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Eur J Trauma Emerg Surg (2011) 37:209–213 DOI 10.1007/s00068-011-0104-7

REVIEW ARTICLE

The surgical and etiology of gastrointestinal fistulas

J. Pfeifer • G. Tomasch • S. Uranues

Received: 17 February 2011 / Accepted: 1 March 2011 / Published online: 22 April 2011 Ó Springer-Verlag 2011

Abstract Introduction Background are abnormal communications between two epithelial surfaces, either between two por- Fistulas are abnormal communications between two epi- tions of the intestine, between the intestine and some other thelial surfaces, either between two portions of the intes- hollow viscus, or between the intestine and the of the tine, between the intestine and some other hollow viscus, or abdominal wall. The etiology of intestinal fistulas is in between the intestine and the skin of the abdominal wall. most cases a result of multiple contributing factors. Despite Despite significant advances in their management over the significant advances in their management over the past past few decades, intestinal fistulas still present a major decades, intestinal fistulas remain a major clinical problem, clinical problem, with a disproportionally high overall with a high overall mortality rate of up to 30% due to the mortality rate of up to 30%, due to the high rate of com- high rate of complications. This paper aims to describe plications including , malnutrition, and electrolyte classification systems based on the anatomy, physiology imbalance [1]. Spontaneous fistula closures are reported to and etiology that may be helpful in the clinical manage- lie between 19.9 and 81.4% [2, 3]. Operative intervention ment of intestinal fistulas. is necessary in 13–80% of patients to achieve closure, Methods On the basis of anatomical differences, fistulas depending on the anatomical and physiological parameters can be classified based by the site of origin, by site of their of the fistula [4]. The aim of this paper is to describe openings, or as simple or complex. Physiologic classification classification systems used in terms of anatomy, physiol- as low, moderate or high output fistulas is most useful for the ogy, and etiology, that may be helpful in the clinical non-surgical approach. Concerning the etiology, we classi- management of intestinal fistulas. fied the possible causes as (postoperative) trauma, inflam- mation, , , radiation injury or congenital. Conclusion formation can cause a number of General remarks serious or debilitating complications ranging from distur- bance of fluid and electrolyte balance to sepsis and even The treatment of gastrointestinal fistulas is a complex death. They still remain an important complication fol- challenge for every gastrointestinal surgeon. Such patients lowing gastrointestinal . are usually best managed by a multidisciplinary team, consisting of a surgeon, gastroenterologist, dietitian, Keywords Gastrointestinal fistula Á Fistula Á Anatomy Á enterostomal therapy nurse, and general nursing staff. The Etiology team members must treat aggressively in order to prevent mortality (which has decreased significantly worldwide in recent decades), and to improve patients’ quality of life, J. Pfeifer Á G. Tomasch Á S. Uranues (&) which can be significantly diminished for a long period of Department of Surgery, Section for Surgical Research, time. Basically, surgical treatment is reserved for patients Medical University of Graz, Auenbruggerplatz 29, 8036 Graz, Austria whose fistulas do not resolve with medical and non-surgical e-mail: [email protected] therapy. 210 J. Pfeifer et al.

Gastrointestinal fistulas are rare, and therefore random- and colon. An enteroenteric fistula may refer to any ized studies are lacking and management is usually based intestinal fistula in the generic , although some may on expert opinions. There are, however, a few generally restrict this term to small bowel fistulas only. Extraintes- accepted empirical principles: (1) treatment of sepsis and tinal internal fistulas imply communication of the gastro- nutritional status are highly relevant for a good outcome, intestinal tract with another system, such as the (2) obstruction distal to the fistula usually prevents spon- , biliary tree, or . taneous healing of the fistula, (3) spontaneous closure is uncommon in fistulas with Crohn’s disease or a malig- Severity classification nancy, (4) low-output fistulas have a greater chance of healing than high-output fistulas, and (5) reconstructive Fistulas can be classified in anatomical terms as simple or surgery should usually be postponed for 3–6 months [1, 4, complex. Simple fistulas have a short, direct tract; there are 5]. no associated and no other organs are involved. There are two types of complex fistulas.AType 1 complex fistula is associated with an or involves multiple Classification organs. A Type 2 complex fistula opens into the base of a disrupted wound (exposed fistula). By nature, complex Many classification schemes have been used to define fis- fistulas have higher morbidity and mortality rates, as well tulas of the . Anatomical, physiologi- as a lower rate of spontaneous closure [7]. cal, and etiological classification schemes are the most commonly used. Each type of classification system carries Physiological classification specific implications, with regard to the likelihood of spontaneous closure, prognosis, operative timing, and non- Physiological classification is most useful if a non-surgical operative care planning. conservative treatment approach is selected. The most useful parameter is the output of the fistula. We distinguish Anatomical classification among low output (\200 ml/24 h), moderate output (200–500 ml/24 h), and high output fistulas ([500 ml/ Site of origin 24 h). The problem with high output is the danger of intestinal failure due to reduced intestinal absorption, so Gastrointestinal fistulas are generally named according to that macronutrient and/or water and electrolyte supple- the anatomical components involved, and virtually every ments are needed to maintain health or growth. By defi- imaginable combination has been reported in the medical nition, in mild intestinal failure oral supplementation or literature. Anatomical information has prognostic signifi- dietary modification is sufficient. In severe intestinal failure cance with regard to spontaneous healing of the fistula and/or fluid replacement are needed. tract. Anatomical segments with favorable closure rates include oropharyngeal, esophageal, duodenal stump, pan- creatobiliary, and jejunal. Anatomical features associated Etiology with non-healing fistulas include large adjacent abscesses, intestinal discontinuity, distal obstruction, poor adjacent The etiology of intestinal fistula formation is important for bowel, short fistula tracts (\2 cm in length), enteral defects subsequent treatment. Table 1 provides an overview of the [1 cm, fistulas with complete epithelialization, and fistu- etiology of acquired enterocutaneous fistulas. Not surpris- las arising from special segments such as the , ingly, many cases are the result of multiple contributing lateral , ligament of Treitz, and [6]. factors; common examples include patients who have undergone radiation therapy and patients with Crohn’s Site of the openings disease who have undergone prior bowel surgery.

