childhood constipation is a common complaint accounting for 3% of visits to pediatricians and 10 - 25% of visits to pediatric gastroenterologist[13 ] . commonly there is no underlying organic cause and the constipation is indentified as functional or idiopathic[4 , 5 ] . functional constipation is identified by rome iii criteria in children over 4 years old and adolescents having two months of at least 2 or more of the following conditions : 2 defecations in the toilet per week , 1 episode of fecal incontinence per week , history of retentive posturing or excessive volitional stool retention , history of painful or hard bowel movements , presence of a large fecal mass in the rectum , history of large diameter stools that may obstruct the toilet . children usually are treated with a combination of toilet training , running a bowel diary , and oral laxatives such as paraffin oil . in many patients there are many articles on the efficacy of probiotics in organic and functional gastrointestinal disorders . probiotics are live microbial food ingredients which are reported to be effective in the treatment of many forms of gastrointestinal disorders[812 ] . prebiotic is a selectively fermented ingredient that changes the composition and/or activity of the intestinal microflora and has shown beneficial effects in host 's health . , we aimed to determine the therapeutic effect of synbiotics ( combination of probiotics containing strains of l. casei , l. rhamnosus , s. thermophilus , b. breve , l. acidophilus , b. infantis , and fructooligo - saccharide as prebiotic ) on childhood constipation . the study was performed at children 's medical center in tehran , iran , from january to december 2009 . children with constipation were referred to the pediatric gastroenterology clinic for evaluation and treatment of constipation . one - hundred two children aged 412 years with chronic functional constipation enrolled in this study , were divided into 3 groups by simple randomization method . exclusion criteria were organic causes for constipation such as hirschsprung 's disease , spina bifida occulta , hypothyroidism , cystic fibrosis , neurologic abnormalities and intestinal pseudo - obstruction . these patients were excluded from the study by history and physical examination and rome iii criteria of childhood constipation . the research protocol was approved by the medical ethics committee of tehran university of medical sciences . label of drugs was replaced by a new label indicating drug a or b. contents of sachets or bottles were not known to the physicians or nurses involved in the study . group a received 1.5 ml / kg / day oral liquid paraffin plus placebo , group b received 1 sachet synbiotic per day ( restore 1x10 cfu/1 sachet , protexin co , uk ) . synbiotic combination consisted of probiotic strains containing l. casei , l. rhamnosus , s. thermophilus , b. breve , l. acidophilus , b. infantis , fructooligosaccharide as prebiotic , and placebo . group c received 1.5 ml / kg / day oral liquid paraffin and 1 sachet synbiotic per day . all patients in the 3 groups received drugs in bottles and sachets with similar shape , taste and color . frequency of bms , stool consistency , number of fecal incontinence , episodes of abdominal pain , painful defecation per week and side effects were determined in each patient before and after treatment . success treatment was defined as 3 bms per week , 2 incontinence per month and no abdominal pain . study design : from seven days prior to study and during the treatment period all children were requested to record frequency of bms , number of fecal incontinence episodes , stool consistency , abdominal pain , painful defecation and effects such as vomiting , diarrhea and oil seepage in a bowel diary . before starting treatment , all children were examined and patients with fecal impaction received rectal enema ( paraffin oil 1530ml / year ) once daily for three days in order to accomplish rectal disimpaction . toilet training consisted of sitting on the toilet 3 times per day for 5 minutes after each meal . patients were not allowed to use any other kind of medication for constipation during the study period . clinical efficacy was recorded , patients were seen at the end of 4 weeks , and their charts were reviewed . outcome measures : primary outcome measures were frequency of bms per week , stool consistency , fecal incontinence episodes per week , presence of abdominal pain , and painful defecation ; secondary outcomes were success treatment and incidence of adverse effects such as vomiting , diarrhea and seepage . stool consistency was rated by the patients as hard , normal or watery . statistical analysis : data of baseline information were analyzed with the spss ( ver . continuous variables were expressed as mean ( sd ) , and categorical data were shown as frequency and percent . number of bms and fecal incontinence episodes in baseline information were analyzed by kruskal - wallis test . change of frequency of bms and fecal incontinence episodes were analyzed by non - parametric paired wilcoxon test . for assessment changes of stool consistency and abdominal pain between baseline and after treatment , the mcnemar test was used . totally , 102 children ( aged 412 years ) with chronic functional constipation enrolled in this study and were divided into 3 groups . five patients were lost to follow - up and remaining 97 patients consisted of 47.4% males and 52.6% females with a mean age of 6.32.1 years . as shown in table 1 , no significant differences were