6 month old baby presents with history of bloody diarrhoea of 2 days duration with abdominal distension and on examination baby screams. What is the most probable diagnosis?: (A) Intussusception, (B) Acute enterocolitis, (C) Meckel's diverticulum, (D) Hemolytic Uraemic syndrome
Answer is A. Intussusception

Short history of bloody diarrhoea.
Extreme tenderness on examination.