Colonic diverticula

　　The etiology of colonic diverticulosis is not yet clear, many theories are widely circulated, generally caused by innate factors, acquired factors, and other factors, detailed as follows:

　　1. Congenital factors

　　Evans proposed that congenital diverticula of the right half of the colon may be caused by abnormal embryonic development of the intestinal wall. Waugh believes that cecum diverticula are due to excessive growth of the cecum during embryonic weeks 7 to 10, where the normal development should be atrophy. Some patients with colon diverticula have a family history. Most diverticulosis is caused by acquired reasons, and tissue studies have not found any congenital abnormalities in the muscular layer of the colon wall. The phenomenon that the incidence of diverticulosis increases with age also provides strong evidence for this. True congenital colon diverticula are rare.

　　2. Acquired factors

　　Some scholars believe that the low-fiber diet in Western developed countries is the main cause of diverticulosis. The following clinical research results can confirm this:

　　① There are obvious geographical distribution characteristics in the incidence.

　　② The incidence has gradually increased since the 1950s.

　　③ The incidence of diverticulosis changes after dietary changes in the mobile population.

　　④ The incidence increases with age.

　　⑤ A high-fiber diet can prevent diverticulosis.

　　(1) Factors affecting the formation of diverticula

　　Firstly, the tension of the colon wall, and secondly, the pressure difference between the colon lumen and the abdominal cavity. The intraluminal pressure at any location can be measured through Laplace's pressure law. Recently, studies using pressure gauges have shown that during continuous segmentation, the colon, especially the sigmoid colon, can produce a very high intraluminal pressure. The highest intraluminal pressure in the colon is located in the descending colon and sigmoid colon, which is sufficient to cause mucosal protrusion and the formation of diverticula in the colon muscle.

　　(2) Structural characteristics of the colon wall

　　It may also be a factor in the occurrence of diverticulosis. The collagen fibers in the circular muscle of the colon are arranged in a crisscross pattern, keeping the colon wall taut. As age increases, the collagen fibers in the internal position of the colon lumen become finer, and the function of elastin fibers weakens, leading to a decrease in the elasticity and tension of the colon wall. Therefore, the most narrow and thick sigmoid colon is a favorable site for diverticula. The muscles of the colon bands are in a state of contraction, making it less likely to form diverticula. It has been confirmed that the smooth muscle bundles in the sigmoid colon of diverticulosis patients are thicker than those of normal people. Even if there is no thickening of the smooth muscle bundles, abnormal smooth muscle bundles are also a manifestation of the early stage of diverticulosis. Abnormal smooth muscle bundles are not limited to the sigmoid colon but can also be expressed in other parts of the colon, such as the upper rectum. This is more evident after sigmoid colon resection. In the early stages of the disease, these weak points in the colon wall have already manifested. In addition, the disorder of connective tissue caused by changes in structural proteins also plays a certain role in the early stage of diverticulosis.

　　(3) Colon movement

　　There are two types of segmentation: rhythmic contraction and propulsive contraction. The former mainly mixes the contents of the right half of the colon back and forth, promoting the absorption of water and salts. The latter moves feces towards the distal end. Mass peristalsis can push feces directly from the right half of the colon to the sigmoid colon and upper rectum, causing the urge to defecate. Colon diverticula are prone to occur on the thin intestinal wall between the colon bands. When segmentation occurs, the intraluminal pressure increases, and these potential weak areas are prone to form diverticula where blood vessels enter the colon wall.

　　(4) Compliance of the intestinal wall

　　Abnormal compliance of the intestinal wall may also be a cause of diverticula. The study of colonic dynamics under resting and stimulated conditions supports this view. Eastwood et al. found that symptomatic colonic diverticula patients have excessive abnormal colonic pressure responses to certain drugs, foods, and expanded bladders. Normally, there is a linear relationship between intraluminal pressure and volume. However, in diverticula patients, the pressure quickly reaches a steady state, and even when the volume increases, the pressure remains stable. The threshold of pressure response in diverticula patients is significantly lower than that in normal people. The reasons for the reduced compliance of the colonic wall may be related to hypertrophied smooth muscle and disordered collagen fibers.

