What Is Diverticular Disease?

Diverticular disease includes diverticulosis and symptomatic diverticular disease.  Symptomatic diverticular disease includes hemorrhage, diverticulitis, or complications of diverticulitis such as abscess, fistula, obstruction, or perforation.

Colonic diverticula are false or pulsion diverticula where the mucosa and submucosa herniate at points of the colonic wall where the circular layer is interrupted by the vasa recta vessels.

The prevalence of diverticulosis in ‘Westernized’ nations increased from 5-10% in 1918 to 35-50% in 1969.  The prevalence of diverticular disease is age-dependent, increasing from less than 20% at age 40 to 60% by age 60.  A U.S. inpatient study showed an increase of 26% in admissions for acute diverticulitis from 1998 to 2005; the largest increase was in patients aged 18-44 years.  There is no clear difference in prevalence among the sexes.

There are geographic variations in both the prevalence and pattern of diverticulosis.  Diverticular disease is more common in ‘Westernized’ nations where it is predominantly left-sided.  In Asia, the prevalence is much lower and predominantly right-sided.  In areas such as Japan and Hong Kong, which have a more Westernized lifestyle, the prevalence of diverticulosis has increased.  The higher incidence in ‘Westernized’ nations suggests environmental and lifestyle factors play an important role in the pathogenesis.

In ‘Westernized’ nations, diverticula are distributed unevenly in the colon. Ninety-five percent of patients have sigmoid diverticula, while 35% also have more proximal disease.  The location of diverticular disease requiring surgery is similar, with 95% of all operative cases involving the sigmoid colon.

Although low dietary fiber has long been recognized to be associated with diverticular disease, complex interactions between colonic structure, motility and diet are likely to be important in the pathogenesis.  For example, localized increases in intraluminal pressure may be due to abnormal motility, which is likely exacerbated by a low-fiber diet.  It has been suggested that dietary fiber, by producing a large bulky stool, results in a wider-bore colon that is less likely to permit efficient segmentation and therefore less likely to develop diverticula.  The observation that diverticular disease is less common among vegetarians is compatible with a role for dietary fiber.

Symptomatic Uncomplicated Diverticular Disease

It is not uncommon for patients with diverticulosis to experience symptoms but without signs of diverticular inflammation.  Symptoms typically include left lower abdominal colicky pain with or without other symptoms including bloating, constipation, or diarrhea.  Treatment includes a high-fiber diet or fiber supplementation (20-35 grams per day) and possibly antispasmodics (e.g. dicyclomine or hyoscyamine).  Anti-inflammatory agents (e.g. mesalamine) may be used to treat the possibility of low-grade inflammation.  The role of probiotics is being defined.

Diverticulitis

Although most people with diverticulosis never have symptoms, 15-25% of people with diverticula develop diverticulitis.  However, recent research has shown that the rate is much lower (<5%) with the greatest likelihood of progression occurring for those patients diagnosed in their 40s. The underlying cause of diverticulitis is micro- or macroscopic perforation of a diverticulum. It was previously believed that obstruction of diverticula by stool increased diverticular pressure and caused perforation; such obstruction is now thought to be rare.  The primary process is likely erosion of the diverticular wall by increased intraluminal pressure or inspissated food particles.  Inflammation and focal necrosis ensue, resulting in perforation.  The inflammation is frequently mild, and a small perforation is walled off by pericolic fat and mesentery. This may lead to a localized abscess or, if adjacent organs are involved, a fistula or obstruction. Poor containment results in free perforation and peritonitis.

Symptoms of diverticulitis include abdominal pain, fevers, chills, a change in bowel habits, nausea, vomiting, and decreased appetite.  Rectal bleeding is rare.  A CT scan with oral and IV contrast is the diagnostic test of choice.  Findings include diverticulosis accompanied by bowel wall thickening, pericolonic fat stranding and possibly an associated abscess.  A colonoscopy is contraindicated in acute diverticulitis due to the potential risk of perforation.  Complications including abscess formation, obstruction, perforation and fistula formation arise in 25% of patients.

Uncomplicated diverticulitis is treated with antibiotics such as Ciprofloxacin and Metronidazole for 10-14 days.  Mild cases can be treated in the outpatient setting.  Hospitalization may be needed for IV antibiotics and IV fluids.  An abscess may require percutaneous or surgical drainage.  Surgery may be required for complications such as a perforation or fistula formation.  Depending on the severity of infection, a clear liquid diet or complete bowel rest is recommended for 2-3 days and then advanced to a low-residue diet until symptoms resolve.  Studies have failed to show that the consumption of seeds, nuts, and popcorn increases the risk of developing diverticulitis.

After recovery from the first episode of acute diverticulitis, one-third of patients will develop a second episode.  After a second attack, another one-third of patients will have a third attack.  Patients with right-sided diverticulitis are at low risk of recurrence, while patients with a long segment of involved colon, diverticular abscess, or a family history of diverticulitis are at a high risk of recurrence.   Surgery for recurrent mild and uncomplicated diverticulitis should be individualized for the patient.  Anti-inflammatory agents (e.g. mesalamine) should be considered after recovery to treat the possibility of low-grade inflammation.

Diverticular Bleeding

Diverticular bleeding is the most common cause of lower GI bleeding and typically occurs in the absence of diverticulitis.  Rupture of the vasa recta vessels that course over the domes of diverticula lead to bleeding.  Most diverticular bleeding occurs from the right colon.

Approximately 5-15% of patients with diverticulosis will experience diverticular bleeding.  Diverticular hemorrhage stops spontaneously in 70–80% of cases. NSAIDs may increase the risk of bleeding from diverticular disease.  Blood loss is usually abrupt, painless, and large in volume.  Once a diverticular bleed is suspected, an upper GI bleed should be excluded.  The patient should be resuscitated with intravenous fluids and blood products if needed.  Although diagnosis can be made with a colonoscopy, active bleeding makes endoscopic visualization difficult.  If the source is localized, treatment with epinephrine injection, clipping, or electrocautery is attempted during a colonoscopy.   A tagged red blood cell nuclear scan or angiography can be helpful in locating the bleeding site.  If the angiogram identifies the bleeding site, treatment with embolization should be performed.  If bleeding cannot be stopped with colonoscopic or angiographic therapy, surgery is typically required.