Experimental study on the feasibility and safety of radiofrequency ablation for secondary splenomagely and hypersplenism

Abstract

Aim: To assess the feasibility and safety of radiofrequency ablation (RFA) in treatment of secondary splenomagely and hypersplenism.

Methods: Sixteen healthy mongrel dogs were randomly divided into two groups, group I (n=4) and group II (n=12). Congestive splenomegaly was induced by ligation of splenic vein and its collateral branches in both groups. At the end of 3rd week postoperation, RFA in spleen was performed in group II via laparotomy, complications of RFA were observed, CT scan was performed and the spleens were obtained. The radiofrequency (RF) thermal lesions and histopathology of spleen were examined regularly.

Results: No complication or death was observed in both groups; CT revealed that the splenomegaly lasted over 2 months after ligation of splenic vein; the segmental RF lesions included hyperintense zone of coagulative necrosis and more extensive peripheral hypointense infarcted zone, the latter was called "bystander effect". The infarcted zone would be absorbed and subsequently disappeared in 4-6 weeks after RFA accompanied with shrinkage of the remnant spleen. The fundamental histopathological changes of splenic lesions caused by RF thermal energy included local coagulative necrosis, peripheral thrombotic infarction zone, subsequent tissue absorption and fibrosis in the zone of thrombotic infarction, the occlusion of vessels in remnant viable spleen, deposition of extensive fibrous protein, and disappearance of congestive splenic sinusoid - "splenic carnification". Those pathologic changes were underline of shrinkage of spleen.

Conclusion: It is feasible and safe to perform RFA in spleen to treat experimental splenomegaly and hypersplenism. The RFA could be safely performed clinically via laparotomy or laparoscopic procedure while spleen was strictly separated from surrounding organs.

Figure 1

Enhanced CT demonstrated multiple segmental ab-lated lesion at the end of 2^nd week after RFA, the splenic cap-sule was continuous, the thermal lesion included 2 zones, namely hyperintense zone of coagulative necrosis and periph-eral hypointense infarcted zone; no perisplenic or splenic abcess was seen.

Figure 2

The lesion of infarcted zone was mostly absorbed at the end of 6^th week after RFA.

Figure 3

The lesion of infarcted zone was absorbed absolutely at the end of 9^th week after RFA, however, the lesion of coagu-lative necrosis hardly altered, the remnant spleen shrinked sig-nificantly (arrow).

Figure 4

The appearance of the spleen the day after RFA, showed the lesion included the zone of soid-yellow dry necrosis (white arrow) and dark-red zone of thrombotic infarction (curve arrow), and the bright red normal spleen (black arrow); each ablation created a lesion with maximum diameter of 9 cm.

Figure 5

The lesion of infarcted zone was absorbed absolutely at the end of 9^th week after RFA, however, the lesion of coagu-lative necrosis hardly altered (arrow).

Figure 6

Light microscopic appearance of the coagulative ne-crosis at the end of 2^nd week after RFA, the intrasplenic hemor-rhage at the probe insertion site could see (arrow), the splenic capsule thickened (HE. × 40).

Figure 7

Microscopic examination at the junction of the ne-crotic region and infarcted region at the end of 2^nd week after RFA, massive fibroblasts and inflammatory cells aggregated, the microthrombus dissolved (HE. × 200).

Figure 8

Microscopic examination of the thrombotic infarc-tion at the end of 4^th week after RFA, the microthrombus dissolved, and extensive macrophages with hemosiderin depo-sition presented (HE. × 100).

Figure 9

Microscopic appearance of “plenic carnification”of the normal viable splenic tissue distant form ablative lesion at the end of 9^th week after RFA, the tissue structure consolidated, larger vessels occluded, extensive fibrous protein deposited, and the congestive splenic sinusoid disappeared; however, the struc-ture of splenic lymphoid nodule was intact (arrow) (HE. × 40).

Figure 10

The typical appearance of poorly vascularized splenic tissue due to “plenic carnification” after RFA. The splenic sinusoid disappeared, tissue structure consolidated, granular hemosiderin deposition and sparsely neovascularized vessels (arrow) presented clearly (HE. × 200).