This "free air under the diaphragm" is not caused by gastrointestinal perforation. Don't be misdiagnosed.

It is only for medical professionals to read for reference.
If you encounter "free air under the diaphragm", don't leak this cause! Free air under the diaphragm is an important imaging manifestation for the diagnosis of free air in the abdominal cavity and perforation of the gastrointestinal tract, which is often seen on the right side.

However, sometimes this kind of biblical traditional teaching experience can easily give clinicians a preconceived illusion, which may cause misdiagnosis and missed diagnosis.

Let us take a look at a case reported by Sofii I and others in January 2021 [1].

A 25-year-old man who was misdiagnosed as a gastric perforation.
This is a 25-year-old man who has a previous physical fitness, no history of smoking, alcohol, or medication.

This time I went to see a doctor due to abdominal discomfort for 1 week.

The patient also has mild dyspnea that has nothing to do with activities.

In addition, the patient has no fever, melena, nausea, vomiting, diarrhea, and constipation.

The chest radiograph of the outer hospital showed enlarged heart shadow and "free air under the diaphragm" was seen in the upper right abdomen.
Considering gastric perforation, he was urgently referred to the emergency department of a higher hospital.

Emergency medical examination: body temperature 36.
5℃, blood pressure 122/58mmHg, pulse 83 beats/min, breathing 20 breaths/min, oxygen saturation (without oxygen) 99%.

Breath sounds in both lungs are clear, without rales.

The heart rhythm was uniform, and no heart murmur was heard.

He had a soft abdomen, no tenderness, muscle tension, no hepatosplenomegaly, and normal bowel sounds.

There was no abnormality in the electrocardiogram.

As shown in the figure below, the inflatable intestine under the right diaphragm and enlarged heart shadow can be seen on the abdominal plain film.

A plain film of the abdomen showed an inflated intestine under the right diaphragm and enlarged heart shadow [1] However, a CT scan showed that there was a colon loop between the right diaphragm and the liver, and there was no free gas in the abdominal cavity, which proved to be a pseudo-pneumoperitoneum sign.

CT showed a colonic loop between the right diaphragm and the liver [1] The patient received conservative treatment, including bed rest, nasogastric tube decompression, analgesia, and intravenous infusion.

After 3 days of observation, the patient was discharged.

One week after discharge, the patient no longer experienced abdominal discomfort.

Chilaiditi sign and Chilaiditi syndrome In the above cases, the "free air under the right diaphragm" is actually a false pneumoperitoneum sign formed on imaging by the right colon embedded between the liver and the diaphragm, called Chilaiditi sign.

In 1910, the Greek radiologist Demetrius Chilaiditi described this phenomenon for the first time.

The global incidence of Chilaiditi’s sign is 0.
025%-0.
28%, and the male to female ratio is 4:1.

The age of onset of Chilaiditi’s sign ranges from a 5-month-old infant to an 81-year-old.
It is most common in the elderly, with an incidence rate of 1%.

The incidence of mental illness patients may be as high as 8.
8% [2].

When this kind of interlocus colon causes gastrointestinal symptoms, it is called Chilaiditi syndrome, also known as colon interlocus syndrome.

Chilaiditi syndrome is a variation of the position of the colon, which is mainly caused by the loss, relaxation or lengthening of the suspensory ligament or falciform ligament of the transverse colon.

Other factors that may cause Chilaiditi syndrome include congenital ectopic disease, dysfunction caused by long colon (such as chronic constipation, gas in the colon), liver cirrhosis or liver resection after liver resection, ascites, excessive weight loss, abnormal elevation of the diaphragm High or diaphragmatic paralysis, chronic obstructive pulmonary disease leads to enlargement of the lower thoracic cavity and multiple pregnancy [2].

Yin AX et al.
once reported a 58-year-old woman with suspected irritable bowel syndrome [3].
CT of the abdomen and pelvis showed no abnormalities.
Colonoscopy only found sigmoid diverticulum and small tubular adenoma.

However, after undergoing colonoscopy, the patient developed severe pain in the upper right abdomen, accompanied by nausea.
The pain continued to aggravate within 2 days, but did not affect gas and defecation.
There was no fever, chills, abdominal distension or blood in the stool.

Enhanced CT of the abdominal and pelvic cavity showed that the cecum and ascending colon were located between the liver and the right diaphragm.
The liver was slightly compressed, but there was no volvulus or thickening of the intestinal wall.

Enhanced CT of the abdomen and pelvis showed Chilaiditi sign [3] Based on symptoms and imaging findings, the patient was diagnosed with Chilaiditi syndrome.

Because conservative treatment failed to relieve symptoms, the patient finally chose surgery.

Therefore, Chilaiditi syndrome may become a complication of colonoscopy or a cause of postoperative pain.

In addition to colonoscopy, iatrogenic operations such as bariatric surgery and enteral nutrition tube placement may cause Chilaiditi syndrome.

