Pneumatosis intestinalis (PI) refers to the presence of gas within the wall of the small or large intestine. Since its first description in 1783 by Du Vernoi, PI has appeared in the literature under many names, including pneumatosis cystoides intestinalis, intramural gas, pneumatosis coli, pseudolipomatosis, intestinal emphysema, bullous emphysema of the intestine, and lymphopneumatosis [1,2]. For the sake of simplicity and to avoid confusion, we will use the term "pneumatosis intestinalis."
The pathogenesis of PI is poorly understood, and is probably multifactorial. PI is not itself a disease, but rather a clinical sign. In some cases, PI is an incidental finding, whereas in others, it portends a life threatening intra-abdominal condition. As a result of the diverse array of clinical settings in which PI is encountered, its implications are often misinterpreted.
The incidence of pneumatosis intestinalis (PI) is difficult to ascertain because most patients are asymptomatic and never come to clinical attention . PI can be seen in infants and adults. The majority of cases in infants are secondary to necrotizing enterocolitis, a disease associated with a high mortality rate. (See "Clinical features and diagnosis of necrotizing enterocolitis in newborns".)
PI in adults typically presents in the fifth to eighth decade and is idiopathic (15 percent) or secondary (85 percent) to a wide variety of gastrointestinal and non-gastrointestinal illnesses (table 1) [3,4]. The course of PI is variable and determined largely by the underlying disorder. Mortality rates are high when PI is associated with diseases that lead to bowel necrosis or perforation. In contrast, the clinical course is generally benign when PI is idiopathic, such as when it occurs in association with obstructive pulmonary disease.
Numerous hypotheses have been proposed to explain the pathogenesis of pneumatosis intestinalis (PI), including mechanical, bacterial, and biochemical causes. For any of these theories to gain acceptance, they must explain the association of PI with many different underlying conditions. Although the theories are distinctly different, they are not necessarily mutually exclusive. It is likely that multiple pathogenic mechanisms are involved in the formation of PI.