By chance? 5 cm? If we are talking about a child - the answers below. If about an adult - go to a surgeon, and then to a psychiatrist or narcologist)) Well, what should happen to a person to "accidentally" do this?
My friend swallowed a 122 mm nail on a bet before my eyes. He walked with this nail for about a year, until during the dance, (he danced breakdance), the nail hit his stomach wall and pierced it, and the ribs, right under the heart. I could not move, my right hand for some reason rose up. They showed an X-ray. The nail was removed successfully and accurately. Horror. But everything ended well. He still lives)
There were even scientific experiments to more accurately find out about the work of the autonomic nervous system of one of the intestinal plexuses. They gave nails to both animals and humans. They did an X-ray and watched how the carnation slides well through the student's gastrointestinal tract. It turns out that it slips well. intestinal loops, a sharp carnation will perfectly pass through the intestines as well as a sharp piece of glass (and there is no need to stir up panic if at some drinking party you are so sucked into a bottle of alcohol that a piece of the neck is swallowed. Yes, this also happens). swallow "can only be inlet and outlet.
I was about three years old when I swallowed just such a nail. I told my older sister about it. They didn't believe me much, but they took me to the hospital just in case. X-rays showed the presence of a nail, which quickly "fell" into the intestines, head first. They took permission from the parents to operate in the place where the piece of iron would stop. According to the stories of mom, she and dad could not breathe for a day. The next day, the nail independently and safely left the patient's body)
As mentioned earlier, if a nail enters the stomach without injuring anything along the way, then, most likely, everything will end well.
If it damages the mucous membrane of the larynx and / or esophagus, or, what is worse, it gets stuck in the esophagus, the development of events can be much more sad. Since the laryngopharynx and esophagus are not sterile, and microorganisms are very fond of colonizing wound surfaces, the risk of infection is very high. Further, the infection spreads to the fatty tissue of the neck (phlegmon of the neck develops, in the English-language literature the designation "deep space neck infections" or "infection of the deep fascial spaces of the neck"), which in itself can lead to death as a result of airway compression and asphyxiation. in the absence of treatment (opening phlegmon, prescribing antibiotics, ensuring airway patency) or if it is ineffective, the purulent process can spread further, causing mediastinitis (this is the name of inflammation of the chest spaces.) Even with medical care, the lethality of mediastinitis is, according to various sources, 30 -50%.
A relatively recent similar case - a patient, while intoxicated, swallowed a tea bag. Deciding that the bag was stuck somewhere in his throat, he began to try to reach it with a curved wire. to myself all the mucous, threw the venture, continued to drink, did not go to the doctors. For some time, he noted an increase in temperature, the appearance of swelling in the neck, difficulty breathing. I went to the doctors, but it was too late. Neck phlegmon turned into mediastinitis, despite opening the neck phlegmon, performing tracheostomy and mediastnotomy, intravenous antibiotic therapy, the patient died.
In general, it is better not to swallow nails. And it is better to eat fish carefully.
... as a child, I swallowed a pin-needle (with a ball at one end, about 3 cm long) - nothing, I lay in the Morozov hospital for a couple of days, the operation was not required, it came out naturally ...) the doctors only gave that something special from medicines, so that this pin is slightly enveloped by a certain protective film inside the body.
ps how he managed to swallow it - a special question - he loved to read and play with the ball with his tongue, apparently ..)) I was about 6 years old.
Depends on where he gets to. If the nail reaches the belly, then everything is fine, most likely there will be no problems, it will come out on its own, without excesses. But if it gets stuck in the pharynx or the respiratory tract or esophagus, then nothing will be fine, and you'd better go to an endoscopy or a surgeon and ask to pick up the nail from there.