Which type of casts in urine is associated with acute pyelonephritis?

The presence of white blood cell (WBC) casts in the urine is a key indicator of acute pyelonephritis. Acute pyelonephritis is an infectious condition of the kidney, often resulting from the ascending spread of bacteria from the lower urinary tract. In response to infection and inflammation within the renal interstitium, neutrophils migrate to the area. This inflammatory response may lead to the formation of WBC casts, which are essentially casts containing white blood cells and are formed in the renal tubules.

WBC casts are specifically significant because they indicate that the inflammation is occurring in the renal parenchyma rather than simply in the bladder or urethra, which would not produce such casts. These casts serve as a marker for a renal process rather than a lower urinary tract infection, where you might find other signs like bacteria and nitrites in the urine but not the casts seen in pyelonephritis.

The other types of casts mentioned—hyaline, fatty, and granular casts—do not specifically correlate with acute pyelonephritis. Hyaline casts can be seen in various conditions, including dehydration, but do not indicate infection. Fatty casts are typically associated with nephrotic syndrome and are indicative