How do I get the size of a Service Broker Queue quickly when the table is >500k rows?

I'm trying to determine the total size of a Service Broker Queue and transmission queue when the queue is very large. The problem is traditional querys like the ones below don't work since it's not a table. Any ideas?

EXEC sp_spaceused 'sys.transmissio开发者_运维知识库n_queue'
SELECT rows FROM sysindexes WHERE id = OBJECT_ID('ConfigMgrDrsQueue') AND indid < 2  

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Remus explains explains how to do it in his blog. Basically you need to query the row count of the underlying b-tree.