Spontaneous aorto-caval fistula is a rare complication of abdominal aortic aneurysm. A definitive diagnosis is sometimes difficult, as the classic diagnostic signs (pulsatile abdominal mass with bruit, high-output hearth failure, and acute dyspnea) are present in about half of the patients. Diagnosis may be suspected from clinical symptoms, but sometimes atypical clinical features may obscure the actual situation. Computed tomography findings include early detection of contrast medium in the dilated inferior vena cava, which is isodense with the adjacent aorta, an associated aortic aneurysm, loss of normal anatomic space between aorta and vena cava, and rarely one can even visualize the abnormal communication between aorta and vena cava. Prompt radiological diagnosis is of key importance in the management of these patients. We describe findings of multislice computed tomography of the patient with dissecting aortic aneurysm and aortocaval fistula, clinically presenting as left renal colic. Multislice computed tomography is the imaging modality of choice for diagnosis of abdominal vascular pathology as it is noninvasive, fast and demonstrates a high diagnostic accuracy.