Acquired gastrointestinal fistulas can be categorized as Congenital external or cutaneous if they communicate with the skin surface, or internal if they connect to another internal organ First, it is useful to differentiate between congenital and system or space, including elsewhere along the gastroin- acquired fistulas, since their clinical settings and implica- testinal tract itself. Internal gastrointestinal fistulas can be tions obviously differ greatly. Congenital gastrointestinal further divided into two types: intestinal and extraintesti- fistulas are best understood in the light of their - nal. Intestinal fistulas refer to a -to-gut connection and logical origin and include such entities as bronchial, tra- may consist of any combination of stomach, small bowel, cheoesophageal, and omphalomesenteric fistulas. The most The surgical anatomy and etiology of gastrointestinal fistulas 211

Table 1 Etiology of acquired enterocutaneous fistulas Patients undergoing extensive adhesiolysis are at highest (I) Post-operative occurrence risk of inadvertent enterotomies. An enterotomy in and of itself is not a complication, but failure to recognize and (A) Anastomotic problems adequately repair an enterotomy may lead to serious (a) Technical factors Tension problems. The result of leakage of bowel content into the Blood supply abdomen can be either within 24–48 h or Technique abscess formation. The latter may erode the abdominal (b) Intestinal factors Inflammation wall, mainly at the incision or drainage site, leading to an Ischemia enterocutaneous fistula. Therefore, in cases with any form Infection of adhesiolysis, the entire bowel should be inspected at the Malignancy end of the procedure. In cases with multiple enterotomies (c) Systemic factors Malnutrition in a short bowel segment, resection of the involved seg- Steroids ment is recommended. The same is true for inadvertent Immunosuppression damage to the bowel , which otherwise can lead Malignancy to partial necrosis of the bowel wall and secondary fistula (d) Systemic disease Diabetes mellitus formation. Renal failure Anastomotic complications are the most feared in (B) Incidental injury . Often anastomotic complications are (a) Lysis of adhesions related to technical factors such as ischemia, tension, poor (II) Spontaneous occurrence technique, stapler malfunction or to a pre-existing condi- (A) Intrinsic disease tion such as systemic , local sepsis, poor (a) Inflammation e.g., IBD, nutrition, immunosuppression, morbid obesity, and/or (b) Infection Tuberculosis sequelae to radiation exposure. The increased use of meshes and other biomaterials in , such as for closure of abdominal wall Other defects or repair, may lead to migration and erosion (c) Malignancy of the bowel wall with enterocutaneous fistula formation (d) Ischemia Embolus [9–11]. While older mesh materials must usually be ex- Thrombosis planted to allow wound healing, newer materials can also Low blood flow be used with good results in suspected contaminated (e) wounds, as in parastomal [12]. (f) vascular disease Intraperitoneal drainage tubes can erode into the intes- (g) Radiation tinal and cause enterocutaneous fistulas. While sur- (B) Extrinsic disease geons long believed that preventing collection of fluid or (a) Trauma hematoma in the would minimize the risk of an (b) Other organs anastomotic leak, more recent data have proven neither benefit nor harm [13–15]. Penetration of the intestinal wall by a foreign body (e.g., ingested metallic objects, toothpick, frequently seen congenital enterocutaneous fistula is a chicken or fish ) can lead to enteroenteric fistula for- patent ductus omphaloentericus, whereby the appearance mation when adjacent bowel loops erode [16, 17]. Inter- of feculent material at the umbilicus suggests the diagnosis estingly, penetrating trauma (i.e., stab wound) rarely causes [8]. Otherwise, congenital fistulas are beyond the scope of enterocutaneous or enteroenteric fistula formation [18]. this review and will not be considered further here. Infection Trauma Intestinal that erode through the wall cause an The most common cause for intestinal fistula formation is abscess and may lead to fistula formation between adjacent (post-operative) trauma, comprising more than 90% in viscus or solid organs, or externally. Intestinal fistula for- some studies. Approximately 50% of small intestinal mation due to infection is more frequent in developing fistulas form because of inadvertent enterotomies in countries [19]. The most common cause of non-traumatic patients who have not undergone intestinal . perforation of the is typhoid (46.4%), fol- The remaining 50% are related to complete or partial dis- lowed by non-specific inflammation (39.2%), tuberculosis ruption of intestinal anastomotic suture lines [7]. (12.8%), and malignant neoplasm (1.6%) [20]. Other 212 J. Pfeifer et al. possible causes are salmonella, amebiasis, actinomycosis, or solid abdominal structures can lead to erosion