Anorectal manometry (ARM) is a medical test used to measure pressures in the anus and rectum and to assess their function.
[1][2] The test is performed by inserting a catheter, that contains a probe embedded with pressure sensors, through the anus and into the rectum.
[9] For example, on a digital rectal exam, a physician may notice specific findings that point to dyssynergic defecation, a cause of chronic constipation.
[4][8] Other abnormal findings on manometry consistent with chronic constipation include an unsatisfactory generation of the propulsive force needed to defecate and a decreased movement of pelvic floor muscles.
[4] Anorectal manometry, especially HR-ARM and HD-ARM, has also been used to evaluate constipation due to structural causes such as a rectocele,[2] an enterocele, or an intra-anal intussusception.
[6] Anorectal manometry is not significantly less sensitive and specific when compared to the gold standard method of diagnosis, rectal suction biopsy.
[4] For example, the degree of anal sphincter hypertension may be determined[7] which may be useful information when treating functional anorectal pain with biofeedback therapy.
[10] Visual feedback tools, such as anorectal manometry, are often used to aid patients in learning how to modify their behaviors.
A systemic review article[11] concluded that although better than placebo, there remained limited evidence demonstrating the effectiveness of anorectal biofeedback for chronic idiopathic constipation.
[8] In patients with defecatory disorders, including dyssynergic defecation, pelvic floor biofeedback therapy had been shown to be more effective than laxatives.
[6][9] An American-European Neurogastroenterology & Motility task force (ANMS-ESNM) recommended the use of biofeedback in the short and long treatment of constipation with dyssynergic defecation and fecal incontinence.
[3][6] An additional benefit to HR-ARM and HD-ARM is the increased ease in analyzing the results as pressure readings are displayed in both color and as a line plot.
Risks include the possibility of developing discomfort, pain, minor bleeding, dizziness or a rare perforation.
[5] In order, the following maneuvers are then performed: During the rectal sensory test, air is placed into the catheter balloon and slowly inflated either continuously or step-wise.
The lack of a rectoanal inhibitory reflex may indicate either the absence or the non-functionality of certain muscle or nerve structures involved in proper defecation.
As the balloon is inflated, its volume is recorded at certain milestones:[5] initial sensation of the equipment, start of the sensory urge to defecate and the point of maximum discomfort.
[7] Centers rely on published data sets from healthy volunteers to evaluate test findings.
[4] However, the lack of standardization in equipment usage and procedural protocol, can in certain cases, impact the ability to determine what may be considered normal or abnormal values.
[4] This is further complicated by the limited amount of data on the impact of different epidemiological characteristics (such as age or gender) on said values.