3. ABNORMAL GAS LOCATION. SHOULD I WORRY?
Clinical manifestations and prognosis can vary from benign cases in which we can consider that gas is not worrisome, to life-threatening situations in which urgent surgery is needed. For this reason, when ectopic gas is found, we must ask ourselves two questions: where does it come from and whether or not it is an alarming finding.
We should remember that gas can dissect between different body spaces as a result of this fascial interconnectivity, distant from its source and causing confusion as to its origin. In order to reach an adequate diagnosis, we must combine the radiological findings with the information obtained from the clinical history.
We report a series of cases from our hospital, where ectopic gas was identified. We made a classification of the most frequent possible pathologies, according to the different tissues and body spaces, from the whole body, where ectopic air can be found.
Head and Neck
Pneumocephalus refers to the presence of intracranial gas, and the term encompasses gas in any of the intracranial compartments.The most common cause is a mechanical trauma when it reveals a bone fracture. It is also very frequent after neurosurgery, external ventricular drain insertion, sinus surgery, peridural anesthesia and in these cases may persist in a minority of patients in the 3rd postoperative week, but is not expected to persist beyond this.
Orbital emphysema have been reported including trauma, infection, pulmonary barotrauma, injury from compressed-air hoses, and complications from surgery including dental procedures. We must be careful not to confuse it with normal air suddenly caught in the eyelid.
Fig. 4: Most frequent causes of ectopic gas in head and neck.
Fig. 9: Pneumocephalus bubbles in a patient after suffering craniocerebral trauma, forcing bone fracture to be ruled out.
Fig. 10: Pneumocephalus in a patient with clinical suspicion of meningitis. The presence of gas suggests complicated sinusitis as the origin of the infection.
Fig. 11: Orbital gas bubbles and pneumocephalus in a patient with facial trauma. We should think about sinus fractures.
Fig. 13: Pre and post septal gas bubbles in a patient after facial trauma.
Fig. 14: Aerial level in ventricles due to intraventricular drain valve placement.
Fig. 15: Inflammatory changes and gas bubbles in cervical spaces originating in odontogenic phlegmon
Fig. 17: Patient after assault with a knife. We observed gas bubbles in soft tissues in the incised wound path and in relation to maxillary sinus fracture.
Being two very communicated spaces, in the neck and mediastinum we find common causes of ectopic gas. In case of previous trauma when it is located around the airway and respiratory structures (pharynx, larynx, esophagus or trachea) we must consider the possibility of rupture of any of these structures or in iatrogenesis secondary to difficult intubation. Strong vomiting, as in Boherave syndrome, can also cause esophageal rupture. In the absence of trauma we must rule out the possibility that it is a diverticulum.
The face, neck and the mediastinum are two frequent locations of necrotizing infections produced by gas-producing organisms, whose origin is mostly dental.
Fig. 16: Cervical ectopic gas in a 70-year-old patient after total larynguectomy.
Fig. 18: Body-CT study in a polytrauma patient in which we observed mediastinal hematoma with gas inside, of iatrogenic origin secondary to failed central venous canalization.
Fig. 19: A 32-year-old female patient who comes to the emergency room due to chest pain. In the X-ray we can see linear radiolucence drawing the cardiac silhouette that indicates the presence of pneumomediastinum. It is subsequently confirmed in thoracic CT.
Fig. 20: Gas in the anterior mediastinum in a patient after thoracic trauma secondary to a sternum fracture.
Fig. 21: Patient with chest pain after esophageal surgery. CT study shows pneumothorax with a hydro-air level that suggests suture dehiscence. After oral contrast administration the leak is confirmed.
Fig. 22: Patient 1. Two patients rescued at sea after shipwreck. They have pneumomediastinum, pneumothorax, pneumoperitoneum and subcutaneous emphysema in the soft tissues of the chest and abdomen. The barotrauma hypothesis by immersion is the most likely.
Fig. 23: Patient 2. Two patients rescued at sea after shipwreck. They have pneumomediastinum, pneumothorax, pneumoperitoneum and subcutaneous emphysema in the soft tissues of the chest and abdomen. The barotrauma hypothesis by immersion is the most likely.
In emergency radiology the finding of gas in the pleural space (pneumothorax) is very frequent. Its severity will vary depending on its volume and whether it is a tension pneumothorax. The most frequent cause is traumatic but it can also be iatrogenic, or due to causes that cause alveolar disruption. It is common to find a small amount of pleural gas after lung biopsies.
Intrapulmonally we can find bronchogram or air level in lung cavities, which are benign pathologies, in relation to malignant neoplasms or interstitial emphysema mainly secondary to mechanical ventilation.
Fig. 5: Most frequent causes of ectopic gas in thorax and mediastinum.
Fig. 24: Patient with multiple cavitated pulmonary lesions with a hydro-air level that in the infectious clinical context of the patient correspond to septic emboli as the most likely cause. In another clinical context they could also indicate malignant origin.
Fig. 26: Small bubbles of pneumothorax in a patient after trauma always force to discard rib fractures.
Fig. 27: Spontaneous pneumothorax secondary to rupture of a pulmonary bulla.
Fig. 28: Frequent pathology in patients after traffic accident. The patient has pneumothorax and pulmonary infiltrates secondary to pulmonary contusion.
Fig. 25: Gas inside pulmonary condensation in a patient with necrotizing numonia....
The causes that produce free gas in the peritoneum and retroperitoneum are mainly due to hollow viscera perforation, and the situation of the bubbles will depend on the location where the damage occurs (table).
