Name can be omiitted from ->dbforge->modify_column()'s 2nd param if you aren't changing the name.
diff --git a/user_guide/database/forge.html b/user_guide/database/forge.html
index 28b32d9..b9e0442 100644
--- a/user_guide/database/forge.html
+++ b/user_guide/database/forge.html
@@ -205,7 +205,7 @@
<p>Used to remove a column from a table. </p>
<p><code>$this->dbforge->drop_column('table_name', 'column_to_drop');</code></p>
<h2>$this->dbforge->modify_column()</h2>
-<p>The usage of this function is identical to add_column(), except it alters an existing column rather than adding a new one. In order to use it you must add a "name" key into the field defining array.</p>
+<p>The usage of this function is identical to add_column(), except it alters an existing column rather than adding a new one. In order to change the name you can add a "name" key into the field defining array.</p>
<p><code>$fields = array(<br />
'old_name' => array(<br />
'name' => 'new_name',<br />