You are in: eMedicine Specialties > Radiology > GASTROINTESTINAL Pneumatosis IntestinalisArticle Last Updated: Sep 21, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Sameer K Goyal, MD, Post Graduate Instructor, Staff Physician, Department of Radiology, Nassau University Medical Center Sameer K Goyal is a member of the following medical societies: American College of Radiology, American Medical Association, and Radiological Society of North America Coauthor(s): David I Weltman, MD, Consulting Staff, S & D Medical, LLP; Director, Department of Radiology, Southside Hospital; Dvorah Balsam, MD, Chief, Division of Pediatric Radiology, Nassau University Medical Center; Professor, Department of Clinical Radiology, State University of New York at Stony Brook Editors: Zahir Amin, MBBS, MRCP, MD, FRCR, Consulting Staff, Department of Imaging, The Middlesex Hospital, University College London Hospitals Trust; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; David Andrew Nicholson, BM, BS, FRCR, Honorary Lecturer, Department of Radiology, University of Manchester; Consultant Gastrointestinal Radiologist, Department of Radiology, Hope Hospital, Salford Royal Hospital NHS Trust; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: intestinal gas cysts, primary pneumatosis intestinalis, secondary pneumatosis intestinalis, pneumatosis cystoides intestinalis, bullous emphysema of the intestine, peritoneal lymphopneumatosis, necrotizing enterocolitis, NEC, bowel necrosis INTRODUCTIONSection 2 of 10
  BackgroundPneumatosis intestinalis, defined as gas in the bowel wall, is often first identified on abdominal radiographs or computed tomography (CT) scans. It is a radiographic finding and not a diagnosis, as the etiology varies from benign conditions to fulminant gastrointestinal disease. Pneumatosis intestinalis is considered an ominous finding in ischemia, especially in association with portomesenteric venous gas. The disease is seen in other conditions, including chronic obstructive pulmonary disease, connective tissue disorders, infectious enteritis, celiac disease, leukemia, amyloidosis, and acquired immunodeficiency syndrome (AIDS); it is also found in association with organ transplantation, steroid use, and chemotherapy. Pneumatosis intestinalis occurs in 2 forms. Primary pneumatosis intestinalis (15% of cases) is a benign idiopathic condition in which multiple thin-walled cysts develop in the submucosa or subserosa of the colon. Usually, this form has no associated symptoms, and the cysts may be found incidentally through radiography or endoscopy. When the cysts protrude into the lumen, they may mimic polyps or carcinomas, as shown on barium enema studies. This primary form is often termed pneumatosis cystoides intestinalis.1 The secondary form (85% of cases) is associated with obstructive pulmonary disease, as well as with obstructive and necrotic gastrointestinal disease. For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center and Imaging Center. Also, see eMedicine's patient education articles Anatomy of the Digestive System, Colitis, and Crohn Disease. PathophysiologySeveral etiologies have been suggested for pneumatosis intestinalis. The formation of pneumocysts results from the interaction of multiple factors, such as mucosal integrity, intraluminal pressure, bacterial flora, and intraluminal gas. Mucosal disruption may be caused by bowel wall trauma, obstruction, ischemia, or inflammation, allowing bacteria or gas to invade the bowel wall. A bacterial origin of the gas is suggested by the high concentration of hydrogen within the cysts. Steroids, immunosuppressants, and chemotherapeutic agents also are thought to lead to pneumatosis through increased mucosal permeability. Disease entities associated with pneumatosis intestinalis can be divided into the following 3 general categories:
Bowel necrosis leading to pneumatosis is seen in necrotizing enterocolitis (NEC), mesenteric ischemia, and caustic ingestions. In neonates, pneumatosis is usually secondary to NEC and indicates a later stage of the disease. NEC is seen almost exclusively in premature infants and is associated with bowel ischemia caused by bacterial invasion and hyperosmolar feeds. Mesenteric vascular occlusion leads to ischemic damage of the mucosa, which allows luminal gas and bacteria to invade the bowel wall. Corrosive agents, including lye, acids, and formaldehyde, also may lead to mucosal disruption and pneumatosis. In the absence of bowel necrosis, many gastrointestinal diseases resulting in obstruction or ulceration can lead to pneumatosis intestinalis. Pneumatosis can be seen in pyloric stenosis and Hirschsprung disease in children, as well as in bowel obstruction in adults. The increased pressure proximal to the obstruction forces intraluminal gas into the bowel wall. Pneumatosis can be present in Crohn disease and ulcerative colitis because of a combination of mucosal ulceration, stenotic segments that increase the luminal