Myoglobinuria
Overview
Myoglobinuria is the presence of myoglobin in the urine, usually associated with rhabdomyolysis or muscle destruction. Myoglobin is present in muscle cells as a reserve of oxygen.
Symptoms
* Asymptomatic * Muscle symptoms * Muscle pain * Rust-colored urine * Myoglobin in the urine
Causes
Trauma, vascular problems, venoms, certain drugs and other situations can destroy or damage the muscle, releasing myoglobin to the circulation and thus to the kidneys. Under ideal situations myoglobin will be filtered and excreted with the urine, but if too much myoglobin is released into the circulation or in case of renal problems, it can occlude the renal filtration system leading to acute tubular necrosis and acute renal insufficiency.
Diagnosis
After centrifuging, the serum of myoglobinuria is clear, where the serum of hemoglobinuria after centrifuge is pink
Treatment
* Fluid rehydration - needs to be prompt. * Treat hyperkalaemia - calcium gluconate (if indicated) and dextrose-insulin infusions. * Diuretics - mannitol has been used but its use is contentious. Other diuretics have not been shown to improve renal impairment. Diuretics should not be used until hypovolaemia is corrected.4 * Alkaline diuresis - alkalinisation of the urine with bicarbonate can reduce the risk of acute renal failure - however, there is no clear evidence as to its benefit or whether it is any better then simple aggressive hydration with intravenous fluids.4 * If renal function fails to improve patients are at risk of acute tubular necrosis in which case haemodialysis may be necessary.5 * Hypocalcaemia and hyperphosphataemia need not be corrected unless dangerously low - they improve as CK falls.