You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
endoscopic internal drainage ( eid ) has been recently introduced for treatment of leaks and fistulas following bariatric surgery .
eid may be applied both as first - line treatment and as rescue therapy 1 
 2 .
fistulas following gastrointestinal surgery both for benign and malign pathologies remain a major clinical problem .
such complications account for significant morbidity and a mortality rate that can reach 60  % if treatment is delayed 3 . here
we report our experience with eid as first - line treatment of fistula following different types of gastrointestinal surgery . to our knowledge , this is the first case series in which eid has been used systematically for fistulas following both upper and lower gastrointestinal surgery .
from march 2013 to november 2015 , 11 patients were treated at our endoscopic tertiary center for fistula following gastrointestinal surgery .
the conditions with which these patients were diagnosed and procedures that they had undergone are as follow : four duodenal fistulas ( biliopancreatic surgery ) , two colic fistulas ( colorectal surgery ) , and five esophagogastric - jejunal fistulas ( foregut surgery ) .
all patients were referred to our endoscopy department by the surgical team performing the surgical procedure .
delay between first surgery and eid averaged 14 days ( range 3    60 ) .
all patients presented either clinical evidence of sepsis ( leukocytosis , fever , elevation on polymerase chain reaction ) or output of enteric fluid from the drainage or medium contrast extravasation at swallow study / pelvic computed tomography scans .
opacification of fistula was always performed during endoscopic examination in order to evaluate the fistula opening , the collection , its shape and size .
endoscopic evaluation was of paramount importance to correctly decide the appropriate diameter and length of pigtail stent and its number .  
as shown in video 1 , whenever feasible , we explored the cavity with the endoscope to clean and to perform necrosectomy ( as reported by lemmers et al.4 ) if necessary .
a duodenoscope or colonoscope was used because of the larger operative channel if a 10 fr pigtail stent was needed .
we believe the key to success for treatment of gastrointestinal fistulas is to accomplish complete internal drainage of any collection and to induce granulation tissue formation by reaction to pigtail , considered as a foreign body , in order to promote healing .  

video 1 endoscopic inspection of an esophago - jejunal anastomotic dehiscence of half the circumference with a concomitant mediastinal collection .  
to simultaneously achieve both aforementioned goals , a tandem catheter ( boston scientific , massachusetts , boston , usa ) was used to cannulate the defect and after guidewire insertion , one or more double pigtail stents ( advanix boston scientific , massachusetts - boston - usa or visio g - flex europe , nivelles - belgium ) were deployed ( video 2 ) . as a general rule ,
if an external drainage is present ( surgical or radiological ) the goal of eid is to reverse the drainage direction in order to remove early external drain , so a short stent usually is sufficient if no external drainage is present ; one or two longer stents must be deployed to achieve complete cavity drainage . 

video 2 endoscopic internal drainage with deployment of two double pigtail stents to treat an anastomotic dehsicence following total gastrectomy .   in five of 11 patients a jejunal feeding tube was left in place .
systematic control was performed at 4 to 6 weeks in order to evaluate the evolution of the collection and to modify stent size according to the reduction of the cavity .
a check endoscopy is important not only to evaluate treatment progression in order to adapt internal drainage , but also to promote healing by inducing trauma in the pseudocavity with the exchange of the double pigtail stents .
after the first check endoscopy , oral diet resumption was allowed in four of five patients .
technical success was defined by achievement of all the following steps : visualization of fistula orifice , opacification of fistula and collection , selective catheterization , and deployment of the double pigtail stent .
technical success was achieved in all patients ( 100  % ) . however , the day after the procedure , one patient presented with a perforation .
this complication was not detected during the procedure and emergency surgery was required for esophago - jejunal anastomosis fistula .
clinical success was defined as follows : no signs of sepsis after oral diet resumption , no extravasation of medium contrast at follow - up procedures ( endoscopy , ct scan , barium enema ) and absence of enteral liquid output from the external drainage / fistula tract .  
seven patients were found to be healed at first check endoscopy after an average of 35.6 days of treatment ( range 28    58 ) ( fig . 
1 ) ; one patient was healed at the second check ( 60 days ) and the last patient was healed after three endoscopic sessions ( 90 days ) .
we reported one clinical failure consisting of one patient still under treatment after 570 days .
that patient underwent total gastrectomy for t3n  +  gastric cancer and developed an anastomotic dehiscence of half of the circumference with a concomitant mediastinal collection after 11 days ( video 1 and fig .  2 ) .
after three endoscopic sessions and two stent replacements ( 90 days ) , there was no extravasation of contrast medium and the stents were removed .
ct scan again showed a 10-cm mediastinal collection due to an anastomotic fistula , and eid therefore was repeated ( fig . 
the span of time between endoscopic sessions was extended to 8 weeks instead of 4 weeks and he was allowed an oral diet . 

