Experimental study of ureteral free grafts. III. Histological findings

To analyze histological findings in rat ureter used as free autologous graft and compare them with two controls.

They were randomly distributed into four groups: NU group (n = 20), ureter from healthy rats; SC group (n = 15), ureter from rats undergoing ureterolysis, the surgical control group; AU group (n = 13), rats with ureter used as ANIFG (autologous non-integrated free graft); RU group (n = 14), rats with ureter used as AIFG (autologous integrated free graft). For the histological study, ureteral cross sections were obtained (A proximal, B middle, and C distal) and kidney (K) was studied. In addition, in the RU group, we obtained one cross section above the proximal suture (D), one below the distal suture (E), and two longitudinal sections of the surgical anastomoses (F and G).

The results showed a histological similarity between the NU, SC and AU groups and an apparent viability of all RU group ureters in which necrosis has not been found. SC group: Mild edema could be noted in the lamina propria in some of the sections. None of the three ureteral layers showed any fibrosis or other lesions. AU group: All layers were preserved. The urothelium showed changes from mild hyperplasia to a wider area of denudation. Some of the sections showed mild fibrosis in the lamina propria. Nearly all sections showed an increased number of blood vessels in comparison to the NU group. Necrosis, fibrosis or loss of ureteral lumen were not usually observed. RU group with correct functional result (RUa): This group consisted of seven cases. The three layer structure was preserved, although some sections showed some ureteral disorganization. Three cases showed foci of fibrosis in the lamina propria. Some ureteral segments had abundant subepithelial blood vessels. The muscle layer was also preserved, with increased vasculature and in some cases partial fibrosis. The RU group with poor functional results comprised six animals. All the ureteral layers could be identified, although they had more abnormalities and "disorderly" appearance than the RUa.

Rat ureter can be used as a free autologous graft. Both AIFG and ANIFG can be utilized as homologous grafts in order to study ureteral immunological changes. When the ureter was used as ANIFG, no significant necrosis or fibrosis were observed and only a slight reduction in diameter was noted. The AIFG graft can result in ureteral integration that allows normal function.