23.6 Urine and Renal Function Tests

urine appearance

ideally faint yellow and transparent

urine specific gravity

urine density compared to water, should be between 1.001 to 1.028

urine pH

range from 4.5-8.2

urine composition

95% water and 5% solutes

diuresis/polyuria

output of urine in excess of 2 L/day

oliguria

output of urine less that 500 mL/day

anuria

output of urine less than 100 mL/day

diabetes

any metabolic disorder resulting in polyuria

diabetes mellitus and gestational

high concentration of glucose in renal tubule; glucose opposes osmotic gradient of water so more water passes in urine; characterized by glycosuria

diabetes insipidus

ADH hyposecretion causes not enough water to be reabsorbed in collecting duct; more water passes in urine

diuretics

any chemical that increases urine volume; some increase GFR while others reduce tubular reabsorption of water; commonly used to treat hypertension and congestive heart failure

loop diuretics

act on nephron loop and inhibit Na⁺-K⁺-Cl^- symport which impairs the countercurrent multiplier

renal clearance

the volume of blood plasma from which a particular waste is completely removed in one minute; represents net effect of glomerular filtration+amount added by tubular secretion+ amount removed by reabsorption

insulin

what is used to measure GFR