Febrile pain in the right iliac fossa is one of the most common reasons for consulting at an emergency service. Within this framework, the main diagnosis that is considered is appendicitis, the main complication of which is perforation. However, a certain number of other conditions can be responsible for this clinical picture, primarily including digestive tract and mesentery disorders including mesenteric lymphadenitis, Crohn’s disease, infectious enterocolitis, small intestine or colonic diverticulitis, ischaemic colitis or cancer of the caecum. This article illustrates the imaging semiology of the various right colonic, iliac, mesenteric and appendicular conditions that could potentially cause an infection of the right iliac fossa. It specifies the indications of ultrasound and CT scans, respectively, which depend on the age of the patient and the clinical signs and symptoms. Though the CT scan is commonly used in abdominal emergencies in general, and particularly in clinical pictures of infection of the right iliac fossa, ultrasound remains recommended as first line imaging when confronted with suspected appendicitis or lymphadenitis in a young subject or in the monitoring of Crohn’s disease.