[Hydronephrosis of unclear etiology with symptoms of acute abdomen - case report].

We report a case of a patient whose clinical status and results of a plain chest X-ray showed digestive tract perforation, but in whom the true cause of the disease appeared to be hydronephrosis, probably caused by a tumour of the pyelo-ureteral junction. The course of the diagnostic process and causes of the false diagnosis and unnecessary laparotomy are discussed. The usefulness of computed tomography scanning with contrast in the detection of clinically unlcear abdominal disorders (i.e. radiologically "silent" perforation) is emphasised.