The disappearance of the anal canal reflex belongs to one of the superficial reflexes of the human nerve reflexes, the person lies flat, the lower limbs are raised and straightened, and the external anal sphincter will be contracted by a small needle crossed in the perineal area. The afferent nerve is the pubic nerve, and the center is in the posterior horn cell column of the sacral medulla 4-5 and the anterior horn cell sex of the same segment. The external anal sphincter receives bilateral perineal innervation when one side of the pyramidal bundle is damaged or peripheral nerves. Normal defecation requires proper anorectal sensation. Pelvic floor receptors are considered very important in detecting the presence of feces in the rectum firepot.com. Patients with fecal impaction and overflow incontinence have decreased rectal sensation, and patients with traumatic and idiopathic fecal incontinence may have abnormal anal canal sensation. Idiopathic fecal incontinence, or neurogenic fecal incontinence, is due to progressive damage to the nerves controlling the transverse muscles of the pelvic floor and the external anal sphincter, as well as hypoplasia of the internal sphincter. Differential diagnosis of the disappearance of anal reflex 1, anal relaxation: anal relaxation, sphincter and anorectal ring contraction is not obvious and completely disappeared when contracting the anal canal, such as caused by the injury, then the anus can be found in the scar tissue, incomplete incontinence can be found in the sphincter contraction force of finger palpation is weakened. It is common in anal incontinence. 2, fecal incontinence: due to anal or nerve damage, resulting in the phenomenon of not being able to control the discharge of feces and gas. Also known as fecal incontinence or anal incontinence. Those who can’t control both dry and loose stools are called complete incontinence; those who can control dry stools but can’t control loose stools and gas are called incomplete incontinence. Defecation is a complex and coordinated reflex action, a reflex activity accomplished under the dual innervation of the visceral vegetative nerves and the central nervous system of the brain. Fecal incontinence can occur with resection of the lower end of the rectum, impairment of nerve reflexes and loss of anal sphincter tone. In the elderly, anal incontinence can be caused by atrophy of the anal sphincter. Temporary fecal incontinence can also occur when there is a sudden shock.