Microorganism inclusion casts

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.

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Crystal casts

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.

Bilirubine casts

Cases of bilirubine crystals embedded in a hyaline matrix have been reported in some cases of high bilirubinuria.

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Other casts

This section is dedicated to special rare casts.

Fibrin thread casts

These casts are hyaline casts embedding, within their matrix, fibrin threads. These threads originate from the passage in the urinary space, of the coagulation proteins (fibrinogen and others). Once in urine, the fibrinogen coagulates and forms fibrin threads. These casts are strongly indicative of glomerulonephritis.

Myeloma casts

The typical myeloma casts are described as rather waxy matrix casts coated with macrophages and tubular cells. These casts are thought to originate from the precipitation of light chains at their acid isoelectric point (4,5- 5,0). Some think that these are not true casts but an inflammatory response to a light chain precipitate. It is not sure that these casts are specific to myeloma.

Unknown casts

Does someone have any idea about this cast? Casts like this one were observed a few times in patients with acute renal failure. Cellular casts, waxy casts, and many tubular cells were also found in all the cases.

A description of a similar cast called "Bubble cast" by N. IMAI is given on his site at http://square.umin.ac.jp/uri_sedi/EBUBBLECAST2.html

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