Glomerular filtration rate (GFR), which is the main biomarker used in clinical practiceto assess kidney function, is usually estimated from the serum concentration ofendogenous markers such as creatinine and/or cystatin C. GFR estimation equations allshare the disadvantage of imperfect accuracy due to non-GFR-related determinants ofcreatinine and cystatin C. When knowing the exact GFR value is necessary for clinicaldecision-making, measurement by clearance of an exogenous tracer is required. Varioustracers are available, some of which are radioactive tracers (99mTc-DTPA and 51Cr-EDTA),while others are iodinated contrast agents (iohexol, iothalamate). GFR measurementprocedures are time-consuming and require significant human resources (4 to 5 hours, oreven 24 hours for plasma clearances at very low GFR values).Urinary clearance methods maybe inaccurate in cases of inadequate voiding. Plasma clearance results may be inaccuratein cases of increased (overestimation) or decreased (underestimation) extracellularvolume, low GFR (unless late sampling is performed), or glomerular hyperfiltration.Measuring tracers requires either warm labs for measuring radioactive markers or labswith HPLC (High Performance Liquid Chromatography) chains for iohexol, which are part ofan external quality assurance program. The complexity and/or length of GFR measurementprocedures, their cost, and laboratory constraints explain why measured GFR is underusedin routine clinical practice. There is a critical need to develop GFR measurement methodsthat are simpler to implement, reliable across the entire GFR spectrum, and widelyavailable. We have demonstrated that it is possible to measure GFR using 4-phase CTurography performed as part of the care of living kidney donor candidates (healthyindividuals with normal GFR). The examination takes 10 minutes, requires no biologicalsampling, and is not subject to potential inaccuracies due to sodium overload or poorbladder emptying.
Objective: To assess whether GFR measurement using 4-phase CT urography is reliable in
patients with GFR below 60 ml/min/1.73 m², as compared with iohexol clearance (reference
method): - Unbiased (mean difference between CT-measured GFR and iohexol clearance not
different from zero). - and accurate: at least 50% and 80% of GFR values measured by CT
urography within 10% and 20% of biological clearance values for iohexol clearance.
Method: Single-center interventional study. After performing a 4-phase CT urography (or
3-phase CT scan, with the addition of a 4th phase for research purposes), performed for
clinical indications as part of the patient's care, and using iohexol as a contrast
agent, patients will undergo a biological measurement of iohexol clearance, based on
serum and urine samples taken over 4 periods of 1 hour, between 3 and 7 hours after the
CT scan. No iohexol will be reinjected to measure GFR. The CT scan images will be
segmented by the investigator to determine the CT-measured GFR.
The inclusion criteria are: - Patients older than 18 years of age - Having given written
consent to participate in the study. - Patient referred to the medical imaging department
of the Henri Mondor University Hospital for a 3-phase or 4-phase abdominal CT scan. -
With an estimated GFR according to CKD-EPIcreat2009 < 60 ml/min/1.73m² - Hospitalized or
outpatient. - Affiliated with French national health insurance.
The exclusion criteria are: - Patients with hip implants, due to artifacts that make
quantification of the contrast agent in the bladder unreliable. - Lack of health
insurance - Patients under legal protection.
Other: Glomerular Filtration Rate measurement with iohexol clearance
After performing a 4-phase CT urography (or 3-phase CT scan, with the addition of a 4th
phase for research purposes), performed for clinical indications as part of the patient's
care, and using iohexol as a contrast agent, patients will undergo a biological
measurement of iohexol clearance, based on serum and urine samples taken over 4 periods
of 1 hour, between 3 and 7 hours after the CT scan. No iohexol will be reinjected to
measure GFR. The CT scan images will be segmented by the investigator to determine the
CT-measured GFR.
Inclusion Criteria:
- Patients older than 18 years of age
- Having given written consent to participate in the study
- Patient referred to the medical imaging department of the Henri Mondor University
Hospital for a 3-phase or 4-phase abdominal CT scan
- With an estimated GFR according to CKD-EPIcreat2009 < 60 ml/min/1.73m²
- Hospitalized or outpatient
- Affiliated with French national health insurance
Exclusion Criteria:
- Patients with hip implants, due to artifacts that make quantification of the
contrast agent in the bladder unreliable
- Lack of health insurance
- Patients under legal protection.
Assistance Publique Hôpitaux de Paris - CHU Henri Mondor - Créteil
Créteil, Île-de-France, France
Investigator: Thomas STEHLE, Dr
Contact: +33145178452
thomas.stehle@aphp.fr
Thomas STEHLE, Dr
+33145178452
thomas.stehle@aphp.fr
Not Provided