OVERVIEW: What every practitioner needs to know

Are you sure your patient has diverticulitis? What should you expect to find?

  • The typical presentation of acute diverticulitis varies depending on the stage of disease and patient characteristics. The patient may have isolated mild tenderness in the left lower quadrant or full-blown peritonitis.

  • Often times, the patient has a prior history of similar episodes or objective evidence from prior colonoscopies of diverticulosis.

  • The exam in diverticulitis can vary. In mild and early disease in which there is a contained microperforation, there may be minimal tenderness in the left lower quadrant. If the process has extended beyond a contained perforation, there may be more severe or diffuse tenderness or peritonitis.

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How did the patient develop diverticulitis?

  • Acquired diverticula are actually false diverticula (i.e., they do not contain all the layers of the bowel wall) and form when the submucosa and mucosa (the inner most two layers of the bowel wall) herniate through the muscular wall of the bowel. This occurs at areas of intrinsic weakness in the bowel where the vasculature enters. This association with vasculature is the reason some patients with diverticulosis experience colonic bleeding.

  • Diverticulitis is the condition in which one or more of these outpouchings perforate (usually a microperforation), causing leakage of colonic material into the surrounding area, leading to localized inflammation with infection or diffuse peritonitis.

  • The reason most cases of diverticulitis do not present with free perforation is that the diverticula initially protrude into the mesentery of the colon or into the appendices epiploicae, which contain the microperforation.

Which individuals are of greater risk of developing diverticulitis?

  • Patients must have diverticulosis to develop diverticulitis. Age is an important risk factor; older adults have a higher incidence of diverticulosis. However, more recently and likely because of popularization of westernized diets, many patients are developing diverticulosis at an earlier age, putting them at risk of subsequent episodes of acute diverticulitis.

  • Low fiber diet is considered a risk factor for diverticular disease, leading to smaller, harder stools that require higher colonic pressures for transit. This pressure leads to formation of more diverticula and a potentially higher chance of perforation.

  • The greatest risk factor for diverticulitis is having had a previous episode of diverticulitis, with around 20% of those treated non-surgically having a repeated episode requiring hospital admission.

Beware: there are other diseases that can mimic diverticulitis:

  • Early or mild diverticulitis may present similarly to gastroenteritis or a urinary tract infection (UTI) with mild abdominal tenderness.

  • If free perforation with peritonitis occurs, the differential diagnosis includes all causes of acute abdomen (e.g., perforated ulcers, perforated appendicitis, biliary tract disease, urinary tract disease, inflammatory bowel disease, ovarian torsion, ectopic pregnancy, Meckel’s diverticulum, etc.).

  • It is important to recognize that any disease process that leads to colonic perforation, the most important of which is perforated colon cancer, mimics diverticulitis. This is especially important as both disease processes are more likely to occur in older adults.

What laboratory studies should you order and what should you expect to find?

Results consistent with the diagnosis
  • There will usually be an elevated white blood cell (WBC) count and left shift, although patients with early and mild diverticulitis may have a normal WBC count.

  • This result may be blunted in the elderly or immunocompromised.

  • Urinalysis should be ordered to rule out a urinary tract source of pain, keeping in mind that a colo-vesical fistula will also cause a UTI.

  • Patients in whom operative intervention is a possibility should have basic chemistries and coagulation studies.

Results that confirm the diagnosis
  • There is no specific laboratory test that will confirm the diagnosis of diverticulitis.

What imaging studies will be helpful in making or excluding the diagnosis of diverticulitis?

  • CT scan of the abdomen and pelvis (estimated cost $2000) is very useful in diverticulitis with sensitivity and specificity reported as high as 98 and 99%. CT scan can not only confirm the diagnosis, but will also provide information about the extent of extra-colonic involvement and involvement of other organs. It is also useful in revealing other possible sources for pain. In some cases of diverticulitis, it also provides a roadmap for percutaneous placement of drainage catheters for abscess treatment.

  • CT scans can also be very useful to rule out the diagnosis of diverticulitis in patients who have a compatible clinical presentation but no signs of inflammation of the colon on routine imaging.

  • Plain films of the abdomen (estimated cost $300) can be obtained and may show free air or pneumoperitoneum in the case of free perforation.

  • Barium enema (estimated cost $200) was once widely used to examine the colon in cases of diverticulitis; now, it is avoided because of the risk of extending the degree of perforation.

