The beneficial effect of colonic or rectal irrigation on neurogenic or congenital defecation disorders is well known, and functional constipation and diarrhea have also been shown to benefit from rectal irrigation . Even though the exact mechanism underlying the response of IBS to colonic irrigation is not known, our results demonstrate its potential benefit as an IBS treatment modality. A recent animal study by Zhang et al.  recognized methylglyoxal as an important cause of IBS symptoms. This bacterial product of anaerobic glycolysis in the large intestine elicits symptoms such as arrhythmia, headache, and diarrhea. Activation of NMDA receptors by methylglyoxol promotes visceral hypersensitivity, resulting in increased 5HT secretion and peristalsis contributing to diarrhea. Visceral hypersensitivity reduces the threshold to noxious stimuli and bowel distension, providing a reasonable explanation for abdominal pain [15, 16], the major feature of IBS. We deduced that methylglyoxol and perhaps other metabolites could be washed out by water irrigation, and reverse visceral hypersensitivity. Zhang’s study may serve to renew interest in the concept “body detoxification” by colonic irrigation, which is at present not well accepted by the medical professions .
Almost all participants with IBS-C experienced more than one additional BM per week than before treatment. Colonic irrigation also improved the stool consistency in most participants, whether this was for hard, lumpy stool in IBS-C or loose, watery stool in IBS-D patients. The results demonstrate colonic irrigation is effective in improving IBS-related constipation and diarrhea.
The influence of treatment duration on efficacy was investigated by dividing the treatment into 1- to 4-week courses. Abdominal pain, satisfaction with BM, and distress/discomfort due to symptoms were improved after initiation of colonic irrigation. This improvement was maintained throughout the treatment phase and even up to the post-treatment phase in every subgroup (data not shown). The treatment effects seemed to be independent of the treatment duration, but our short-term data are not adequate to support this conclusion.
Safety is always the greatest concern with bowel irrigation therapy, and rectal perforations and sepsis are not uncommon. Such complications have been attributed to malpractice by patients and non-medical personnel [18–21]. However, the estimated rate of bowel perforation resulting from transanal irrigation is low, with a reported rate of <0.002 % [5, 7]. A well-devised treatment protocol used by experienced practitioners might reduce the risk of bowel perforation [20, 21]. Conversely, undiscovered conditions such as stercoral ulcer  or tumors could increase the risk of perforation. In this study, we provided complete colonic evaluations and detailed instructions for the treatment. Our patients experienced only mild adverse events such as sensation of abdominal fullness, weakness, and anal pain which did not necessitate either discontinuation of treatment or medical intervention.
A series of 36 cases of amebiasis cross-infection with 10 colectomies, in which 6 patients at a chiropractic clinic in Western Colorado died, was previously reported . The outbreak led to the use of disposable, single-use parts of colonic irrigation devices , and patient-specific colonic irrigation system for defecation disorders are necessary to prevent cross-contamination.
Eight liters of water was required for a complete 1-day treatment, and water intoxication is an important safety concern in colonic irrigation. However, no neurological symptoms or altered serum biochemistry parameters, such as hyponatremia were observed in this study. In addition, since patients were allowed to defecate at any time during irrigation, the amount of water absorption via the colonic mucosa was very small. Lower than normal limit basal serum GOT, GPT, γGT, and BUN levels were observed in about 45 % of the participants, suggesting these could be clinical signs of IBS. Moreover, colonic irrigation did not cause impairment in blood serum biochemistry or electrolyte imbalance. Chronic consumption of alcohol appeared to account for the only candidate with impaired basal and post-treatment GOT and GPT levels. Sacral nerve stimulation and the Malone antegrade continence enema procedure have been shown to be effective in patients with unremitting constipation and defecation disorders, improving QoL [23–26]. However, those are invasive procedures that come with a risk of surgical complications. Rectal or colonic irrigation is considered to be less invasive and effective as well [7, 8]. Irrigation treatment should be considered as the treatment of choice prior to surgical interventions [4, 13]. The concept behind ACIA is no different from that behind the ordinary colonic irrigation sets [4, 7–9], but ACIA is simpler and more convenient.
Our results demonstrated that colonic irrigation with ACIA can be effective for IBS treatment. The improvement of abdominal pain, satisfaction with BM, and distress/discomfort due to symptoms indicated there was good relief of IBS-related problems and the patients were satisfied with the treatment. However, a placebo effect  should be taken into consideration. The positive effects on BM frequency and stool consistency are encouraging, and those are objectively measurable. QoL is always an important parameter for the effectiveness evaluation of IBS treatment. In this study, we focused on the feasibility of colonic irrigation on IBS treatment and QoL evaluation is therefore lacking.
The limitations of this study are the small sample size and short follow-up time.