Urine sediment, 400x

Granular casts have a rectangular shape, often with rounded extremities. Note that sometimes debris such as mucus and desquamated cells can resemble casts. True casts can be differentiated from these artefacts by their parallel sides.  Casts are formed in the renal tubules, and no more than 0-1 are normally present per 100x field. When these casts are abundant, tubular damage should be suspected. Finally, there are other kinds of casts (hyaline casts, waxy casts).