Pancreatic carcinoid: diagnosis

Pancreatic carcinoid with absent or incomplete carcinoid syndrome (about 80% of cases) remains unrecognized or is diagnosed accidentally. At the expressed carcinoid syndrome the diagnosis is proved (in the presence of a pancreatic tumor) by definition of the raised maintenance in blood of a serotonin and the increased excretion with urine of its metabolite 5-GOIUK. Before the study within 3-4 days, all medicines (primarily phenothiazines, reserpine-containing, laxatives, diuretics) should be canceled. From food should be excluded serotonin and tryptophan-containing foods (bananas, walnuts, pineapples, avocados, plums, currants, tomatoes, eggplant, cheddar cheese). The upper limit of normal daily excretion of 5-GOIUK is 10 mg. Isolation of 10-25 mg of 5-GOIUK per day is suspicious for the presence of carcinoid. Values above 25 mg / day are pathognomonic for this pathology. In doubtful cases, a provocative test is performed with reserpine releasing serotonin both from brain cells and from peripheral depots and preventing its binding in tissues and platelets. In healthy individuals, the daily urinary excretion of 5-GOIUK after taking reserpine increases only in the first hours, then normalizes.

In carcinoid tumors, a dramatically increased release of 5-HONUC is observed for many hours.

In addition to carcinoid, increased excretion of 5-GOIUK can be observed in a number of diseases that must be borne in mind in differential diagnosis - sprue, Whipple's disease, intestinal obstruction, malabsorption. In all these cases, if an increase in the daily excretion of 5-GOIUK is determined, then it is small, often transient, not accompanied by other symptoms of carcinoma and an increase in serotonin concentration in the blood.

Portal hypertension often leads to an increase in blood serotonin. But in such patients there are no signs of a general endocrine action of the amine and there are symptoms of liver pathology, in which the metabolism of serotonin is often disrupted.

At the beginning of the disease, there may be some similarity of the clinical picture with pheochromocytoma, due to the proximity of the chemical structure of humoral substances produced by both tumors. In addition, with pheochromocytoma, excretion of 5-GOIUK can be increased due to the displacement of serotonin from the depot by excess amount of catecholamines. In contrast, an excess of serotonin in carcinoid can displace catecholamines from the depot and cause adrenergic effects. This explains the similarity of a number of symptoms in the two tumors under consideration. But with carcinoid, there are no metabolic disorders characteristic of pheochromocytoma, - violations of carbohydrate metabolism, an increase in basal metabolism. If patients with a carcinoid tumor have arterial hypertension, it is short-lived, occurs during high tide, followed by a drop in blood pressure. With pheochromocytoma, an increase in blood pressure can be both paroxysmal and persistent, accompanied by changes in the left ventricle of the heart, rather than its right divisions. Of decisive importance in differential diagnosis is the determination in the blood and urine of humoral substances produced by these tumors and their metabolites.

A carcinoid tumor in a clinical picture may have a similarity to a mastocytoma, the cells of which produce histamine and heparin. Measuring their concentration in the blood helps to avoid a diagnostic error.

[1], [2], [3], [4], [5]