　　(5) Colonic lumen pressure

　　Through measurement, it was found that the basic pressure of diverticulosis patients is significantly higher than that of normal people. When the intraluminal pressure of the sigmoid colon is abnormally increased, the patient may experience left iliac fossa pain and delayed defecation. The electromyogram frequency of diverticulosis patients is 12-18Hz, higher than that of normal people (6-10Hz). The electromyogram of the colon of diverticulosis patients is different from that of irritable bowel syndrome, and the relationship between the two is still unclear. Diverticulosis patients with pain often have irritable bowel syndrome, and the basic pressure of such patients is often increased. The colonic motility index of diverticulosis patients is significantly higher than that of normal people after eating, administration of neostigmine, or morphine. Pentazocine does not increase the intraluminal pressure of the sigmoid colon, while Probenecid and bran can reduce the intraluminal pressure of the colon. Abnormal pressure under resting and stimulated conditions cannot be improved after sigmoid colectomy, suggesting the dysfunction of the entire colon.

　　In summary, the pathogenesis of diverticula needs to be elucidated, and it may be the result of the combined action of various factors, such as abnormal colonic smooth muscle, increased intraluminal pressure during segmental contraction, decreased compliance of the intestinal wall, and low-fiber diet.

　　3. Related factors

　　(1) Obesity

　　It was previously believed that obesity was related to diverticular disease, but research has confirmed that this is not the case. Hugh et al. found that subcutaneous fat thickness is not related to the incidence of diverticulosis.

　　(2) Cardiovascular disease

　　There is no correlation between hypertension and diverticular disease, but the incidence of diverticulosis in patients with atherosclerosis increases, which is speculated to be related to mesenteric ischemia. Male patients who have had a previous myocardial infarction have a diverticulosis incidence of 57%, significantly higher than that of male patients of the same age group (25%). The incidence of diverticulosis in patients aged 65 and over with cerebrovascular accidents is significantly higher than that in the control group.

　　(3) Emotional factors and irritable bowel syndrome

　　No psychological and emotional factors were found to be related to diverticulosis, which is different from irritable bowel syndrome. There are many similarities between irritable bowel syndrome and diverticular disease (such as the weight of stool, fecal bile acids, and fecal electrolyte content), and the former also has increased intraluminal pressure. Electromyogram examination shows that both have fast waves, and they both have excessive pressure responses to food and neostigmine stimulation. High-fiber diet can correct the abnormal defecation time of both, increase the weight of stool, and reduce intraluminal pressure. It is generally believed that inhibiting defecation and flatus can increase intraluminal pressure and promote the formation of diverticula, but this is not the case. Because the sphincter function of young people is strong, the incidence of diverticulosis is not high. On the contrary, elderly people with rectal sphincter relaxation have a higher incidence. In addition, diverticula are not common in patients with megacolon and constipation.

　　(4) Inflammatory bowel diseases

　　The relationship between inflammatory bowel diseases and diverticular disease is complex. When diverticular patients have ulcerative colitis, the intracolonic pressure increases. About 2/3 of patients with diverticular disease and Crohn's disease have perianal symptoms such as ulcers and low rectal fistulas. The incidence of Crohn's disease complicated by diverticula is five times higher than that in the general population, with the main clinical features being pain, incomplete intestinal obstruction, abdominal mass, rectal bleeding, fever, and leukocytosis. Berridge and Dick studied the relationship between Crohn's disease and colon diverticulosis using radiological methods and found that as Crohn's disease gradually progresses, diverticulosis gradually 'disappears'. Conversely, when Crohn's disease gradually improves, diverticulosis reappears. This peculiar phenomenon is prone to complications such as inflammatory masses, abscesses, and fistulas, especially in the elderly, which are more likely to form granulomas. Radiological examination, in addition to finding abscesses and strictures, shows that the mucosa of the diverticula is intact, while the mucosa of Crohn's disease is ulcerated and edematous. Left-sided Crohn's disease often coexists with diverticulosis.

　　(5) Others

　　Diverticular disease is associated with biliary tract disease, hiatus hernia, duodenal ulcer, appendicitis, and diabetes, often accompanied by hemorrhoids, varicose veins, abdominal wall hernia, gallstones, and hiatus hernia. However, small sample studies have found no significant relationship between diverticular disease and duodenal ulcer or arterial disease. Case-control studies have found that intake of non-steroidal anti-inflammatory drugs is more likely to cause severe diverticular complications.

