Medical students struggle to reconcile contradictory osmolarity concepts between plasma and interstitial fluid

Medical and physiology students encounter conflicting information in textbooks and lectures: they're taught plasma and interstitial fluid have equal osmolarity, yet the Donnan equilibrium principle suggests plasma should have higher total solute concentration due to non-diffusible proteins. This conceptual gap creates confusion during exams, clinical reasoning, and understanding fluid dynamics, and existing educational resources fail to adequately explain this apparent paradox.