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Urinary casts are formed only in the distal convoluted tubule (DCT) or the collecting duct (distal nephron). The proximal convoluted tubule (PCT) and loop of Henle are not locations for cast formation. Hyaline casts are composed primarily of a mucoprotein (Tamm-Horsfall protein) secreted by tubule cells. The Tamm-Horsfall protein secretion (green dots) is illustrated in the diagram below, forming a hyaline cast in the collecting duct: Cast Formation
Cast are molded in the lumen of the renal tubules • Formed in Distal and Collection tubules • Composed of plasma proteins of Glomerular Filtrate • Tamm-Horsfall Protein makes up matrix Cast Formation
Named by how they appear • Convoluted • Broad • Granular (Finely or Coarsely granular) • Waxy Cast Names
Named by what is in casts • Cells WBC, RBC, Renal Epithelial or Mixed • Substances Fat Hemoglobin Cast Names
Low refractive Index Difficult to see Use low light Hyaline Casts
Cylindroid Hyaline cast with tail Hyaline Casts
Mucous Threads Phase Contrast Hyaline Cast
Spermatozoa Tortuouse Cigar Shaped Phase Contrast Hyaline Cast
Tortuous Interference Contrast Hyaline Cast
Hyaline Cast • Triple Phosphate • Note how Hyaline Casts are barely visible Hyaline Cast
Convoluted • Note cells on matrix Hyaline Cast
Formed by the breakdown of cellular casts • In patients with renal disease the granules become more fine as they progress through the nephron and eventually become Waxy Granular Casts
C Finely Granular Cast
Higher refractive index than Hyaline cast • May be present in urine of healthy person after severe physical exercise • Found in all forms of renal disease Finely Granular Cast
Granules may be disintegrated RBC’s due to reddish color Coarse Granular Cast
Sternheimer-Malbin Stain Coarse Granular Cast
Note mucous threads in background Coarse Granular Cast
In early stage of evolving into waxy cast Notched margins Broad Finely Granular Cast
High Refractive Index • Notched parallel margins • “Broken Off” ends • Chronic renal disease Waxy Cast
High Refractive Index • Notched parallel margins • “Broken Off” ends • Chronic renal disease Waxy Cast
High Refractive Index • Notched parallel margins • “Broken Off” ends • Chronic renal disease Waxy Cast
SM Stain • High Refractive Index • Notched parallel margins • “Broken Off” ends • Chronic renal disease Waxy Cast
Note Spheric lipid globules on surface • Notched parallel margins • “Broken Off” ends • Chronic renal disease Waxy Cast
Casts that contain free fat or oval fat bodies • Fat appears as globular lipids of varying size • Often have a yellow tan color • Lipid has high refractive index • Lipid is birefringent • Maltese Cross in polarized light Fatty Casts
Lipid globules on surface • RBC in background • Nephrotic Syndrome Fatty Cast
Lipid globules on surface • RBC in background • Nephrotic Syndrome • Polarized Maltese Cross Fatty Cast
Lipid globules on surface • RBC in background • Nephrotic Syndrome • Polarized Maltese Cross Fatty Cast
Lipid globules on surface • RBC in background • Nephrotic Syndrome • Polarized Maltese Cross Fatty Cast
Lipid globules on surface • RBC in background • Nephrotic Syndrome Fatty Cast
Cellular Cast are named for the types of cells they contain Cast Formation in Nephron
Reddish color Hemoglobin Cast ??
RBC in hyaline cast matrix • RBC more concentrated at one end RBC Cast
RBC in hyaline cast matrix • Surrounding urine filled with PMN’s and RBC RBC Cast
RBC in hyaline cast matrix RBC Cast
RBC in hyaline cast matrix • Very difficult in this cast to see intact RBC’s • Hb granules RBC Cast
Epi’s • WBC • Note yeast Cellular Cast Mixed
Renal Tubular Cells Cellular Cast