  • Colonoscopy is useful in the non-inflamed colon (once the acute inflammatory process has resolved, typically 4-6 weeks after medical treatment of the acute episode) to determine the presence and location of diverticula, but it is contraindicated in the setting of acute inflammation because of risk of extending the degree of perforation.

  • Previous studies, such as barium enema and/or colonoscopy, should be reviewed to determine whether the patient had diverticula and their location.

What consult service or services would be helpful for making the diagnosis and assisting with treatment?

Any patient admitted with diverticulitis should have a surgical consultation.

If you decide the patient has diverticulitis, what therapies should you initiate immediately?

In 1978, Hinchey described four stages of diverticulitis, and this classification is still used today to help determine the extent of the infectious process and guide therapy:

  • Stage I: pericolic abscess or phlegmon

  • Stage II: pelvic, intra-abdominal, or retroperitoneal abscess

  • Stage III: generalized purulent peritonitis

  • Stage IV: generalized feculent peritonitis

This classification system was modified by Sher in 1997 and Wavery in 1999:

Adding a stage 0: mild disease.

Dividing stage I into Ia and Ib: Ia being confined pericolic inflammation and Ib being confined pericolic abscess.

Dividing stage II into IIa and IIb: IIa being abscess amenable to percutaneous drainage and IIb being complex abscess with possible fistula.

Using clinical exam and imaging (CT scan) to stratify patients into these groups may be helpful when deciding on treatment.

In stage 0 and stage Ia, antibiotic treatment alone is usually adequate. In mild cases in patients tolerating an oral diet, this treatment may be given with oral antibiotics on an outpatient basis.

In stages Ib, IIa, and IIb, a combination of IV antibiotics +/- percutaneous drainage (for abscesses greater than 3cm) is usually attempted, with surgery reserved for those who fail to improve or develop peritonitis.

In stages III and IV, surgical resection is usually required to control the intra-abdominal spillage and inflammation (source control). Historically, this operation has been done in two stages with resection of the diseased colon and drainage of all infectious material, along with formation of a temporary ostomy, followed by a second stage in which re-anastomosis of the colon after the inflammation has resolved is performed (usually >6 weeks following the initial surgery).

More recent studies have shown similar outcomes after a single surgery during which the diseased colon is removed and the remaining colon is anastomosed together in one step, in well selected patients. These studies are almost all retrospective and may have a large amount of selection bias. One small randomized controlled trial compared a two stage approach with end colostomy followed by colostomy takedown to patients who underwent primary anastomosis with diverting loop ileostomy followed by ileostomy takedown. Although outcomes after the first surgery were similar, patients who underwent primary anastomosis and loop ileostomy were more likely to have their ostomy reversed and had fewer complications during the second surgery.

This is still an area of controversy and surgical decision making should be individualized to the patient and to the surgeon’s experience with these often complicated procedures.

In addition, there has been recent interest in laparoscopic lavage as a definitive treatment for Hinchey III diverticulitis. Evidence from recent randomized trials has been mixed, with one small trial favoring lavage with shorter hospitalization times and fewer reoperations and another showing a higher rate of reoperations in the lavage group. At this time there is not sufficient evidence to recommend laparoscopic lavage for as treatment for severe diverticulitis.

1. Anti-infective agents

If I am not sure what pathogen is causing the infection what anti-infectives should I order?

  • The infection in diverticulitis is caused by normal colonic bacteria that have reached the peritoneal cavity through colonic perforation.

  • Antibiotic treatment must, therefore, cover gram-negative rods and anaerobes (the normal flora of the colon).

  • Treatment in all but the mildest cases starts with IV antibiotics as the gastrointestinal (GI) tract is unavailable due to ileus from the inflammatory process.

  • Treatment for diverticulitis is generally empirical as the infection is polymicrobial (Table I).

  • Cultures can be obtained intra-operatively or from drains; some clinicians feel these are likely not helpful because of the large number of bacteria present at the site of infection.

