• Kt/V overestimates dialysis adequacy in thin, malnourished patients and elderly females due to sarcopenia and a low ‘V’. This may lead to under-dosing of dialysis. Kt corrected for body surface area may be a more accurate measure of dialysis dose in these patients.
• There is a high index of error related to inaccurate post-dialysis BUN measurement.
• Single treatment may not represent other treatments ( missed or shortened)
• spKt/V or eKt/V is not applicable to daily or nocturnal dialysis. It is useful only for conventional 3 times a week intermittent hemodialysis.
• Kt/V is a marker only of urea clearance and not of other toxic/uremic solutes that exist.
• Other uremic toxins such as phosphate, β2 microglobulin, guanidino compounds etc. do not follow the same hemodialysis kinetics as urea and therefore their clearances are not accurately reflected by Kt/Vurea.¹
• A high Kt/V(>1.4) has not been shown to predict better survival in any randomized controlled studies (e.g. HEMO study²).This implies that there are other determinants of poor survival in hemodialysis patients besides urea clearance and that despite a high dialysis urea clearance (Kt/V), patients may retain other toxic solutes that ultimately are equally or more important than urea in influencing prognosis on dialysis.³
• Despite these controversies surrounding KT/Vurea, it remains the most frequently used parameter for determining dialysis adequacy and its routine monitoring may help to identify problems of dialysis delivery such as access recirculation etc.

Sources:

1. Comparing the urea reduction ratio and the urea product as outcome-based measures of hemodialysis dose. AU Li Z, Lew NL, Lazarus JM, Lowrie EG SOAm J Kidney Dis. 2000;35(4):598.
2. Eknoyan G, Beck, GJ Cheung AK, et al. Effect of dialysis dose and membrane flux in maintenance hemodialysis. N Engl J Med 2002; 347:2010.
3. Meyer TW,Sirich TL,Fong KD et al. Kt/Vurea and non urea small solute levels in the hemodialysis study. JASN 2016;27:3469