Abstract

The sieving characteristics of the normal and inflamed rectal mucosa are studied in three healthy volunteers and five patients with ulcerative colitis. Following rectal instillation of ¹²⁵I-polyvinylpyrrolidone (PVP), the molecular size distribution of labelled PVP in urine samples was determined by Sephadex gel filtration. The results of the study suggest that the increased permeability of the inflamed rectal mucosa to electrolytes and small hydrophilic compounds is due primarily to ultrastructural changes since only the low molecular fractions of PVP were found in the urine.