Drugs for Mild to Moderate Infection Dose Drugs for Severe Infection Dose
Single-drug Regimen
1g IV qd
1g IV q6h
400mg IV qd
100mg IV x1 then 50mg IV q12h
3.1mg IV q6h
1g IV q8h
1g IV q8h
500mg IV q8h
3.375mg IV q6h
Multi-drug Regimen
1g IV q6h
1g IV q8h
1g IV qd
2gm IV q8h
400mg IV q12h
750mg IV qd
2g IV q12h
1g IV q8h
400mg IV q12h
750mg IV qd
(above with) metronidazole 500mg IV q8-12h or 1500mg q24h (above with)
500mg IV q8-12h or 1500mg q24h

2. Other key therapeutic modalities

  • Hospitalized patients with diverticulitis are generally kept without diet (npo) until their pain resolves. This is to allow for bowel rest and to avoid emesis that may occur because of the generalized ileus that accompanies the intra-abdominal inflammation.

  • When the acute episode has been successfully treated and the inflammatory process has completely resolved, all patients should have a complete colon evaluation, usually with colonoscopy or barium enema. This is typically done 4-6 weeks after the acute episode (allowing for seal of the microperforation). This is done to define the extent and location of disease and to rule out malignancy or coexisting malignancy, as the primary reason for the perforation and pain.

  • In those requiring surgery for the management of acute diverticulitis, colon evaluation should also be completed either between the two stages or after surgery, when a one-stage approach is used.

  • A recent randomized controlled trial has challenged the routine use of antibiotics in mild diverticulitis. This study showed no differences in outcomes or recurrence rates in patients with mild uncomplicated diverticulitis treated with antibiotics to those who only received only IV fluids. This new evidence needs confirmation from additional trials before changes in practice can be supported, Currently, most experts still recommend antibiotic coverage.

  • Probiotics have been proposed as a means to alter the local flora in the colon and possibly prevent future episodes of diverticulitis. There have been few studies that address this, and a firm recommendation for or against probiotics cannot be made.

  • Similarly, there have been claims that non-absorbable antibiotics and anti-inflammatory agents may be useful in treatment and prevention of diverticulitis, but, again, more, well designed studies are needed.

  • There is no evidence to support the common recommendation for patients with diverticulosis to avoid seeds, nuts, or popcorn.

  • Another controversy is whether to, and when to, operate electively for diverticulitis. If complications, such as a colo-vesical fistula, colo-vaginal fistula, entero-colonic fistula, or stricture, are present and were managed acutely non-operatively, then most advocate operating electively when there is minimal inflammation.

  • Management of patients with stage I-II diverticulitis, after successful management without surgery, is another area of controversy. It was thought and previously recommended that any patient who had more than two episodes of diverticulitis or any young person (younger than 40 years of age) with one attack should undergo elective sigmoid colectomy to avoid future recurrences. This was based on the belief that these patients were more likely to have attacks of severe diverticulitis in the future and would possibly require emergent surgery. Recent studies have challenged this, and patients should now be assessed on an individual basis to decide on the need for elective sigmoidectomy. Increasing numbers of hospital admissions for diverticulitis are actually associated with a decreasing risk of free perforation requiring emergent surgery.

What should you tell the family about the patient's prognosis?

  • In general, the prognosis after an episode of uncomplicated diverticulitis is good.

  • For patients treated with antibiotics in whom colectomy was avoided, the recurrence rate may be as high as 20%, with about 5% requiring emergent surgery during a subsequent hospital admission.

  • As diverticulitis is a disease in which the incidence increases with age, many patients are elderly and may have coexisting health problems. These are risk factors for poor outcome and may also make surgery itself riskier.

  • Patients who require emergency surgery generally have a worse prognosis, with a major post-operative complication rate of 30-40% and a mortality rate of up to10% (partly due to the associated comorbidities).

  • Patients who do need a colostomy during emergent surgery have to undergo a second major abdominal surgery to reverse the colostomy. Some elderly patients are deemed too unfit to undergo this electively, which leads to long-term colostomies and the complications that accompany this.

What-if scenarios

  • During initial work-up or even during surgery, unrecognized complications, such as a colo-vesical fistula, colo-vaginal fistula, or entero-colonic fistula, may be discovered. In this case, the diseased colon is removed as usual, and the small bowel, bladder, or vagina may need to be repaired or partially resected.

  • Discovering these complications in a patient who would otherwise be treated non-operatively usually mandates a subsequent elective operation to address the complication.

How do you contract diverticulitis and how frequent is this disease?