　　(6) Malignant tumors of the colon and rectum

　　The relationship between diverticular disease and colorectal polyps and tumors is still unclear. Edwards found that the incidence of malignant tumors and benign adenomas in diverticular patients is lower than that in the general population, and they also rarely have polyps and colorectal cancer.

　　Fecal stones blocking the entrance of the diverticulum or damaging the mucosa can cause diverticulitis. Initially, it presents as mild chronic inflammatory changes, with the most obvious lesion at the tip of the diverticulum being lymphoid hyperplasia, which gradually spreads to the surrounding colon and mesenteric fat, and finally covers the entire diverticulum and the surrounding colon wall. Therefore, localized peritonitis is a common early complication.

　　Diffuse and localized peritonitis can be caused by diverticular perforation, and infection localized to form abscesses. The sigmoid colon adheres to surrounding tissues, causing intestinal obstruction, or forming fistulas to surrounding organs, such as: diverticular small intestine fistula, diverticular bladder fistula, diverticular vaginal fistula, or diverticular skin fistula. Sometimes, the inflammatory response is severe, forming larger inflammatory masses composed of the sigmoid colon, omentum, small intestine, fallopian tubes, uterus, bladder, and peritoneum.

　　1, Mass

　　After inflammation is localized, inflammatory masses are formed, which adhere to surrounding tissues. If the diverticular inflammation starts at the mesenteric margin, it is easy to form inflammatory masses. If there have been previous episodes of inflammation, the omentum usually adheres tightly to the intestinal tract, and even if the inflammation eventually subsides, the sigmoid colon lesions cannot return to normal.

　　2, Abscess

　　If there has been no peridiverticular inflammation before, it is easy to form an abscess when diverticulitis occurs. Abscesses are the most common complications of diverticulosis, with 10% to 57% of diverticulosis patients developing localized abscesses. The sources of the condition include:

　　① A pericolonic abscess formed at the mesenteric margin.

　　② An omental abscess formed in the mesentery due to diverticula.

　　③ An abscess caused by purulent lymph nodes. Abscesses are prone to be surrounded by surrounding tissues, such as small intestine, omentum, parietal peritoneum, or uterus, etc. Abscesses can cause buttock symptoms when they spread along the mesentery, colon, into the retroperitoneum or posterior rectum.

　　3, Purulent peritonitis

　　It can be diffuse or localized. The characteristics of diffuse purulent peritonitis are cloudy exudate in the peritoneal cavity, thickening of the serous membrane of the intestinal wall, and obvious peritoneal edema. If the perforation is localized, the sigmoid colon may be wrapped by omentum, small intestine, bladder, pelvic peritoneum, rectum, and uterus. Gangrenous sigmoid colitis can also cause purulent peritonitis, but it is less common and has a higher mortality rate.

　　4, Fecal peritonitis

　　Perforation of diverticula can cause fecal peritonitis, with fecal fluid accumulation in the peritoneal cavity. There is communication between the cavity and the colon, although it is relatively rare, the mortality rate can reach as high as 75%. Fecal peritonitis can cause severe circulatory failure, endotoxemia, and Gram-negative septic shock.

　　5, Obstruction

　　Obstruction caused by sigmoid colon diverticula is mostly incomplete obstruction. If the mucosa is edematous and the feces are dry and hard, the obstruction will worsen. If it is combined with sigmoid colon inflammation, it can also cause complete sigmoid colon obstruction, which will be relieved as the inflammation subsides. If the obstruction is caused by纤维素 adhesion from pericolonic abscess, it is not easy to relieve. Adhesion of small intestine and pericolonic inflammatory masses can cause acute small bowel obstruction.

　　6, Fistula

　　Pericolonic abscess or localized peritonitis may develop into a fistula. If it penetrates the abdominal wall, it may form a colonic cutaneous fistula. Other common fistula sites include: bladder, vagina, uterus, ureter, colon, and small intestine. Skin fistula and other organ fistula may coexist.

