Diverticulitis

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Contributors: Cafer Zorkun M.D., PhD.

Overview
Diverticulitis is a common digestive disease particularly found in the colon (the large intestine). Diverticulitis develops from diverticulosis, which involves the formation of pouches (diverticula) on the outside of the colon. Diverticulitis results if one of these diverticula becomes inflamed or infected. The colon can become infected with craters of food stuck inside, which causes abdominal pain.

Epidemiology
Diverticulitis most often affects middle-aged and elderly persons, though it can strike younger patients as well. Abdominal obesity may be associated with diverticulitis in younger patients, with some being as young as 20 years old.

In Western countries, diverticular disease most commonly involves the sigmoid colon - section 4 - (95% of patients). The prevalence of diverticular disease has increased from an estimated 10% in the 1920s to between 35 and 50% by the late 1960s. 65% of those currently 85 years of age and older can be expected to have some form of diverticular disease of the colon. Less than 5% of those aged 40 years and younger may also be affected by diverticular disease.

Left-sided diverticular disease (involving the sigmoid colon) is most common in the West, while right-sided diverticular disease is more prevalent in Asia and Africa. Among patients with diverticulosis, 10-25% patients will go on to develop diverticulitis within their lifetimes.

Peanuts and seeds may aggravate diverticulitis.

Causes
Although not proven, the dominant theory is that a low-fiber diet causes diverticular disease. The disease was first noticed in the United States in the early 1900s, around the time processed foods were introduced into the American diet. Consumption of processed foods greatly reduced Americans’ fiber intake.

Diverticular disease is common in developed or industrialized countries—particularly the United States, England, and Australia—where low-fiber diets are consumed. The disease is rare in Asia and Africa, where most people eat high-fiber diets.

Fiber is the part of fruits, vegetables, and grains that the body cannot digest. Some fiber, called soluble fiber, dissolves easily in water. It takes on a soft, jelly-like texture in the intestines. Insoluble fiber passes almost unchanged through the intestines. Both kinds of fiber help prevent constipation by making stools soft and easy to pass.

Constipation—or hard stool—may cause people to strain when passing stool during a bowel movement. Straining may cause increased pressure in the colon, which may cause the colon lining to bulge out through weak spots in the colon wall. These bulges are diverticula.

Lack of exercise also may be associated with a greater risk of forming diverticula, although the reasons for this are not well understood.

Doctors are not certain what causes diverticula to become inflamed. The inflammation may begin when bacteria or stool are caught in the diverticula. An attack of diverticulitis can develop suddenly and without warning.

Presentation
Patients often present with the classic triad of left lower quadrant pain, fever, and leukocytosis (an elevation of the white cell count in blood tests). Patients may also complain of nausea or diarrhea; others may be constipated.

Less commonly, an individual with diverticulitis may present with right-sided abdominal pain. This may be due to the less prevalent right-sided diverticula or a very redundant sigmoid colon.

Diverticulitis
The most common symptom of diverticulitis is abdominal pain. The most common sign is tenderness around the left side of the lower abdomen. If infection is the cause, fever, nausea, vomiting, chills, cramping, and constipation may occur as well. The severity of symptoms depends on the extent of the infection and complications.

Diverticulosis
Most people with diverticulosis do not have any discomfort or symptoms. However, symptoms may include mild cramps, bloating, and constipation. Other diseases such as irritable bowel syndrome (IBS) and stomach ulcers cause similar problems, so these symptoms do not always mean a person has diverticulosis.

Differential Diagnosis
The differential diagnosis includes colon cancer, inflammatory bowel disease, ischemic colitis, and irritable bowel syndrome, as well as a number of urological and gynecological processes.

Some patients report bleeding from the rectum.

Patients with the above symptoms are commonly studied with a computed tomography, or CT scan.

Diagnosis
Because most people do not have symptoms, diverticulosis is often found through tests ordered for another ailment. For example, diverticulosis is often found during a colonoscopy done to screen for cancer or polyps or to evaluate complaints of pain or rectal bleeding.

When taking a medical history, the doctor may ask about bowel habits, pain, other symptoms, diet, and medications. The physical exam usually involves a digital rectal exam. To perform this test, the doctor inserts a gloved, lubricated finger into the rectum to detect tenderness, blockage, or blood. The doctor may check stool for signs of bleeding and test blood for signs of infection. If diverticulitis is suspected, the doctor may order one of the following radiologic tests:


 * Abdominal ultrasound.
 * Computerized tomography (CT) scan.

The CT scan is very sensitive (98%) in diagnosing diverticulitis. It may also identify patients with more complicated diverticulitis, such as those with an associated abscess. CT also allows for radiologically guided drainage of associated abscesses, possibly sparing a patient from immediate surgical intervention.

Other studies, such as barium enema and colonoscopy are contraindicated in the acute phase of diverticulitis due to the risk of perforation.

Computed Tomography

 * Colonic and paracolic inflammation in the presence of underlying diverticula (diverticula are identified on CT scans as outpouchings of the colonic wall).
 * Symmetric thickening of the colonic of approximately 4-5 mm is common.
 * Enhancement of the colonic wall is commonly noted. This usually has inner and outer high-attenuation layers, with a thick middle layer of low attenuation.
 * Free diverticular perforation results in the extravasation of air and fluid into the pelvis and peritoneal cavity.
 * Air in the bladder in the presence of a nearby segment of diverticulitis is suggestive of a colovesical fistula.

