| disease | Colonic Diverticulosis |
Colonic diverticula are outpouchings of the colonic wall forming sac-like structures. They can be single, but more commonly appear as a series of sac-like protrusions extending outward from the intestinal lumen. Colonic diverticula can be classified into two types: true and acquired. True diverticula are congenital weaknesses involving all layers of the colonic wall, with the diverticulum containing all layers of the intestinal wall. Acquired diverticula, on the other hand, result from the herniation of the mucosa through weak points in the muscular layer of the intestinal wall. They are secondary to increased intraluminal pressure, which forces the mucosa to protrude outward through the weakened areas of the intestinal muscle.
bubble_chart Epidemiology
Acquired colonic diverticulosis is present in a significant portion of the population in Western countries, but the true prevalence of this disease is difficult to determine. Radiographic data overestimate the prevalence because the subjects examined are patients with gastrointestinal symptoms. Conversely, autopsy data underestimate the prevalence because small colonic diverticula are easily overlooked during postmortem examinations. Approximately 5–10% of individuals over 45 years old develop acquired colonic diverticulosis, and this increases to two-thirds of those over 85 years old. In summary, regardless of the exact numbers, both autopsy and barium enema X-ray studies show that acquired colonic diverticulosis increases with age.
Reports of acquired colonic diverticulosis were rare before the 20th century. Although anatomical descriptions of colonic diverticulosis date back to the early 18th century, the relationship between clinical manifestations and pathological findings was not recognized until the 20th century. The rapid rise in the prevalence of acquired colonic diverticulosis in Western countries during the 20th century can be attributed to a decrease in dietary fiber consumption. Painter and Burkitt noted that not a single case of diverticulitis was encountered in Africa over 20 years, suggesting that the increased prevalence of diverticulosis and its complications in industrialized nations is due to the replacement of coarse, fibrous foods with refined flour and sugar. While most evidence for this theory is circumstantial and observational, support for the importance of dietary fiber comes from epidemiological studies of first-generation Japanese immigrants in Hawaii, whose diet had become Westernized. The incidence of diverticulitis was indeed higher compared to those born in Japan.
Acquired colonic diverticulosis is more common in women, with a reported male-to-female ratio of 2:3 by Parks (1969). The average age at presentation is 61.8 years, with over 92% of cases occurring in individuals over 50 years old. The sigmoid colon is affected in 96% of patients, and in 65.5% of cases, it is the only affected site. About half of the patients report symptoms lasting less than one month before seeking medical attention. Symptoms tend to be shorter in duration for those with more extensive disease compared to those with localized disease. Among initially hospitalized patients, 65% are treated medically, while 35% require surgical intervention. Of those successfully treated medically, 26% require further management. Over 90% of patients experience their first episode within five years. The mortality rate for recurrent cases is twice that of first-time episodes. Moreover, regardless of medical or surgical treatment, persistent or recurrent symptoms are common.bubble_chart Clinical Manifestations
(1) Colonic Diverticulosis
Approximately 80% of patients with colonic diverticulosis are asymptomatic. If eventually discovered, it is usually an incidental finding during barium enema X-ray or endoscopy. Symptoms related to diverticula are actually manifestations of complications—acute diverticulitis and bleeding. In uncomplicated colonic diverticulosis, symptoms such as occasional abdominal pain, constipation, or diarrhea are due to associated motility disorders, with the presence of diverticula being coincidental. Physical examination may reveal grade I tenderness in the left lower abdomen, and sometimes the left colon can be palpated as a firm, tubular structure. Despite abdominal pain, there is no fever or leukocytosis because infection is absent. Barium enema imaging may show segmental intestinal spasm and muscular thickening, leading to luminal narrowing and a sawtooth appearance, in addition to diverticula.
During an acute episode, patients experience varying degrees of localized abdominal pain, which may be stabbing, dull, or colicky. The pain is most commonly in the left lower abdomen but occasionally occurs in the suprapubic region, right lower abdomen, or throughout the lower abdomen. Patients often report constipation or frequent bowel movements, or sometimes both, with pain relief after passing gas. Inflammation adjacent to the bladder may cause urinary frequency and urgency. Depending on the location and severity of inflammation, nausea and vomiting may also occur. Physical examination findings include low-grade fever, grade I abdominal distension and fullness, tenderness in the left lower abdomen, and a palpable mass in the left lower abdomen or pelvis. Fecal occult blood is common, while gross bleeding is rare unless peridiverticulitis is present. Additionally, mild to grade II leukocytosis may be observed.
