Pyelonephritis is inflammation of the kidney linings resulting from a urinary tract infection in the upper urinary tract. What is the most common cause of urinary tract infections?

• A. Dehydration
• B. Bacterial contamination
• C. Catheter use
• D. Kidney stones

Answer: (C)

Urinary tract infections happen when bacteria invade and multiply in the urinary tract. The usual culprits are bacteria from the body's own gut flora, most often Escherichia coli, which can ascend from the urethra into the bladder and, if unchecked, reach the kidneys. Catheter use greatly increases the risk because a catheter provides a direct route for bacteria and supports biofilm formation, making catheter-associated UTIs common in hospital settings. Dehydration does not by itself cause infection, and while kidney stones can predispose to infections by obstructing flow, the infection itself is a bacterial invasion. So, the underlying cause is bacterial infection from the urinary tract flora, with catheterization being a major risk factor that elevates the likelihood of developing an infection.