Waxy Casts

Sunday, December 6, 2009

Waxy casts are urinary cast which suggest the very low urine flow associated with severe, longstanding kidney disease such as renal failure. Waxy casts are nephrology homogeneous cylindrical structures which are seen in the urine, and correspond to the degenerated cellular casts, and are typical of long-term oliguria and tubule obstruction. Additionally, due to urine stasis and their formation in diseased, dilated ducts, these casts are significantly larger than hyaline casts. While cylindrical, they also possess a higher refractive index and are more rigid, demonstrating sharp edges, fractures, and broken-off ends. Waxy casts also fall under the umbrella of “broad” casts, a more general term to describe the wider cast product of a dilated duct.

Although Waxy casts have a smooth consistency, they are more refractile and easier to see compared to hyaline casts. They commonly have squared off ends, as if they were brittle and easily broken. Waxy casts are a sign of tubular injury of a more chronic nature than granular or cellular casts and are always of pathologic significance.