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A cast is a structure found in the urine sediment of patients with a wide variety of diseases relating to kidney damage or failure. Casts are composed of urinary proteins and various types of cells. Several types of renal casts are shown and discussed. Formed in the collecting ducts of the kidney, renal casts have parallel sides and blunt ends.
The granular cast is the most common type of urine cast and may be found in normal individuals under certain conditions such as exercise, fever, or dehydration. Granular casts occur in increased numbers in patients with diseases such as diabetes. Papanicolaou Stain, 400X magnification.
Renal Tubular Cast. This cast is composed of a granular protein matrix and has two collecting duct cells imbedded in it. Papanicolaou stain. 400x magnification.
A hemoglobin cast is composed of a protein matrix and broken down or hemolized red blood cells. This cast is indicative of renal parenchymal bleeding and is usually accompanied by increased numbers of red blood cells. This cast shows coarse granules which stain red in color with the Papanicolaou stain. 400x magnification.
A white blood cell cast is composed of neutrophils. These inflammatory cells are embedded throughout various levels of the cast and are usually found with renal tubular cells and moderate to many neutrophils. This cast is indicative of tubulo-interstitial inflammation (pyelonephritis). Papanicolaou stain. 200x magnification.
A waxy cast is composed of urinary proteins and broken down cells of various types. This cast represents the urinary stasis and takes approximately 48 hours to form in the tubules. Note the “buttery” consistency and “cracked” edges of this brittle cast. The most serious of all renal casts, widened or broad waxy casts indicate a poorer the prognosis for the patient. Compare the typical waxy cast (Figure 4E) to a wide, “renal failure” cast (Figure 4F). Papanicolaou stain. 400x.
Waxy cast
Waxy renal failure cast
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