of Benign Anorectal Disorders. The American Journal of Gastroenterology. 2021;116(10):1987-2008.
Zhang YB, Huang ZY, Jin JW, et al. Rectal Sensitivity and Associated Factors in Patients With Different Subtypes of Functional Defecation Disorder. European Journal of Gastroenterology & Hepatology. 2023;35(12):1370-1374.
Wald A, Bharucha AE, Cosman BC, Whitehead WE. ACG Clinical Guideline: Management of Benign Anorectal Disorders. The American Journal of Gastroenterology. 2014;109(8):1141-57.