Unusual etiology of slow colonic transit constipation: visceral hypertophic myopathy

Background: Slow transit constipation (STC) is a disorder of intestinal motility of unknown etiology. Myogenic or neural mechanisms have been implicated in its pathophysiology. Morphological changes seen in intestinal myopathies include fibrosis, hypertrophy or atrophy of muscle fibers, vacuolation of myocytes, and alteration in the immunohistochemical staining patterns of myocyte contractile proteins, abnormal muscle layering, and presence of intracellular inclusion bodies.

Patient and method: A 48 year-old woman came up with chronic constipation. Slow colonic transit was demonstrated by radio-opaque marker retention. Anorectal manometry showed positive recto-anal inhibitory reflex, with normal perception thresholds. Evacuation proctography detected small anterior rectochele. Subtotal colectomy, ileorectal anastomosis formation was performed. Segmental muscle wall thickening was found at several sites of the colon, with dilation of the colon in between the thickened area. Tissue blocks were taken from all the segments with thickened wall or dilated lumen. Haematoxylin and eosin (H&E), desmin, smooth muscle actin (SMA), muscle specific actin (MSA), vimentin, CD45 and c-kit (CD117) and S-100 stainings were performed. A segmentally hypertrophyzed internal muscle layer was found with disarray of the muscle cells mimicking that found in hypertrophic obstructive cardiomyopathy. Ganglion cells of Auerbach are intermuscular and Meissner's submucosal plexus were found normal. S-100 immunostaining clearly demonstrated the increased number and arborisation of nerve fibers in the muscularis propria. Around the nerves slightly increased number of interstitial cells of Cajal was found by the c-kit immunostaining.

Conclusion: These morphological findings were previously unknown in any part of the gastrointestinal tract and might indicate a new type of myopathy which may play a role in the pathogenesis of the slow transit constipation.