I. Overview, classification and pathophysiological changes of parenteral fistula
A fistula is a medical concept that refers to a non-physiologic channel, and an enterocutaneous fistula is one in which one end of the non-physiologic channel is connected to the intestine and the other end is connected to other organs or tissues, or directly to the outside of the body. The pathophysiological changes, symptoms and treatment of internal fistulas vary according to the organ or tissue to which they are connected, with more characteristics than commonalities, while external fistulas have more commonalities than commonalities, although they have their own characteristics according to their different subtypes or classifications, and can be summarized in one category.
An extraintestinal fistula should be considered a complication, often secondary to injury, surgery, inflammation, infection, and other diseases or medical operations, and a few are congenital malformations. In clinical practice, sometimes external decompression of the intestine is performed for certain therapeutic purposes, or the distal end is absent and the proximal intestine is externalized outside the abdominal cavity, although there is also spillage of intestinal fluid outside the abdominal wall, but it is very different from the extra-intestinal fistula discussed as a complication in this section, so it is not discussed in this section. In general, the etiology of extra-intestinal fistulae is broadly based on the following.
1, congenital malformations: because the yolk duct is not closed can form an extra-intestinal fistula in the umbilicus, and the intestinal end of the yolk duct is not closed but the abdominal wall has been closed forms a Meckel’s diverticulum, congenital intestinal fistula is very rare.
2, surgery: surgical causes of extra-intestinal fistula is the most important cause of the formation of extra-intestinal fistula clinically, although strictly speaking is also the injury caused by extra-intestinal fistula, but has its own characteristics and a large number, so listed separately. The percentage of post-surgical complications is 77.1%, mostly seen in gastrointestinal and biliary surgery, renal, ureteral and obstetrical and gynecological surgery can also be complicated by an extra-intestinal fistula, mostly due to surgical misadventure.
3, injury: intestinal injury after the initial treatment, and then due to infection or tissue ischemia, the breakage by repair or anastomosis ruptured again into a fistula, or treatment with omission, accounting for 13.3%; radiation therapy after intestinal injury caused by fistula, can occur in the early post-radiation therapy, can also occur in the late, accounting for 2%.
4, tumor or inflammatory disease: tumor penetration into fistula mostly occurs in the colon (1.2%), inflammatory lesions such as Crohn’s disease of the small intestine, ulcerative colitis or leukoplakia can also peep through into fistula (1.2%). Intestinal tuberculosis and general septic infection in the abdominal cavity also have the potential to cause necrosis and perforation of the intestinal wall into a fistula.
There are various classifications or subtypes of extra-intestinal fistulas according to different criteria. The fistulae are divided into tubular fistula, labyrinthine fistula and disconnected fistula according to the condition of the fistula; simple fistula and complex fistula according to the condition of the sinus.
The pathophysiological changes of extra-intestinal fistula are mainly caused by the spillage of intestinal fluid outside the intestinal lumen.
(1) Water, electrolyte and acid-base disorders: This is mainly due to the large amount of intestinal fluid loss in patients with extra-intestinal fistulas, which should be paid particular attention to in patients with high level high flow fistulas; another reason is the amount of rehydration given in the management of patients with extra-intestinal fistulas or improper clinical nutrition, which artificially causes water, electrolyte and acid-base imbalance due to medical factors, which should be paid more attention in clinical work.
(2) Circulatory disorders: This is mainly due to the failure to effectively replenish after a large loss of intestinal fluid, resulting in insufficient circulating volume and even prerenal renal impairment. Until the 1970s, endostatic imbalance and circulatory disorders were the main causes of death in patients with extraintestinal fistulae. With advances in clinical nutrition, these two pathological alterations should now be corrected without difficulty, provided that clinicians pay attention to them.
(3) Infection: For high intestinal fistulas, the intestinal fluid contains a large amount of digestive enzymes, which on the one hand corrode the tissues through which they flow, creating conditions for infection by pathogenic microorganisms, and on the other hand, the loss of a large amount of digestive enzymes causes malnutrition and lowered immunity in patients, creating conditions for infection. Low-grade enterocutaneous fistulas contain a large number of bacteria in the leakage fluid itself, so they can show early signs of infection. If the leaking fluid is not adequately drained before the formation of the sinus tract, it may contaminate the entire abdominal cavity and form a diffuse peritonitis, which, if not properly controlled, may even develop into multiple organ failure and lead to death. In high intestinal fistulas, due to the erosion of digestive fluid, there is a risk that the blood vessels around the fistula may be broken by erosion and cause bleeding, which aggravates this vicious circle and leads to ischemia of the patient’s vital organs, increasing the patient’s mortality. Infection has now become the leading cause of death in patients with parenteral fistulas, and 90% of the deaths reported by the Nanjing General Hospital of the Nanjing Military Region were caused by infection.