  • Diverticulitis occurs when diverticula, or outpouchings of the colon, perforate and spill colonic contents and bacteria into adjacent tissues or the peritoneal cavity. This causes inflammation and infection, which may be contained by the mesentery and omentum or there may be free rupture with spillage into the whole peritoneal cavity. In the latter scenario, the patient usually develops peritonitis and systemic illness.

  • Diverticula themselves are usually fairly asymptomatic and are found in 10% of patients younger than 40 years of age and in up to 60% of patients older than 80 years of age.

  • 10-25% of people with diverticulosis have an attack of diverticulitis at some time in their lives.

  • There is no reported seasonal variation in the incidence of diverticulitis.

  • The infection in diverticulitis results from normal colonic flora released into the peritoneal cavity through a colonic perforation. The disease is not spread from person to person.

  • Several studies have shown a higher incidence of diverticula and, therefore, diverticulitis in Western countries. This may be related to the lower-fiber diet in the West, which leads to smaller stools that require higher colonic pressures for transit.

  • Different racial groups also show different rates of diverticulitis, but it is hard to discern whether this is driven more by genetic differences than environmental factors (diet).

What pathogens are responsible for this disease?

  • The infection in diverticulitis results from normal colonic flora released into the peritoneal cavity through a colonic perforation.

  • This is, therefore, a polymicrobial infection.

  • The most common organisms cultured include anaerobes, such as Bacteroides fragilis, and gram negatives, such as Escherichia coli.

How do these pathogens cause diverticulitis?

  • Diverticulitis is caused by normal colonic flora released into the peritoneal cavity. The resultant inflammation may be localized, causing a peri-colonic abscess, or it may be a free rupture, causing peritonitis.

  • In addition, complications of diverticulitis can occur because of the inflammation. These include a connection between the colon and the bladder, termed a colovesical fistula, which can lead to UTIs.

  • There can also be connections between the small bowel and the colon (entero-colonic fistula) and between the vagina and the colon, termed a colo-vaginal fistula.

  • Repeat bouts of inflammation can lead to colonic narrowing or stricture.

What other clinical manifestations may help me to diagnose and manage diverticulitis?

  • Diverticulitis can present with symptoms ranging from mild left lower quadrant tenderness to peritonitis.

  • Elderly patients and those who are immunocompromised may have very mild symptoms because of a lack of inflammatory response

  • Patients may present with complications of diverticulitis causing their initial symptoms. For example, a colovesical fistula may cause flatus or stool to pass from the patient’s urethra. In this case, a history of repeated and hard to eradicate UTIs may also be present.

  • In females, a connection between the vagina and colon may develop, especially in the case of a woman who has had a previous hysterectomy when a vaginal cuff is present, and the patient may report passing stool and/or gas from the vagina.

  • Another complication is an entero-colonic fistula, which may present with episodes of diarrhea or electrolyte abnormalities

  • Patients may present with symptoms of bowel obstruction (i.e., inability to pass flatus or stool accompanied by abdominal distention and possibly vomiting) if the inflammation from diverticulitis has caused a colonic stricture.

  • Although, in all of the mentioned scenarios, the patient normally gives a history of an episode (or episodes) of abdominal pain, the patient may not have sought medical attention for this and the complication may be the initial presenting symptom.

How can diverticulitis be prevented?

Diverticulitis cannot be prevented, but all patients should be encouraged to eat food that is high in fiber to bulk up stools and decrease the amount of colonic pressure needed for transit.

WHAT'S THE EVIDENCE for specific management and treatment recommendations?

Alonso, S, Pera, M, Pares, M. “Outpatient treatment of patients with uncomplicated acute diverticulitis”. Colorectal Dis. vol. 12. 2010. pp. 278-2.

Anaya, DA, Flum, DR. “Risk of emergency colectomy and colostomy in patients with diverticular disease”. Arch Surg. vol. 140. 2005. pp. 681-5.

Beckham, H, Whitlow, CB. “The medical and non-operative treatment of diverticulitis”. Clin Colon Rectal Surg. vol. 22. 2009. pp. 156-60.

Beilman, G. “Controversies in the diagnosis and management of diverticulitis coli”. Surg Infect. vol. 12. 2011. pp. 231-4.

