diet, physical activity, and health

factors that vary normal ranges as urine volume and solute composition

osmolality (osmoses per kilogram) (Os/kg)

affected by solute number, not size or weight; determined in distal and collecting tubules when ADH is present

275-300 mOsm/kg

normal range of serum osmolality

275-900 mOsm/kg

normal range of urine osmolality

1.0-3.0

normal urine to serum ratio

specific gravity

comparison of density of urine to that of water; depends on number of particles and mass

1.002-1.035

normal urine specific gravity range

>1.010

specific gravity of concentrated urine

<1.010

specific gravity of diluted urine

>1.050

specific gravity not physiologically possible occurring due to contrast media

polyuria

issues leading to greater than 3L of urine per day;

water diuresis <200 mOsm/kg

ADH secretion inadequate or ineffective receptors leading to polyuria

solute diuresis >300 mOsm/kg

no common feature, but involve glucose, urea, or sodium leading to polyuria

oliguria

less than 400 mL/day of urine due to urinary obstruction, tubular dysfunction, and fluid loss

anuria

absence or cessation of urine excretion due to progressive renal disease or renal failure

osmolality

more accurate reflection of kidney's concentrating ability, since only solute number affects it

urea, chloride, and sodium

three most prevalent solutes

neurogenic diabetes insipidus

diabetes insipidus caused by defective ADH production

nephrogenic diabetes insipidus

diabetes insipidus caused by lack of renal response to ADH

renal clearance tests to assess glomerular filtration rate

volume of plasma in mL that is completely cleared of a substance per unit of time

C(mL/min)= U (mg/dL) x V (Ml/min) /P (mg/dL

GFR calculation C = calculated renal clearance P = plasma concentration U = urine concentration V = volume of urine

creatinine clearance

calculated measurement of the rate at which creatinine is removed from the plasma by the kidneys; used to measure renal function (GFR)

creatinine

an endogenous substance not affected by diet; filtered by glomerulus but not secreted or absorbed by renal tubules

24 hour urine collection

specimen for creatinine clearance

clearance = U x V / P x 1440

creatinine clearance

90-130 mL/min

basic creatinine clearance reference range

albuminuria

appears early in diabetic nephropathy; early detection of low levels signals need for additional testing and aggressive intervention; linked to hyperglycemia