In contrast to the preservation of submucosal ganglion cells on rectal biopsies, there may be significant histological changes in the deep layers (observed especially on resection specimens), such as decreased Cajal interstitial cell counts [ 54 , 55 ], decreased myenteric ganglia [ 56 ], decreased density of neural enteral structures [ 57 ] and/or smooth muscle hypertrophy [ 58 ].
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