title: Clinically Diagnosed Acute Diverticulitis in Outpatients: Misdiagnosis in Patients with Irritable Bowel Syndrome.
abstract: BACKGROUND
  Physicians often diagnose diverticulitis and prescribe antibiotics in outpatients with abdominal pain and tenderness without other evidence.
  
  
  OBJECTIVE
  We investigated the misattribution of irritable bowel syndrome (IBS) symptoms to diverticulitis in outpatients.
  
  
  METHODS
  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.
  
  
  RESULTS
  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 ≤ .015), all three dyads (p ≤ .05), and dispensing of three drug classes (p ≤ .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 ≤ .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 ≤ .0226).
  
  
  CONCLUSIONS
  Multiple types of indirect and concordant evidence suggest misattribution of IBS pain to diverticulitis and unnecessary antibiotic therapy in outpatients.
authors.affiliation: Department of Research and Evaluation, Kaiser Permanente Southern California, 100 South Los Robles, Second Floor, Pasadena, CA, 92201, USA. george.f.longstreth@kp.org.|, 4152 Palmetto Way, San Diego, CA, 92103, USA. george.f.longstreth@kp.org.
authors.forename: George F
authors.identifier: http://orcid.org/0000-0001-8585-167X
authors.initials: GF
authors.lastname: Longstreth
authors.affiliation: Department of Research and Evaluation, Kaiser Permanente Southern California, 100 South Los Robles, Second Floor, Pasadena, CA, 92201, USA. ryan.s.tieu@kp.org.
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Tieu
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use; D002491:Central Nervous System Agents / Q000008:administration & dosage / Q000627:therapeutic use; D003951:Diagnostic Errors; D004238:Diverticulitis / Q000175:diagnosis* / Q000188:drug therapy; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D010276:Parasympatholytics / Q000008:administration & dosage / Q000627:therapeutic use; D012189:Retrospective Studies
chemical_list: D000900:Anti-Bacterial Agents; D002491:Central Nervous System Agents; D010276:Parasympatholytics
keywords: Anxiety; Comorbidity; Drug abuse; Functional; Opioids; Psychosomatic