Application of the paraboloidal model to assess mucosal changes following segmental intestinal transplantation in...

Segmental living related small intestinal transplantation (LRSITx) is a therapeutic option for conditions that present with short gut syndromes. Recovery of small intestinal mucosa after transplantation is critical to function. We examined the posttransplant mucosal changes to understand the absorptive capabilities of transplanted small intestine. The study of human subjects is constrained by limited biopsy material; therefore, we developed a technique of villus area measurement by extrapolation from two-dimensional surgical biopsy images. Using a detailed model of the villus as the gold standard, two simpler models (cylindrical and paraboloid) were tested. Comparisons with the accurate measurement revealed that the cylinder model does not compare well in early posttransplant biopsies. The paraboloid function developed in this article worked very well under all conditions. The simplicity of the paraboloid model and its robustness made high-quality estimates of the absorptive surface area from abundant data relatively easy. The remodeling expected in the initial stages of growth was also captured by this model. Time-dependent villus growth curves were obtained for transplanted bowel. Serial biopsies showed an initial "reconstruction" dip around 2 weeks after transplant, followed by continuous growth of villus surface area. An eventual plateau resulted at an average of 6 months after transplant. This growth of villi was shown to parallel the improved absorption of electrolytes, amino acids, and water.