Context: Acute appendicitis is the most common abdominal surgical. This study has a medical interest because of this frequency and urgency. Our aim was to determine the current sensitivity of ultrasound in the diagnosis of acute appendicitis Materials and method: It was a prospective descriptive study; from December 2016 to April 2017 at the Joseph Ravoahangy Andrianavalona Hospital Center, Antananarivo Madagascar. The sensitivity was calculated by the formula TP x 100 / TP + FN. The results of the ultrasound examinations were compared with those of the anatomopathological examinations of the operating pieces. Results: The average age of the study population was 31.11 years with a sex ratio of 1.61 in favor of men. Alvarado scores were 1 to 4 in 11.76%, 5 to 6 in 35.3% and 7 to 10 in 52.94%. Ultrasound sensitivity was 91.18%. In 88.23% of cases, appendicitis was diagnosed by visualization of the appendix and, in 11.76%, suspected by evidence of infiltration of peri-appendicular fat. The 8.82% of cases that escaped ultrasound were non-visualized appendages due to their position in the retro-cecal without indirect signs of appendicitis. Conclusion: Despite its operator dependent nature and its limits in the non-visualization of appendages, ultrasound remains a sensitive examination to diagnose appendicitis