He then spent the 1820s in Paris, a student of surgery under Jean Civiale, Guillaume Dupuytren and Charles Louis Stanislas Heurteloup.
He wrote journal articles, and lectured in the transient Brewer Street medical school, with John Epps and Michael Ryan.
[2] Costello edited the Cyclopædia of Practical Surgery, including a copious bibliography; of which 12 parts were published in London, 1841–3.
Contributors included Walter Hayle Walshe, and John Gay who wrote on "cleft palate".
[2][3][4] In his Paris years, Costello was able to complete the work in four volumes (1861), using his own English translations of articles by French surgeons.