Eosinophilic enteritis is one of the eosinophilic gastrointestinal disorders characterised by various clinical symptoms. Histopathologic proof of dense eosinophilic infiltration is the cornerstone for the diagnosis. There is no consensus on how dense the infiltration should be, and cut-off values of the eosinophilic count in HPF have not been defined yet. Therapy for eosinophilic enteritis is based on an elimination diet and corticosteroid treatment. Herein the authors report a case of 14-year-old boy who suffered from acute abdominal pain. Computer tomography of the abdomen revealed a thickening of the duodenal wall mimicking a tumour, which seemed to infiltrate the gallbladder and omentum. Histopathological examination of samples taken during laparoscopy showed eosinophilic infiltration and sclerotic changes of the gallbladder and duodenum. Follow-up endoscopy proved extensive eosinophilic infiltration of the gastrointestinal tract: eosinophilic esophagitis, duodenal ulcer with dense eosinophilic presence and eosinophilic proctitis. The patient recovered after dietary restrictions and prednisone.