Acute diverticulitis is the most common complication of colonic diverticulosis. According to Rodkey and Welch, 43% of colonic diverticulosis cases admitted to Massachusetts General Hospital involved acute diverticulitis and localized infection. Acute diverticulitis can occur anywhere in the colon, including the rectum. In Western countries, the sigmoid colon is the most frequent site, whereas in Japan and China, the right colon is more commonly affected. Among patients with known diverticulosis, about 10–25% experience at least one episode of acute diverticulitis. Although massive rectal bleeding is rare in diverticulitis, 30–40% of patients with acute diverticulitis initially present with fecal occult blood positivity. Approximately 10–25% of patients show no improvement or worsen despite 48 hours of treatment, requiring emergency surgery. About 70% of patients undergoing emergency surgery present with severe initial symptoms. Immunocompromised patients respond poorly to medical therapy. Perkins et al. reported that treatments such as fasting, fluid replacement, and antibiotics failed in 100% of these patients, while surgery carried high morbidity and mortality rates. Therefore, most transplant centers recommend elective colectomy for confirmed diverticulitis before transplantation. Acute diverticulitis is uncommon in patients under 40 years old, and its clinical course is often severe. Freishlay et al. reported that 77% of patients under 40 required surgery during their first episode, often presenting with serious complications such as free perforation. Right-sided colonic diverticula may be part of generalized colonic diverticulosis, an isolated process involving a few diverticula in the right colon, or, more commonly, a single true diverticulum. In young patients, right-sided diverticulitis often mimics acute appendicitis.
The most common complication of acute diverticulitis is abscess or cellulitis formation, which may occur in the mesentery, abdominal cavity, pelvis, retroperitoneum, buttocks, or scrotum. A tender mass is often palpable during abdominal or pelvic examination, including digital rectal examination. Abscesses caused by diverticulitis are also accompanied by varying degrees of sepsis.
(4) Acute Diverticulitis Complicated by Diffuse Peritonitis
When a localized abscess ruptures or a diverticulum perforates freely into the peritoneal cavity, it can cause purulent or fecal peritonitis. Most of these patients present with acute abdominal pain and varying degrees of septic shock. It has been reported that the mortality rate of purulent peritonitis is 6%, while that of fecal peritonitis is as high as 35%.
(5) Acute diverticulitis with fistula formation
Approximately 2% of all patients with acute diverticulitis develop fistulas, but among patients who ultimately undergo surgery for diverticular disease, 20% have fistulas. Internal fistulas may arise from adjacent organs adhering to the inflamed colon and adjacent mesentery, with or without the presence of an abscess. As the inflammatory process worsens, the abscess in the diverticulum decompresses spontaneously, rupturing into the adherent hollow organ, thereby forming a fistula. Since the abscess is effectively drained, this outcome often eliminates the need for emergency surgery. About 8% of patients will develop multiple fistulas, with males more likely than females to have multiple fistulas. This is presumed to be because the uterus in females acts as a barrier separating the sigmoid colon from other hollow organs. Most patients with diverticular colovesical or colovaginal fistulas have previously undergone a hysterectomy. Fistulas caused by diverticulitis can involve many organs. Most cases of colocutaneous fistulas—external fistulas—occur in patients who develop anastomotic complications after bowel resection for diverticular disease, specifically anastomotic fistula disease.
(6) Acute diverticulitis complicated by intestinal obstruction
Abroad, diverticular disease accounts for about 10% of large intestine obstructions. In domestic cases, complete colonic obstruction caused by diverticular disease is rare, but partial obstruction due to edema, spasms, and inflammatory changes from diverticulitis is common.
Accurate diagnosis is a crucial step in determining the condition and deciding on the treatment plan. Some patients with mild symptoms and signs of diverticulitis can be successfully treated in an outpatient setting, while others presenting with acute, life-threatening conditions require emergency resuscitation and life-saving surgery. Therefore, the most important assessment involves clinical examination and frequent re-evaluation of the patient. This includes not only medical history and physical examination, pulse and temperature, but also continuous blood tests, as well as upright and supine abdominal X-rays. When all typical symptoms and signs are present, the diagnosis of left-sided colonic diverticulitis is straightforward. In such cases, no additional tests are needed, and treatment should be initiated based on the presumptive diagnosis. Unfortunately, most cases are often unclear, and the diagnosis and severity of the episode may remain uncertain after the initial clinical examination. In cases of acute right-sided colonic diverticulitis, only 7% are correctly diagnosed before surgery. Preoperative studies are generally unhelpful and may only delay appropriate treatment.
