AIM: Gastrointestinal spontaneous hematomas (GSHs) represent 5-10% of patients with acute abdomen. Conservative treatment is the most common approach but the bowel perforation can be a fatal complication. In patients with spontaneous rectal wall hematoma, high comorbidity and abdominal signs of acute abdomen but without radiological signs of intestinal perforation, an early exploratory laparotomy should be considered. CASE PRESENTATION: A 70-year-old man with severe dilatative cardiomyopathy and chronic obstructive pulmonary disease (COPD) on anticoagulant therapy was admitted with acute abdominal pain and anemia. An abdominal CT scan showed a perihepatic, perisplenic and parietocolic effusion associated with a retro-rectal hematoma measuring 6×6×14 cm without signs of active bleeding. Because of sudden onset of signs of peritonitis, a laparotomy was performed which showed an ischemic perforation of the sigmoid-rectal junction. We performed a recto-sigmoid resection (Hartmann operation) but the patient died twelve days later for septic shock. DISCUSSION: In patients with GSH the main problem is represented by the choice between conservative and surgical treatment. In case of complications, such as active and persistent intra-abdominal bleeding, wall ischemia with or without bowel perforation and peritonitis, surgical treatment is mandatory. The absence of radiological signs of perforation can cause a delay of surgical treatment with unfavourable outcome expecially in patient with rectal hematoma and severe comorbidity. CONCLUSIONS: GSHs of rectum are uncommon but a strict clinical monitoring is crucial because the extraperitoneal position make it possible a late clinical or radiological identification of perforation and a late laparotomy.