Colitis from low blood flow with ulcers, elev Herat rate blood in stool and dark urine. Is this still IBS?

Probably, UC or ER. Colitis untreated can lead to many complications, including colon cancer. I am hoping a colonoscopy with biopsy has already been done. However, there is no rule that there cannot be more than one process going on, although less likely. There could be viral hepatitis causing dark urine or acute nephritic syndrome with tea-colored urine. The pancreatitis and weight loss is scary in someone so young.