This is the first report of B-RTO using CARTO-II for an ascending colonic varix. B-RTO has been performed for various ectopic varices, such as duodenal, stomal, and small intestinal varices, as well as colonic varices (Watanabe et al. 2010). There have been only two reports of B-RTO for an ascending colonic varix (Matsumoto et al. 2018; Liu et al. 2020). In these reports, conventional B-RTO was performed via the right renal vein. Similarly, in the present case, the varix was also located at the ascending colon, and B-RTO was performed via the same route. The present report reconfirmed the importance of B-RTO for ascending colonic varices by demonstrating no recurrence or complications during long-term follow-up. Furthermore, this report showed that CARTO-II procedure could be also applied for ascending colonic varices.
The physiological normal connections between the portal and the systemic veins have been known to portosystemic anastomoses. The recanalization of these embryonic channels results from portal hypertension, which causes an inflow from the high-pressure portal system to low-pressure venous systems (Sharma and Rameshbabu 2012). The venous blood from the right colon drains into the right gonadal, right renal, and right lumbar veins as draining veins (Sharma and Rameshbabu 2012). The feeding veins flowing into the right colon are the ileocolic, right colic, and middle colic veins. In the present case, the draining vein was the right renal vein and the feeder vein was the ileocolic vein.
Recently, modified versions of B-RTO have been developed, such as CARTO and plug-assisted retrograde transvenous obliteration (PARTO) (Lee et al. 2014; Gwon et al. 2013). CARTO procedure has two subtypes: CARTO or CARTO-I, and CARTO-II (Kim et al. 2018; Yamamoto et al. 2020). In CARTO, coil embolization of the draining vein is performed first, prior to injection of sclerosant, without balloon occlusion, whereas in CARTO-II, coil embolization of the draining vein is performed after injection of sclerosant under balloon occlusion. The balloon catheter is finally deflated and removed after the procedure in CARTO-II (Yamamoto et al. 2020). A recent study of CARTO-II demonstrated that this modified technique has two advantages compared to the original CARTO: keeping cost down and saving time (Yamamoto et al. 2020). One advantage derives from the use of a smaller number of coils than CARTO, the other from the lack of any need to wait for complete occlusion before injecting sclerosants. In the present case, only two microcoils were used to embolize the draining vein, and it took less than 2 h to complete the procedure using CARTO-II. With respect to the number of coils used and the procedure length, this case was similar to the previous study of CARTO-II (Yamamoto et al. 2020). Figure 2a shows that the draining vein was very tortuous and long to reach near the varix. PARTO would be difficult for treating the ascending colonic varix due to the difficulty of delivering a plug through the tortuous vein (Kim et al. 2018). CARTO-II procedure might be applied for other ectopic varices with tortuous veins, including ascending colonic varices. From an anatomical viewpoint, B-RTO using CARTO-II would be effective for ascending colonic varices.
BRTO using N-butyl-2-cyanoacrylate (NBCA) is one of the treatment options for varix therapy (Nakai et al. 2018). NBCA is a liquid sclerosing agent that polymerizes immediately on contact with anions in the blood (Nakai et al. 2018). Injection of a mixture of NBCA is more difficult than that of EOI, because NBCA causes adherence of the balloon catheter, microcatheter, and the blood vessel wall (Okahara et al. 2012). In this regard, the use of NBCA for BRTO requires considerable technical skill and experience.
An endoscope may not always reach the ascending colon due to its anatomical location (Hitoshi and Fukuji 1989). In the case of lower gastrointestinal bleeding, colonoscopy is ineffective because of poor visibility (Lopes et al. 2006). When the endoscope does not reach the ascending colonic varix, B-RTO using CARTO-II might be an alternative treatment.
In conclusion, this successful case suggests that B-RTO using CARTO-II can be one of the effective treatment techniques for ascending colonic varices.