What Is Meckel Syndrome?

Except for the esophagus, carcinoid tumors can occur in any part of the digestive tract, and those in the appendix account for 1/3. They are more common in women and rarely metastasize. 2% are located in the stomach, and the rest are located in the duodenum, colon (mostly in men), gallbladder, and Merkel's diverticulum. They can also occur in the bronchi and ovaries, but they are rare. Occurred in the small intestine, the degree of malignancy is large, and can be transferred to the lungs, bones and other abdominal organs. Bronchial carcinoid with carcinoid syndrome has a poor prognosis. Carcinoids can occur at any age. The onset age of carcinoids in the appendix is mostly 30 to 40 years old, and the carcinoids in other parts are mostly 50 to 60 years old.

Basic Information

nickname: Carcinoid
English name: carcinoidsyndrome
Visiting department: Endocrinology

Common locations: appendix
Common causes: Not clear
Common symptoms: Abdominal pain, intestinal bleeding, flushing of the skin

Causes of carcinoid syndrome

Cancerous cells can produce a variety of biologically active substances, the most important of which are serotonin, bradykinin, histamine, and prostaglandins. Serotonin is derived from tryptophan in food. After carcinoid disease occurs, 60% of tryptophan in food is converted to serotonin in cancerous cells, so serotonin in the blood of carcinoid patients has increased significantly.

Bradykinin is another major biologically active substance that causes clinical manifestations. In carcinoid tissues, there is a large amount of kallikrein, which is a proteolytic enzyme that acts on kininogen to generate lysine bradykinin (pancreatic kallikrein). Under the action of amine peptidase, lysine Bradykinin is converted into bradykinin. Bradykinin causes skin flushing, skin temperature is not high, and it is cold. Serotonin caused by serotonin is hot and the skin is warm. If there is liver metastasis, it is because serotonin is produced too much, on the one hand, it can directly enter the hepatic vein and enter the systemic circulation. In addition, the liver has reduced clearance due to extensive carcinoid invasion. Therefore, carcinoid syndrome can occur after liver metastases.

Clinical manifestations of carcinoid syndrome

The appendix is a carcinoid site, and it can be found by accident when young people undergo appendix surgery. Carcinoids that occur in the small intestine have local manifestations such as abdominal pain and intestinal bleeding. The cause of pain can be caused by intestinal obstruction and intussusception. Carcinoid syndrome is more common after liver metastasis of intestinal carcinoid. The main clinical manifestations of skin flushing. The typical appearance is a sudden appearance of skin flushing, which only lasts for 10 to 15 minutes, and occurs once every few weeks to several months. After that, the attacks become more frequent and can occur several times a day; the duration is also getting longer and longer, up to Hours. Flushing is divided into three stages:

1. The skin of the cheeks and nose is brick red at the beginning, and then spreads to the neck, chest and limbs. The binding membrane can also be hyperemic. At the same time, eyelid and lips edema, and the skin became hot.

2. The skin becomes purplish and the skin becomes cold. Output decreases, heart rate increases, and blood pressure decreases slightly.

3. Hypotension or shock may occur due to vasodilation, which is called a carcinoid crisis. Skin flushing can also be persistent, with blood stasis caused by local capillary dilatation. The nasal and buccal skin shows typical vasodilation. If the carcinoid is removed, this change can disappear. Because tryptophan in food is converted to serotonin by carcinoids, pellagra due to niacin deficiency occurs.

Carcinoid syndrome test

1. 24-hour urine 5-hydroxyindole acetic acid is greater than 30 mg. In gastric carcinoid cells, the lack of dehydrogenase results in a low serotonin concentration in the blood and an increased serotonin concentration. 24-hour urinary 5-hydroxyindole acetic acid excretion fluctuates greatly and is affected by food. For example, after eating potatoes, bananas, and pineapples, the 5-hydroxyindole acetic acid excretion in urine increases. Therefore, repeated urine tests are required for a more reliable diagnosis.

