Spleen pain during physical activity?

Side stitch. Pain under your diaphram/ribs on the left or right especially during running sports usuallly is caused by a spasm of your diaphragm. Of it is on the left side it may be interpretted as "spleen" pain. True spleen pain during physical activity may be a serious sign of have enlargement or an injury to your spleen. See a doctor for evaluation and possibly an MRI or ct scan.