Osmolality and Urinary Specific Gravity

what analytical test assesses urine solute concentration by refractometry?

urine specific gravity

what is the USG for a dog that is dehydrated and can adequately concentrate?

> 1.030

what is the USG for a dog that is dehydrated and cannot adequately concentrate?

< 1.030

what is the USG for a cat that is dehydrated and can adequately concentrate?

>1.040

what is the USG for a cat that is dehydrated and cannot adequately concentrate?

<1.040

what is the usual range of USG for a dog that is normal hydration?

1.015 - 1.045

what is the usual range of USG for a cat that is normal hydration?

1.036-1.060

what is the usual range of USG for large animals that is normal hydration?

1.015-1.030

as osmolality increases……. also increases

urinary specific gravity

what molecules can increase USG values and need to be taken into consideration when running a UA?

proteins and glucose

what tubular segment reabsorbs water under the influence of ADH?

collecting duct

in what part of the loop of henle does the urine become more concentrated?

the descending limb

in what part of the loop of henle is osmolality very low?

the ascending limb

proximal CT

removes volume and solutes, no change in concentration

descending LOH

removes H2O, concentrates tubular fluid

ascending LOH

removes solutes, dilutes tubular fluid

collecting duct

removes H2O, concentrates tubular fluid

to produce concentrated urine..

1. ADH must be present

2. tubules must respond to ADH

3. concentration gradient must be present

what is necessary to produce concentrated urine?

increased medullary tonicity

what portion of the nephron reabsorbs water and electrolytes resulting in osmolality same as plasma?

proximal convoluted tubule

for kidneys to produce a urine with a specific gravity of 1.001 to 1.003 or osmolality of 100, what nephron segment must be functional?

ascending loop of henle

hypersthenuria

very concentrated

cat: >1.060

dog: > 1.050

eusthenuria

normal concentration

isosthenuria

USG 1.007-1.013

urine osmolality = plasma osmolality

hyposthenuria

USG < 1.007

urine osmolality < plasma osmolality

high USG =

low urine volume

low USG =

high urine volume