Growth of the lower spleen pole remaining after subtotal splenectomy in rats.

PURPOSE To determine whether the lower pole of the spleen grows after subtotal splenectomy following ligature of major spleen blood vessels. METHODS Thirty-nine Wistar rats (328.8 +/- 27.8 g) submitted to subtotal splenectomy with preservation of the lower splenic pole were divided into two groups: group 1 (control, n=20), immediate removal of the lower pole; group 2 (n=19), removal of the pole on postoperative day 80. The length, width and thickness of the pole were measured. In the control group, mean percent pole weight was calculated immediately after surgery in a direct and indirect manner. In the first case, the weight of the lower pole was divided by overall spleen weight; in the second case, pole weight was divided by the ideal weight of the spleen obtained by linear regression analysis. The results of the two calculations were compared. Macro- and microscopic examinations of the pole were performed. RESULTS In group 1, no significant difference in mean percent pole weight was observed between the direct and indirect method. In group 2, mean percent pole weight obtained by indirect calculation on day 80 was higher than in group 1 (p<0.001). In group 2, mean length, width and thickness of the pole remnant increased from the first to the 80th day (p<0.05). Histological analysis showed preserved tissue architecture and features compatible with cell hyperplasia in group 2. CONCLUSION The lower pole splenic remnant presented statistically significant growth up to postoperative day 80 after subtotal splenectomy, even after ligature of the major spleen vessels. Light microscopy revealed changes compatible with cell hyperplasia.