What is a significant risk factor for developing pyelonephritis?

Frequent urinary tract infections are a significant risk factor for developing pyelonephritis because these infections can ascend from the lower urinary tract (such as the bladder) to the upper urinary tract, including the kidneys. When bacteria enter the kidneys, it can lead to inflammation and infection, resulting in pyelonephritis. Individuals with recurrent urinary tract infections may have anatomical or functional abnormalities of the urinary tract that predispose them to ascending infections, thereby increasing their risk of pyelonephritis.

Other options such as high blood pressure, diabetes mellitus, and low fluid intake can have various impacts on overall health and might contribute to the risk of urinary tract issues, but they do not directly correlate with the mechanism of how pyelonephritis develops as clearly as recurrent urinary tract infections do. Thus, frequent urinary tract infections stand out as a primary precursor to this specific renal condition.