Constipation refers to the difficulty of defecation, reduced frequency of defecation, or the feeling of incomplete defecation caused by various reasons. Physiologically, defecation consists of two processes: the production of the urge to defecate and the action of defecation. When the rectum is full, the rectal wall is stimulated by pressure and exceeds a threshold value, causing the urge to defecate. This impulse travels along the pelvic and infra-abdominal nerves to the defecation centers in the lumbosacral spinal cord and then ascends to the thalamus and reaches the cerebral cortex. If the environment permits, the puborectalis and anal sphincter relax and the levator ani muscle contracts to induce defecation. Failure of any of these processes can cause constipation. Fecal volume and consistency, rectal compliance, internal and external sphincter function, puborectalis and anorectal angle, and rectal infections can all influence the defecation process. Functional constipation in the pathogenesis of factors, often not a factor alone, but several factors coexist. 1, morbidity and morbidity factors Constipation is an extremely common clinical symptom, at present, due to the definition of constipation standards are not uniform and the use of different information, the results of its epidemiological investigations have greater differences. For example, the incidence of constipation in the U.S. population ranges from 2% to 28%, and the incidence of constipation in adults in Beijing is 6%. This disease is more common in the elderly, and the incidence of constipation in the elderly over 65 years old is about 30% [1]. In recent years, with the change of dietary structure and the influence of mental and psychological factors and social factors, the incidence of constipation in young people also has a tendency to increase year by year, which seriously affects the quality of life of modern people and causes inconvenience in work and life [2]. Broadly speaking, constipation is divided into two categories: functional constipation and secondary constipation. Clinical constipation is usually functional constipation, including colon slow transmission constipation, functional outlet obstruction constipation and mixed constipation where both exist at the same time. At present, the so-called functional constipation is not accurate, many data show that functional constipation has anatomical and organic abnormalities [3]. For example, the colon wall of patients with constipation often has muscle fiber degeneration, muscle atrophy, intestinal wall intermuscular plexus degeneration, deformation, reduction in the number of pathological changes; some patients in the intestinal wall of the release of neurotransmitter Ach is significantly reduced, and vasoactive intestinal peptide content is significantly higher than that of normal people. The common diseases of slow-transmission constipation include Hirchsporung’s disease, secondary megacolon, spastic colon, partial colonic redundancy, and colonic incompetence. Outlet obstructive constipation (OCC) refers to the difficulty of defecation caused by the obstruction of fecal passage through the rectum and anal canal [4].OOC is mostly organic pathology, and can be divided into two main categories according to pathological features:The first category is pelvic floor relaxation syndrome, including rectal bulge, rectal intramucosal prolapse, rectal intussusception, perineal descent, intestinal hernia, sacral rectal separation, visceral prolapse, etc. The first category is pelvic floor relaxation syndrome. This kind of patient’s X-ray manifestation is perineal descent, so it is also called “perineal descent syndrome”. Due to the easy pelvic floor injury, pelvic supportive tissue weakening and relaxation in the process of pregnancy and childbirth, so it is more common in women who have given birth. The second category is pelvic floor spasm syndrome, including puborectalis syndrome and internal sphincter dystocia. This syndrome is manifested as a continuous contraction of the pelvic floor muscles when straining to defecate, and the anus rectus angle does not open when straining to defecate. Since the anal canal pressure is normal at rest and during anal lifting in these patients, it is presumed to be a normal muscle hypofunction rather than a continuous spasm of abnormal muscles, and thus the nomenclature of pelvic floor dystocia syndrome is considered to be closer to the actual situation [5]. The occurrence of this syndrome may be related to psychological factors, congenital anomalies, inflammatory stimuli, laxative abuse and long-term conscious inhibition of defecation, or abnormalities in the