Patient #1: CT images demonstrate diverticulitis
Images courtesy of RadsWiki

Patient #2: CT images demonstrate a diverticular abscess
Images courtesy of RadsWiki

Histopathological Findings: Actinomycosis diverticulitis & abscess


Treatment
An initial episode of acute diverticulitis is usually treated with conservative medical management, including bowel rest (ie, nothing by mouth), IV fluid resuscitation, and broad-spectrum antibiotics which cover anaerobic bacteria and gram-negative rods. However, recurring acute attacks or complications, such as peritonitis, abscess, or fistula may require surgery, either immediately or on an elective basis.

Upon discharge patients may be placed on a low residue diet. This low-fiber diet gives the colon adequate time to heal without needing to be overworked. Later, patients are placed on a high-fiber diet. There is some evidence this lowers the recurrence rate.

In some cases surgery may be required to remove the area of the colon with the diverticula. Patients suffering their first attack of diverticulitis are typically not encouraged to undergo the surgery, unless the case is severe. Patients suffering repeated episodes may benefit from the surgery. In such cases the risks of complications from the diverticulitis outweigh the risks of complications from surgery.

When is surgery necessary for diverticulitis?
If symptoms of diverticulitis are frequent, or the patient does not respond to antibiotics and resting the colon, the doctor may advise surgery. The surgeon removes the affected part of the colon and joins the remaining sections. This type of surgery—called colon resection—aims to prevent complications and future diverticulitis. The doctor may also recommend surgery for complications such as a fistula or partial intestinal obstruction.

Immediate surgery may be necessary when the patient has other complications, such as perforation, a large abscess, peritonitis, complete intestinal obstruction, or severe bleeding. In these cases, two surgeries may be needed because it is not safe to rejoin the colon right away. During the first surgery, the surgeon cleans the infected abdominal cavity, removes the portion of the affected colon, and performs a temporary colostomy, creating an opening, or stoma, in the abdomen. The end of the colon is connected to the opening to allow normal eating while healing occurs. Stool is collected in a pouch attached to the stoma. In the second surgery several months later, the surgeon rejoins the ends of the colon and closes the stoma.

Complications
In complicated diverticulitis, bacteria may subsequently infect the outside of the colon if an inflamed diverticulum bursts open. If the infection spreads to the lining of the abdominal cavity, (peritoneum), this can cause a potentially fatal peritonitis. Sometimes inflamed diverticula can cause narrowing of the bowel, leading to an obstruction.

Also, the affected part of the colon could adhere to the bladder or other organ in the pelvic cavity, causing a fistula, or abnormal connection between an organ and adjacent structure or organ, in this case the colon and an adjacent organ.

These complications always require treatment to prevent them from progressing and causing serious illness.

Bleeding
Rectal bleeding from diverticula is a rare complication. Doctors believe the bleeding is caused by a small blood vessel in a diverticulum that weakens and then bursts. When diverticula bleed, blood may appear in the toilet or in the stool. Bleeding can be severe, but it may stop by itself and not require treatment. A person who has bleeding from the rectum—even a small amount—should see a doctor right away. Often, colonoscopy is used to identify the site of bleeding and stop the bleeding. Sometimes the doctor injects dye into an artery—a procedure called angiography—to identify and treat diverticular bleeding. If the bleeding does not stop, surgery may be necessary to remove the involved portion of the colon.

Abscess, Perforation, and Peritonitis
Diverticulitis may lead to infection, which often clears up after a few days of treatment with antibiotics. If the infection gets worse, an abscess may form in the wall of the colon.

An abscess is a localized collection of pus that may cause swelling and destroy tissue. If the abscess is small and remains in the wall of the colon, it may clear up after treatment with antibiotics. If the abscess does not clear up with antibiotics, the doctor may need to drain it using a catheter—a small tube—placed into the abscess through the skin. After giving the patient numbing medicine, the doctor inserts the needle through the skin until reaching the abscess and then drains the fluid through the catheter. This process may be guided by sonography or x ray.

Infected diverticula may develop perforations. Sometimes the perforations leak pus out of the colon and form a large abscess in the abdominal cavity, a condition called peritonitis. A person with peritonitis may be extremely ill with nausea, vomiting, fever, and severe abdominal tenderness. The condition requires immediate surgery to clean the abdominal cavity and remove the damaged part of the colon. Without prompt treatment, peritonitis can be fatal.

Fistula
A fistula is an abnormal connection of tissue between two organs or between an organ and the skin. When damaged tissues come into contact with each other during infection, they sometimes stick together. If they heal that way, a fistula may form. When diverticulitis-related infection spreads outside the colon, the colon’s tissue may stick to nearby tissues. The organs usually involved are the bladder, small intestine, and skin.

The most common type of fistula occurs between the bladder and the colon. This type of fistula affects men more often than women. It can result in a severe, long-lasting infection of the urinary tract. The problem can be corrected with surgery to remove the fistula and the affected part of the colon.

Intestinal Obstruction
Scarring caused by infection may lead to partial or total blockage of the intestine, called intestinal obstruction. When the intestine is blocked, the colon is unable to move bowel contents normally. If the intestine is completely blocked, emergency surgery is necessary. Partial blockage is not an emergency, so the surgery to correct it can be planned.

Controversy
There is no scientific evidence that suggests the avoidance of nuts and seeds prevents the progression of diverticulosis to an acute case of diverticulitis, and as such the widely held belief that small undigestable foods like seeds becoming lodged in the diverticula appears to be nothing more than an 'old wives' tale. Further, in a survey of fellows of The American Society of Colon and Rectal Surgeons, although the majority of the surgeons responding to the survey favored adherence to a low residue diet, half of them still saw no value in specifically avoiding seeds and nuts.