Hyaline casts consist of only the uromodulin protein matrix. A few hyaline casts (0–2/low power field) are normal. They may be visible in the urine sediment if the individual has been exercising heavily, has a fever, or is undergoing diuretic therapy.
Pathologically, hyaline casts may be seen with congestive heart failure and may be seen together with other types of casts in a variety of renal diseases.
Hyaline casts are generally translucent and homogeneous but may contain a few granules within the matrix. They have a refractive index similar to urine and are easily missed. Visualization of these casts is enhanced by using subdued light or phase-contrast microscopy.
The formation of hyaline casts between the juncture of the ascending loop of Henle and the distal convoluted tubule may result in a cylindroid (tail) appearance at one end.
