What are the causes of air under the diaphragm?

Question

Please tell me the differential diagnosis. Thanks!

Answer 1

Years ago, when I was a resident, a very clever older surgeon once joked, "I don't know why they call it 'free air'. It always ends up being very expensive!"

Note that the "free air" can only get to the point of being "under the diaphragm" on an upright X-ray. If you do a CT scan on a patient who is lying down, the air will go to the highest point which is under the bellybutton. The detection of free air is best done with an upright chest X-ray series including a lateral view.

Free intraperitoneal gas is almost always an immediate indication for emergency surgery. The cause is perforation of a hollow viscus, almost all of the time. The gas itself isn't dangerous, but the fact that enteric content is leaking out along with it is deadly. Free air is the harbinger of intra-abdominal catastrophe.

Perforation of the stomach or duodenum can occur as a result of peptic ulceration. Gastric cancers can also erode through the wall of the stomach and perforate. The inability to tell the difference between benign and malignant gastric perforation is why all of these lesions should be excised and sent for pathologic evaluation rather than just sewn up.

Perforation of the small intestine is much less common, and is typically casued by either an inflammatory bowel disease such as Crohn's, or by cancers - although primary cancer arising in the small bowel is very rare. Adjacent cancers in the colon or in the small bowel mesentery (cancers such as lymphoma or "GIST", gastrointestinal stromal tumor) are more common reasons for small bowel perforation, but are still unlikely to cause perforated small bowel rather than colon, except in AIDS patients where it becomes more common. I've seen a perforated "Meckel's diverticulum" which a rare lesion of the small bowel, and I've seen perforated appendicits lead to free air, but this is also super-duper rare.

Colonic perforation is relatively common. The most common lesion of the colon to perforate is diverticulitis, and this will most likely occur in the sigmoid colon or at least on the left side. There are occassional cases of right colon diverticular inflammation and infection, however, and the right colon is thinner than the left. If this perforates, it leads to disasterous leakage of liquid stool. Colon cancers sometimes perforate too, and because of that, any questionable perforated lesion of the colon at the time of emergency surgery needs to be treated like a cancer, and be fully removed with appropriate margins of normal tissue along with it.

I've seen the rectum and vagina both become the targets of perforation as a result of trauma from "aggressive" activities there, and lead to free air in the peritoneal cavity... enough said.

Perforation of the esophagus can happen but rarely leads to abdominal air, because it will more likely leak into the chest. Perforation of the bile system can happen, but even though this is connected to the gastrointestinal tract, gas does not typically climb out of the leak - just fluid (bile).

Another source of free air is abdominal trauma such as stabs, gunshot wounds, or even blunt force injury from things like car accidents. In these cases, anything and everything must be suspected of leaking.

I have had two patients who manifested intra abdominal gas as a result of a process in the chest. One had a centrally located lung cancer that had not yet been diagnosed, and this led to airway blockage, pneumonia and respiratory failure. I was consulted by the medical team when the abdomen became distended and a CT scan showed air in the abdominal cavity. I looked at the scan, and I saw extensive air in the retroperitoneal space which had been tracking down from the primary disease locus at the hilum of the right lung. Another patient popped a "bleb" in the lung, leading to extensive gas climbing out of the chest, under the skin and into the neck. This was also associated with gas inside the tissues of the abdomen. I did not operate on either patient because there were no abdominal processes occurring.

On another occassion, a debilitated and bed bound psychiatric patient who had not been "acting herself" lately was evaluated and found to have enormous amounts of intra-abdominal air in the walls of the intestine. This is usually the marker of an extremely aggressive process that has killed a tremendous amount of intestine and will soon be the cause of the patient's death. In this case, however, the patient was doing fine. I had no explanation other than the fact that this patient also suffered from some chronic "rectal prolapse" which is where the rectum can invert and protrude from the anus. I theorized that the lining of the rectum had been injured from chronically being inside out, through the anus, and a small opening had let intestinal gas (farts) dissect back up along the walls of the intestine for a great distance. I let that patient get better by herself for several weeks before I performed a surgical correction aimed at her rectal prolapse, and she did well.

These last two cases are examples of air in the abdomen that doesn't represent FREE air (because it was trapped in the retroperitoneal space or in the walls of the intestine) but it LOOKS a lot like free air on an imaging study. It is for reasons like this that not every patient who has "free air" needs emergency surgery.

Also, there will sometimes be tiny bubbles of gas that escape the colon when there is diverticulitis, but it will be captured and held in place by the surrounding tissue layers. I don't necessarily take these people for emergency surgery if they're otherwise doing ok. I will probably recommend that after the acute episode is over, they consider elective colon surgery to prevent a subsequent and potentially more morbid episode, but its an open conversation with pluses and minuses in many cases.

