Getting metadata to show in widget

Hi,

It is my first time creating a widget. The widget shows X’s number of post from a selected category (which works fine), but It needs also to show a metadata value that I have created. Is this possible to do? My question is because it does not show. I am using the following:

$loop = new WP_Query ( 'cat='.$catid.'&showposts='.$numberposts.'' );
  while ( $loop->have_posts() ): $loop->the_post();
		$do_not_duplicate = $post->ID;
			 echo '<li>';
			 echo '<h2><a href="'.get_permalink($post->ID).'">'.get_the_title($post->ID).'</a></h2>';
			 echo '<span class="publish_by">by';
			 echo get_post_meta($post->ID, 'author_source', true);
			 echo '</span>';
			 cidd_excerpt('cidd_excerptlength_widget', 'cidd_excerptmore');
  			 echo '<div class="clear"></div>';
             echo '</li>';				 

  endwhile;
  wp_reset_query();
  echo '</ul></div>';
  echo '</div></li>';

Any advice is welcome. Thank you in advance for the time given.