double - balloon enteroscopy ( dbe ) , first described by yamamoto et al 1 , allows examination of the small intestine , and retrograde dbe ( rdbe ) permits access to the distal small intestine .
mehdizadeh et al 2 found a 79  % success rate , defining success as intubation of the ic valve , in their review .
may et al 3 , however , failed to reach the terminal ileum ( ti ) in 7  % of patients while ell et al 4 and heine et al 5 reported 14  % and 58  % failure rates , respectively .
the highest success rate was achieved by the group with the most experience , yamamoto et al 6 , who successfully intubated the ic valve in all of their 89 patients who underwent rdbe .  
mehidizadeh et al 7 found no significant improvement in the endoscopist s performance with increased experience , and found only a significant decline in overall procedure and fluoroscopy times . while dbe has been shown to facilitate difficult colonoscopies 8 , we noted that performing a pre - dbe colonoscopy using a pediatric colonoscope improved rdbe ic intubation rates .
the rationale for such a procedure is that conventional colonoscopy is quick and the more rigid colonoscope facilitates the initial ic valve intubation .
we therefore examined the ic intubation rates , procedure duration , and maximal depth of enteroscope insertion among those patients who received a pre - colonoscopy followed by rdbe and compared the results with those who received a conventional rdbe .
this study was approved by the institution s committee for the protection of human subjects in research .
a computer program randomly chose 45 patients from a pool of all patients who underwent rdbe procedures during 2011    2013 . 
all procedures were performed by either of two experienced endoscopists , who had both performed approximately 50 rdbes prior to the study period , and a gastroenterology fellow .
consent was obtained for all procedures and all patients underwent a bowel - cleansing regimen consisting of four liters of polyethylene glycol and overnight fasting . the fujinon double - balloon enteroscopy system ( fujinon en-450t5 enteroscope ; jujifilm medical systems , wayne , new jersey , usa ) was used in all procedures and the pediatric colonoscope ( olympus pcf 160 or 180 ; olympus america , inc . , melville , new york , usa ) was utilized in those procedures involving a pre - rdbe colonoscopy .
sedation was achieved by either conscious sedation with fentanyl and midazolam or with general anesthesia at the discretion of the endoscopist in conjunction with the anesthesiologist , depending on the cardiovascular and respiratory status of the patient .   in patients who received a pre - rdbe colonoscopy ,
the colonoscope allowed easy cleaning of the cecum , and dilation and orientation of the ileo - cecal ( ic ) valve . after advancing approximately 20  cm into the ileum , which took 5    15 minutes , the colonoscope was removed and the standard rdbe method was followed as described by yamamoto et al 1 .
deeper intubation of the ileum by colonoscopy or by rdbe was facilitated by placing the patient supine .
stability of enteroscope intubation was deemed as reaching 15    20  cm proximal to the ic valve .
the duration of the procedure was defined as the time of endoscope insertion ( including the pre - rdbe colonoscope ) to the time of removal of the enteroscope .
the maximal depth of insertion was defined as the distance encompassed by the enteroscope until advancement was no longer possible .
demographic data , including age , gender , height , weight , indications for rdbe , sedation method , procedure duration , interventions , and immediate adverse effects were electronically documented at the time of the procedure .
the mean , standard deviation ( sd ) , and range were calculated for the continuous data obtained for each patient .
comparisons between the two groups were carried out using the mann - whitney u test . a p value of  <  0.05 was considered to be statistically significant .
the mean , standard deviation ( sd ) , and range were calculated for the continuous data obtained for each patient .
comparisons between the two groups were carried out using the mann - whitney u test . a p value of  <  0.05 was considered to be statistically significant .
twenty - three of the patients were women ( 51.1  % ) and twenty - two of them were men ( 48.9  % ) .
the mean ( sd ) patient age was 59.7 ( 16.0 ) years ( range 22    84 ) .
the mean ( sd ) patient body mass index ( bmi ) was 30.1 ( 7.33 ) kg / m(range 16.2    52.4 ) and 12 of 45 patients ( 26.7  % ) had a bmi over 30 . 