(4) Malnutrition: Without good clinical nutritional support, patients will become malnourished within 2 to 3 weeks after the occurrence of parenteral fistula, depending on the site and flow of the fistula. Infection and malnutrition interact with each other to form a vicious circle. Patients with enterocutaneous fistula are protein-energy deficient malnutrition, which affects both wound healing and organ function, and is not conducive to infection control.
(5) Changes in the primary disease: Generally, the primary disease has been treated when the parenteral fistula occurs, but some parenteral fistulas occur when the primary disease is not effectively controlled, and the occurrence of parenteral fistula even aggravates the progress of the primary disease.
Clinical manifestations of parenteral fistula
The clinical symptoms of parenteral fistula can be divided into two stages. Stage II symptoms. The second stage of symptoms is clearly related to the amount of intestinal fluid flow and the degree of abdominal infection, as well as to the appropriateness of treatment, from a small amount of intestinal fluid flowing from the fistula in mild cases to all five pathophysiological changes mentioned above in severe cases, which can lead to death. Generally speaking, the clinical manifestations of parenteral fistula are mainly the following.
1. local symptoms of the fistula: due to the corrosive effect of the leaking intestinal fluid, redness and swelling around the fistula often occur, accompanied by intense pain, especially in the case of high level and high flow enterocutaneous fistulas. In the case of tubular fistula, since the intestinal fluid leaks into the abdominal cavity first, some patients may have a limited abdominal infection or abscess formation, forming a pus cavity between the internal and external fistula openings.
2. Internal homeostatic imbalance: due to a large amount of intestinal fluid loss, patients may show loss of water and electrolytes, most commonly low potassium and sodium, especially in high-grade, high-flow fistulas. .
3. Malnutrition: It may not be obvious in the early stages of extra-intestinal fistula, but as the disease progresses, malnutrition may develop to a life-threatening degree if good intervention is not obtained under the effect of infection, food restriction and increased consumption.
4. Infection: After the occurrence of an extra-intestinal fistula, if it is not adequately or incompletely drained, the patient may develop a limited or diffuse peritonitis, which may induce multi-organ failure until death in severe cases. Currently, infection is the number one cause of death in extra-intestinal fistulas, accounting for 80% to 90% of deaths.
5. Multisystem or multiorgan failure: This is one of the most serious consequences of parenteral fistula. Multi-organ failure may result from infection, but also from systemic infections and pneumonia due to severe malnutrition or decreased immune function. Acute respiratory distress syndrome, jaundice, stress ulcers, and gastrointestinal erosion and bleeding are also seen in the course of patients with parenteral fistulas, and about 80% of patients who eventually die show multiple organ failure.
III. Diagnosis of extraintestinal fistula and prevention of diagnostic risks
The diagnosis of an extra-intestinal fistula is easily established when there is intestinal fluid flowing from the drainage port or wound. However, when the fistula is small, deep, or early due to inflammatory bowel disease, the diagnosis of an extraintestinal fistula can be more difficult. Clinically, the wound may not heal for a long time, or it may heal and then rupture, or there may be retroperitoneal infection and systemic toxicity, while the trabecular orifice only has unhealthy granulation tissue or increased purulent secretions. For this reason, some imaging and laboratory tests are necessary for extra-intestinal fistulas.
1, oral dye or carbon end examination: this is one of the methods commonly used in early clinical practice, but at present this examination is rarely used in the clinic.
2. Sinus imaging: This is one of the most valuable tests for extraintestinal fistula. By injecting the contrast agent directly through the fistula and taking continuous radiographs, combined with the patient’s change of position, it is possible to clearly obtain many valuable information about the length of the sinus tract of an extra-intestinal fistula, its course, whether there is a pus cavity in the middle, whether there are multiple sinus tracts, the location of the sinus tract in the intestine, whether there is obstruction in the distal intestine, and whether the drainage tube is properly positioned. Therefore, this test is not only of diagnostic value, but also of positive significance in the evaluation of the sinus tract of an extra-intestinal fistula. However, sometimes due to the thinness or deep location of the sinus tract, the contrast agent may not be able to enter the intestinal cavity and the intestinal canal where the fistula is located cannot be clearly displayed.
3, whole gastrointestinal tract imaging: The purpose of whole gastrointestinal tract imaging is to understand the situation of the intestine proximal to the fistula and the distal intestine, and to understand the situation of the entire gastrointestinal tract.
4, abdominal CT examination: it has a greater diagnostic significance for the localization of abdominal abscesses, and also has a higher value for the diagnosis and evaluation of the primary disease of extra-intestinal fistula. Most of the time, it is recommended that patients take diluted contrast agent (commonly iodine rather than barium) orally before performing abdominal CT examination to increase the contrast between the intestinal cavity and the abdominal cavity, which is more conducive to the detection and assessment of the lesion site.
5, laboratory tests: dynamic observation of the patient’s blood image, liver and kidney function, electrolytes and changes in acid-base balance is needed, and the patient’s nutritional status and immune status, as well as cardiopulmonary function, should be assessed regularly to prevent damage to other organs. Special attention should also be paid to the causes of extra-intestinal fistulae and the primary disease.