Symptoms and Diagnosis of Chilaiditi Syndrome Chilaiditi syndrome usually does not cause symptoms.
This type of patient is mainly found accidentally by X-ray examination or CT scan.

For patients with Chilaiditi syndrome, the most common symptoms are abdominal pain, anorexia, nausea, vomiting, abdominal distension, constipation, changes in bowel habits, severe respiratory distress, or chest pain or arrhythmia similar to coronary heart disease.

Okiro JO reported a case of Chilaiditi syndrome disguised as congestive heart failure in BMJ Case Rep magazine [4].

These symptoms are usually more pronounced when lying supine at night.

A small number of patients may have multiple system symptoms at the same time, or start with acute abdomen, such as cecum or transverse volvulus and cecal perforation.

It may be challenging to diagnose Chilaiditi syndrome on an orthotopic chest radiograph, because it is sometimes impossible to determine whether there is really free air under the diaphragm, so it is easy to be misdiagnosed as a gastrointestinal perforation.

For example, the following is a 32-year-old man with a blunt chest and abdomen injury after a car accident.
The patient complained of pain in the right chest and upper right abdomen.
The appearance of the chest radiograph is almost the same as the free air under the right diaphragm caused by gastrointestinal perforation.

CT of the abdomen was finally confirmed as Chilaiditi syndrome, with no post-traumatic lesions in the chest and abdomen [5].

Abdominal CT shows that the colonic loop is located between the liver and the right diaphragm.
[5] The presence of the colonic pocket is an important imaging point for Chilaiditi syndrome.
Lateral chest radiographs may help to observe the colonic pocket.

A plain radiograph of the left side of the abdomen may also be helpful for the identification, because the gas shadow of the Chilaiditi syndrome patient still stays in the subdiaphragmatic area after the position change.

Abdominal CT is the preferred imaging method for accurate diagnosis.

When diagnosing Chilaiditi’s sign based on imaging findings, the following criteria must be met: ①Intestinal dilatation to form a false pneumoperitoneum; ②The right diaphragm is raised above the liver by the intestine; ③The upper edge of the liver should be lower than the level of the left diaphragm.

The most commonly involved bowel sites are the liver flexure of the colon, the ascending colon or the transverse colon, but in rare cases it can also be found in the small intestine [2].

Treatment of Chilaiditi syndrome Chilaiditi syndrome is usually a benign disease, but life-threatening complications can also occur.

For asymptomatic patients with Chilaiditi sign, intervention is usually not required.

The initial treatment of Chilaiditi syndrome includes intravenous fluids, nasogastric tube decompression, bed rest, stool softeners or enema, and follow-up imaging after bowel decompression.

For those who have not alleviated symptoms after conservative treatment, and still have signs of intestinal obstruction or intestinal ischemia or other serious complications, the necessity of surgical treatment needs to be evaluated in time.

In summary, Chilaiditi sign is an imaging sign that is easily confused with free air under the right diaphragm, especially for Chilaiditi syndrome with gastrointestinal symptoms, which is easily misdiagnosed as gastrointestinal perforation.

However, Chilaiditi syndrome usually requires conservative treatment.

Therefore, deepening the understanding of this sign and confirming it by abdominal CT and other imaging studies will help avoid unnecessary exploratory laparotomy.

Reference: [1]Sofii I,Parminto ZA,Anwar SL.
Differentiating Chilaiditi's Syndrome with hollow viscus perforation:A case report.
Int J Surg Case Rep.
2021 Jan;78:314-316.
doi:10.
1016/j.
ijscr.
2020.
12.
029.
Epub 2020 Dec 16.
PMID:33387865;PMCID:PMC7779831.
[2]Kumar A,Mehta D.
Chilaiditi Syndrome.
[Updated 2020 Apr 27].
In:StatPearls[Internet].
Treasure Island(FL):StatPearls Publishing;2021 Jan-.
[3]Yin AX,Park GH,Garnett GM,Balfour JF.
Chilaiditi syndrome precipitated by colonoscopy:a case report and review of the literature.
Hawaii J Med Public Health.
2012 Jun;71(6): 158-62.
PMID:22787564;PMCID:PMC3372788.
[4]Okiro JO.
Chilaiditi syndrome mimicking congestive heart failure.
BMJ Case Rep.
2017 Jul 14;2017:bcr2017220811.
doi:10.
1136/bcr-2017-220811.
PMID:28710199 ;PMCID:PMC5535131.
[5]Ben Ismail I,Zenaidi H,Rebii S,Yahmadi A,Zoghlami A.
Chilaiditi's sign:A rare differential diagnosis of pneumoperitoneum.
Clin Case Rep.
2020 Sep 21;8(12):3102-3104.
doi:10.
1002/ccr3.
3346.
PMID:33363889;PMCID:PMC7752635.