Due to a child's small size, abdominal trauma can result in multiple organs being injured. Abdominal presentations can be vague and the abdomen can hold a large blood volume without obvious signs. Evaluate the abdomen for distension, lacerations, echymoses or evisceration. Periumbilical (Cullen's) or flank (Grey-Turner's) bruising is suggestive of retroperitoneal or intra-abdominal hemorrhage. The abdomen should be palpated in each quadrant, the left upper, right upper, left lower and right lower. Each quadrant should be assessed for tenderness, rigidity, guarding, rebound, pulsations or masses. Being familiar with abdominal anatomy may help determine which organs are injured. In children, the liver, spleen and kidneys are more vulnerable, as they are less protected by the ribs. The liver is a solid and extremely vascular organ located in the right upper quadrant. Circulation through the liver is via the hepatic artery and portal vein and blood flow to the liver is approximately one-third of the total cardiac output. Due to its vasculature, injury to the liver can be responsible for massive hemorrhage. The most common cause of liver injury is blunt trauma. The spleen is located in the left upper quadrant, under the diaphragm. The spleen receives about five percent of cardiac output via the splenic artery. It acts as a blood filter and reservoir. Injury to the spleen is usually caused by blood trauma. Fractures to the tenth through twelfth ribs are associated with penetrating damage.