found with respect to demographic data and recorded baseline characteristics between the three treatment groups . characteristics of the patients and the main outcomes are summarized in table 1 and 2 . as shown in table 2 , the frequency of bms per week increased in all groups , the highest rise occurring in group c ( p=0.03 ) . improvement in stool consistency and decrease in number of fecal incontinence episodes happened in all groups ( p=0.2 , p=0.3 respectively ) without any statistically significant difference . also , abdominal pain and painful defecation per week decreased ( p=0.6 , p=0.9 respectively ) similarly and there was no statistically significant difference between groups . no side effects were reported in group b but in group a 18 patients and in group c 21 patients had seepage ( p<0.001 ) . treatment success in group a was 24/29 ( 82.8% ) , in group b 22/31 ( 71.0% ) and in group c 28/37 ( 75.7% ) without statistically significant difference between them ( p=0.6 ) . new investigations have shown that gut bacterial colonization has an important role in health and disease . there are several hypotheses about the effectiveness of this microbial flora in treatment of constipation . according to some investigations gut microbial flora in chronic constipation is different from that in healthy persons[17 , 18 ] . short chain fatty acids produced by probiotics reduce colon ph and by this mechanism enhance colon motility and finally transit time will decrease . there are a few rcts about probiotics in the treatment of constipation in children . in rcts study by banaszkiewicz and szajewska it was concluded that l. rhamnosus 
 gg was not an effective adjunct to lactulose in treating constipation in children . bu et al evaluated the effect of l. casei rhamnosus 
 lcr35 compared to magnesium oxide(mg0).comparisons of the frequency of defecation , consistency of stool and the use of lactulose or enema during the period of treatment were made among the groups . the patients who received mgo or probiotics had a higher defecation frequency , percentage of treatment success ( defined as 3 spontaneous defecations per week with no episodes of fecal soiling ) and less hard stool . there is no statistically significant difference in efficacy between mgo and lcr35 , but less abdominal pain occurred when using lcr35 . in a study by coccorullo et al the beneficial effects of l. reuteri ( dsm 17938 ) in infants with functional chronic constipation was evaluated . administration of l. reuteri had a positive effect on bowel frequency , even when there was no improvement in stool consistency and episodes of inconsolable crying episodes . for example , in children with constipation defined according to the rome iii criteria , administration of bifidobacteria ( b. bifidum , b. infantis , b. longum ) and lactobacilli ( l. casei , l. plantarum , l. rhamnosus ) to 20 children aged 416 years resulted in an increased frequency of bowel movements , a decreased number of fecal incontinence episodes , and reduced abdominal pain , although there was no change in stool consistency . it seems that our study is the first rct study which investigates the synbiotics effects in childhood constipation . according to our study , mixtures of different strains of probiotics and their specialized prebiotics are more effective than each of them alone and this combination augments their efficacy in all parameters of study , but in previous researches improvement had been seen only in some of symptoms and signs . also adjunctive therapy of synbiotic and liquid paraffin could be more effective to improve bms than any of them alone . according to this rct , synbiotic have got beneficial effects on symptoms of childhood constipation similar to liquid paraffin without any side effects and synbiotic is an effective adjunct to liquid paraffin to improve bms .
objectiveconstipation is a common problem in children . 
 there is some clinical evidence for the role of probiotics and prebiotics in the treatment of constipated children . 
 this is the first study on the therapeutic effect of synbiotics ( combination of probiotics and prebiotic ) in treatment of childhood constipation.methodsin a double - blind randomized placebo controlled study 102 children aged 412 years with functional constipation were assessed according to rome iii criteria for 4 weeks . 
 they were divided into 3 groups : group a , received 1.5 ml / kg / day oral liquid paraffin plus placebo , group b , 1 sachet synbiotic per day plus placebo and group c , 1.5 ml / kg / day oral liquid paraffin plus 1 sachet synbiotic per day . 
 frequency of bowel movements ( bms ) , stool consistency , number of fecal incontinence episodes , abdominal pain , painful defecation per week , success of treatment and side effects were determined in each group before and after treatment.findingsthe frequency of bms per week increased in all groups ( p<0.001 ) , but it differed between groups and was higher in group c ( p=0.03 ) . 
 stool consistency increased and number of fecal incontinence episodes , abdominal pain and painful defecation per week decreased in all groups similarly and there was statistically no difference between them . 
 no side effects were reported in group b ; the main side effect in group a and c was seepage of oil ( p<0.001 ) . 
 treatment success was similar in all groups without any significant difference between them ( p=0.6).conclusionthis study showed that synbiotics have positive effects on symptoms of childhood constipation without any side effects .