category ids for a product

I'm trying to get the category ids for products using nlapiSearchRecord('item', null, filters, columns) where filters and columns are both arrays.  I am able to get most of the product data just fine, so there is nothing wrong with my call.

I get duplicate records when there is more than one category assigned to a product.  I assume this is just how multiple values are handled.

My question is this.  Is there a column for category id?  If not, is there some other call I should be doing to get this?

Thanks,
Tyler