Which condition is characterized by lipiduria and fatty casts?

Nephrotic syndrome is characterized by lipiduria and fatty casts due to the significant protein loss that occurs in this condition. The syndrome typically results from damage to the glomeruli, which leads to increased permeability and allows proteins, especially albumin, to leak into the urine. In nephrotic syndrome, the liver responds to the low plasma albumin levels by increasing lipoprotein synthesis, resulting in elevated lipid levels in the blood.

As the kidneys filter this excess lipoprotein, fat droplets can appear in the urine, leading to lipiduria. The presence of fatty casts—cylindrical structures created when lipoproteins aggregate within the renal tubules—is a key diagnostic indicator of nephrotic syndrome. This finding is significant because it helps differentiate nephrotic syndrome from other kidney conditions that may not present with lipiduria or fatty casts in the same way.

In contrast, other conditions such as acute pyelonephritis, diabetic nephropathy, and acute glomerulonephritis do not typically feature these specific findings, as their pathophysiological processes and effects on renal function and urine composition differ significantly from those seen in nephrotic syndrome.