1 Obstructive mechanism High-pressure anal cushion or non-prolapsed hemorrhoids can produce anal resistance. During defecation, the patient can only overcome by increasing intra-abdominal pressure, resulting in increased rectal pressure; the harder the defecation, the higher the intravascular pressure in the anal cushion, making defecation more difficult. After defecation, normal people can quickly return to normal, while the patient has a higher residual pressure [7.35kPa (75cmH20)] due to the resistance of the high-pressure anal cushion, which continues to affect the passage of feces, and returns to normal after 18-36h. Patients often feel incomplete emptying. In addition, it should be noted that when feces forcefully pass through a partially obstructed anal canal, an abnormal shear force will be generated, which will not only affect the return of blood in the anal cushion, cause more serious congestion, but also pull Long and tear the supporting tissues of the anal cushion, which causes the anal cushion to develop from intermittent prolapse to continuous prolapse; once the hemorrhoids prolapse, the anal pressure drops to normal. From this point of view, hemorrhoid constipation is related to the resistance of the anal canal and the congestion of the hemorrhoid itself, and it does not seem to be accompanied by an increase in sphincter tension.
2. Reflexive mechanism Hypertensive anal pads or non-prolapsed hemorrhoids stimulate the anal canal wall due to swelling and hypertrophy, causing abnormal contraction of the sphincter, which increases the workload of the external sphincter and increases the tension of muscle hypertrophy, leading to increased anal pressure and difficulty in excretion of feces. In addition, due to the contraction of the sphincter muscles, the anal cavity cannot be opened, and the rectal reflex expands (Debrey reflex), and the stool stagnates in the rectum, leading to constipation.