Which solid organ located in the left upper quadrant filters blood?

• A. Liver
• B. Pancreas
• C. Spleen
• D. Kidney

Answer: (C)

The organ that best fits both the location and the function described is the spleen. It sits under the left side of the diaphragm in the left upper quadrant and specializes in filtering blood: red pulp removes old or damaged red blood cells and recycles iron, while white pulp provides immune defense. This makes the spleen the primary blood-filtering organ in that region.

The liver also processes blood and is a major filter, but it is mainly in the right upper quadrant and extends into the left, so it’s less specifically the left-upper-quadrant blood-filter in common practice. The pancreas is a retroperitoneal organ in the upper abdomen involved in digestion and glucose regulation, not a primary blood filter. The kidneys filter blood to form urine, and the left kidney is in the LUQ, but their primary description isn’t “filters blood” in the sense of the spleen’s immune and removal role.