The primary aim is to evaluate if introduction of eHealth in its form of the web application Constant-Care (https://ibd.constant-care.com) could reduce the length of hospitalization in patients with acute severe Ulcerative Colitis treated with infliximab. This is relative to historical controls extracted from medical records.||Patients will self-measure on the web-application while hospitalized as well as after discharge. At the web-application different questionnaires are filled out and a fecal calprotectin (FC) analysis is performed on a smartphone. The final follow up is one year after admission.