function of the nerves innervating the internal and external anal sphincters. Clinically, constipation in young adults is mostly related to poor dietary habits, such as eating less, drinking less water, partiality, do not like to eat vegetables and poor defecation habits, such as often ignoring the urge to defecate, etc. often may be the cause of the formation of chronic constipation. Elderly constipation is related to the amount of food and physical activity to reduce the lack of dietary fiber in the diet, gastrointestinal secretion of digestive juices to reduce the intestinal tension and peristalsis, gastrocolic reflexes weakened rectal sensitivity, rectal anorectal anatomical and functional anomalies, gastrointestinal hormone disorders and so on. Secondary constipation refers to constipation caused by systemic organic diseases of the intestinal tract itself, such as intestinal smooth muscle or neuronal lesions, neurological disorders (such as multiple sclerosis, stroke or spinal cord lesions), endocrine or metabolic diseases (such as diabetes mellitus, hypothyroidism, parathyroid disorders, etc.), intestinal organisms (such as tumors, inflammation, or other causes of intestinal luminal stenosis or obstruction), drug factors ( such as long-term use of calcium aluminum antacids, iron, antidepressants, opioids, anti-Parkinson’s disease drugs, calcium channel blockers, diuretics, antihistamines, long-term abuse of laxatives, etc.). Clinical diagnosis of constipation usually need to identify whether it is secondary constipation. 2, diagnosis of constipation diagnosis is mainly based on the typical symptoms such as difficulty in defecation, decreased frequency of defecation, or the feeling of incomplete defecation. Some authors suggest that the diagnostic criteria should emphasize the presence of symptoms for at least 12 weeks, either consecutively or intermittently, over the past 12 months, but there is no consensus on this. Attention should be paid to the nature of the stool during the consultation, and Brisˉtol stool shape tracing may be performed if necessary to determine the degree of constipation or for comparison of treatment efficacy. Medical history is suggestive of etiologic diagnosis, and it is important to ask whether there is a history of poor dietary habits and laxative abuse. Some more specific manifestations such as prolonged defecation time, repeated excessive straining, rectal distension, incomplete defecation, hand-assisted defecation (i.e., using the finger into the anus or vagina to assist defecation) are often indicative of pelvic floor outlet pathology. Chronic constipation is mostly functional constipation, and the diagnosis needs to pay attention to exclude organic diseases secondary to the intestinal tract itself or the whole body. Currently, the relevant clinical examination is mainly aimed at differential diagnosis to exclude organic lesions. If there is no abnormality in the anatomy of the intestinal tract, and the constipation has a long duration and is not effective in the serious cases of general treatment, relevant functional examinations should be carried out in order to determine the pathophysiological type of constipation and guide the rational treatment Patients who are clearly identified as functional constipation can be further classified according to the characteristics of the symptoms and the relevant examinations. Slow-transmission constipation is characterized by decreased frequency of bowel movements, lack of bowel movements, or hard stools. Imaging or laboratory tests suggest that there is a delay in total gastrointestinal or colonic passage time or hypodynamic colon. Functional outlet obstruction is characterized by a sense of incomplete evacuation, straining to pass stools, or low stool volume, often accompanied by anorectal drop. These patients often have anal sphincter dysfunction and pelvic floor muscle dysfunction. In the mixed type, slow transmission coexists with functional outlet obstruction. In the history, it should be noted that if the patient’s main manifestation is abdominal pain, the constipation is mostly irritable bowel syndrome. 