What do WBC casts indicate?

• A. Renal amyloidosis
• B. Tubulointerstitial inflammation or pyelonephritis.
• C. Liver disease
• D. Biliary obstruction

Answer: (B)

White blood cell casts form when leukocytes invade and move through the renal tubules during tubulointerstitial inflammation or infection. They consist of a mucoprotein matrix that traps the WBCs, making the cast visible in urine sediment. Their presence is a strong clue that the problem involves the renal tubules, as seen in acute pyelonephritis or tubulointerstitial nephritis, rather than in diseases that primarily affect other parts of the body.

Renal amyloidosis, liver disease, and biliary obstruction don’t typically produce WBC casts because they don’t chiefly involve tubular inflammation. So, the finding points toward tubulointerstitial inflammation or pyelonephritis.