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How can a urinary tract obstruction allow infection to spread toward the kidneys?

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The most common cause of urinary tract infection is invasion into the urethra of Escherichia coli, a type of bacterium that normally inhabits the bowel. — urinary tract infection The most common cause of urinary tract infection is invasion into the urethra of *Escherichia coli*, a type of bacterium that normally inhabits the bowel.

A urinary tract obstruction facilitates the spread of infection to the kidneys primarily by impeding the normal flow of urine, which creates a stagnant environment prone to bacterial colonization.12

When the urinary tract is blocked, urine can back up into the ureters and the renal pelvis, a condition known as hydronephrosis. This stasis allows bacteria to ascend the urinary tract more easily, leading to intractable infections within the kidney tissue and the renal pelvis. Furthermore, the resulting distension and inflammation of the bladder and ureter walls can exacerbate the vulnerability of these tissues to infection.12

It is important to note that such infections are often difficult to eradicate with antibiotics alone until the underlying obstruction is surgically or mechanically relieved. If left untreated, these ascending infections can lead to severe complications, including chronic pyelonephritis, the formation of fibrous scar tissue, and potentially renal failure.12