Much more about kidney disorders can be learned by determining kidney function. This research
proposes to study the kidneys function by several parameters known as glomerular filtration
rate (GFR), Renal Plasma Flow (RPF), and Glomerular Capillary Wall Permselectivity.
The study will select patients suffering from different types of kidney diseases. These
patients will be selected based on the presence of significant amounts of protein in their
Standard blood and urine tests are often unable to provide completely accurate information
about the kidney. In order for researchers to have a more accurate idea of kidney function,
they will use alternative tests. Test materials (para aminohippurate and inulin) will be
injected into patients veins that provides information based on their filtration through the
The study of various kidney disorders will be facilitated by determinations of true
glomerular filtration rate and/or effective renal plasma flow employing inulin or
non-radioactive iothalamate and/or para aminohippurate (PAH), respectively.
Selected patients with proteinuria will be asked to participate in studies of glomerular
capillary wall permselectivity calculated from the fractional clearances of the endogenous
proteins, albumin and IgG and from the fractional clearances of polydisperse neutral dextran
with effective molecular radii ranging from 20-60 angstroms. To achieve this, low molecular
weight dextran will be administered by slow IV injection immediately following the inulin or
iothalamate and/or PAH priming doses.
Glomerular filtration rate, effective renal plasma flow and/or glomerular permselectivity can
be measured simultaneously during a standard hydrated urinary clearance study. Timed urine
and blood collections will be obtained, typically requiring a total of 60 to 90 minutes. The
total test time, including pre-test hydration, is 4 to 5 hours.
Alternatively, glomerular filtration rate can be measured by one of two plasma clearance
methods that do not require urine collections. For one method, a steady-state plasma
concentration of iothalamate will be achieved in ambulatory patients by a 24-hour
subcutaneous infusion of iothalamate using an insulin pump. For the second method, the
decline in plasma concentration of iothalamate will be measured after an intravenous dose of
- INCLUSION CRITERIA:
Ability to provide informed assent to all aspects of the study after full information is
An indication to measure kidney function as accurately as possible in the context of an
approved clinical protocol within the intramural programs of the National Institutes of
- For minor subjects, a clinical indication will be required.
- For adult subjects, a clinical and/or research indication will be required.
Pregnant females or nursing mothers will be excluded from all aspects of this study (at
least until the infant is stable on a regimen of formula feeding).
Patients will not receive a test material if there is a history of allergy to that
Patients with a history of bronchial asthma or allergy to iodine-containing contrast
material will not receive iothalamate.