An 18-year-old young man came to a doctor with complaints of cramping abdominal pain, frequent liquid stools with mucus and fresh blood. The symptoms have been observed for the last four months, during which the patient lost 10 kg. Physical examination shows soft abdomen, painful on the left along the large intestine; the sigmoid colon is spastic. Complete blood count shows the following: erythrocytes-3.2-10¹2 / L, hemoglobin-92 g / L, leukocytes -10.6 10 % / L, ESR-34 mm/hour. Bacteriological culture of feces shows negative results. Colonoscopy revealed inflammation of the large intestine with the loss of vascular pattern, as well as an area of increased bleeding with clear boundaries. What treatment tactics should be chosen for this patient?