Three tests are helpful in confirming the clinical diagnosis of acute left-sided colonic diverticulitis and detecting significant inflammatory complications: endoscopy, double-contrast barium enema, and abdominal and pelvic CT scans. In acute cases, endoscopy should generally be avoided because insufflation may induce perforation or worsen an existing perforation. If other rectosigmoid pathologies are suspected—conditions that could alter treatment—endoscopy may be performed but should avoid insufflation.
Barium enema can be used emergently to diagnose diverticulitis, but there is a risk of barium leakage into the peritoneal cavity, which can cause severe vascular collapse and death. Hackford et al. recommend performing a barium enema 7–10 days after the inflammatory process subsides to confirm the diagnosis. If a more urgent diagnosis is needed to guide treatment, a water-soluble contrast enema can be used, as any leakage into the peritoneal cavity would not cause severe reactions.
CT scanning is a non-invasive test that can generally confirm clinically suspected diverticulitis. Enhanced rectal imaging during the scan makes it more sensitive than plain X-rays in detecting diverticular abscesses or fistulas. Labs et al. reported that CT scans are more effective in diagnosing complications of diverticulitis: CT scans identified 10 out of 10 abscesses and 11 out of 12 fistulas, whereas contrast X-rays identified only 2 out of 8 abscesses and 3 out of 8 fistulas. Another advantage of CT scans is their ability to guide percutaneous drainage of abscesses.
Colovesical fistulas due to diverticulitis are best diagnosed by CT scans, which can confirm the diagnosis in over 90% of cases. Cystoscopy may also be necessary, revealing focal inflammatory changes at the fistula site. Barium enema and flexible sigmoidoscopy are less effective, with positive findings in only about 30–40% of cases.
Abdominal plain films may reveal colonic obstruction secondary to sigmoid pathology. A water-soluble contrast enema can confirm the diagnosis.
bubble_chart Treatment Measures
(1) Medical Treatment
For uncomplicated acute diverticulitis, medical treatment can be initially adopted, including fasting, gastrointestinal decompression, intravenous fluid replacement, broad-spectrum antibiotics, and close clinical observation. Generally, gastrointestinal decompression is only used when there is vomiting or evidence of colonic obstruction. There are many antibiotics available to control gram-negative aerobic and anaerobic bacilli, and cases of acute diverticulitis resolving spontaneously without antibiotics are also frequently observed. Dietary fiber supplements and antispasmodics have no role in the management of acute diverticulitis. In most cases, symptoms will rapidly improve with medical treatment.
(2) Indications for Surgery
Currently, conditions requiring surgical intervention can be divided into two major categories: one involves uncomplicated diverticular disease, and the other involves various complications caused by diverticulosis. In summary, surgical treatment should be considered for the following situations: ① First episode of acute diverticulitis unresponsive to medical treatment; ② Recurrent acute diverticulitis—even if the first episode responded well to medical treatment, elective resection should be considered upon recurrence; ③ Patients under 50 years old who have had one episode of acute diverticulitis successfully treated medically should undergo elective surgery to avoid emergency surgery later; ④ Immunocompromised patients with diverticulitis cannot mount an adequate inflammatory response, making it a potentially fatal condition. Perforation and rupture into the free peritoneal cavity are extremely common. Therefore, patients with a prior episode of acute diverticulitis who require long-term immunosuppressive therapy should undergo elective resection to eliminate the risk of recurrence and complications; ⑤ Acute diverticulitis complicated by abscess or cellulitis; ⑥ Acute diverticulitis with diffuse peritonitis; ⑦ Acute diverticulitis complicated by fistula formation; ⑧ Acute diverticulitis complicated by colonic obstruction.
Among the above surgical indications, particularly in uncomplicated cases, special care must be taken not to misdiagnose patients with irritable bowel syndrome (IBS) and colonic diverticulosis as having diverticulitis and subject them to unnecessary surgery. According to Morson, about one-third of specimens from elective surgeries for diverticulitis show no pathological evidence of inflammation. Therefore, in the absence of objective signs of inflammation such as fever or leukocytosis, IBS with colonic diverticulosis should be managed as a functional colonic disorder and not as a candidate for unnecessary resection.
(3) Surgical Treatment
1. For elective surgery cases, preoperative comprehensive examination and thorough preparation are required, including bowel cleansing and antibiotic prophylaxis. Since the sigmoid colon is the most commonly affected site, it is the primary segment to be resected. The extent of resection is debatable, but appropriate proximal and distal margins must be determined. The colon should be fully mobilized, and the anastomotic segments must have good blood supply and be tension-free. Benn et al. suggest that placing the anastomosis in the rectum significantly reduces the recurrence of diverticulitis. Not all colonic diverticula need to be removed, but no diverticula should remain distal to the anastomosis. The colon previously affected by diverticulitis often shows changes on the serosal surface and mesenteric infiltration due to prior inflammation, aiding identification. However, even after satisfactory resection, many patients experience enlargement of pre-existing diverticula, progression of diverticulosis, and a recurrence rate of acute diverticulitis of about 7–15%. The recurrence rate of symptoms over time is similar between medically and surgically treated patients.