3, related examination and clinical significance (1) endoscopy can observe the mucosa of the colon and rectum, to exclude organic lesions. Some patients can see diffuse dark brown spots on the mucosa of the colon, which is called colon darkening sign, which is lipofuscin deposition on the intestinal mucosa, mostly related to long-term use of laxatives. (2) Imaging X-ray film of the abdomen can show dilatation of the intestinal lumen, fecal retention and gas-liquid planes. Barium enema can detect megarectum and megacolon.CT or MRI is mainly used to detect patients with or without intestinal mass or stenosis. (3) Functional tests are suitable for patients who are initially diagnosed with functional constipation by the above tests. ①Colonictransittime (CTT) examination technique is one of the important methods for the diagnosis of constipation. Oral intake of different forms of impermeable X-ray markers can be measured by regular filming of gastrointestinal transit time, understanding of intestinal function, and obtaining CTT data [6]. At present, the CTT is generally determined using a simplified method: swallow a capsule containing impermeable X-ray markers (such as SITZMARKS capsule, each capsule contains 24 markers) with the test meal at breakfast, and then take a flat film of the abdomen at 24h, 48h, 72h (if necessary) to calculate the rate of elimination. Under normal circumstances, the elimination rate at 72h is >90%. The location of the marker in the colon is usually determined from the bony landmark in the abdominal plain film. On the right side of the spine, markers above the line between the fifth lumbar vertebra and the pelvic outlet are localized in the right hemicolon; on the left side of the spine, markers above the line between the fifth lumbar vertebra and the left anterior superior iliac spine are localized in the left hemicolon; and markers below the above mentioned line are localized in the ethmoid rectum. Markers that remain mostly above the sigmoid colon are slow-transmitting and those located in the sigmoid rectum are outlet-obstructing. This method is also helpful in differentiating functional constipation from constipated irritable bowel syndrome [7]. The prolongation of colonic transit time in constipated IBS is mainly in the right half of the colon, and in functional constipation there is prolongation in all segments of the colon, with the prolongation in the rectosigmoid region being more pronounced. ② Defecography (bariumdeˉfeckgraphy, BD) can make a definitive diagnosis of functional and organic lesions in the recto-anal region, especially in chronic constipation due to functional outlet obstruction. The changes in anorectal angle during general resting pressure, anal retraction and forceful evacuation assess the contraction and relaxation function of the puborectalis muscle, and can diagnose anatomical abnormalities of the rectopelvic floor. If the photographs taken for forceful rows and sitting comparisons, such as perineal descent forceful rows on the anus distance ≥ 31mm, pelvic floor spasm syndrome for forceful defecation when the pelvic floor muscle contraction without relaxation, forceful rows on the anorectal angle does not increase and more spasticity of the puborectal muscle pressure marks. ③Anorectal manometry (anorectalmanometry, ARM) can be measured by perfusion or balloon method, which can determine the function of internal and external anal sphincter, and help to diagnose and evaluate the exit obstruction type of constipation such as anorectal spasms, congenital megacolon, and rectal sensory abnormalities. For example, in patients with spastic pelvic floor syndrome, the external anal sphincter, puborectalis, and levator ani muscles do not relax during defecation. Congenital megacolon anorectal inhibitory reflex is significantly weakened or disappeared. The method can also be used as a monitoring tool for biofeedback therapy. For example, when simulating defecation action, by observing the waveform of anorectal pressure change, informing the patient of the normal and abnormal power change, guiding the adjustment of their own defecation action, relaxing the anal sphincter muscle while increasing the abdominal pressure, so that the anorectal pressure curve is restored to the normal physiological state. Through training, the patient’s symptoms can be significantly improved, the number of bowel movements increased and discontinued the use of laxatives [8]. (4) Other blood routine, stool routine, fecal occult blood test are routine examinations for patients with constipation, which can provide clues to colorectal and anal organic pathology. Rectal fingerprinting can determine whether there are fecal impaction, anal stenosis, rectal prolapse, rectal mass and other lesions, and can understand the muscle status of the anal sphincter. Pelvic floor electromyography shows the electrical activity of the pelvic floor muscles and is used to diagnose pelvic floor muscle dysfunction. For example, pelvic floor spasm syndrome may reveal abnormal discharge of the puborectalis and external sphincter muscles during simulated defecation. The balloon forced out test can be placed in the subject’s rectal abdomen, injected into the 37 ℃ warm water 50 ml. Ask the subject to take the habitual defecation position as soon as possible to expel the balloon, normal in 5min. It helps to determine whether the function of the rectum and pelvic floor muscles is abnormal. 