Rectal histopathology in endemic Shigella and Salmonella diarrhea

Rectal histopathology was evaluated in 34 cases (2 months-12 yrs old) of endemic "invasive diarrhea" [> 20 WBCs per high-power field on stool microscopy with (RBC positive) or without (RBC negative) associated RBCs] where S. dysenteriae (n = 9), S. flexneri (n = 11), and nontyphoidal Salmonella were isolated as the sole identifiable enteropathogens. Persistent diarrhea (> 14 days duration) was more common with Salmonella infection whereas RBC-positive "invasive diarrhea" was more frequent with Shigella, particularly S. dysenteriae (all cases) infection. The histopathological profile was comparable to the earlier descriptions of infective colitis to a large extent and the nature of the infecting organism could not be determined on the basis of rectal histology alone. The other noteworthy features were as follows: (i) mild crypt distortion (26%) and branching (21%) in both Shigella and Salmonella infection; in Salmonella infection, dilation of the glands was significantly greater with persistent diarrhea; (ii) presence of chronic inflammatory cells either alone or in combination with neutrophils in 62%; a predominant neutrophilic response was significantly higher with S. dysenteriae infection and an acute presentation; (iii) pseudomembrane formation (six subjects; 18%) especially in S. dysenteriae (four cases); and (iv) a significant association of neutrophilic response, edema, and neutrophils within the vessels in the lamina propria and mucin depletion in the glands with RBC-positive "invasive diarrhea."