PubMed1990
Strenuous exercise makes extraordinary demands. The transition from rest to intensive physical activity can cause pathological changes in various organs, particularly in the urinary tract. Hematuria (microscopic or macroscopic) is one of the abnormalities commonly found after sports activity. This phenomenon can occur in noncontact sports (such as rowing, running and swimming) as well as in contact sports (boxing, football and so forth). The pathophysiology can be either traumatic or nontraumatic. Renal trauma and/or bladder injury due to repeated impact of the posterior bladder wall against the bladder base can cause vascular lesions and consequently hematuria. There are 2 mechanisms of nontraumatic injury. 1) Vasoconstriction of the splanchnic and renal vessels occurs during exercise in order that blood can be redistributed to the contracting skeletal muscles, thus causing hypoxic damage to the nephron. This results in increased glomerular permeability which would favor increased excretion of erythrocytes and protein into the urine. 2) A relatively more marked constriction of the efferent glomerular arterioli results in an increased filtration pressure, which favors increased excretion of protein and red blood cells into the urine. It must be noted that sports hematuria differs from other conditions that may cause reddish discoloration of the urine due to physical exercise, such as march hemoglobinuria and exercise myoglobinuria. In the latter 2 abnormalities there is excretion of hemoglobin and myoglobin molecules in the urine and not whole blood or intact red blood cells. Sports hematuria usually has a benign self-limited course. However, coexisting urinary tract pathological conditions should be excluded carefully.