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Lymphocytes in urine indicate an inflammation, usually a chronic condition like bladder stones. Other causes may be associated with viral diseases. In kidney transplant patients, the presence of lymphocytes in urine indicates the early stages of physiological rejection of the implanted organ. Rarely, urine containing lymphocytes may be an early warning sign of bladder cancer. The most common cause of lymphocytes in urine is bacterial infection, such as a urinary tract infection.
Lymphocytes are produced by the body's immune system, with one of the many different types of white blood cells, called leukocytes. These tiny cells are divided into two types — large granular lymphocytes and smaller agranular cells. Many of the granular lymphocyte types are called "natural killer cells," as these cells watch for and destroy mutations in normal cells that may form into tumors or cancers. Granular lymphocytes include "t cells" and "b cells," which are the smaller white blood cells that roam the circulatory system, seeking and destroying invading pathogens.
The presence of lymphocytes in urine usually belies an underlying medical condition, as lymphocytes reproduce in abundance in the presence of cell mutations or invading pathogens in the body. These lymphocytes are eventually passed out of the body through the urine. In most cases, lymphocytes in the urine indicate some kind of bacterial or viral infection. The infection can be minor or serious, depending on the condition and cause. A microscopic laboratory test is usually required to determine the exact type of lymphocyte in the urine and the cause of increased lymphocyte production.
Lymphocyte count may be high after surgery, indicating an infection or internal lesions. In rare cases, lymphocyte production in urine may be severe enough to taint the urine a milky color, called chyluria. Chyluria can be caused by tuberculosis or a parasitic infection in tropical climates. In developed countries, chyluria may be caused by trauma, kidney lesions, pregnancy or injury to the lymphatic system, although this condition is extremely rare. Infections such as these are easily treated with a regimen of rest and antibiotics.
More seriously, increased lymphocytes in urine may indicate bladder stones or bladder cancer. Some lymphocytes are manufactured by the bone marrow, meaning that an increase of lymphocytes may be an early warning sign of leukemia — a cancer of the bone marrow and blood cells. Successful cancer treatment depends on early cancer detection, so a medical professional may schedule laboratory tests to determine which type of lymphocytes are abundant. The type of lymphocyte in the urine is usually an indicator of the type of infection, since certain lymphocytes multiply profusely when they detect certain conditions. T and B lymphocyte cells usually indicate a viral or bacterial infection, while the granular natural killer cells indicate the presence of cancer cells in the body.