　　Colonic vesicoureteral fistula is a common complication of diverticulosis, and diverticula are also the most common cause of colonic vesicoureteral fistula. Colonic vesicoureteral fistula manifests as special symptoms of urinary gas and fecal urine. Barium enema can confirm the presence of diverticula, but it is rarely able to find the fistula, which can be seen during cystoscopy, bladder造影, or intravenous pyelography. Because the intestinal lumen pressure is high, the fistula is prone to be epithelialized, and it is not easy to close spontaneously after the fistula is formed. The incidence of male vesicoureteral fistula is higher than that of female, and about 20% of patients require surgical treatment.

　　Spontaneous colonic cutaneous fistula is less common, often seen after surgery, or associated with coexisting Crohn's disease. Colonic cutaneous fistula can be demonstrated by injecting contrast material through the skin sinus tract, or by barium enema.

　　Colonic vaginal fistula ranks third, far less than skin fistula and bladder fistula, and is more likely to occur in female patients who have had a hysterectomy in the past. Colonic colonic fistula is related to inflammatory masses and can involve the small intestine, large intestine, skin, and bladder.

　　7, Other

　　Giant colonic diverticula are not common, only 52 cases were reported in the UK in 1984. Diverticula appear as gas-filled cysts communicating with the intestinal tract, with inflammatory changes in the mucosa, thickening of the sigmoid colon, and adhesion to surrounding tissues. Intestinal volvulus is extremely rare.

　　Diverticula without complications are asymptomatic, sometimes with constipation, or alternating diarrhea and constipation. There is persistent dull pain or spasmodic pain in the left, middle, and lower abdomen. It is often palpable to the cord-like sigmoid and descending colon, with tenderness, which is caused by dyskinesia and spasm of the sigmoid colon. When complicated with diverticulitis, there are both acute and chronic types.

　　(1) Acute diverticulitis

　　Symptoms are obvious, mainly including abdominal pain, fever, abdominal distension, constipation, nausea, and vomiting. Since diverticula are often located in the sigmoid colon, the site of abdominal pain is in the lower left abdomen or suprapubic area, with persistent pain accompanied by spasmodic pain. There is marked tenderness and rebound tenderness in the lower left abdomen, which is very similar to acute appendicitis and is often called left-sided appendicitis. Diverticulitis often complicates with perforative peritonitis, or the formation of an abdominal abscess or inflammatory mass, or the formation of internal fistula or external fistula. Internal fistula can communicate with the bladder and ureter, causing difficulties in urination, gas in urine, and urinary tract infection. Hemorrhage may occur as periodic small amount of hemorrhage or acute massive hemorrhage. The former comes from the inflammatory granulation tissue at the bottom of the diverticulum, and the latter is often caused by inflammation eroding or penetrating a larger blood vessel in the diverticular wall. Hemorrhage is more common in the elderly and can appear as the initial symptom, with an incidence rate of 22%. In addition, there may be complications such as portal vein thrombophlebitis sepsis and secondary liver abscess.

　　(2) Chronic diverticulitis

　　Its characteristics include edema, thickening, fibrosis of the intestinal wall, and adhesion to surrounding tissues. Due to repeated infections, incomplete or complete intestinal obstruction often occurs, or it may manifest as refractory constipation. Because the intestinal lumen narrows, there are often spasmodic abdominal pain, and the thickened and widened intestinal tube in the lesion area can often be palpated.

　　(3) Diverticular hemorrhage

　　10% to 30% of patients may develop hemorrhage, especially in the elderly. Due to the presence of arteriosclerosis and vascular malformations in elderly diverticulosis, they are prone to chemical or mechanical damage, leading to diverticular hemorrhage. Therefore, diverticulosis is a common cause of lower gastrointestinal hemorrhage in the elderly, with hemorrhage usually occurring in the right half of the colon. Patients may experience discomfort in the lower abdomen, followed by the excretion of dark purple stools, with 80% of the hemorrhage stopping spontaneously. The recurrence rate of hemorrhage is 20% to 25%.

　　How to prevent colonic diverticula?

　　If colonic diverticula with diverticulitis are not treated in a timely manner, there may be colonic perforation, bleeding, fistula, and intestinal obstruction. So, how should it be prevented?

　　1. Prevention measures

　　(1) First-level prevention

　　Early identification of diverticular symptoms and early diagnosis are considered as the second-level prevention. Typical diverticulitis can be diagnosed based on symptoms and signs, but elderly, hormone-dependent, and immunodeficient patients may have delayed reactions and atypical symptoms. Colonoscopy, abdominal X-ray, or barium enema examination can be performed.

