Antibiotics in Acute Uncomplicated Diverticulitis

March 2016


You are halfway through an average weekday shift in EM-2 when you encounter a very pleasant 50-year-old gentleman with abdominal pain. He reports the pain began three days ago and has progressively worsened. It is a dull, moderate pain located in the left lower quadrant with no radiation. He denies fevers or chills, endorses some nausea but no vomiting. He has had some loose stools, but no hematochezia or melena. His past medical history includes hypertension, for which he takes Lisinopril. He has had no previous abdominal surgeries and has no allergies.

His vitals are: T 37.0 BP 135/80, HR 86, RR 16, SpO2 99%. His exam is remarkable for LLQ tenderness with no rebound or guarding. He is comfortable, well-appearing, and nontoxic.

Suspecting diverticulitis as the likely cause of his symptoms, you check basic labs and order a CT scan of the abdomen and pelvis with IV contrast. His WBC is 14K and his CT reveals uncomplicated sigmoid diverticulitis without perforation of abscess formation.

As you are ordering antibiotics, you remember seeing a recent article in ACEPNow suggesting that antibiotics may not actually be necessary to treat diverticulitis. You had previously scoffed at the suggestion and tossed the magazine in the trash, but now wonder if the assertion was based on real science. Aware that evidence has disproven previous dogma regarding the universal need for antibiotics in a variety of conditions (including simple abscesses and acute sinusitis), you open PubMed and begin looking up articles.

PICO Question

Population: Adult patients with acute uncomplicated diverticulitis, without perforation, abscess, or signs of sepsis.

Intervention: Conservative management without the use of antibiotics, either at home or as inpatient.

Comparison: Management with oral or IV antibiotics.

Outcome: Mortality, complication rate, duration of symptoms, recurrence of disease, need for surgical intervention, cost, quality of life.

Search Strategy
MEDLINE was searched via PubMed using the Mesh terms “Diverticulitis, Colonic/therapy” and “Anti-Bacterial Agents” to identify 144 articles ( These were searched and three primary clinical studies and one systematic review were identified. The Cochrane Database of Systematic Reviews was also searched, and a systematic review was identified. As this article provided no additional information, it was not included in the discussion.


Article 1: Chabok A, Påhlman L, Hjern F, Haapaniemi S, Smedh K; AVOD Study Group. Randomized clinical trial of antibiotics in acute uncomplicated diverticulitis. Br J Surg. 2012 Apr;99(4):532-9

Article 2: Hjern F, Josephson T, Altman D, Holmström B, Mellgren A, Pollack J, Johansson C. Conservative treatment of acute colonic diverticulitis: are antibiotics always mandatory? Scand J Gastroenterol. 2007 Jan;42(1):41-7.

Article 3: de Korte N, Unlü C, Boermeester MA, Cuesta MA, Vrouenreats BC, Stockmann HB. Use of antibiotics in uncomplicated diverticulitis. Br J Surg. 2011 Jun;98(6):761-7.

Article 4: Isacson D, Thorisson A, Andreasson K, Nikberg M, Smedh K, Chabok A. Outpatient, non-antibiotic management in acute uncomplicated diverticulitis: a prospective study. Int J Colorectal Dis. 2015 Sep;30(9):1229-34.

Bottom Line

Despite the increased use of evidence-based medicine to guide clinical practice, brought on in part by the popularity of social media and FOAMed resources (The Skeptics Guide to Emergency Medicine, Life in the Fast Lane, the EMJClub), many of our practices today are still grounded in dogma rather than medical research. The management of acute, uncomplicated diverticulitis has long involved the administration of broad-spectrum antibiotics to theoretically battle the bacteria that have invaded the occluded diverticuli and adjacent colonic wall. This practice is, however, based on no direct evidence. Recent research has challenged the notion that all such patients require antibiotics, and has even led to some guidelines suggesting that antibiotics be used selectively, rather than routinely.

As early as 2007, a paper published out of Sweden began to suggest that select patients treated without antibiotics fared just as well as those treated with antibiotics (Hjern 2007). In this observational study, 193 patients who were not given antibiotics were followed, along with 118 patients who were given antibiotics. The failure rate was low in both groups, with only 7 patients in the no antibiotics group eventually being given antibiotics and none requiring surgery. Among patients initially given antibiotics, 3 required surgery. While this study was observational and patients chosen to receive antibiotics were overall sicker than those chosen not to receive antibiotics, the study does at least suggest that there is a large subset of patients who will do well without the administration of antibiotics.

This study was later followed by a randomized controlled trial, also performed in Sweden, with one Icelandic hospital also being involved (Chabok 2012). In this trial, 309 patients were randomized to not receive antibiotics, while 314 were randomized to receive antibiotics. The risk of an early complication (bowel perforation, abscess formation, or fistula formation) was not statistically different between the two groups (relative risk [RR] of 2.0, 95% CI 0.51-8.0). Slightly more patients in the no antibiotics group required surgery during follow-up compared to the antibiotics group, but this also did not achieve statistical significance (RR 3.0, 95% CI 0.61-15). There was no difference in hospital length of stay or the recurrence of diverticulitis.

One additional observational trial was identified, again out of Sweden (Isacson 2015). They enrolled 161 patients with uncomplicated diverticulitis who were treated as outpatients without antibiotics, and found that only 4 patients (2.6%, 95% CI 1.0-6.5%) required readmission within 14 days. Two of these patients had perforation and one had an abscess, while the fourth had no signs of complication on CT scan. None of these patients required surgery and all were treated successfully with antibiotics.

Overall, this data suggests that select patients with uncomplicated diverticulitis can be treated successfully without the need for antibiotics. The data is quite limited, as evidenced by a systematic review on the topic published in 2011. While the authors performed a thorough search for comparative studies of antibiotics vs. no antibiotics, the only study they identified was the initial paper by Hjern et al. They were therefore unable to draw any conclusions beyond those proposed by the initial paper itself. While we were able to identify two additional articles published since then, even these provide only limited evidence. A single randomized controlled trial was identified, suggesting the need for further research on this topic. While the current body of evidence, all coming from Sweden, may be enough to change practice in Scandanavia, it is doubtful that significant reductions in the use of antibiotics for diverticulitis will be seen in the US until these results are validated in more diverse populations, and until additional guidelines recommend the select use of antibiotics, rather than their routine use.