NEPHRITIS, RENAL CASTS 251 



Whatever increases blood pressure increases the amount of 

 urine; many diuretic medicines act in this manner. Muscle 

 exercise not only increases blood pressure, but stimulates the 

 secreting cells by the toxic substances which arise normally from 

 rapid metabolism and are carried to the kidney by the quickened 

 circulation. 



Nervous excitement and hysteria cause an abundant pale urine. 

 Cold weather and moist air both discourage the activity of the skin 

 therefore, they increase the action of the kidneys. 



On the other hand, if the system rids itself of water in other 

 ways, as by excessive perspiration, diaphoretic medicines, hot packs, 

 etc., the urine will be diminished, but it will have a high specific 

 gravity. 



Clinical notes. i. The toxic substances which are present in the blood in 

 fevers are abnormal to the kidney and modify its action so that the urine is 

 scanty and dense. 



2. Nephritis is inflammation of the kidney. In one form (acute 

 Bright* s disease} it causes a scanty and dense urine; in another and 

 chronic form an abundant dilute urine. (When waste ceases to 

 appear we know that the cells are not secreting.) 



3. Certain poisons which are swallowed (bichloride of mercury for 

 example) cause such intense irritation of the cells in the tubules that 

 they are seriously injured and may be destroyed. 



4. Renal casts. (Tube Casts.} Irritation of the kidney struc- 

 ture so changes its tissue that plastic material from the blood 

 exudes into the tubules and is there moulded into their shape, 

 forming casts. Hyaline casts are transparent (being the simplest 

 form). Granular casts show a more advanced stage of trouble. 

 Epithelial casts have epithelial cells added ; urate casts are common 

 in rheumatism and tonsillitis, etc., etc. 



5. Casts signify renal congestion, always; if persistent they 

 indicate inflammation. 



6. Albuminuria, or the presence of albumin in the urine, is also 

 an evidence of congestion or of disease. It is often temporary, 

 disappearing with the disappearance of the cause, which may be 

 fever, the inhalation of ether, the use of alcohol, etc. 



7. Albumin is often due to conditions outside of the kidney 



