Abdominal pain and muco-bloody stool in a patient who had a transplant: a diagnostic imaging challenge

A 36-year-old man presented with abdominal pain lasting 5 months and muco-bloody stools for 1 month. Subsequently, he progressed to incomplete intestinal obstruction (defaecation difficulty and colonic distension). The patient had a history of acute B lymphoblastic leukaemia 3 years ago and underwent allogeneic haematopoietic stem cell transplantation (allo-HSCT). Post-transplant, he developed acute graft-versus-host disease (GVHD) involving the oral cavity and skin, managed with ciclosporin and ruxolitinib until the onset of abdominal pain. Laboratory findings indicated normal white blood cell count, haemoglobin and platelets, but elevated D-dimer (1.34 mg/L FEU) and high-sensitivity C-reactive protein (35.9 mg/L). Colonoscopy revealed sigmoid and rectal mucosal hyperaemia, nodularity and snowflake-like erosions ( figure 1A-C). CT imaging demonstrated diffuse sigmoid and rectal wall thickening, mucosal enhancement and collateral vasculature (figure 1D,E). Initial suspicion of ulcerative colitis (UC) led to unsuccessful mesalazine therapy.