What characterizes leukocyte casts?

Leukocyte casts are characterized by containing intact white blood cells. These casts form in the renal tubules when there is inflammation or infection present in the kidneys, often associated with conditions like pyelonephritis. The presence of intact white blood cells within the cast serves as an indicator of the body’s immune response to such renal conditions.

The formation of leukocyte casts specifically reflects a pathological process occurring within the renal tubules, making their identification significant for diagnosing kidney-related ailments. In contrast, the other options do not accurately describe leukocyte casts: fat cells refer to a different type of cast often seen in lipiduria; high refractility can be more characteristic of different casts such as hyaline casts; and wider casts with square ends relate more closely to certain types of non-leukocyte casts, such as those made up of renal epithelial cells.