Nephritis is often caused by infections, toxins, and autoimmune diseases. It can be caused by infection, but is most commonly caused by autoimmune disorders that affect the major organs. For example, those with lupus are at a much higher risk for developing nephritis. In rare cases nephritis can be genetically inherited, though it may not present in childhood.
Athletic nephritis is nephritis resulting from strenuous exercise. It may result in the presence of protein and blood in the urine. In most persons these are transient findings that disappear within hours to days after the end of exercise. The findings generally increase by increasing severity and duration of physical stress. 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 blood.
Nephritis is the most common producer of glomerular injury. It is a disturbance of 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). Low renal blood flow activates the renin-angiotensin-aldosterone system (RAAS), causing fluid retention and mild hypertension.
Nephritis is a serious medical condition which is the eighth highest cause of human death. As the kidneys inflame, they begin to excrete needed protein from the body into the urine stream. This condition is called proteinuria. 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.