During a red cell sequestration study, counts are obtained from which organ?

In a red cell sequestration study, the organ primarily involved is the spleen. The spleen plays a crucial role in the sequestration and removal of older or damaged red blood cells from circulation. During the study, the focus is on measuring the uptake and retention of radiolabeled red blood cells within the spleen to assess its functionality and ability to remove these cells.

The kidneys, while important for other functions in the body, do not specifically participate in the sequestration of red blood cells like the spleen does. The atria of the heart and the liver also do not have a primary role in this particular process. Thus, the correct choice for the organ from which counts are obtained during a red cell sequestration study is the spleen, as it is the primary organ responsible for this function in the body.