1- IBD A 21-year-old woman presented to clinic with a one-week history of bloody diarrhoea eight times per day, with nocturnal motions and generalized abdominal pain. She had a long history of arthralgia in the hands and recurrent mouth ulcers. Her father had ankylosing spondylitis. Examination revealed aphthous mouth ulcers, a small ulcer in the right leg with a violaceous border, and mild right iliac fossa tenderness. Her temperature was 38°C, heart rate 110 beats per minute and blood pressure 100/60 mmHg. What is the most appropriate first investigation?