For patients undergoing resection due to unresponsiveness to medical treatment, preoperative bowel preparation may not be suitable. In such cases, Hartmann’s procedure may be chosen, or intraoperative proximal colonic irrigation followed by initial-stage (first-stage) end-to-end anastomosis without colostomy may be performed. Recent trends favor initial-stage anastomosis, even after abscess resection, without fecal diversion.
2. During surgery for acute inflammatory complications of diverticulitis, second or third-generation cephalosporins and metronidazole should first be administered intravenously. Some patients may require intravenous stress-dose steroids. Before surgery, the surgeon should assess pelvic anatomical factors, as temporary colostomy or ileostomy may be necessary. This should be explained to the patient and their family preoperatively to prepare them mentally. Additionally, due to the acute inflammatory response, the ureters are often involved, increasing the risk of accidental injury during emergency surgery. Therefore, preoperative bladder endoscopy is recommended to place ureteral stents for support.
Emergency surgery patients should be placed in the lithotomy position, and exploration is performed through a midline laparotomy incision. The purpose of exploration is to confirm the diagnosis, assess the extent of peritoneal inflammation, evaluate the adequacy of bowel preparation, and identify any other pathologies. According to Colcock, up to 25% of patients preoperatively diagnosed with diverticulitis accompanied by abscess or fistula are later found to have perforated carcinoma. Clearly, if it is carcinoma, the goals and extent of resection will change. For this reason, Hughes et al. (1963) classified the inflammatory complications of diverticular disease into four categories: ① localized peritonitis; ② localized pericolonic or pelvic abscess; ③ diffuse peritonitis following rupture of a pericolonic or pelvic abscess; and ④ diffuse peritonitis secondary to free colonic perforation. Later, Hinchey et al. (1978) proposed a similar classification: ① pericolonic or mesenteric abscess; ② walled-off pelvic abscess; ③ diffuse purulent peritonitis; and ④ diffuse fecal peritonitis. This classification has been widely adopted. In 1983, Killingback proposed a more complex and detailed classification.
For complicated diverticular disease, the optimal approach is to drain the abscess, control peritonitis, and resect the inflamed bowel segment. Recent data have shown that conservative drainage and ostomy procedures are associated with significantly higher morbidity and mortality rates compared to resection. The traditional late-stage (third-stage) surgery has been replaced by initial-stage (first-stage) and intermediate-stage (second-stage) procedures. Current evidence suggests that initial-stage (first-stage) surgery is safe, but several critical factors must be considered when deciding between initial-stage (first-stage) and intermediate-stage (second-stage) surgery: ① an empty bowel lumen free of fecal matter, indicating satisfactory bowel preparation or the ability to achieve this through intraoperative irrigation; ② absence of bowel wall edema; ③ adequate blood supply to the intended anastomotic segment; ④ localized and not overly severe intra-abdominal infection or contamination; and ⑤ the surgeon's understanding of the patient's overall condition and any other specific risk factors. The recent enthusiasm for initial-stage (first-stage) anastomosis is largely due to the challenges of restoring bowel continuity in patients who previously underwent Hartmann's procedure for diffuse peritonitis.
As for intermediate-stage (second-stage) surgery, there are two options. The first is the Hartmann procedure, where the distal end is closed, and a proximal colostomy is performed, with anastomosis deferred to the intermediate stage (second stage). This approach is generally suitable for cases of diffuse purulent peritonitis or diffuse fecal peritonitis requiring resection. The second option is initial-stage (first-stage) anastomosis with adjunctive proximal colostomy, ileostomy, or colonic bypass, typically used for cases not involving diffuse purulent or fecal peritonitis but where other factors preclude initial-stage (first-stage) anastomosis.
There remains disagreement regarding surgery for right-sided colonic diverticulitis. According to Schmit et al., if carcinoma can be ruled out, limited colonic resection is sufficient. If carcinoma cannot be excluded or bowel viability is in question, a right hemicolectomy should be performed. However, Fischer and Farkas argue that patients with acute diverticulitis and localized cellulitis can be successfully treated with antibiotics postoperatively, provided carcinoma is excluded and resection is not feasible.