pressure, and bacterial invasion. Pneumatosis has also been associated with collagen vascular disease and celiac sprue. Abdominal trauma may lead to mucosal disruption; pneumatosis has been found secondary to motor vehicle accidents, child abuse, and endoscopy. Immunosuppression is one of the more common causes of pneumatosis. It has been suggested that steroid therapy and immunosuppressed states lead to the depletion of Peyer patches, resulting in loss of structural integrity of the bowel wall. Pneumatosis has been reported to occur after solid organ and bone marrow transplantation. Concomitant infection in these patients increases the risk of pneumatosis intestinalis. Graft-versus-host disease can lead to enterocolitis and pneumatosis in the absence of necrosis. The most common associated infections include those resulting from cytomegaloviruses, rotaviruses, Clostridium difficile, and human immunodeficiency virus (HIV) enterocolitis. Finally, severe obstructive pulmonary disease may result in pneumatosis. Rupture of pulmonary blebs in obstructive lung disease may cause air to dissect through the retroperitoneum, into the mesentery, and, finally, to the bowel subserosa and submucosa. FrequencyUnited StatesPneumatosis intestinalis is a rare condition, although the exact prevalence is unknown. It is seen in 80% of cases of NEC. Mortality/Morbidity
RaceNo race predominance is reported. SexNo sex predominance is reported. AgeThe incidence is highest in neonates because of the condition's association with NEC; however, pneumatosis intestinalis may occur in any age group. Primary pneumatosis intestinalis typically occurs in adults. AnatomyPrimary pneumatosis intestinalis, which usually affects the descending colon, consists of cystic gas collections. Secondary pneumatosis typically involves the small intestine, but it may occur throughout the gastrointestinal tract, and the collections are linear or curvilinear. Secondary pneumatosis is most frequently seen in the small bowel, but it can involve the colon, stomach, and esophagus as well. Microvesicular gas collections, defined as 10-100 mm cysts or bubbles within the lamina propria, are predominantly associated with primary (benign) pneumatosis intestinalis, whereas linear or curvilinear gas collections seen parallel to the bowel wall are found in secondary pneumatosis. Therefore, linear gas collections are usually an ominous sign. Clinical DetailsPrimary pneumatosis is often asymptomatic. Rarely, patients may experience symptoms secondary to the cysts. Signs and symptoms include diarrhea, bloody stools, abdominal pain, abdominal distention, and constipation. The physical findings are usually unremarkable. In neonates, the elderly, and immunosuppressed patients, pneumatosis may be a sign of underlying disease. In these patients, the most life-threatening causes of secondary pneumatosis intestinalis, including bowel necrosis, should be investigated. The decision to proceed with surgical intervention is based on a combination of radiographic findings, laboratory markers, and clinical examination findings. Preferred ExaminationPneumatosis intestinalis is usually identified on plain radiographs of the abdomen. Occasionally, submucosal cysts may be identified during endoscopy. The cysts, which may appear similar to polyps, may be examined at biopsy for signs of inflammation. Gas may collect peripherally in the lumen of the bowel, around fecal or contrast material. This gas can simulate pneumatosis and is usually depicted on CT scans. Rarely, emphysematous ureteritis may simulate pneumatosis of the descending or sigmoid colon on plain radiographs. Colitis cystica profunda is an extremely rare disease in which mucin-filled cysts form in the wall of the rectum. DIFFERENTIALSSection 3 of 10
Other Problems to Be ConsideredColitis cystica profunda
RADIOGRAPHSection 4 of 10
FindingsThe patterns of the radiolucencies are seen as linear, curvilinear, small bubbles, or collections of cysts. Cystic collections of gas localized to the wall of the colon are suggestive of primary pneumatosis intestinalis. Pneumoperitoneum may represent rupture of subserosal cysts in benign primary pneumatosis, or it may occur after perforation in the setting of intestinal necrosis. Linear or curvilinear gas collections may be seen throughout the intestinal wall in secondary pneumatosis. Portal venous gas, which is tubular and peripherally located in the liver (as opposed to biliary air, which is centrally located), is an ominous finding, often occurring with ischemic bowel. Degree of ConfidenceAbdominal radiographic findings are detected in approximately two thirds of patients with pneumatosis. Radiographs are sufficient for diagnosis of pneumatosis, although additional studies, such as CT scans, ultrasonograms, or water-soluble enema studies, may be considered to delineate pneumatosis or the site of perforation. The concomitant finding of portal venous gas does not always suggest bowel ischemia. Other etiologies must be clinically correlated with the patient's history. False Positives/NegativesRarely, emphysematous ureteritis may simulate pneumatosis of the descending or sigmoid colon on plain radiographs. CT SCANSection 5 of 10
