Urinary excretion and blood concentrations of trace elements and electrolytes during total parenteral nutrition in Crohn's disease.

Urinary excretion of trace elements (Cr, Co, Cu, Fe, Mn, Se, Zn, Sb, Cs, Rb), electrolytes (Na, K, Ca, Mg, phosphate), and nitrogen were determined during days 1-5 and 54-79 of total parenteral nutrition (TPN, nil per os) given to six patients with Crohn's disease. Whole-blood concentrations of Cr, Fe, Zn, Cs, and Rb and serum concentrations of electrolytes were determined before the TPN and on days 54-79 of TPN. The 24-hr urinary excretion of zinc was lower on days 54-79 than on days 1-5, but the rates of excretion of the other essential trace elements during TPN displayed no significant change. The urinary excretion of Cu, Fe, and Mn was numerically lower than the intravenous administration of these elements during days 1-5 and 54-79 of TPN, whereas the urinary excretion of zinc was lower than the supply only during days 54-79. The whole-blood concentration of zinc was low but constant during TPN, whereas the initially low levels of Cr and Fe were normalized on days 54-79. The results suggest that the supply of the essential trace elements Cr, Co, Cu, Fe, Mn, and Zn was largely adequate during two to three months of TPN and that the human body may adapt to a somewhat low supply of zinc, 20-30 mumol/24 hr.