Accuracy of urine collection methods compared to measured GFR in adults with liver disease

Assessment of kidney function is necessary to stage kidney disease, dose medications, and to make decisions about organ allocation. Estimating equations that incorporate serum creatinine (SCr) are not consistently reliable. However, assessment of creatinine clearance (CrCl) using 24-hour urine collection methods is also prone to errors. The purpose of this study was to evaluate the accuracy of measured CrCl determined using shorter urine collection times compared to glomerular filtration rate measured by (125)I-iothalamate clearance ((125)I-CL) in patients with liver disease.

Adult patients with chronic liver disease were enrolled. All patients received (125)I-iothalamate and had a catheter placed for urine collection. Blood samples were collected at designated times over 8 hours to determine (125)I-CL. CrCl was determined from a 1-hour and a 4-hour urine collection and compared to (125)I-CL.

Characteristics of the eight patients enrolled included age 52 ± 6 years; SCr 1.2 ± 0.4 mg/dL; and Model for End-stage Liver Disease score of 13 ± 3. All patients were Child-Pugh Class B. Mean estimates of kidney function (mean ± SD, mL/min/1.73 m(2)) by method were 74 ± 38 for (125)I-CL, 79 ± 28 for the 1-hour urine collection, and 72 ± 26 for the 4-hour urine collection. Measured CrCl did not differ significantly from (125)I-CL (P = .641 for 1-hour CrCl versus (125)I-CL, and P = 1.0 for the 4-hour CrCl versus (125)I-CL).

When urine collection methods are necessary for an individualized assessment of kidney function, shorter collection times can provide accurate results and would be more feasible for the patient.