Sediment Constituents (Casts) Flashcards
What is the term for molds of the renal tubule?
Cylindruria
What does cylindruria represent?
Biopsy of individual tubule
What is the uniform diameter of the renal tubule mold in relation to RBCs?
7-8 times the diameter of RBCs
What is the most difficult and most important urinary sediment constituent?
Casts
Where are casts primarily formed in the kidney?
DCT and Collecting Duct
What is the major constituent of casts?
Uromodulin (Tamm Horsfall Protein)
What has the same significance as casts?
Cylindroids
How are casts examined?
Along the coverslip edges with subdued light
Under what magnification are casts counted?
LPF (Low Power Field)
Under what magnification are casts identified?
HPF (High Power Field)
What is the first step in the formation of casts?
Aggregation of uromodulin into individual protein fibrils attached to RTE cells
What is the last step in the formation of casts?
Excretion of casts
What is the order of cast degeneration?
Hyaline, Cellular, Degenerating cellular, Coarsely Granular, Finely granular, Waxy
What is the prototype cast and most frequently encountered?
Hyaline cast
What is the appearance of a hyaline cast?
Colorless and translucent, requires subdued light
What is the normal value of hyaline cast in urine?
0-2/LPF
What pathologies cause hyaline casts?
Glomerulonephritis, pyelonephritis, CHF, CKD
What is the most fragile cast that indicates bleeding within the nephron?
RBC Cast
What is the color of an RBC cast?
Orange-red
In what conditions is RBC cast significant?
Glomerulonephritis, strenuous exercise (physiologic cause in hyaline cast)
What is a muddy brown cast composed of?
Hemoglobin from lysed RBCs