Chabok, A, Pahlman, L, Hjern, F. “Randomized clinical trial of antibiotics in acute uncomplicated diverticulitis”. Brit J Surg. vol. 99. 2012. pp. 532-9. (This is a multicenter clinical trial that randomized patients to receive antibiotics vs. no antibiotic treatment for acute uncomplicated diverticulitis.)

Commane, DM, Arasaradnam, RP, Mills, S. “Diet, ageing, and genetic factors in the pathogenesis of diverticular disease”. World J Gastroenterol. vol. 15. 2009. pp. 2479-88.

deKorte, N, Unlu, C, Boermeester, MA. “Use of antibiotics in uncomplicated diverticulitis”. Brit J Surg. vol. 98. 2011. pp. 761-7.

Feingold, D, Steele, S, Lee, S. “Practice parameters for the treatment of sigmoid diverticulitis”. Dis Colon Rectum. vol. 57. 2014. pp. 284-94. (These practice parameters were developed by the clinical practice guideline taskforce for the American Society of Colon and Rectal Surgeons and provide a good overview of the current surgical management of diverticulitis.)

Hinchey, EJ, Schaal, PG, Richards, GK. “Treatment of perforated diverticular disease of the colon”. Adv Surg. vol. 12. 1978. pp. 85-109.

Klarenbeek, BR, Korte, N, van der Peet, DL. “Review of current classifications for diverticular disease and a translation into clinical practice”. Int J Colorectal Dis. vol. 27. 2012 Feb. pp. 207-14.

Kotzampassakis, N, Pittet, O, Schmidt, S. “Presentation and treatment outcomes of diverticulitis in younger adults: a different disease than in older patients”. Dis Colon Rectum. vol. 53. 2010. pp. 333-8.

Martel, J, Raskin, JB. “History, incidence, and epidemiology of diverticulosis”. J Clin Gastroenterol. vol. 42. 2008. pp. 1125-27.

Oberkofler, C, Rickenbacher, A, Raptis, D. “A multicenter randomized clinical trial of primary anastomosis or Hartmann's procedure for perforated left colonic diverticulitis with purulent or feculent peritonitis”. Annals of Surgery. vol. 256. 2012. pp. 819-27. (A recent multicenter clinic trial comparing complications after colonic resection with primary anastomosis and diverting ileostomy versus Hartmann's procedure in Hinchey III and IV diverticulitis.)

Ritz, JP, Lehmann, KS, Frericks, B. “Outcome of patients with acute sigmoid diverticulitis: multivariate analysis of risk factors for free perforation”. Surgery. vol. 149. 2011. pp. 606-13.

Sarma, D, Longo, WE. “Diagnostic imaging for diverticulitis”. J Clin Gastroenterol. vol. 42. 2008. pp. 1139-41.

Schultz, J, Yaqub, S, Wallon, C. “Laparoscopic lavage vs primary resection for acute perforated diverticulitis”. JAMA. vol. 314. 2015. pp. 1364-75. (A recent multicenter randomized clinic trial examining severe post-operative complications after laparoscopic peritoneal lavage vs. colon resection for perforated diverticulitis.)

Shabanzadeh, DM, Wille-Jørgensen, P. “Antibiotics for uncomplicated diverticulitis (review)”. Cochrane Database of Systematic Reviews 2012. vol. 11. (This is a comprehensive review of randomized controlled trials examining antibiotic treatment for left sided uncomplicated diverticulitis.)

Solomkin, JS, Mazuski, JE, Bradley, JS. “Diagnosis and management of complicated intra-abdominal infection in adults and children: guidelines by the surgical infection society and the infectious diseases society of America”. Surg Infect. vol. 11. 2010. pp. 79-109.

Strate, LL, Liu, YL, Syngal, S. “Nut, corn, and popcorn consumption and the incidence of diverticular disease”. JAMA. vol. 300. 2008. pp. 907-14.

Thornell, A, Angente, E, Bisgaard, T. “Laparoscopic lavage for perforated diverticulitis with purulent peritonitis, a randomized trial”. Ann Intern Med. vol. 164. 2016. pp. 137-145. (This is a recent small randomized trial that compared laparoscopic lavage to open colon resection and colostomy in patients with Hinchey III diverticulitis.)

DRG CODES and expected length of stay

329-331 (surgical) and 371-373 (medical)

The expected length of stay is quite variable, ranging from 2-5 days for uncomplicated diverticulitis to weeks or more for complicated cases that may require multiple procedures or surgeries.