Renal tubular function tests

Electrolyte disorders can be the consequence of acquired or inherited renal
tubular defects. Most often, these abnormalities are explained by
malfunctioning of the channels or transporter proteins that are critically
involved in the transport of the electrolytes. These tubular disorders are
rare, and mostly knowledge about validated clinical diagnostic tools is
lacking. These tubular function tests on the other hand are very helpful in the
understanding of (an) underlying defect(s) and can help directing more specific
and expensive diagnostic tests and direct therapy.
In this study we will therefore determine reference values for tubular function
tests for which we have developed standard operating procedures (SOP*s) for.
The aim of this study is to develop standardized tubular function tests with
reference intervals/values. In the future, these tubular function test can be
used in clinical practice to investigate the underlying tubular defect in a
patient with an unknown tubular disease or to relate phenotype and genotype in
special patient groups.

to develop standardized tubular function tests with reference
intervals/values.

This is an observational study in which several tubular function tests
(furosemide test, hydrochlorothiazide test, DDAVP test and
furosemide-fludrocortisone test) will be performed in a group of volunteers.
These individuals will differ in age and glomerular filtration rate. The tests
will be performed in the Radboud University Hospital by a group of trained
nurses at our well equipped dialysis unit.

Adverse reactions occurring most often (but still infrequently) with furosemide
and hydrochlorothiazide include hyponatremia, hypokalemia, hypovolemia and
hypotension.
Adverse reactions occurring most often (but still infrequently) with
fludrocortison include hypertension, edema, hypokalemia and heart failure.
Adverse reactions occurring most often (but still infrequently) with
desmopressin include headache, nausea and flushing along with mild abdominal
cramps. Desmopressin should be used with caution in patients with fluid and
electrolyte inbalances such as heart failure and concomitant administration of
tricyclic antidepressants/NSAID*s/carbamazepine.
Patients will therefore be observed for signs or symptoms associated with
hyponatremia ( headache, nausea/vomiting, restlessness, fatigue, lethargy,
disorientation, confusion) and heart failure (shortness of breath).
Furthermore, body weight, blood pressure and heart rate will be recorded and a
blood gas will be drawn at the end of the test for fast determination of
potassium and sodium.