the main indications for the procedure were occult gastrointestinal bleeding ( 50  % ) , masses ( 26  % ) , video capsule endoscopies with abnormal findings ( 11  % ) , and iron - deficiency anemia ( 8  % ) .
in comparing the results of the group that received the pre - rdbe colonoscopy with those of the group that received the traditional method , the only statistically significant difference was within the gender .
the group that underwent the novel procedure had fifteen men and eight women , while the group that underwent the traditional procedure had seven men and fifteen women ( p  <  0.0004 ) .  
the pre - rdbe colonoscopy method was used in 23 patients ( 51.1  % ) and the standard dbe method was used in 22 patients ( 48.9  % ) . among the patients who received the pre - rdbe colonoscopy , successful , stable intubation of the ic valve
was achieved in all 23 patients ( 100  % ) , compared to only 16  /22 ( 72.7  % ) of those who underwent the traditional procedure ( p  <  0.003 ) .
the mean ( sd ) of maximal depth of insertion was 78.2 ( 18.1 ) cm and 67.2 ( 17.1 ) cm in the novel procedure group and the traditional procedure group , respectively , which were not significantly different ( p  <  0.65 ) .
in addition , the mean ( sd ) for the duration of the procedure in the novel and the traditional procedure groups were 81.6 ( 8.9 ) minutes and 95 ( 13.2 ) minutes , respectively . these results were not significantly different ( p  <  0.53 ) .
successful diagnosis and intervention ( identification and treatment of bleeding source or lesion ) was performed in 13  /23 ( 56.5  % ) in the novel procedure group and 7  /22 ( 32  % ) in the traditional procedure group , and these results were not significantly different ( p  <  0.09 ) .
the novel procedure group and the traditional procedure group had 3  /23 patients ( 13.0  % ) and 3  /22 patients ( 13.6  % ) with poor bowel preparation , respectively .
the two endoscopists performed 25 and 20 rdbes , and the failure rates when they used the traditional method were 3  /13 ( 23.1  % ) and 3  /9 ( 33.3  % ) , respectively ( p  <  0.01 ) .
intubation rates for men ( 90.9  % ) and women ( 82.6  % ) were not significantly different ( p  <  0.41 ) .
twenty - three of the patients were women ( 51.1  % ) and twenty - two of them were men ( 48.9  % ) .
the mean ( sd ) patient age was 59.7 ( 16.0 ) years ( range 22    84 ) .
the mean ( sd ) patient body mass index ( bmi ) was 30.1 ( 7.33 ) kg / m(range 16.2    52.4 ) and 12 of 45 patients ( 26.7  % ) had a bmi over 30 . 
the main indications for the procedure were occult gastrointestinal bleeding ( 50  % ) , masses ( 26  % ) , video capsule endoscopies with abnormal findings ( 11  % ) , and iron - deficiency anemia ( 8  % ) .
in comparing the results of the group that received the pre - rdbe colonoscopy with those of the group that received the traditional method , the only statistically significant difference was within the gender .
the group that underwent the novel procedure had fifteen men and eight women , while the group that underwent the traditional procedure had seven men and fifteen women ( p  <  0.0004 ) .
the pre - rdbe colonoscopy method was used in 23 patients ( 51.1  % ) and the standard dbe method was used in 22 patients ( 48.9  % ) . among the patients who received the pre - rdbe colonoscopy , successful , stable intubation of the ic valve
was achieved in all 23 patients ( 100  % ) , compared to only 16  /22 ( 72.7  % ) of those who underwent the traditional procedure ( p  <  0.003 ) .
the mean ( sd ) of maximal depth of insertion was 78.2 ( 18.1 ) cm and 67.2 ( 17.1 ) cm in the novel procedure group and the traditional procedure group , respectively , which were not significantly different ( p  <  0.65 ) .
