As a disease commonly encountered in daily practice,acute appendicitis is usually diagnosed and managedeasily with a low mortality and morbidity rate.However,acute appendicitis may occasionally becomeextraordinarily complicated and life threatening.A56-year-old man,healthy prior to this admission,wasbrought to the hospital due to spiking high fever,poorappetite,dysuria,progressive right flank and painfulswelling of the thigh for 3 d.Significant inflammatorychange of soft tissue was noted,involving the entireright trunk from the subcostal margin to the kneejoint.Painful disability of the right lower extremity andapparent signs of peritonitis at the right lower abdomenwere disclosed.Laboratory results revealed leukocytosisand an elevated C-reactive protein level.AbdominalCT revealed several communicated gas-containingabscesses at the right retroperitoneal region with masseffect,pushing the duodenum and the pancreatic headupward,compressing and encasing inferior vena cava,destroying psoas muscle and dissecting downward intothe right thigh.Laparotomy and right thigh explorationwere performed immediately and about 500 mL of frankpus was drained.A ruptured retrocecal appendix was thecause of the abscess.The patient fully recovered at theend of the third post-operation week.This case remindsus that acute appendicitis should be treated carefullyon an emergency basis to avoid serious complications.CT scan is the diagnostic tool of choice,with rapidevaluation followed by adequate drainage as the key tothe survival of the patient. As a disease commonly encountered in daily practice, acute appendicitis is usually diagnosed and managedeasily with a low mortality and morbidity rate. Even, acute appendicitis may occasionally becomeexordordarilyarily complicated and life threatening. A56-year-old man, healthy prior to this admission, wasbrought to the hospital due to spiking high fever, poorappetite, dysuria, progressive right flank and painfulweweing of the thigh for 3 d .Significant inflammatorychange of soft tissue was noted, involving the entireright trunk from the subcostal margin to the kneejoint. Painful disability of the right lower extremity andapparent signs of peritonitis at the right lower abdomenwere disclosed. Laboratory results revealed leukocytosis and an elevated C-reactive protein level. Abdominal Tested several communicated gas-containing abscesses at the right retroperitoneal region with masseffect, pushing the duodenum and the pancreatic headward, compressing and encasing inferior vena cava, destroying psoas muscle and dissecting downward intothe right thigh. Laparotomy and right thigh explorationwere performed immediately and about 500 mL of frankpus was drained. A ruptured retrocecal appendix was thecause of the abscess.The patient fully recovered at theend of the third post-operation week.This case remindsus that acute appendicitis should be treated carefully on an emergency basis to avoid serious complications. CT scan is the diagnostic tool of choice, with rapidevaluation followed by adequate drainage as the key tothe survival of the patient.