Abstract
A lactose tolerance test was performed and small intestinal mucosal disaccharidase activity was determined in 12 patients operated upon for peptic ulcer who had lactose malabsorption. Most patients were misjudged, since they were considered to suffer from post-operative complaints (vagotomy diarrhoea, afferent loop syndrome, recurrent ulcer and dumping). Three patients did not develop symptoms of milk intolerance until immediately after an operation for peptic ulcer; in 3 other patients this operation exacerbated the existing symptoms after consumption of milk. Two patients had steatorrhoea, which disappeared or diminished when lactose excluded from the diet.