A 40-year-old man under evaluation and treatment for renal dysfunction due to suspected antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis presented at our nephrology department with sudden onset of epigastric pain following three cycles of steroid pulse therapy. The results of a recent renal biopsy were unavailable. Despite constant and severe abdominal pain, the patient's abdomen was soft and flat. Serum creatinine was 5.65 mg/dl, and blood urea nitrogen was 47.9 mg/dl. Although initial vital signs were within normal ranges (heart rate, 97 beats per minute, blood pressure, 109/69 mmHg, and respiratory rate, 24 per minute), the patient's blood pressure gradually dropped and the patient became unconscious. The laboratory findings were as follows: serum hemoglobin, 3.4 g/dl; hematocrit, 10.3%; leukocytes, 20,230/mm3; and serum C-reactive protein, 0.55 mg/dl. The patient slipped into hemorrhagic shock and was referred to the surgery department for further investigations. Contrast-enhanced computed tomography revealed intraabdominal hemorrhaging, hematomas around the spleen, and extravasation of contrast medium within the spleen (). Due to the lack of any recent trauma, we diagnosed atraumatic splenic rupture. The hemorrhagic shock led to cardiopulmonary arrest, from which the patient recovered spontaneously. Trans-arterial embolization was contraindicated because of a previous history of aortic arch replacement for Stanford type B aortic dissection. An anastomotic aortic aneurysm was formed following the surgery, and the celiac artery originated from the false lumen, so emergency splenectomy was scheduled. A large volume of intraabdominal blood and hematoma was removed during emergent laparotomy. Bleeding was observed from the superior border of the spleen, and intraoperative blood loss was 880 ml, including the evacuated hematoma. Because CT had confirmed arterial bleeding within the spleen, splenectomy was performed after ligation of the splenic artery. The spleen weighed 582 g, and the resected specimen contained a splenic hematoma (). Pathological examination revealed a mixture of hematomas and infarcted lesions, along with severe neutrophil infiltration (a, b). Necrotic vessels were present in the infarcted area, with surrounding micro-abscess formation. The histopathological diagnosis was splenic rupture with splenic infarction. The histopathological findings of the earlier renal biopsy became available after the splenectomy, and revealed infiltration to the intestinal cells and renal tubules (c). Infiltration of plentiful inflammatory cells indicated infection-related glomerulonephritis rather than ANCA-associated vasculitis. The patient was ventilated postoperatively, and received dialysis in the intensive care unit. The postoperative course was uneventful, and the patient was transferred to the nephrology department on postoperative day 8 for continuation of treatment for renal failure. On postoperative day 10, the patient became febrile and infection was suspected, although blood cultures were negative. Repeat contrast-enhanced computed tomography revealing enlargement of an aortic pseudoaneurysm that had been present prior to splenectomy (). Infected aortic aneurysm with poorly controlled infection was suspected. Although aortic replacement is indicated for treatment of infected aortic aneurysm, the patient's general condition was poor, so thoracic endovascular aortic repair (TEVAR) was performed as a bridging therapy on postoperative day 12. The patient was then discharged on postoperative day 51, with no complications.