4.Treatment The constipation caused by organic lesions and other diseases can be treated for the cause, and the primary disease can be actively treated. If there is no obvious organic changes in the intestinal tract, diagnosed as functional constipation, the principle of treatment is based on the regulation of diet and defecation habits, supplemented by medication, but attention should be paid to avoiding the abuse of laxatives, pay attention to the individualization of the use of medication [9]. (1) Adaptation of dietary habits to increase water intake, fiber diet can increase and retain water in the feces, so that the feces become softer and increase in volume. Abstain from gas-producing and strong stimulating condiments, encourage patients to drink more water, vegetable juice, fruit juice or honey juice in the morning, eat fiber-rich foods such as wheat gum, fruits, vegetables, corn, etc., and appropriately increase the amount of activity. Radish, beans, pumpkin and yams can produce large amounts of gas, promote intestinal peristalsis and laxative. Currently marketed drugs are non-bi bran (Fiberform) for wheat cellulose, usually 1 bag each time, 2 ~ 3 times / d. Because the fiber itself is not absorbed, can make the stool expansion to stimulate colonic movement. (2) Adaptation of defecation habit to develop the habit of regular defecation can prevent the accumulation of feces. Encourage patients to have a bowel movement after breakfast, if they still can’t have a bowel movement, they can have a bowel movement again after dinner, so that the patients can gradually restore the normal bowel movement habit. In the training of defecation habits can be combined with medication to clean the intestines. Generally, saline enema can be used 2 times/d for 3d, and then oral balanced salt solution can be used to make the bowel movement at least once/d. (3) Drug therapy should emphasize the principle of rational use of drugs and individualization. The selection of drugs should be based on the principle of reducing toxicity, side effects and drug dependence. Commonly used laxatives are polyethylene glycol (Macrogol, Fosamax, Forlax) and lactulose (Lactulose, Duphalac), both of which are non-absorbable in the intestinal tract and have few adverse reactions. Fosamax, a product of Beaufort Pharmaceuticals, is an osmotic laxative. Its active ingredient is polyethylene glycol 4000, which is a long-chain polymer that fixes water molecules in the intestinal lumen with the help of hydrogen bonds, thus softening the stool. Since the drug is not absorbed or metabolized, it has fewer side effects, especially no flatulence, and is well tolerated and adhered to. The medicine is available in 10g sachets of powder with a fruity flavor. It is usually taken 1 to 2 sachets per day, each sachet dissolved in 1 cup of water, fully dissolved. Duphixol is commonly taken orally at 15 to 30 ml/d. Suliton (Agiolax) is mainly composed of ovine psyllium and a small amount of senna fructoside, ovine psyllium fibers swell in water to form a mucus mass to ensure that there is enough water in the stool to increase the volume of stool in the colon, complete rectal filling to stimulate the bowel reflex. Senna fructoside then stimulates peristalsis. This product is available as granules and is usually taken as 1 to 2 teaspoons after dinner or before breakfast with a glass of liquid. The low sensitivity, high tolerance and high compliance of the rectal wall to volume expansion is one of the causes of constipation, pro-dynamic drugs such as cisapride (trade name Prevacid) is not recommended as a routine use of constipation, but the ability to agonize the intestinal wall 5-HT4 receptors to stimulate intestinal interosseous plexus release of acetylcholine and promote intestinal motility [10], to increase the resting pressure of the rectum of patients with constipation and constipated patients, to accelerate the constipation of patients with colonic transit speed, and to stimulate the rectum of patients with constipation. It can be used in the treatment of slow-passage constipation without bowel movement [11, 12]. The dose is 5-10mg orally, 3 times / d. The therapeutic effect of the drug is obvious, the side effects of the conventional dose is generally less, almost does not affect the blood and biochemical indicators, to avoid the colon and rectum damage caused by long-term use of laxatives, but the use of attention should be