Why does GFR have such a strange unit of measurement?

Question

I have learned the unit of glomerular filtration rate (GFR) is commonly reported in mL/min/1.73m².

I cannot figure out the 1.73, is it just a scaling factor to get a number around 100 or does it have medical relevance?

Answer 1

From the National Kidney Foundation:

Kidney function is proportional to kidney size, which is proportional to body surface area (BSA). Adjustment for BSA is necessary when comparing a person’s GFR to normal values, to the GFR criterion for the diagnosis of CKD, and to levels defining the stages of CKD. A BSA of 1.73 m2 was the normal mean value for young adults when indexing was proposed.