Dear mirajb, as I know there are no colonic irrigations/hydrotherapies available in Doha due to national rules and regulations.
But a good alternative is a detoxification that is available in many resorts throughout the world, or in Doha at the six senses spa http://www.sixsenses.com/six-senses-spas/Sharq-Village/index.php

Has a very similar effect on your body, feels more comfortable - just takes a little bit longer than the colonic irrigation.