Clinically Diagnosed Acute Diverticulitis in Outpatients: Misdiagnosis in Patients with Irritable Bowel Syndrome

Physicians often diagnose diverticulitis and prescribe antibiotics in outpatients with abdominal pain and tenderness without other evidence. We investigated the misattribution of irritable bowel syndrome (IBS) symptoms to diverticulitis in outpatients. In patients diagnosed with diverticulitis and dispensed antibiotics in an integrated healthcare system, we retrospectively compared 15,846 outpatients managed without computed tomography (CT) versus 3750 emergency department/inpatients who had CT. We assessed demographics and past history, including 17 symptom-based somatic and 11 mental disorders and three somatic-mental comorbidity pairs (dyads) coded over 3 years and seven drug classes dispensed over 1 year before diagnosis. Univariate analysis showed small intergroup demographic differences. Outpatients had increases in prior diverticulitis, including outpatient-managed episodes, total somatic diagnoses (p < .0001), eight somatic and three mental disorders (p a parts per thousand currency sign .015), all three dyads (p a parts per thousand currency sign .05), and dispensing of three drug classes (p a parts per thousand currency sign .016). IBS had been diagnosed in 2399 (15.1 %) outpatients versus 361 (9.6 %) emergency department/inpatients (p < .0001), the greatest increase in any comorbidity. Emergency department/inpatients had no somatic comorbidity more often but more alcohol dependence, non-dependent drug abuse, and opioid dispensing (p a parts per thousand currency sign .05). Regression analysis revealed outpatient care was independently positively associated with younger age, non-Hispanic white race/ethnicity, less Charlson comorbidity, diverticulitis history, IBS, chest pain, dyspepsia, fibromyalgia, low back pain, migraine, acute reaction to stress, and antispasmodic and anxiolytic dispensing and negatively associated with non-dependent drug abuse and opioid dispensing (p a parts per thousand currency sign .0226). Multiple types of indirect and concordant evidence suggest misattribution of IBS pain to diverticulitis and unnecessary antibiotic therapy in outpatients.