Bacteria
The presence of microorganism within a cast is naturally specific to infection of the kidney. Lindner has shown that the presence of bacteria within a cast was pathognomonic of pyelonephritis. These casts are described as a hyaline matrix with bacterial inclusions. As expected, white blood cell inclusions are also present. The detection of the bacillus is quite difficult in bright field microscopy. The cocci will probably be interpreted as granules in a routine specimen. Phase contrast or interference microscopy makes the detection much easier.
Yeast
Schumann, using the PAP staining procedure, has demonstrated the importance of the identification of the yeast casts. These casts are usually found in specimens of immunosuppressed patient. Yeast casts are also a very important finding in the diabetic patients. With immunosuppressed patients the route of introduction is usually the blood. Reflux with a yeast infected urine is also a possible route of entry, specially with the diabetic patient. The "Candida" casts are described, by
Schumann, as casts with a rather waxy matrix with yeast inclusions. As for bacteria casts, cell inclusions, specially white blood cells, are expected.
Crystal casts are defined as a hyaline matrix casts with inclusions of crystals. The presence of these casts indicates an intratubular crystallization. This crystallization can provoke renal damages. These damages can be created by an inflammation process or by obstruction. The sediment with crystal casts will usualy show other figures like renal tubular cells and other casts.
Oxalate casts These casts are seen in cases of hyperoxaluria like in ethylene glycol poisoning. In this context, crystallization is massive and the calcium oxalate crystals are of the Whewellite type (egg shape). Oxalate casts can also be seen in hypercalcemic patients. These casts could indicate a risk toward nephrocalcinosis. The example presented here is from a myeloma patient with a renal failure. |
Uric acid casts Uric acid casts are usualy associated with gout nephropathy.
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Bilirubine casts
Cases of bilirubine crystals embedded in a hyaline matrix have been reported in some cases of high bilirubinuria.