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<\/div>Urinary tract infections frequently cause people to need to urinate more often than usual<\/p>\n
SimpleImages\/Getty Images<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Pain that persists even after a urinary tract infection has supposedly passed seems to be down to an overgrowth of nerve cells in the bladder.<\/p>\n
Urinary tract infections (UTIs) are most commonly caused by the bacterium Escherichia coli<\/em> making its way from faecal matter to the urethra, bladder or kidneys. Common symptoms include pain while urinating and the urge to urinate more often than normal. These infections mainly affect women, of whom around half develop a UTI at some point in their life<\/a>.<\/p>\n \u201cOne of the major issues regarding urinary tract infections is its pretty high rate of recurrence,\u201d says Soman Abraham<\/a> at Duke University in North Carolina. \u201cBut after treatment, some people seem to have the same UTI symptoms even when there\u2019s no longer an infection.\u201d<\/p>\n To understand the root of the ongoing symptoms, Abraham and his colleagues analysed bladder tissue biopsies from eight women who reported continued pelvic pain<\/a> from recurrent UTIs, despite tests revealing there was no E. coli<\/em> in their urine. They also collected biopsies from three women who had never knowingly had a UTI. No transgender people were included in the study.<\/p>\n <\/p>\n The team found that those with persistent UTI symptoms had abnormal overgrowths of nerve cells in their bladders, compared with the other women. These nerve cells also had higher levels of a peptide called substance p, which causes pain and inflammation.<\/p>\n Next, the team induced recurrent UTIs in mice, which similarly showed signs of lasting pain after their infections<\/a> had cleared. Taking a closer look at the mice\u2019s bladders, the researchers found that immune cells called mast cells that were located near nerve cells were highly activated. Mast cells produce so-called nerve growth factors, which stimulate nerve cell production.<\/p>\n