The study includes every patient undergoing ERCP above the age of 18 years. Patients are excluded if they have active acute pancreatitis, previous sphincterotomy (cut in the sphincter at the end of the biliary and pancreatic ducts in the duodenum) or chronic pancreatitis with calcifications. Also, patients may not take sildenafil (Viagra) as GN should not be taken together with sildenafil. Patients allergic to glyceryl nitrate or glue should not be included. Patients with constrictive pericarditis (inflammation and fibrosis in the sack around the heart); pericardial tamponade (blood or liquor in the sack around the heart); low blood pressure; aortic stenosis (stenosis of the aortic valve); hypertrophic obstructive cardiomyopathy (a special disease with thickness of the heart); mitral stenosis (stenosis of the mitral valve); anemia (low hemoglobin); and untreated hypothyroidism (thyroid disease) are excluded because these are other diseases to which glyceryl nitrate should not be used. Pregnant women are excluded. Patients can only be included once.