　　(2) Second-level prevention

　　(3) Third-level prevention

　　Diverticula often occur in the elderly, and their rehabilitation and prevention of complications are considered as the third level of prevention.

　　2. Risk factors and intervention measures

　　(1) Risk factors

　　Temporary intestinal obstruction, constipation, colonic spasm, and drugs can all increase intraluminal pressure, and the mucosa can herniate through the weak spots in the intestinal wall.

　　(2) Intervention measures

　　Choose high-fiber diets, such as bran treatment, and avoid factors that may increase intraluminal pressure.

　　(3) Social intervention

　　Health education for patients, changing dietary habits and bad living habits.

　　Diverticula of the colon are formed by the outward bulging of the colonic wall into a bag-like shape. They can be single, but more often they are a series of sac-like protrusions from the lumen of the intestine. Diverticula of the colon can be divided into true and acquired types. True diverticula are congenital thin-walled colonic defects, and the diverticula contain all layers of the colonic wall. What auxiliary examinations are needed to diagnose colonic diverticula?

　　1. X-ray examination

　　(1) Abdominal X-ray examination

　　Routine abdominal X-ray examination for simple diverticular disease is usually normal, so it is not very valuable. The imaging features of diverticulitis are: displacement or narrowing of the intestinal wall, mucosal changes, and multiple diverticula can be seen in the proximal or distal intestinal segments near the lesion. Abdominal X-ray examination can detect peritoneal abscesses, multiple air-fluid levels and distended intestinal tubes caused by small and large bowel obstruction.

　　(2) Barium enema examination

　　The use of barium or water-soluble contrast agents for contrast enema is of great value in diagnosing asymptomatic diverticular disease, which is more reliable than colonoscopy. The diverticula filled with barium appear as spherical protuberances protruding from the colonic wall, and the diverticula can still be seen after the barium is excreted, without signs of inflammation. Colonic spasm or barium filling may mask the diverticula. Sometimes, inversion of the diverticula or accumulation of feces may be confused with polyps, so multiple-directional observation and filming are recommended, and filming after defecation can improve the accuracy of diagnosis.

　　2. CT scanning

　　The application of CT scanning for the diagnosis of diverticulitis has gradually increased abroad. During an attack of inflammation, barium enema imaging has no specificity, while CT scanning can detect thickening of the colonic wall, inflammation around the colon, fistulae, sinus tracts, abscesses, and strictures. CT diagnosis can detect peripheral colonic inflammation in 98% of patients with diverticulitis, with high sensitivity. Although enema can detect lesions within the lumen, it is not easy to detect inflammation around the colonic lesions. CT examination is used in the following situations:

　　① Suspected fistula or abscess formation.

　　② Patients who have not improved after conservative treatment.

　　③ Cases with unclear diagnosis.

　　④ Patients with right hemicolonic diverticulitis or giant colonic diverticula.

　　CT scanning is helpful in locating percutaneous needle drainage of abscesses before surgery. It also has significant value in diagnosing colovesical fistula.

　　3, Sigmoidoscopy

　　It is also commonly used during the onset of diverticulitis, especially when there is colonic obstruction. To distinguish from polyps and tumors, a small amount of air should be infused during endoscopy. However, it is not advisable to perform colonoscopy during the acute phase of diverticulitis, but rather after the inflammation has subsided.

　　4, Ultrasound examination

　　Colonic diverticula are less commonly used, but they have the advantages of being non-invasive, economical, and convenient, and are often used for percutaneous puncture drainage of extracolonic abscesses. Ultrasound is effective in distinguishing inflammatory masses from abscesses; however, if small bowel bloating, inflammatory masses, and abscesses are small, the diagnostic value of ultrasound is not significant.

　　5, Selective mesenteric angiography

　　Used for patients with diverticulosis complicated by massive hemorrhage, especially in the acute hemorrhagic phase (>0.5ml/min), where extravasation of contrast medium in the diverticula can be diagnosed clearly. Angiography can not only determine the bleeding site but also inject drugs to constrict blood vessels for hemostasis. For patients unsuitable for surgery, embolization therapy can be performed. Elective surgery to remove the diseased intestinal segment can significantly reduce the mortality rate of emergency surgery.