2. In patients with a high degree of suspicion of carcinoid tumors, when the 5-hydroxyindole acetic acid excretion does not increase, it can be used as a challenge test. The test method is to drip intravenously with 5% glucose and 500ml, and measure blood pressure and pulse every half minute, but after the blood pressure and pulse are stable, intravenous injection of 1g epinephrine. There was a response. However, the maximum dose cannot exceed 15 g each time, and this test is not performed when 15 g still does not respond. Because provocation tests can cause severe hypotension and bronchospasm, this test should be done with extreme caution.

3. Carcinoids of the gastrointestinal tract can be examined by X-rays. B-mode ultrasound and CT have diagnostic value in patients with liver metastases. Carcinoids of the bronchus can be found in sputum for bronchoscopy, chest tomography and other tests. When carcinoid tumors occur in the pelvis, tumors can be found by gynecological examination, B-mode ultrasound, and CT.

Carcinoid syndrome diagnosis

It can be diagnosed based on onset of skin flushing, diarrhea, and increased 5-oxindoleacetic acid in urine.

Differential diagnosis of carcinoid syndrome

Need to identify the following diseases:

1. Menopausal skin flushing

It is a kind of skin flushing that lasts for a long time, but it is not serious, and it has skin fever. No skin cyanosis, no abdominal pain, diarrhea, wheezing and other symptoms.

2. Neuroedema

Localized edema due to soft tissue that suddenly occurs after various stimuli. It is an allergic angioedema, which often occurs in the face, lips, eyelids, and also in the mouth and throat; severe edema in the throat can cause suffocation.

3. Systemic mastocytosis

Because of its increased production of histamine, causing skin flushing, erythema may appear on the skin mucosa, and there may also be urticaria-like changes. Longer duration, diarrhea can occur. When the skin is flushed, histamine in the blood increases.

4. Autonomic dysfunction

Flushing of the skin can occur during stress. However, blood serotonin and urine 5-hydroxyindole acetic acid do not increase.

5. Diarrhea without skin flushing

It should be distinguished from diarrhea caused by other reasons, such as gastrinoma can cause ulcers and diarrhea.

6. Carcinoid patients need to be distinguished from bronchial asthma when wheezing occurs.

7. Tricuspid valve lesions of the heart caused by carcinoids need to be distinguished from rheumatism, right ventricular papillary muscle dysfunction, and infective endocarditis.

Carcinoid Syndrome Treatment

Surgical treatment

For carcinoids without metastasis. Carcinoids that occur in the appendix, bronchi, or ovaries can be treated surgically. If the intestinal tract has caused intestinal obstruction and intussusception, even if it has metastasized, surgery is needed. For those with severe symptoms, if the effect of medical treatment is not good, if the tumor is removed, although it cannot be cured, the symptoms can be relieved for a long time.

2. Medical treatment

There are three main aspects:

(1) General treatment Give patients adequate nutrition and vitamins, especially niacin or nicotinamide. If the patient has diarrhea, the water and electrolyte balance disorders need to be corrected. In addition, you should avoid mental irritation, do not drink alcohol, and do not eat foods that contain more tryptophan, such as milk, orange fruits, pineapples, potatoes, etc. Prohibition of adrenaline and morphine.

(2) Symptomatic treatment Use serotonin antagonists such as melamine or cyproheptadine when diarrhea is present, or atropine. -methyldopa can interfere with the effect of catecholamines on the release of enzymes from carcinoid cells, and also inhibit the synthesis of serotonin, which is effective for diarrhea and skin flushing. If there is steatosis, membrane protease can be used. Alpha-blockers for the treatment of skin flushing can prevent the release of serotonin and may also release the release of kallikrein. Blockers such as diphenhydramine and cimetidine are taken orally. The above two drugs can also be used in combination for patients with skin flushing. When wheezing occurs, epinephrine is disabled and can be treated with isoproterenol spray and aminophylline. In the event of hypotension or shock, norepinephrine is contraindicated, but it can be treated with methoxamine (Mexicosin) and angiotensin II.

(3) Treatment of tumors The effects of radiotherapy and drug treatment are not satisfactory.