Rectal bleeding is not uncommon in newborn infants. Anal fissures are
regarded as the most common cause. We report two cases in which the pr
esence of an anal fissure delayed the diagnosis of nonspecific colitis
in premature infants. Rectosigmoidoscopic and biopsy findings are dis
cussed with regard to the heterogeneous group of disorders associated
with isolated rectal bleeding in young infants. These procedures may b
e helpful in ruling out necrotizing enterocolitis in premature infants
.