FindingsAbdominal CT scanning can depict small amounts of intramural gas not shown on routine radiographs. Depending on the morphology, distention, and thickness of the bowel loops, CT scanning helps to provide clues to the cause of pneumatosis intestinalis. With contrast enhancement, thickened bowel wall may suggest ischemia in the setting of pneumatosis. Dilated bowel loops and abnormal fluid levels suggest an obstructive cause of pneumatosis.2, 3, 4 Sensitivity in detecting small, gaseous inclusions in the mesenteric vein or intrahepatic branches of the portal vein is increased with abdominal CT scanning. In this circumstance, pneumatosis is 1 of the signs of mesenteric ischemia. CT scans provide additional details, such as various morphologic changes (including mural wall thickening, dilatation, abnormal or absent wall enhancement), mesenteric stranding, edema or hemorrhage, vascular engorgement, ascites, and portomesenteric gas.2, 3, 4 Degree of ConfidenceCT scanning is often helpful in determining the primary cause of pneumatosis intestinalis, and it can demonstrate important coexistent findings or complications. The use of multidetector-row CT scans, thin sections, and high-quality portal venous phase scans are advantageous for providing greater accuracy in the detection of ischemia, as well as for diagnosing other causes of acute abdomen, such as perforation, abscess formation, and peritonitis. The sensitivity of CT scanning (82%) for the diagnosis of acute bowel ischemia is comparable to that of angiography (87.5%). MRISection 6 of 10
FindingsMagnetic resonance imaging (MRI) may be useful for identifying intestinal ischemia as a cause of pneumatosis. High signal intensity on T1- and T2-weighted images suggests ischemia. Gas bubbles within the bowel wall have been described on abdominal magnetic resonance images of neonates with NEC. ULTRASOUNDSection 7 of 10
FindingsUltrasonography of the abdomen shows within the bowel wall circumferential, bright, echogenic foci that represent the gas bubbles. The pattern of gas distribution, particularly within the dependent wall, should raise the suspicion of pneumatosis intestinalis in a patient with the appropriate clinical history.5 Degree of ConfidenceMisregistration artifact occurs only on the nondependent wall and usually involves the superficial wall layers, in contrast to pneumatosis intestinalis, which is typically circumferential and often has a submucosal or subserosal location. False Positives/NegativesIn addition to the familiar artifacts of dirty shadowing and small reverberation artifacts, a bubble of intraluminal gas may falsely lie within the gut wall, producing an artifact called pseudo-pneumatosis. It is more likely seen with thickening of the gut wall. INTERVENTIONSection 8 of 10
Multiple factors can contribute to the development of pneumatosis intestinalis. Finding the underlying cause can help in tailoring the appropriate medical and/or surgical treatment to the patient. Most patients with primary pneumatosis intestinalis require no treatment. The cysts usually resolve spontaneously. Symptomatic primary pneumatosis may be treated with oxygen therapy, which reduces the partial pressure of hydrogen gas in the capillaries and increases resorption of the cystic gas. Occasionally, recurrent pneumatosis is treated with antibiotics in an effort to decrease bacterial production of gas. In neonates, the elderly, and immunosuppressed patients, pneumatosis may be a sign of underlying disease. In these patients, the most life-threatening causes of secondary pneumatosis intestinalis, including bowel necrosis, should be investigated. The decision to proceed with surgical intervention is based on a combination of radiographic findings, laboratory markers, and clinical examination findings. Pneumatosis intestinalis may be complicated by pneumoperitoneum, which can be detected as free air on a simple upright or cross-table lateral view of the abdomen. The presence of gas in the mesenteric and portal circulation is an ominous radiographic finding in bowel ischemia. Angiography can provide insight into the nature of vascular compromise. Surgical intervention is recommended if bowel ischemia or perforation is present. Pneumatosis is an ominous radiographic finding in patients who are suspected of having bowel ischemia, and surgery should be performed in patients who are not responding to nonoperative treatment, especially those with signs of perforation, peritonitis, or abdominal sepsis. As many as 50% of patients may require surgery for perforation. MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
Pneumatosis Intestinalis excerpt Article Last Updated: Sep 21, 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
