Use of computed tomography assessed kidney length to predict split renal GFR in living kidney donors

Objectives: Screening of living kidney donors may require scintigraphy to split glomerular filtration rate (GFR). To determine the usefulness of computed tomography (CT) to split GFR, we compared scintigraphy-split GFR to CT-split GFR. We evaluated CT-split GFR as a screening test to detect scintigraphy-split GFR lower than 40 mL/min/1.73 m²/kidney.

Methods: This was a monocentric retrospective study on 346 potential living donors who had GFR measurement, renal scintigraphy, and CT. We predicted GFR for each kidney by splitting GFR using the following formula: Volume-split GFR for a given kidney = measured GFR*[volume of this kidney/(volume of this kidney + volume of the opposite kidney)]. The same formula was used for length-split GFR. We compared length- and volume-split GFR to scintigraphy-split GFR at donation and with a 4-year follow-up.

Results: A better correlation was observed between length-split GFR and scintigraphy-split GFR (r = 0.92) than between volume-split GFR and scintigraphy-split GFR (r = 0.89). A length-split GFR threshold of 45 mL/min/1.73 m²/kidney had a sensitivity of 100 % and a specificity of 75 % to detect scintigraphy-split GFR less than 40 mL/min/1.73 m²/kidney. Both techniques with their respective thresholds detected living donors with similar eGFR evolution during follow-up.

Conclusion: Length-split GFR can be used to detect patients requiring scintigraphy.

Key points: • Excellent correlation between kidney length and scintigraphy predicted GFR • Kidney length screening detects all donors with GFR lower than 40 mL/min/1.73 m ² • Kidney length screening can replace scintigraphy screening.