I would like to explore this issue with you in greater detail. The web site at the following link emphasizes that very little published research deals with controlled studies of the benefits and risks of colon hydrotherapy and enemas.
Schmelzer et al. point out that both tapwater and soapsuds enemas have been given routinely for over 100 years, but that little is known about their effectiveness, the precise indications for their use, or their side effects.
As Schmelzer et al. describe it, the ideal enema would effectively cleanse the colon with minimal side effects, essentially the same as the goal of the colonic irrigation. Enemas, like colonics, cleanse the colon by stimulating propulsion and secretion. The relevant factors include enema volume, the presence of chemical irritants, and the osmolality or tonicity of the solution. The instillation of a large fluid volume into the colon stimulates propulsion; this is especially relevant to colonic irrigations which typically use pure tap water with a larger fluid volume than enemas. Chemical irritants stimulate both propulsion and secretion to rapidly empty the colon; using a hypertonic solution to draw fluid from the body into the colon through osmosis, and directly irritating the mucosa are the principles of the popular Fleets sodium phosphate enema. Soapsuds enemas use the principles of high volume and chemical irritation.
Schmelzer et al. (2000) found that soapsuds enemas produced significantly greater output than tap water and were equally well tolerated. Most subjects who received tap water enemas retained more fluid than was eliminated. Based on these findings, they advised that nurses should use caution when giving repeated enemas to patients sensitive to large fluid loads. This is relevant to the question of the fluid load resulting from a colonic irrigation, in which a larger volume of water is used than in the typical enema.