Background The prevalence of chronic opioid use among non-cancer patients presenting with acute abdominal pain (AAP) is unknown. The aim was to characterize opioid use, constipation, diagnoses, and risk factors for surgical diagnoses among non-cancer patients presenting with AAP to an emergency department (ED). Methods We performed a retrospective, observational cohort study of all (n=16,121) adult patients (88% from Minnesota, Iowa and Wisconsin) presenting during 2014 with AAP. We used electronic medical records, and focused on 2352 adults with AAP who underwent abdominal CT scan within 24 hours of presentation. We determined odds ratios of association with constipation and features predicting conditions that may require surgery (surgical diagnosis). Key Results There were 2,352 eligible patients; 18.8% were opioid users. Constipation was more frequent in opioid (35.1%) compared to non-opioid users [OR 2.88 (95% CI 2.28, 3.62)]. Prevalence of surgical diagnosis in the opioid and non-opioid users was 35.3% and 41.7% respectively (p=0.019). By univariate analysis, age and neutrophil count independently predicted increased risk, and chronic opioid use decreased risk of surgical diagnosis. Internal validation of logistic models using a randomly selected validation subset (25% of entire cohort, 587/2352) showed receiver operating characteristic (ROC) curves for the validation and full cohorts were similar. Conclusions & Inferences Approximately 19% of adults presenting with AAP were opioid users; constipation is almost 3 times as likely in opioid users compared to non-opioid users presenting with AAP. Factors significantly associated with altered risk of surgical diagnoses were age, opioid use, and neutrophil count.

Background Diagnosis of rectal evacuation disorders (RED) is currently based on anorectal manometry and evacuation tests in specialized laboratories; we recently showed higher rectal gas volume (RGV) and maximum rectal gas transaxial area (MRGTA) measured on abdominal and pelvic computed tomography (CT) in patients with documented RED. Aim To obtain cut-off values of RGV, MRGTA and rectal area on scout film (RASF) to differentiate constipated patients with RED from those without RED, based on anorectal manometry (ARM), balloon expulsion test (BET), and colon transit test. Methods We identified 118 constipated patients (65 with RED) with prior record of CT. Using standard CT software, we used a variable region of interest (ROI) program to measure RGV, MRTGA and RASF, as previously described. We constructed ROC curves based on different values, and we estimated AUC, specificity and positive predictive value (PPV) to detect RED in patients with constipation. Key Results ROCs of the models to predict RED showed AUC 0.751 for RGV and 0.737 for MRGTA (both p<0.001), and 0.623 for RASF (p=0.029). At specificity of 90%, RGV of 30mL had a PPV 77.3%, MRGTA of 10cm2 had a PPV 75.0%, and RFAS of 9cm2 had a PPV of 68.8% for identifying constipated patients with RED. Conclusions and Inferences Rectal gas measurements on abdominal imaging may indicate RED in patients with constipation. At ~90% specificity for RED, RGV of 20 or 30mL or MRGTA of 10cm2 on CT have PPV ~75%, and RASF of >9cm2 has PPV of ~69%.