Misdiagnosis of Diverticulitis After a Prior Diagnosis of Irritable Bowel Syndrome (IBS)

George F. Longstreth, MD; Carrie Wong, MD; Qiaoling Chen, MS


J Am Board Fam Med. 2020;33(4):549-560. 

In This Article

Abstract and Introduction


Introduction: Irritable bowel syndrome (IBS) and diverticulitis share clinical features. Misdiagnosed diverticulitis can cause unnecessary antibiotic therapy. Among IBS and non-IBS patients, we compared outpatient, clinically diagnosed (no computed tomography) diverticulitis rates. Among primary-care, diverticulitis-diagnosed IBS patients, we assessed imaged diverticulosis and probable misdiagnosed diverticulitis.

Methods: Among 3836-patient IBS and 67,827-patient non-IBS cohorts identified from 2000 to 2002, we retrospectively compared the frequency of outpatient, clinically diagnosed, antibiotic-treated diverticulitis from 2003 to endpoints of December 31, 2017, disenrollment, or death. In IBS patients, we reviewed records of initial, primary care-managed episodes for misdiagnosis.

Results: In 3836 clinically diagnosed IBS and 63,991 non-IBS cohorts, followup (median [interquartile range]) was 12.4 (3.9 to 15.0) years versus 10.2 (3.0 to 15.0) years, respectively (P < .001). The incidence rate/1000 patient-years (95% CI) of diagnosed diverticulitis was 14.0 (12.1 to 16.3) and 4.2 (4.0 to 4.5), respectively, (crude incidence rate ratio, 3.3 [2.8–3.9]; P < .001). Of examined features, the diagnosis of IBS was most strongly associated with clinically diagnosed diverticulitis (adjusted incidence rate ratio [95% CI]; 2.64 [2.21–3.15], P < .001). Of initial diverticulitis diagnoses in 189 IBS patients, objective evidence-based diagnosis revision or exclusion occurred in 12 (6.3%), including 6 hospitalized; 29 (15.3%) had colon imaging before and/or afterward without diverticulosis reported; 143 (75.1%) had image-documented diverticulosis; and 6 (3.2%) had no imaging.

Conclusions: Outpatient, clinically diagnosed, antibiotic-treated diverticulitis was increased 3-fold in IBS patients. Primary care clinical misdiagnosis of initial episodes occurred in 1 of 5 patients, but additional misdiagnosis due to misattribution of IBS pain to diverticulitis is suggested.


Irritable bowel syndrome (IBS), a common functional disorder, is clinically diagnosed by typical symptoms and exclusion of organic disease, usually by limited testing. It is characterized by recurrent abdominal pain and disordered bowel habits.[1] Colonic diverticulosis is also common, but only a minority of patients with it develop acute diverticulitis.[2,3] Abdominal pain is the most common gastrointestinal symptom prompting outpatient visits,[4] and diverticulitis is often diagnosed in outpatients.[5,6] Abdominal pain varies from mild to severe in both IBS[7] and diverticulitis, and abdominal tenderness is found with both disorders.[1,7–9] Furthermore, many patients with diverticulitis report constipation or diarrhea.[8,10,11] These shared clinical features, the frequent absence of fever and leukocytosis,[8] and common uncertainty about whether a patient has diverticulosis promote confusion of IBS with diverticulitis.[11,12] Outpatients diagnosed with diverticulitis are often treated with antibiotics, so misdiagnosis can result in unnecessary antibiotic therapy.

In a retrospective long-term cohort study, we aimed to 1) compare health examinees with and without IBS regarding the frequency of outpatient clinically diagnosed (no computed tomography), antibiotic-treated diverticulitis and assess associated patient features; and 2) assess imaging reports of diverticulosis, a prerequisite for diverticulitis, and documented misdiagnosis among IBS patients who had an initial primary care diagnosis of diverticulitis.