Histamine metabolism in severe obesity before and after jejuno-ileostomy

Histamine metabolism was studied in three patients during histamine-reduced diet before and at intervals after jejuno-ileostomy by analyses of the urinary excretion of non-labelled and 14C-labelled histamine and its metabolites. Labelled histamine was administered intravenously and orally. The preoperative excretion of free histamine and its endogenously formed metabolites was essentially the same as in controls. After intestinal bypass the inactivation of [14C]histamine by both routes of administration was not impaired. Pronounced increases in the excretion of non-labelled conjugated histamine (acetylhistamine) and methylimidazoleacetic acid were found at different intervals postoperatively. This was probably due to histamine synthesis by intestinal bacteria since the diet only contained minute quantities of histamine. It is concluded that the increased urinary excretion of conjugated histamine after intestinal bypass indicated an abnormal bacterial activity in the intestine.