Isosthenuria refers to the excretion of urine whose
specific gravity (concentration) is neither greater (more concentrated) nor less (more diluted) than that of protein-free
plasma
Plasma or plasm may refer to:
Science
* Plasma (physics), one of the four fundamental states of matter
* Plasma (mineral), a green translucent silica mineral
* Quark–gluon plasma, a state of matter in quantum chromodynamics
Biology
* Blood pla ...
, typically 1.008-1.012. Isosthenuria reflects damage to the kidney's tubules or the
renal medulla.
A closely related term is hyposthenuria, where the urine has a relatively low specific gravity "due to inability of the kidney to concentrate the urine normally". This specific gravity is not necessarily equal to that of plasma. Therefore, unlike isosthenuria, this condition is not associated with
kidney failure as the kidney tubules have altered the
glomerular filtrate
In renal physiology, ultrafiltration occurs at the barrier between the blood and the filtrate in the glomerular capsule (Bowman's capsule) in the kidneys. As in nonbiological examples of ultrafiltration, pressure (in this case blood pressure) ...
.
Clinical significance
Isosthenuria may be seen in disease states as
chronic kidney disease
Chronic kidney disease (CKD) is a type of kidney disease in which a gradual loss of kidney function occurs over a period of months to years. Initially generally no symptoms are seen, but later symptoms may include leg swelling, feeling tired, vo ...
and
acute kidney injury in which the
kidneys lack the ability to concentrate or dilute the
urine and so the initial filtrate of the blood remains unchanged despite the need to conserve or excrete water based on the body's hydration status.
Sickle-cell trait, the heterozygous form of
sickle-cell disease, presents with a normal hematological picture but is associated with hyposthenuria.
[Gupta AK, Kirchner KA, Nicholson R, ''et al.'' Effects of alpha-thalassemia and sickle polymerization tendency on the urine-concentrating defect of individuals with sickle cell trait and increased frequency of urinary tract infections J. Clin. Invest. Vol 88, Issue 6, pgs 1963-8. Dec 1991. PMC = 295777. DOI = 10.1172/JCI115521]
See also
*
Hypersthenuria
References
Abnormal clinical and laboratory findings for urine
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