PWE-161 The Macrogol Drink Test To Distinguish Functional Constipation (fc) And Constipation Predominant Irritable Bowel Syndrome (ibs-c): Underlying Mechanisms Demonstrated Using Mri

Introduction Patients with constipation may have either FC or IBS-C which require different treatments. They are often dissatisfied with their treatment because diagnosis relies on symptoms which frequently overlap. Methods 46 CC patients (24 FC and 22 IBS-C), age 18–68 years, unresponsive to simple laxatives, were compared with 11 healthy volunteers (HV). Whole gut transit (WGT) was assessed using a MRI scan 24 h following ingestion of 5 marker pills as previously validated. Patients then consumed 1 litre of macrogol (MCG) followed by hourly MRI scans for 4 h and scored bowel symptoms from 0–10 (none-severe). Colonic movements were assessed using a motility index (MI) based on colonic wall movement and hypersensitivity index (HI) was calculated as bloating symptom/ascending colon (AC) volume. Results Mean (SD) See Table 1. FC and IBS-C have slower WGT and higher HI than HV. FC showed significantly greater fasting SBWC, AC volume and reduced MI following ingestion of MCG compared to HV and IBS-C. Moreover, FC showed impaired response to MCG with longer time to first bowel movement and reduced stool frequency on the study day when compared with HV and IBS-C. Time to 1st bowel movement correlated significantly with AC volume 2h post MCG, r = 0.44, p = 0.004 and fasting SBWC,r = 0.34,p = 0.035. Using a cut-off >230 min distinguishes FC from IBS-C with sensitivity 55% and specificity 95%; this needs validation in a repeat study. Abstract PWE-161 Table 1 Mean (SD) HV (n = 11) FC (n = 23) IBS-C (n = 20) P value WGT (h) 30.4 108.2 * , ** 71.4 * <0.0001 Fasting small bowel water content (SBWC) (ml) 83 (64) 114 (97) ** 57 (61) 0.0383 Fasting AC (ml) 193 (84) 314 (100) * , ** 219 (66) 0.0002 AC volume 2h post ingestion of MCG (ml) 357 (153) 597 (170) 376 (163) <0.0001 MI 2h post ingestion of MCG (s) 80.2 (48.1) 28.3 (35.1) * , ** 56.4 (42.9) 0.0044 Time to first bowel movement (min) 117.3 (62.4) 588 (1034) * , ** 97.3 (72) 0.0001 Bowel frequency on study day 7.8 (2.7) 3.9 (4.1) * , ** 7.8 (3.0) <0.0001 Hypersensitivy Index (l -1 ) 5.7 (4.9) 12.3 (6.6) * 16.6 (14) * 0.0133 * p < 0.05 compared to HV ** p < 0.05 compared to IBS-C. Conclusion Time to first bowel movement >230 min makes IBS unlikely and should help target treatments. Our MI studies show this is dueto greater motility response to distension in IBS-C who has lower fasting SBWC and AC volumes versus FC. IBS-C showed similar features to HV but can be distinguished by greater HI following distension which suggest hypersensitivity. This inexpensive test done without MRI could help clinicians to distinguish these 2 conditions. Disclosure of Interest C. Lam: None Declared, G. Chaddock: None Declared, C. Hoad: None Declared, C. Costigan: None Declared, E. Cox: None Declared, S. Pritchard: None Declared, K. Garsed: None Declared, L. Marciani: None Declared, P. Gowland Consultant for: Merck, Ironwood, Unilever, R. Spiller Grant/research support from: Lessaffre, Ironwood, Consultant for: Almirall, Astellas, Danone and Sanofi, Conflict with: Free drug for clinical trial from Norgine.