Test Catalog

Test ID: HEXU    
Iohexol, Timed Collection, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

Determining glomerular filtration rate in urine specimens

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The assessment of glomerular filtration rate (GFR) is an important parameter of renal function utilized by clinicians in the care of patients with varying renal diseases, and for clinical research when precise assessment of renal function is necessary. The GFR is the sum of all the filtration rates of the individual nephrons within the kidney and, as such, reflects the number of functioning nephrons.


Urine concentrations of iohexol can be used for measurement of GFR following a subcutaneous injection of iohexol (plasma disappearance), or during a continuous infusion of iohexol when used in conjunction with plasma iohexol determinations (HEXP / Iohexol, Plasma). The results can be used to determine the clearance of iohexol, which is a measure of GFR.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Not applicable

Interpretation Provides information to assist in interpretation of the test results

Low glomerular filtration rate (GFR) values indicate abnormal renal function, which may be either reversible/transient or irreversible/permanent. GFR tends to decline with age.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

A theoretical complication to injection of iodinated contrast media (one that has not been observed clinically to date) is the transient suppression of thyroid function in premature and newborn infants. Therefore, a sensitive thyrotropin test is suggested approximately 2 to 3 weeks after an iohexol clearance in that age group.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Brown SC, O'Reilly PH: Iohexol clearance for the determination of glomerular filtration rate in clinical practice: evidence for a new gold standard. J Urol 1991;146:675-679

2. Gaspari F, Perico N, Ruggenenti P, et al: Plasma clearance of nonradioactive iohexol as a measure of glomerular filtration rate. J Am Soc Nephrol 1995;6:257-263

3. Schwartz GJ, Abraham AG, Furth SL, et al: Optimizing iohexol plasma disappearance curves to measure the glomerular filtration rate in children with chronic kidney disease. Kidney Int 2010;77:65-71