Symfony2 is refreshing a twigs block with ajax possible?

Lets say I have a block in my layout:

{% block sidebar %} {% render url( 'sidebar' ) %} {% endblock %}

Is it possible to refresh the block with ajax without making a div around it? In my example I cant make a div, because it crashes my whole template so I need to know is that even possible?

For example I can refresh a div like this(.test is the class of the table):

$('.test').load(" .test");

Can I make something like this to refresh the block?

$('sidebar').load(" sidebar");

Any ideas?