Pneumatosis cystoides intestinalis in infancy

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Despite advances in neonatal care, the incidence of necrotizing enterocolitis (NEC) has remained unchanged over the last three decades. Mortality remains high at 25% to 30% of affected infants. The radiographic and pathologic hallmark of NEC is pneumatosis intestinalis. The report from Leonard Paris in 1955 provided detailed pathologic findings from a 5-month-old infant diagnosed with “pneumatosis cystoid intestinalis.” He summarized epidemiologic findings from the literature at the time as they pertained to infants, and he offered a theory to NEC's pathogenesis. There are clear differences in the epidemiologic characteristics of affected infants from those we find today, reflecting improvements in neonatal care. At the same time, it is humbling to find that progress in understanding pathophysiology has not progressed in a similar fashion.

The cases of pneumatosis intestinalis in Paris's report were term or near-term infants who were presented at 2 to 14 weeks of age, some with underlying pathology such as “congenital megacolon” and some without. Today, prematurity is the single most important risk factor in the development of pneumatosis intestinalis, with gestational age indirectly related to incidence. Term infants comprise only approximately 10% of infants with NEC. Despite this striking difference, the similarities also are apparent. No infant is born with NEC, intestinal inflammation is always present, and mucosal integrity has been altered. Clues from these similarities have been applied to understanding the pathogenesis.

Paris summarized the major theories of his time regarding pneumatosis intestinalis: mechanical, related to the break in mucosal integrity; bacterial, causing mucosal ulceration, and; chemical, from defective carbohydrate metabolism. These same themes of mucosal integrity, bacterial colonization, and the presence of substrate continue at the core of current theories. Despite advances in laboratory research, we have yet to identify the “unknown factor” hypothesized by Paris that sets into motion a final common mechanism to produce disease.