The gas is preferentially located in retroperitoneum due to pancreatitis, episematous pyelonephritis and perianal fistula. We can find periaortic or pericave gas in relation to infected prostheses. It is also common for bubbles from spondylodiscitis to reach the psoas muscle.
Post-surgical pneumoperitoneum and post-surgical retroneumoperitoneum are considered normal up to 3-6 days after the operation.
There are multiple benign etiologies that can produce gas inside the intestinal wall, but their findings always oblige us to consider the possibility of intestinal ischemia, colitis or collagen disease.
A special, rare case is the presence of emphysema in the gastric wall secondary to the intake (accidental or voluntary) of caustics.
If we find gas bubbles inside solid viscera, in the absence of previous invasive procedures, we should think of emphysematous infection.
The diffusion of air into the biliary tract is frequent after ERCP or in patients with incompetent sphincter of Oddi. Other causes of greater severity may be emphysematous cholecystitis, cholangitis or liver abscesses. Less common biliar ileus, neoplasm or a ruptured hydatid cyst.
A particularly alarming condition, although benign causes may exist, is the finding of gas inside the portal vein, since it constitutes a pre-mortem sign when associated with intestinal ischemia, necrotizing enterocolitis, colorectal carcinoma or abdominal sepsis.
Fig. 6: Most frequent causes of ectopic gas in the abdominal compartments.
Fig. 29: Patient with abdominal pain, fever and infectious analytical parameters. We can observe endoluminal gas and gallbladder walls related to emphysematous cholecystitis.
Fig. 30: Another case of emphysematous cholecystitis. On this occasion the presence of pneumoperitoneum and intra-abdominal abscess indicate vesicular perforation.
Fig. 31: Free gas bubbles around the rectal anastomosis indicate the possibility of suture dehiscence.
Fig. 32: Abdominal Ct is performed due to suspected suture dehiscence in postoperative colon resection seven days after surgery. The presence of free pneumoperitoneum in large quantities confirms the suspicion.
Fig. 33: Lithiasis and dilation of renal pelvis with gas bubbles indicating possible emphysematous pyelonephritis.
Fig. 34: Pneumoperitoneum and pneumoretroperitoneum secondary to colon perforation due to impacted fecaloma.
Fig. 36: Emphysematous gastritis as a complication of a patient with gastrostomy.
Fig. 39: Emphysematous gastritis secondary to accidental ingestion of caustics
Fig. 37: A 72-year-old female patient with an unusual case of emphysematous hepatitis. The presence of large abscess in the hepatic dome with parenchymal necrosis and gas collections can be seen.
Fig. 41: Free gas bubbles near the hepatic hilum secondary to duodenal ulcer perforation.
Fig. 45: Aerobilia, a frequent finding in patients with a recent history of ERCP papillotomy
Fig. 46: Intrahepatic and extrahepatic bile duct aerobilia in a patient with liver metastases.
Fig. 42: Intra-abdominal abscess with gas bubbles secondary to perforated diverticulitis
Fig. 43: Patient with abdominal pain after colonoscopy. Pneumoperitoneum in CT confirms the suspicion.
Fig. 40: Pneumoperitoneum in a patient who comes to the emergency department for abdominal pain. We can see the larger bubble located next to the back wall of the stomach, which indicates possible gastric perforation, which was subsequently confirmed in surgery.
Fig. 35: Patient with an aortic aneurysm in which we find the presence of gas in the aortic hematoma in contact with a small intestine loop, which suggests the presence of aorto-enteric fistula
Fig. 44: Dilated colon with gas bubbles in its wall, intestinal pneumatosis that indicates intestinal suffering.
In case of presence of gas in soft tissues we must be alert to two entities that constitute medical emergencies: necrotizing fasciitis, caused by infection by anaerobic organisms, which can occur anywhere in the body although it is especially frequent in lower limbs; and Fournier's gangrene, which is a type of fasciitis that affects the perineum and leads to high mortality. Both require urgent surgery.
There are multiple causes that can cause gas to enter the vessels; situation that is worrying in arteries or in the pulmonary vein and that constitutes banal situation in intravenous location or in pulmonary artery.
Fig. 8: Most frequent causes of ectopic gas in the soft tissues.
Fig. 48: Patient with anal fistula complicated with gas dissecting the perineal soft tissues, characteristic of Fournier's gangrene.
Fig. 47: 32-year-old patient with pain in the left leg, with no important medical history Necrotizing fasciitis originating in a small foot wound facilitated by immunosuppression secondary to unknown leukemia.
Fig. 38: Patient with aortic prosthesis with abdominal pain and analytical parameters of infection. In CT study there is a periprosthetic gas bubble that indicates infection of the prosthesis.
When we talk about the presence of spinal gas we can distinguish three locations. Gas in the vertebral disc facet joints, intravertebral or in epidural space. In all three compartments it is common to see bubbles due to degenerative vaccum effect but we must be alert to the possibility of avascular necrosis or infection with gas forming organism (spondylodiscitis) that are entities with high vital risk. The presence of pneumorrachis after lumbar punctures can also be seen.
Fig. 7: Most frequent causes of ectopic gas in the spine.
Fig. 50: Fracture in vertebral body of L1 with subcortical intravertebral gas along with some small bubble in right perivertebral soft tissues, suggestive of secondary avascular vertebral osteonecrosis (Kummel's disease).
Fig. 49: A spectacular case of Gangrena de Fournier in which we can observe ectopic gas dissecting the tissues reaching the retroperitoneal periaortic space and the interior of the lumbar spinal canal.