Describe the factors that determine glomerular filtration rate (GFR) in the kidney 
(70% of marks). Outline methods by which GFR can be measured (30% of marks).

[Click here to toggle visibility of the answers]

College Answer

Good answers included a description of Starling forces acting at the glomerular basement 
membrane. A description of the local and systemic factors influencing each component was 
expected.
It was expected candidates would discuss autoregulation of GFR & RBF, tubuloglomerular 
feedback, and integrated responses the body uses to keep GFR steady. 
Confusion about the nature of induced effects on afferent or efferent arteriolar dilation and 
constriction limited marks for some candidates. Many failed to mention the effects of mesangial 
surface area, Bowmans space pressure or serum protein content.
Candidates were expected to outline the methods of GFR estimation. Better responses 
described the rationale behind the use and limitations. Creatinine clearance, inulin and nuclear 
medicine techniques all scored marks. Some candidates made no attempt at this section and 
missed the opportunity to score marks. Estimates of CrCl/GFR [eGFR by formulae such as 
Cockcroft Gault, and serum Cr] are not measurement of GFR.