in addition , the mean ( sd ) for the duration of the procedure in the novel and the traditional procedure groups were 81.6 ( 8.9 ) minutes and 95 ( 13.2 ) minutes , respectively . these results were not significantly different ( p  <  0.53 ) .
successful diagnosis and intervention ( identification and treatment of bleeding source or lesion ) was performed in 13  /23 ( 56.5  % ) in the novel procedure group and 7  /22 ( 32  % ) in the traditional procedure group , and these results were not significantly different ( p  <  0.09 ) .
the novel procedure group and the traditional procedure group had 3  /23 patients ( 13.0  % ) and 3  /22 patients ( 13.6  % ) with poor bowel preparation , respectively .
the two endoscopists performed 25 and 20 rdbes , and the failure rates when they used the traditional method were 3  /13 ( 23.1  % ) and 3  /9 ( 33.3  % ) , respectively ( p  <  0.01 ) .
intubation rates for men ( 90.9  % ) and women ( 82.6  % ) were not significantly different ( p  <  0.41 ) .
retrograde dbe poses a technical challenge to the endoscopist and requires a significant learning curve 7 .
thorough and consistent training under thoughtful mentorship is crucial to not only intubate the ic valve , but also to avoid non - spiral looping and enteroscope withdrawal upon engagement of the ileum .
consistent with this challenge , various groups have reported unsuccessful ic valve intubation rates ranging from 7  %    58  % .
the difficulty in successful intubation occurs when the valve orifice can not be oriented appropriately or the valve itself can not be intubated 10 . by performing a pre - rdbe colonoscopy , which is usually a quick procedure , the more rigid pediatric colonoscope allowed for easier intubation by dilating and orienting the valve to later facilitate ic intubation with the more flexible dbe .
in addition , although not quantified , using the colonoscope allowed easier cleaning of the residual luminal contents from the cecum due to its suction channel , which is larger than that of the dbe .
rapid withdrawal of the colonoscope left a straightened colon that facilitated rapid insertion of the dbe .  
retrograde dbe utilizing this novel method of performing a colonoscopy before the rdbe had a significantly higher ic intubation success rate , compared to rdbes using the traditional method . within the traditional method group , a similar success rate to that of the mehdizadeh et al 2 group was found ( 72.7  % vs 79  % ) .
however , with the novel method , we achieved successful intubation in 100  % of our patients . while not statistically significant , the mean procedure time was shorter on average , despite the additional colonoscopy .  
the main limitation of this study is that it is a small , retrospective , single - center study .
multi - center prospective studies are needed to compare the results of this novel method with those obtained with the traditional method .
the gender disparity between the two groups does present a potential confounding variable ; there were fifteen women in the traditional procedure group and only eight women in the novel procedure group . 
alternative techniques to improve ic valve intubation have been described , including a study by ross et al 11 in which a balloon was inflated over a guidewire passed through the ic valve , and despott et al 10 in which the enteroscope balloon was inflated in the ti while the enteroscope and overtube were pulled back to straighten the ileo - colonic angle .
the study reported herein offers another option the endoscopist may use when confronted with a difficult rdbe intubation .
 
 background and study aims : retrograde double - balloon enteroscopy ( rdbe ) has a high failure rate due to difficulty intubating the ileo - cecal ( ic ) valve . 
 we examined the utility of a pre - rdbe colonoscopy using a pediatric colonoscope to clean the cecum and perform an initial intubation of the ic valve . 
 
 patients and methods : this study is a retrospective review of rdbe procedures for 45 patients at a single tertiary - care center to examine the success of ic intubation , maximal depth of enteroscope insertion , and duration of the procedure . 
 
 results : the ic intubation success rate among patients who underwent rdbe using this novel method was 100  % as compared to 72.7  % using the traditional method ( p  <  0.003 ) . 
 
 conclusions : rdbe preceded by colonoscopy had a significantly higher ic intubation success rate , compared to rdbes performed using the traditional method . 
 results support the use of this novel method when ic valve intubation using standard methods is difficult , and it may limit the need for repeat procedures or the use of other modalities for examining the small bowel . 