Traditionally, in the diagnosis of acute appendicitis and endogenous intoxication that accompanies its course, hemogram indicators and a wide range of proposed hematological indices are widely used. However, as practice shows, the isolated study of the hemogram, even with the involvement of its integral indices, especially in the early stages of pathology, is not enough for its timely diagnosis, and even more so the differential diagnosis. An important additional method of diagnosing acute appendicitis is ultrasound. Purpose – on the basis of specific clinical observation in the dynamics of the abdominal pain syndrome to determine the complex diagnostic significance of the integrated indicator of endotoxicosis of the body and ultrasound. Materials and methods. As an integral indicator of endogenous intoxication, the integrated indicator proposed by the authors was chosen, which was calculated based on the indicators of the general analysis of peripheral blood: the number of leukocytes, ESR and leukogram indicators according to the formula. To facilitate the calculation of the value of the total index of endogenous intoxication, a calculator based on a program for working with Excel spreadsheets was developed, in the environment of which the proposed index formula was integrated. Ultrasound examination was performed with Doppler scanning on ultrasound machines «SAMSUNG H60» (manufactured in South Korea) and «SAMSUNG» LS22EMU1HS (Seoul. Korea, 2016). Results. Simultaneous comparison of the dynamics of local changes in the clinical picture, hemogram, the magnitude of endogenous intoxication and visual findings in ultrasound of the abdomen allows to avoid unwarranted surgery in patients with abdominal pain. Conclusions. Properly collected anamnesis, assessment of physical and clinical and laboratory parameters and data of laboratory methods of examination, the involvement of the necessary narrow specialists allows to avoid mistakes in the diagnosis of acute appendicitis in children. It is expedient and justified in the diagnostic assessment of the clinical picture in case of suspicion of acute appendicitis to compare the indicators of the integrated index of endogenous intoxication, namely the total index of endogenous intoxication with ultrasound visualization of the appendix in the dynamics of the pathological process. The research was carried out in accordance with the principles of the Helsinki declaration. The study protocol was approved by the Local ethics committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: intoxication index, ultrasound, appendicitis.