endoscopic view of esophago - jejunal anastomotic fistula with surgical drainage in place ( red arrow ) .
b radiological view of esophago - jejunal anastomotic fistula with surgical drainage in place ( yellow arrow ) .
f healed fistula with no extravasation of medium contrast ( yellow arrow ) . 
 radiological visualization of perianastomotic collection .  

table  2 lists the type of scope used , the number of pigtail stents deployed , the number of overall and average endoscopy sessions , feeding method , and outcomes   p : positive ; n : negative ; ut : under treatment . if present , the external drainage tube was removed before the first check endoscopy ( 4    6 weeks after start of eid ) .
overall we achieved clinical success in nine patients after an average of 44 days ( 28   
90 ) treatment with a median of 2.3 endoscopic sessions ( 2    4 ) and deployment of 1.8 pigtail stents per patient ( 1    4 ) .
the overall clinical success rate was 82  % , with eid failure in two of 11 patients ( 18  % ) .
no stent - related bleeding or stent migrations inside the abdominal cavity were observed in the study . at a median follow up of 291 days ( 10   
leak and fistula following gastrointestinal surgery are usually treated minimally invasively with drainage tubes , oral alimentary stream diversion , and/or plugging .
the most common approaches are insertion of temporary covered self - expandable metal stents ( csems ) ; clipping ; plugging ; gluing ; and vacuum therapy 5 
 6 
 7 .
overall clinical success rate varied greatly among these different techniques without assurance of optimal results .
moreover , the rate of success decreases with the interval between initial surgery and endoscopic treatment .  
the most common treatment is with deployment of csems , but they are burdened by a high rate of migration due to altered anatomy and absence of stenosis coupled with the physiologically large diameter of the gastrointestinal tract .
these factors do not allow the csems to guarantee watertight exclusion of a leak . even if the stent remains in place , fluids pass in the space between the external sheets of the stent and the wall of the gastrointestinal lumen .  
endoscopic internal drainage of intraabdominal collection was first used in the 1980  s by biliopancreatic endoscopists to treat pancreatic pseudocyst .
one or several pigtails were introduced under endoscopic vision , puncturing the bulging collection in order to perform an anastomosis between the cavity and the gastrointestinal tract .
later , thanks to the advent of interventional endoscopic ultrasound , we had the opportunity to drain and create anastomosis between an abdominal collection that was neither bulging nor endoscopically visible and the gastrointestinal tract .  
today newly designed , lumen apposing , fully covered self - expandable metal stent ( la - fcsems ) may be used for this purpose 8 , enabling the emptying of the collection with resolution of this virtual third space .
the wall defect ( fistula - leak orifice )  is already present . in our previous studies we demonstrated that a pigtail stent acts as a foreign body on the edge of the leak and inside the cavity , promoting its reepithelialization 1 
 9 
 10 .
the new concept in our series is that eid can be used to internally drain perianastomotic fluid collection all along the gastrointestinal tract ( esophagus , duodenum , colon ) .
application of pigtail drainage is feasible even in the colon and rectum , as shown in an interesting article by calzolari et al .
we decided to systematically evaluate each patient after 4 to 6 weeks because pigtail stents have a small caliber and can easily get blocked .
more importantly we believe that the stent being a foreign body promotes granulation tissue formation , as demonstrated by spontaneous double pigtail migration ( fig .  4 ) . 

d endoscopic view of a double pigtail stent migrated in the duodenal lumen 28 days after eid treatment .
it is well known that early management of fistula should always be advocated because it correlates with higher clinical success rates . therefore , we advocate eid as an early first - line treatment .
although eid often requires multiple endoscopic sessions , it is cost - saving compared to sems . 
eid should be considered as an effective first option for leaks throughout the gastrointestinal tract .
eid is a valuable and efficient technique not only for leaks following bariatric surgery but even for leaks and fistulas following other type of upper and lower gastrointestinal surgery .
as long as eid can achieve access to the fluid collection , internal drainage can be achieved all along the gastrointestinal tract .
background and study aims : leaks following gastrointestinal surgery are a dreadful complication burdened by high morbidity and not irrelevant mortality.endoscopic internal drainage ( eid ) has showed optimal results in the treatment of leaks following bariatric surgery . 
 we report our experience with eid as first - line treatment for fistulas following surgery along all gastrointestinal tract .