avoided to avoid patients with serious cardiac, renal and respiratory insufficiency, and attention should be paid to avoid and can prolong the QT interval of the drug or tricyclic antidepressants, macrolide antibiotics, Antifungal drugs, etc. [13]. Stimulating laxatives have certain side effects in long-term use. Elderly patients with constipation have a large amount of feces in the rectum, which can be appropriately applied to soften the feces with Keserol suppositories or soapy water enemas. Magnesium sulfate (Magnesiumsulfate) contains non-absorbable cations and anions, due to the role of osmotic pressure can make the intestinal lumen to retain a sufficient amount of water and stimulate intestinal peristalsis, commonly used 33% concentration of orally, but need to pay attention to the magnesium ions can be absorbed in patients with constipation in renal insufficiency should be used with caution. Bisacodyl can stimulate the sensory nerve endings through direct contact with the intestinal mucosa, causing intestinal reflex peristalsis and leading to defecation. Bisacodyl can be taken orally at 5~10mg/d. It should not be chewed or crushed when taking the medicine, and no milk or acidifier should be taken before or after taking the medicine for 2h. Occasionally may cause abdominal pain, but relieved after defecation. Castor oil (Casˉtoroil), senna (Senna), phenolphthalein (Phenolphthalein, fruit guide), rhubarb (Rheum, rhubarb soda tablets), etc. can stimulate intestinal peristalsis and reduce absorption. Note that pregnant and lactating women should avoid drugs that may cause contractions, such as magnesium sulfate and senna. For patients with concomitant hypertension, heart disease, renal insufficiency and diabetes mellitus, care should be taken to avoid water and electrolyte imbalance caused by stimulating laxatives during treatment. Constipated patients often have intestinal flora disorders and overgrowth, can be appropriate application of microecological agents such as Rejuveno, Pepcid and other oral. (4) Psychological and biofeedback treatment of constipation patients are often accompanied by depression and anxiety, which can aggravate constipation, and thus need to receive psychological treatment. Although antidepressants have caused constipation adverse effects, but some constipation is more serious day-to-day worry about how to defecate, mental abnormal tension by the psychological treatment is ineffective to try drug treatment. For patients with rectal sphincter and pelvic floor muscle dysfunction of constipation, biofeedback therapy can be used. This method is a kind of training to control the function of the body with the idea, which was used to treat fecal incontinence, and recently used to treat the spasticity of pelvic floor muscle constipation, including two kinds of airbag biofeedback method and electromechanical biofeedback method. Biofeedback method can improve the symptoms of patients with outlet obstruction type, with significant improvement in parameters related to defecation, increased defecation rate, anorectal angle blunted at rest and forceful defecation compared with the previous one, significant decrease in voltage of external anal sphincter electromyography during defecation, decrease in paradoxical movement index of puborectalis muscle, and change in rectal sensation. (5) Surgical treatment is mainly suitable for the ineffective treatment by internal medicine, and all kinds of examination show a clear pathologic anatomy and conclusive functional abnormality site, surgical treatment can be considered. The indications are mainly secondary megacolon, partial colonic redundancy, colonic incompetence, anterior dilatation of the rectum, rectal intussusception, rectal intramucosal prolapse, pelvic floor spasticity syndrome and so on. At present, it is generally accepted that surgical treatment of constipation with colonic transport dysfunction is effective, but the surgical approach has not been fully finalized. Subtotal colectomy is more commonly used, followed by partial colectomy, but the latter generally has a poor prognosis. It is worth noting that the anterior wall of the rectum in women is supported by the rectovaginal septum formed by the endopelvic fascia, and patients with constipation often have a combination of both colonic transport dysfunction and rectal emptying obstruction, so surgical treatment should be accompanied by simultaneous resolution of the disease or abnormality that causes the rectal emptying obstruction. Surgical treatment of outlet obstruction type constipation combined with anatomical abnormalities of the anorectum and pelvic floor is not definitively effective.