The study aims to describe alterations in the contact activation system during active and inactive ulcerative colitis.

Contact activation system measures are compared in a cross sectional (healthy controls vs. active disease) and longitudinal (active diasese vs. inactive disease) fashion.

We include and follow up on 102 adults with active ulcerative colitis. Visits are week 0 (inclusion), 6, 12 and 26 (end of study). We obtain plasma and fecal samples at each visit. Whereas we obtain colonic tissue samples only at inclusion and end of study.

Registered data are:

• Demographics realate to UC and general wellbeing.
• Clinical parametres used for UC evaluation are PRO2, SCCAI, CRP, fecal calprotectin, Mayo endoscopic subscore and Nancy index.
• The contact activation system is characterised by FXII, prekallikrein, kallikrein generation, HK, cHK (specific to plasma kallikrein), cHK (specific to tissue kallikrein), C1 inhibitor and Kallistatin.
• Polymerized alpha-1-antitrypsin is characterised by the degree of polymerization and the capacity to activate the contact activation system.

Inclusion Criteria:

• Fulfill diagnostic criteria of ulcerative colitis
• SCCAI score ≥ 5
• Mayo Endoscopic Subscore ≥ 1
• Age ≥ 18 years
• Most understand written and oral information in Danish
• Informed consent must be given

Exclusion Criteria:

• Pregnancy

• Infection at inclusion

• Any existing disease at inclusion:

  • liver disease or defect in CAS
  • inflammatory rheumatologic or dermatologic disease
  • cardiovascular or renal disease
  • immunodeficiency or hematologic diseases
  • malignancies

• Medication with

  • Systemic corticosteroids at inclusion
  • ACE-inhibitor
  • Acetylsalicylic acid/NSAID
  • Warfarin, Phenprocoumon, NOAC and heparins

Patients are enrolled from the Department of Medical Gastroenterology at the Hospital of Southwest Jutland, Region of Southern Denmark, Denmark