Athletic nephritis is nephritis resulting from strenuous exercise. Bloody urine after strenuous exercise may also result from march hemoglobinuria, which is caused by trauma to red blood cells, causing their rupture, which leads to the release of hemoglobin into the urine.
Nephritis can produce glomerular injury, by disturbing the glomerular structure with inflammatory cell proliferation. This can lead to reduced glomerular blood flow, leading to reduced urine output (oliguria) and retention of waste products (uremia). As a result, red blood cells may leak out of damaged glomeruli, causing blood to appear in the urine (hematuria).
Loss of necessary protein due to nephritis can result in several life-threatening symptoms. The most serious complication of nephritis can occur if there is significant loss of the proteins that keep blood from clotting excessively. Loss of these proteins can result in blood clots, causing sudden stroke.
The diagnosis depends on the cause of the nephritis, in the case of lupus nephritis, blood tests, X-rays and an ultrasound can help ascertain if the individual has the condition.