A medical apparatus (100) for dilating a narrowed or blocked opening (A) of a subject, the medical apparatus (100) comprising: a guiding tube (201)； a dilator system tube (202) guidable inside the guiding tube (201). The dilator system tube (202) includes a near end (202a) and a far end (202b), said far end (202b) is configured with a dilating element (204) and a retention element (203), configured adjacent to the dilating element (204), wherein the retention element (203) is expanded inside the subject to identify the cavity (C). The dilator system tube (202) is retractable for anchoring the dilator system tube (202) by the expanded retention element (203) inside the cavity (C), to position the dilating element (204) at the narrowed or blocked opening (A) for dilating the narrowed or blocked opening (A) upon expanding the dilating element (204).
