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Urine casts


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The value of Urine casts in diagnosis of underlying disease

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Urine casts

  1. 1. INTERPRETATION OF URINALYSIS URINARY CASTS Hossein Emad momtaz Pediatric nephrologist
  2. 2.  Case1: Three y/o febrile girl has a urinalysis report showing: Many WBC / WBC casts/ 2-3 RBC / many bacteria What is your possible diagnosis? A) glomerulonephritis B) Acute interstitial nephritis C) Pyelonephritis D) Cystitis
  3. 3.  Case 2 : Five y/o girl has a urinalysis report showing:  +3 protein , 10 -15 RBC, 3 - 4 WBC, fatty casts. No bacteria What is your possible diagnosis? A) Glomerulonephritis B) Nephrotic syndrome C) Acute interstitial nephritis D) Cystitis
  4. 4.  Case 3 : Seven y/o boy has a urinalysis report showing: +3 blood , many RBC , many dysmorphic RBC, RBC casts, WBC cast. No bacteria What is your possible diagnosis? A) Pyelonephritis B) Renal stone C) Glomerulonephritis D) Nephrotic syndrome
  5. 5. • Casts are the only elements found in the urinary sediment that are unique to the kidney. • They are formed within the lumens of the distal convoluted tubules and collecting ducts.
  6. 6.  Their shape is representative of the tubular lumen with parallel sides and somewhat rounded ends.  Examination of the sediment for the detection of casts is performed using lower power magnification.  low-power scanning should be performed along the edges of the cover slip.
  7. 7.  Observation under subdued light is essential, because the cast matrix has a low refractive index.  Once detected, casts must be further identified as to composition using high- power magnification.  They are reported as the average number per 10 lpfs.
  8. 8. CAST COMPOSITION AND FORMATION • The major constituent of casts is Tamm- Horsfall protein, a glycoprotein excreted by the RTE cells of the distal convoluted tubules and upper collecting ducts. • Other proteins present in the urinary filtrate, such as albumin and immunoglobulins, are also incorporated into the cast matrix.
  9. 9.  The rate of excretion of Tamm-Horsfall protein appears to increase under conditions of stress and exercise ( transient appearance of hyaline casts).  The protein gels more readily under conditions of urineflow stasis, acidity, and the presence of sodium and calcium. The extent of protein glycosylation is also important.
  10. 10.  Step-by-step formation of the Tamm-Horsfall protein matrix: 1. Aggregation of Tamm-Horsfall protein into individual protein fibrils attached to the RTE cells. 2. Interweaving of protein fibrils to form a loose fibrillar network (urinary constituents may become enmeshed in the network at this time)
  11. 11. 3. Further protein fibril interweaving to form a solid structure 4. Possible attachment of urinary constituents to the solid matrix 5. Detachment of protein fibrils from the epithelial cells 6. Excretion of the cast
  12. 12. • As the cast forms, urinary flow within the tubule decreases as the lumen becomes blocked. • The accompanying dehydration of the protein fibrils and internal tension may account for the wrinkled and convoluted appearance of older hyaline casts.
  13. 13.  The width of the cast depends on the size of the tubule in which it is formed.  Broad casts may result from tubular distention or, in the case of extreme urine stasis, from formation in the collecting ducts.
  14. 14.  Formation of casts at the junction of the ascending loop of Henle and the distal convoluted tubule may produce structures with a tapered end.
  15. 15.  Any elements present in the tubular filtrate, including cells, bacteria, granules, pigments, and crystals, may become embedded in or attached to the cast matrix.
  16. 16. Hyaline Casts  The most frequently seen cast is the hyaline type, which consists almost entirely of Tamm-Horsfall protein.  The presence of zero to two hyaline casts per lpf is considered normal.  the finding of increased numbers following strenuous exercise, dehydration, heat exposure, and emotional stress is normal too.
  17. 17.  Pathologically, hyaline casts are increased in acute glomerulonephritis, pyelonephritis, chronic renal disease, and congestive heart failure.
  18. 18.  Hyaline casts appear colorless in unstained sediments and have a refractive index similar to that of urine; they can easily be overlooked if specimens are not examined under subdued light.  The presence of an occasional adhering cell or granule may also be observed but does not change the cast classification.
  19. 19. RBC Casts  RBC casts is much more specific, showing bleeding within the nephron.  RBC casts are primarily associated with damage to the glomerulus.
  20. 20.  RBC casts associated with glomerular damage are usually associated with proteinuria and dysmorphic erythrocytes.  RBC casts have also been observed in healthy individuls following participation in strenuous contact sports.
  21. 21.  RBC casts are easily detected under low power by the orange-red color. They are more fragile than other casts an may exist as fragments.  It is highly improbable that RBC casts will be present in the absence of free-standing RBCs and a positive reagent strip test for blood.
  22. 22. WBC Casts  The appearance of WBC casts in the urine signifies infection or inflammation within the nephron.  They are most frequently associated with pyelonephritis and are a primary marker for distinguishing pyelonephritis (upper UTI) from lower UTIs.
  23. 23.  Most frequently, WBC casts are composed of neutrophils; therefore, they may appear granular, multilobed nuclei will be present.  Observation of free WBCs in the sediment is also essential.  Bacteria are present in cases of pyelonephritis, but are not present with acute interstitial nephritis;
  24. 24. Clump of WBC , no cast matrix
  25. 25. Epithelial Cell Casts  Casts containing RTE cells represent the presence of advanced tubular destruction.  Similar to RTE cells, they are associated with heavy metal and chemical or drug-induced toxicity, viral infections, and allograft rejection.
  26. 26.  Owing to the formation of casts in the distal convoluted tubule, the cells visible on the cast matrix are the smaller, round, and oval cells.  Bilirubin-stained RTE cells are seen in cases of hepatitis.
  27. 27. Fatty Casts  Fatty casts are seen in conjunction with oval fat bodies and free fat droplets in nephrotic syndrome, but are also seen in toxic tubular necrosis, diabetes mellitus, and crush injuries.
  28. 28.  cholesterol demonstrates characteristic Maltese cross formations under polarized light and triglycerides and neutral fats stain orange with fat stains.
  29. 29. Granular Casts  Coarsely and finely granular casts may be of pathologic or nonpathologic significance.  It is not considered necessary to distinguish between coarsely and finely granular casts.
  30. 30.  The origin of the granules in nonpathologic conditions appears to be from the lysosomes excreted by RTE cells during normal metabolism.
  31. 31.  Increased cellular metabolism occurring during periods of strenuous exercise accounts for the transient increase of granular casts that accompany the increased hyaline casts.  Urinary stasis allowing the casts to remain in the tubules must be present for granules to result from disintegration of cellular casts.
  32. 32. Waxy Casts  Waxy casts are representative of extreme urine stasis, indicating chronic renal failure.
  33. 33.  Waxy casts are more easily visualized than hyaline casts because of their higher refractive index. As a result of the brittle consistency of the cast matrix, they often appear fragmented with jagged ends and have notches in their sides.
  34. 34. Broad Casts  Often referred to as renal failure casts, broad casts like waxy casts represent extreme urine stasis.  The presence of broad casts indicates destruction (widening) of the tubular walls. sts form in this area and appear broad.
  35. 35.  All types of casts may occur in the broad form. commonly seen broad casts are granular and waxy.  Bile-stained broad, waxy casts are seen as the result of the tubular necrosis caused by viral hepatitis.
  36. 36.  The lecturer has no conflict of interests. Thanks for your attention