　　6, 99mTc examination

　　99mTc-labeled red blood cells and 99mTc sulfur colloid for diagnosing diverticular hemorrhage are not specific, but 99mTc sulfur colloid scanning can detect bleeding points as small as 0.1ml/min. The drawback is that the liver's uptake of sulfur colloid may mask bleeding points. 99mTc-labeled red blood cells are suitable for patients with intermittent bleeding because red blood cells are cleared from the circulation not as quickly as colloidal sulfur, and are generally not used for patients undergoing planned surgery.

　　Patients with colonic diverticula should eat more fruits with high residue or coarse fiber vegetables and spicy foods to increase intestinal peristalsis and maintain smooth bowel movements. During the acute phase, a liquid diet should be consumed to make the feces soft and slippery, reduce constipation, and facilitate easy excretion from the diverticula. It is recommended to take 5ml of liquid paraffin or senna leaves as a tea drink before bedtime, and it is not advisable to perform colonic irrigation to avoid perforation.

　　Simple diverticulosis usually does not cause symptoms and does not require treatment. It can be managed through dietary adjustments, consuming foods rich in fiber to maintain smooth bowel movements. Some scholars have found that a high-fiber diet not only controls the symptoms of diverticulosis but also reduces intraluminal pressure, preventing complications such as diverticular inflammation and bleeding. Since the 1980s, statistical data has confirmed that a high-fiber diet has kept the number of acute hospital admissions for diverticulosis stable, without an increasing trend. The treatment of diverticulitis usually involves non-surgical methods, including dietary adjustments, antispasmodics, and the use of antibiotics in the intestines (such as salicylate-azosulfapyridine). If the patient has no fever, relief of abdominal symptoms, and recovery of intestinal function, they can start with liquid foods and gradually transition to a regular diet. In the past, a diet low in residue was used, but now a diet high in residue and water-absorbing colloidal substances is more commonly used.

　　(1) Non-surgical treatment

　　It is reported that after increasing the dietary fiber content and reducing the carbohydrate content, diverticulosis patients generally get controlled, the defecation returns to normal, abdominal pain relieves, and a few need to continue taking laxatives. However, some studies believe that for asymptomatic diverticulosis patients, there is no significant difference between high-fiber diet and placebo. It is generally believed that for patients with simple diverticulosis, any treatment has a significant placebo effect. The study found that half of the patients with high-fiber diet showed symptom relief, and only 1/4 of the patients needed surgical treatment.

　　Antispasmodics and antidiarrheal drugs have a certain effect on controlling the symptoms of diverticulosis, especially for patients with irritable bowel syndrome. Commonly used antispasmodics include Probenecid and Mebeverine, the former acts on the autonomic nervous system of the colon, but has side effects such as dry mouth and urinary retention; the latter acts directly on the smooth muscle, with fewer side effects. Methylcellulose can improve the defecation habits of patients with diverticulosis.

　　(2) Surgical treatment

　　It is not reasonable to perform prophylactic colectomy (especially sigmoid colectomy) for patients with mild diverticulosis. If symptoms do not improve after non-surgical treatment or to prevent complications of diverticulosis, elective myotomy or colectomy can be performed.

　　Myotomy

　　The method of myotomy is to separate the thickened muscle layer to expand the diameter of the intestinal lumen, reduce the intraluminal pressure, and attracted the attention of surgeons in the 1960s. But this concept has been abandoned, and it is currently believed that the purpose of cutting through the thickened muscle layer is to allow the mucosal layer to protrude through the weak spot of the muscle layer to reduce functional intestinal obstruction.

　　There are 3 methods for myotomy: longitudinal myotomy, transverse myotomy, and combined myotomy. The purpose of longitudinal myotomy is to cut through the thickened circular muscle to avoid intestinal stricture, but it cannot reduce the contraction and expansion effect of the colon band. Transverse myotomy bends and extends the longitudinal muscle, and has little effect on the circular muscle, so it has little effect on the diameter of the intestinal lumen. The method of combined myotomy is to cut through both the longitudinal and circular muscles simultaneously. In summary, it is not advisable for patients with mild diverticulosis to undergo colectomy, because surgical treatment cannot guarantee the effect, and the incidence of postoperative complications is high. For elderly patients, the effects of diet therapy and surgery are similar.