Like momof5boys, I've heard of splenic aneurysms. They occur in the artery leading to the spleen. A co-worker unknowingly had one and it ruptured while he was at work. He was found on the floor by a co-worker and luckily survived the ordeal, but he was very close to not making it since ruptures have a high fatality rate.
I'm sorry to say this, but I would not trust a dr that said that aneurysms are nothing to worry about. My mother died of an unknown abdominal aneurysm rupture. We were told that she would have survived the heart attack which triggered the rupture, but she died because of the blood loss from the ruptured aneurysm. My sister is currently on medication to keep an abdominal aneurysm from growing larger. It is something that should be monitored and I'm not sure why a dr would tell you otherwise. Please get a second opionion from a specialist.