URINE 



489 



(Fig. 154, page 488). Such casts occur in several forms of nephritis, 

 but do not appear to characterize any particular type of the disorder 

 except amyloid disease, in which they are rather common. 



(g) Pus Casts. Casts whose surface is covered with pus cells or 

 leucocytes are termed pus casts (Fig. 1 52, p. 487). They are frequently 

 mistaken for epithelial casts. The differentiation between these two 

 types is made very simple, however, by treating the cast with acetic 

 acid which causes the nuclei of the leucocytes to become plainly visible. 

 The true pus cast is quite rare and indicates renal suppuration. 



Cylindroids. These formations may occur in normal or pathological 

 urine and have no particular clinical significance. They are frequently 



FIG. 155. CYLINDROIDS. (After Peyer.) 



mistaken for true casts, especially the hyaline type, but they are 

 ordinarily flat in structure with a rather smaller diameter than casts, 

 may possess forked or branching ends, and are not composed of homo- 

 geneous material as are the hyaline casts. Such " false casts" may 

 become coated with urates, in which event they appear granular in 

 structure. The basic substance of cylindroids is often the nucleo- 

 protein of the urine (Fig. 155, above). 



Erythrocytes. These form elements are present in the urinary 

 sediment in various diseases. They appear as the normal biconcave, 

 yellow erythrocyte (Plate IV, opposite page 252) or may exhibit 

 certain modifications in form, such as the crenated type (Fig. 156) 

 which is often seen in concentrated urine. Under different condi- 



