Anorectal Manometry in Obstructive Defecation

Anorectal manometry is an important test to evaluate patients with obstructive defecation syndrome. In obstructive defecation or dyssynergic defecation the patients are unable to adequately relax the pelvic floor muscles/anal sphincter during defecation. Some may even have poor rectal propulsion associated with it. This test is usually recommended for patients who have symptoms such as constipation, fecal incontinence, or pelvic pain. Patients with obstructive defecation syndrome may have coexisting symptoms of urinary incontinence or urgency or frequency and pelvic organ prolapse.

To diagnose dyssynergic defecation patients should satisfy the criteria of chronic constipation along with impaired relaxation of the anal sphincter and inability to expel a 50cc water filled balloon during anorectal manometry.

Anorectal manometry will help measure the anal resting and squeeze pressures and provide information on the sensations in the rectum. It will help determine if there is weakness or spasm of the anal sphincter. The balloon expulsion test it will provide information regarding the rectal propulsive forces and anal sphincter relaxation to help diagnose if there is problem with coordination of the pelvic floor muscles.

The reason that many patients are delayed in their diagnosis of obstructive defecation is that many physicians don’t suspect it during the patient’s first to the clinic. Symptoms of prolonged straining, digitation for assisted fecal evacuation, sense of incomplete evacuation, and sense of anal blockade should make us suspect obstructive defecation. A rectal examination is not done by many physicians which may lead to a delay in the diagnosis. Physicians who do perform rectal examination need to ask their patient to expel their palpating finger by bearing down. If during this manuvere there is paradoxical contraction of the anal sphincter around the palpating finger instead of relaxation, a diagnosis of obstructive defecation/dyssynergic defecation should be suspected. As the very old saying goes in Love and Baileys Textbook of Surgery, ”if you don’t put your finger in the rectum, you will put your foot into it.” The phrase emphasizes the importance of performing a thorough rectal examination. Thus, early suspicion of the problem by history taking and rectal examination can lead to early referral for anorectal manometry for diagnosis of this dyssynergic defecation.

Biofeedback is the therapy essential to relieve the symptoms of obstructive defecation. In this treatment, rectal/anal sensors along with computer technology and the physiotherapist help teach the patient the correct way to generate rectal propulsion and simultaneously relax the anal sphincter to help fecal evacuation.

Overall, anorectal manometry will help in treatment planning to determine if biofeedback, pelvic floor physical therapy, medications, or surgery will be helpful to alleviate patient symptoms.