into coccidioidomycosis, , HIV, and possibly adjacent bowel loops and subsequently to fistulas, which do hookworms [19, 20]. A solid organ abscess, such as an not usually heal spontaneously. amebic hepatic abscess, can erode into small bowel loops. Similarly, rupture of a perinephric abscess can cause a Radiological diagnosis nephroenteric fistula. Diverticular and appendiceal abscesses can also cause enteroenteric, enterovesical, en- has come to play a prominent role in the diag- terovaginal or enterocutaneous fistulas. Appendico-cuta- nosis of gastrointestinal fistulas and has increasing thera- neous fistulas are uncommon and occur most frequently peutic potential. This development is surely the result of after percutaneous drainage of an appendiceal abscess [21, the application of modern diagnostic tools such as ultra- 22]. In patients with Crohn’s disease, fistulas that occur in sonography, computed tomography, and magnetic reso- the right lower quadrant after an usually nance imaging. As an alternative to surgery, interventional arise from the involved terminal ileum and not from the radiology and percutaneous techniques have been shown to appendiceal stump [23, 24]. be advantageous, lowering the morbidity and mortality rate, and allowing superior access to the fistulous tracts Inflammation with fistulography. Collaboration between the interven- tional radiologist and surgeons can significantly improve Fistula formation is a typical feature of Crohn’s disease, treatment results [28]. occurring in up to 20–40% of patients described in surgical Enterocavitary fistulas occur or develop with an inci- literature [25, 26]. Sinus tracts and fistulas often involve the dence of 15–44% [29, 30]. More than 80% of these fistulas distal small bowel, and peritoneal abscess or phlegmon may can be treated with percutaneous drainage [31]. With be an associated finding. The chronic transmural inflam- interventional radiology, it is also possible to drain com- mation of the intestinal wall in Crohn’s disease causes plications following enterocutaneous fistulas such as healthy organ structures to adhere to the serosa of the dis- residual abscesses or fluid collections that occur after the eased segment. When inflammation gradually progresses, removal of long-term surgical drains. microabscess formation and internal perforation in the ulcerated areas are the consequences. The ulcerated areas may then penetrate through the bowel wall into the adjacent Discussion involved structure, leading to formation of enteroenteric, enterovesical, enterovaginal or perineal fistulas; most Regardless of the cause, discharge of intestinal content commonly, adjacent bowel loops, bladder, colon, and leads to a cascade of after effects from localized infection are affected. Another possibility in Crohn’s disease to abscess formation, and finally to fistula formation at the is the formation of interloop abscesses that may also erode septic focus. According to their etiology, more than 60% of into adjacent bowel loops, resulting in fistula formation. gastrointestinal fistulas are accidental, if there is no distal passage obstruction, no foreign body, and low-output Radiation injury secretion without active infection. The natural course of the underlying disease will usually Delayed or chronic radiation lesions can be seen from determine the further course. Some studies show that post- 6 months to 30 years after therapy, but usually manifest operative fistulas develop more often after cancer surgery themselves within 1–5 years. The pathophysiological than after operations for benign disease. Fistula formation mechanism is mainly delayed submucosal damage to the can cause a number of serious or debilitating complica- blood vessels and connective of the bowel wall, tions, ranging from disturbance of fluid and electrolyte which causes progressive ischemia. Erosions and dense balance to sepsis and even death. The patients will almost adhesions can result in enteroentetric, enterovaginal or en- always suffer from severe discomfort and pain. They may terovesicular fistula. While several are used to reduce also have psychological problems, including anxiety over the side-effects of radiation therapy, reduction of radiation the course of their disease, and poor body image due to the dose and field size are still the most important factors in the malodorous drainage fluid [32]. prevention of acute and chronic radiation [27]. The most important therapeutic measures are adequate nutrition, control and maintenance of the fistula drainage Malignancy site, appropriate treatment of infection, and avoidance of sepsis. Spontaneous healing of gastrointestinal fistulas has As in the case of the destruction of tissue due to radio- been well documented in quite a large proportion of therapy, degeneration of malignant tumors of the intestine patients. The surgical anatomy and etiology of gastrointestinal fistulas 213

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