nephritis (nəfrī´təs), inflammation of the kidney. The earliest finding is within the renal capillaries (glomeruli); interstitial edema is typically followed by interstitial infiltration of lymphocytes, plasma cells, eosinophils, and a small number of polymorphonuclear leukocytes. The disease is thought to be immunological, but immunoglobulins and drug antigens have been found in only a few cases. The damage is usually reversible when the cause is recognized and removed, but severe cases can progress to fibrosis and renal failure. The disease can take several forms. Pyelonephritis is usually associated with a bacterial infection transmitted from the bladder or blood; it affects the renal pelvis and is treated with antibiotics. Glomerulonephritis, or Bright's disease, causes degenerative changes in the glomeruli and is believed to be an allergic response to infection elsewhere in the body. Symptoms include headache, mild fever, puffiness of the eyes and face, high blood pressure, and discoloration of the urine. Treatment includes bed rest and limiting the intake of water, sodium, and proteins, and, if necessary, dialysis; antibiotics are given to halt infections (e.g., streptococcal) invasion. The disease occurs more frequently among the young. About 95% of patients recover from the acute phase of the disease; however, if glomerulonephritis becomes chronic, renal damage results after many years, causing kidney failure.