In the final analysis, you asked about FREE AIR and that it be UNDER THE DIAPHRAGM (which indicates that there's a reasonable amount of it... not just a couple of bubbles), therefore my differential diagnosis comes as a list from proximal to distal:

1) Boerhaave's syndrome (esophageal tear) - rare cause
2) Perforated peptic ulcer (stomach or duodenum) - common
3) Perforated gastric cancer - less common
4) Spontaneous perforation of the small intestine - rare
4) Perforated diverticulitis of the colon - common
5) Perforated colon cancer - common
6) Abdominal trauma

In almost every case of free air, the treatment is to prepare the patient for surgery as quickly as possible (involving replacing lost fluids and balancing electrolytes) and then performing an abdominal exploration with repair of whatever derrangement is found.

In cases of critical illness, the operation may be done in stages because the patient may not be stable enough to tolerate an extensive operation. This is called "damage control surgery". The first stage is to obtain initial source control, stopping the leakage by removing the offending tissue. Subsequent to this, the patient will be resuscitated in the intensive care unit, kept completely sedated and on mechanical ventilation with the abdomen packed, and the incision left open. After the patient is more stabilized, a secondary operation to repair the damage can be performed. Following this, there may be several operations that involve nothing more than washing out the abdomen, to reduce the amount of infection and contamination present, until it is safe to close the incision.

Perforation of hollow organs leading to "free air" and the presence of partially digested food and digestive juice in the abdominal cavity is a disaster. Many people do not survive this catastrophe.

I hope that helps.

Answer 2

Free Air Under Diaphragm

Answer 3

Bellydoc's answer is wonderful - go there for the full detail. Though I'm sure all the above answerers know it, no one so far has mentioned the commonest cause of free air under the diaphragm - namely, post laparotomy (or laparoscopy). Since the abdomen here is opened (by the surgeons), air enters, landing up under the diaphragm on an upright X-ray film. If you don't consider this, you can get quite a fright looking at a patient's X-ray after surgery!

In a similar vein, trauma (e.g. gunshot wounds to the abdomen) can be a common cause, depending on the local crime statistics!

Amongst the non-traumatic causes, the top three to remember are:
#1. Perforated duodenal ulcer (70% of above category)
#2. Perforated gastric ulcer (10%)
#3. Perforated colonic diverticulum (5%)

Hope that helps!

Answer 4

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Excellent question - one of the many "secrets" professionals are taught. Imagine your lungs are in two parts: top and bottom. You need to breathe in the bottom part, before the top part. Sounds obvious, but most people naturally just use the top. This is shallow and easy, therefore more common. Filling the bottom of your lungs is harder and takes a bit longer. The lungs are small at the top and much larger at the bottom (up to four times as large!). As your lungs fill up at the bottom the side of your chest/rib cage will open out. This is facilitated by your diaphragm (a muscle just under your lungs, which is normally curved, but will flatten the more you breathe at the base of your lungs). Without seeing you personally, I can only suggest you practice it a lot, and notice for yourself how your ribcage moves, and how long you can exhale steadily (a sign you are retaining more air in your lungs). I was taught this lying on the floor, which is a very good method, because you feel your ribs move against the floor surface. Once you get it, keep practicing so this becomes the most natural way to breathe - in through the nose and out through the mouth. Always breathe in through your nose. If I can help further, do email me. All the best.

Answer 5

Bellydoc's extensive differential is almost all inclusive. I had a 13 year old patient present with very sudden onset of abdominal pain. There was free air in the abdomen. I was discussing it with the surgeon in the doctor's lounge within earshot of a geneticist. She asked if the patient was had excessive bruising or hyperextensible joints (ie. was double jointed). The family said yes to this. Pathology and fibroblast culture later confirmed her suspicion that this was Ehlers-Danlos Syndrome type IV, a rare connective tissue disorder where a ruptured aorta or intestine is common.

It was serendipity that the geneticist overheard us. The surgeon and I had not thought of it.

Answer 6

Nothing good causes air under the diaphram. A perforated bowel is usually the cause. A consultation with a gastric surgeon is indicated and surgery is more than likely the solution with a strong course of antibiotics.

Answer 7

Free Air In Abdomen

Answer 8

Im still a begginner myself, but i think one of the ways to start is: you have to keep your neck and back straight and push your chest out. It will give you a lot more support and help you control where your singing from. It should just make it easier. It works for me... But I could be wrong! : /

Answer 9

The other possible cause of "free air" is post-coital bubbles from intercourse. This would an incidental finding in an asymptomatic patient.
(I'm a gynecologist)

Answer 10

the other possible causes might be presence of intestine bn liver & diaphragm, presence of infection of with gas forming microbes.....

Answer 11

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RE:
What are the causes of air under the diaphragm?
Please tell me the differential diagnosis. Thanks!