Under what condition are casts typically found in urine?

Casts in urine are formed when proteins from the renal tubules precipitate in the renal tubule lumen. This process often occurs in conditions where the renal tubules are experiencing some form of injury or stress. When the lumens are blocked—due to inflammation, infection, or other pathological conditions—there is less urine flow, leading to stagnation that allows for the precipitation of these casts.

In a healthy state with normal renal function, you would typically not find casts because the renal tubules are functioning properly, allowing for normal flow and dilution of these proteins. Similarly, during hydration or excess fluid intake, the increased urine output can help to wash out the proteins, reducing the likelihood of cast formation. Thus, the presence of casts is indicative of some underlying renal pathology rather than normal physiological conditions.