Why does physical examination always require fasting?


My husband is a medical [small white], that is, he has no medical foundation and knows little about medical common sense. A few days ago, before his physical examination, he suddenly asked me, why does the physical examination need an empty stomach? How long does it take to eat on an empty stomach? Can I drink water? I believe this is also the doubt of many friends. Dr. Clove specially invited doctors who can draw, write and speak to give advice to everyone, so that everyone can quickly remember which examinations should be on an empty stomach and know why.

How long does it take to have an empty stomach?

Fasting generally refers to 8 ~ 14 hours don’t eat. That is to say, if you need to check up at 8 o’clock in the morning on a certain day, the night before blood is drawn, it is best to eat at about 6 o’clock. Don’t eat food taken late at night after that. Of course, breakfast in the morning the next day can also be carried out after the physical examination. Also don’t fasting for too long, so as not to cause inaccurate blood sugar and other tests. Can you drink? Let’s talk about clear water first. Different tests, The requirements for drinking water are different. Drink in large quantities: Before many ultrasound examinations, All need water, Such as urinary ultrasound, gynecological ultrasound, These tests also require holding urine, The aim is to inflate the bladder, The organ to be examined should be pushed to the abdominal wall as far as possible to facilitate examination. Must not drink: Painless (anesthesia) gastrointestinal endoscopy is absolutely not allowed to drink water, because after anesthesia, it is easy to cause choking and suffocation. Other examinations can drink a little water, because everyone will lose water at a different speed, so it is better not to feel thirsty. Other beverages should not be drunk as much as possible. For example, sugar-containing fruit juice, milk and tea will directly change the test indicators in blood. And like coffee, Even black coffee, It can also be infected with changes in hormone levels in the blood, Affect blood biochemical indexes. Patients with chronic diseases, There is no need to be afraid to take even drugs because of fear of drinking water. As long as the water is taken, it will not affect the above examination. Because clear water stays in the stomach for a short time. In order to maintain your various conditions, you should not stop taking the medicine rashly. If you are not sure whether you should drink water or not, you should follow the doctor’s instructions or physical examination instructions before the physical examination. Which examinations require fasting? 1. Need to directly observe the examination barium meal of digestive tract: Barium meal is an X-ray examination to observe the digestive tract. Barium sulfate contrast agent should be taken to observe the wall of digestive tract. The barium meal was coated on the surface of digestive tract under X-ray, Bright white, If there is food shelter, It will be displayed as a black shadow protruding from the surface of the digestive tract. Gastrointestinal endoscope: When gastroscopy, colonoscopy and other gastrointestinal endoscopy, A slender mirror is put into the digestive tract for observation. Therefore, the undigested food is the barricade on its way forward. It will also block the doctor’s view. 2. Examination of dorsal organs of digestive tract pancreatic ultrasound examination: The pancreas is usually examined by ultrasound. The pancreas is located behind the intestinal tract. The middle part of the abdominal cavity, Neither can we see it from behind, Nor is it close to the belly. The ultrasound examination needs to pass through the belly, intestinal tract, To reach the pancreas. After eating, There will be a lot of air swallowed with the food, Food and air lie in ambush like mountain thieves on the way of ultrasonic waves. Loses a lot of sound waves. In this way, Ultrasound cannot pass through the intestinal tract to reach the dorsal side, That is, it will interfere with the observation of pancreas. 3. Examination of organs that change after eating Gallbladder: Bile is actually secreted by the liver, And stored by the gallbladder. Bile plays an important role in the process of digesting fat. When eating, the gallbladder contracts and bile is squeezed into the intestinal tract. Therefore, after eating, the gallbladder will contract, which is difficult to observe. Therefore, fasting is required before relevant examinations. 4. Some biochemical examinations on an empty stomach can prevent the ingredients in food from interfering with the results of relevant blood test indicators. Such indicators as blood sugar and blood lipid are bound to rise after eating. And some indicators such as insulin, Will cause fluctuations due to eating, Interference with the examination results. 5. The examination mouth, which needs to stimulate the digestive tract, acts as the front desk hall for both respiratory tract and digestive tract. Divided into two lines at the throat, Forming the trachea and esophagus next to each other. If you eat, Vomitus travels from the stomach to the mouth, You have a chance to get into the trachea, Causing life-threatening suffocation. Stimulates the throat and is prone to nausea. Such as laryngoscopy, gastroscopy, bronchoscopy, transesophageal echocardiography and other examinations, Must be on an empty stomach. In addition, Some imaging tests, Such as enhanced CT, enhanced magnetic resonance, Need to inject contrast agent, Contrast agents may cause allergy and then vomiting, Therefore, it is recommended to be on the safe side and have an empty stomach. In short, friends who do not have a chronic disease foundation, Should do normal diet, normal work and rest, Don’t eat foods that are too greasy, stimulating and difficult to digest. The amount is also controlled as usual. Do not eat food taken late at night. On the day of physical examination, do not eat breakfast, drink a small amount of water before drawing blood, and bring a bottle at the same time, so that some examinations need a large amount of water to hold urine can be drunk immediately. General physical examination center will have breakfast, after drawing blood and B ultrasound examination, can eat breakfast as soon as possible to avoid hypoglycemia for too long fasting time.