Diseases affecting the kidneys can be broadly classified into congenital and genetic disorders; autoimmune disorders; malfunctions caused by impaired blood supply; infections; metabolic disorders; and tumours of the kidney. Outside factors may cause functional disturbances for example, obstruction in the urinary tract preventing normal urinary flow may result in hydronephrosis, and the crush syndrome, which releases proteins into the blood as a result of seriously damaged muscles (rhabdomyolosis), can result in impaired kidney function. Another outside factor, medicinal drugs, can also be hazardous to the kidney. Large quantities of analgesics taken over a long time damage the kidneys and acute tubular necrosis can result from certain antibiotics.