Once the intestinal fluid leaks into the abdominal cavity, the peritoneum is stimulated and toxins are rapidly absorbed into the blood by the peritoneum, leading to systemic inflammatory response syndrome and acute respiratory distress syndrome. It has been found that acute respiratory distress syndrome is the most common manifestation of enterocutaneous fistulas, especially high-grade enterocutaneous fistulas; therefore, surgeons should consider the possibility of enterocutaneous fistulas in patients presenting with symptoms of peritonitis, unexplained fever and acute respiratory distress syndrome after any abdominal surgery.
Given that abdominal infection is the most common complication of enterocutaneous fistula and has a high lethality rate, it is important to determine the status of infection in patients with extraintestinal fistula. peritonitis; cessation of anal evacuation after recovery of bowel function, along with abdominal pain, abdominal distension, and diminished or absent bowel sounds; extremely high peripheral blood leukocyte count, or even immature granulocytes, or extremely low peripheral blood leukocyte count. Ultrasound or CT examination is decisive in diagnosing the presence of abdominal infection in patients with enterocutaneous fistula. However, ultrasound often affects the examination results due to intra-abdominal bowel distension.
Treatment of extra-intestinal fistula and prevention of treatment risks
According to its pathophysiological characteristics, there are several aspects of treatment for extra-intestinal fistulas, as follows.
1. correction of endostatic imbalance: if an extra-intestinal fistula occurs, especially a high-flow fistula, if it is not treated properly or in a timely manner, the patient will soon develop an endostatic imbalance. When the body loses more fluid components and requires peripheral nutrition, deep venous cannulation is often required to achieve effective fluid replacement.
The importance of adequate and comprehensive drainage for the prevention and treatment of patients with parenteral fistula cannot be overemphasized. In the case of extra-intestinal fistula patients with signs of abdominal infection, it is advisable to perform a timely dissection to remove intra-abdominal pus and secretions and to provide adequate drainage. If the extent of the infection is large and heavy, and it is difficult to close the abdomen due to intestinal edema, open abdominal cavity is feasible, i.e., sterile polyester sutures are used in the abdominal wall incision, and then secondary surgery is performed after the abdominal infection is controlled.
Nanjing General Hospital of Nanjing Military Region has a lot of more mature experience in this area, including
(1) double cannula negative pressure flushing drainage method;
(2) water pressure, tube plugging and adhesive plugging method;
(3) silicone film internal plugging method, etc. The introduction of these experiences and methods are common in the monographs and literature, and are now familiar to most clinical specialists, so I will not repeat them here.
4. Nutritional support: For patients with extra-intestinal fistula, nutritional support is a priority. Before the 1970s, malnutrition was a major cause of treatment failure in patients with parenteral fistulas, and after the 1970s, due to advances in clinical nutrition, malnutrition gradually receded as a secondary cause of treatment failure in patients with parenteral fistulas. In particular, it should be noted that some clinicians lack modern and comprehensive understanding of clinical nutrition, resulting in insufficient knowledge of clinical nutrition and rushing to perform definitive surgery before the patient’s nutritional status is effectively improved, which ultimately leads to treatment failure, increasing the patient’s pain and economic burden, and putting themselves in unnecessary medical risks.
In the early stage of extraintestinal fistula, intravenous hydration and electrolyte supplementation should be used to restore the patient’s internal homeostasis as soon as possible. After the patient’s endostasis is balanced, clinical nutritional therapy with parenteral nutrition is appropriate because it can effectively reduce the amount of fluid secreted by the gastrointestinal tract and facilitate the healing of the fistula. In the 1990s, growth inhibitors were used to reduce the amount of gastrointestinal secretion in patients with parenteral fistulas. The combination of growth inhibitors and parenteral nutrition can sharply reduce the amount of fluid secreted by the gastrointestinal tract and reduce the amount of leaking intestinal fluid by more than 70% in patients with parenteral fistulas.
Enteral nutrition should be selected according to the patient’s condition. For patients with small intestinal fistulas with low flow, an elemental diet can be given orally or intranasally. For high flow small intestinal fistulas, the principle of “eating while leaking” is also advocated, and if combined with the technique of filtering the intestinal fluid back into the distal intestine, enteral nutrition is preferred. Enteral nutrition is a physiological way to give clinical nutrition, and it is believed that enteral nutrition has many advantages over parenteral nutrition, including.
(1) It facilitates the restoration of intestinal barrier and prevents dysbiosis and intestinal bacterial translocation;
(2) Avoiding metabolic complications associated with parenteral nutrition;
(3) It helps to reduce intestinal edema, prevent disuse atrophy and thinning of the intestine, make the intestine healthier, and facilitate the reconstruction of the gastrointestinal tract in the postoperative period;
(4) Enteral nutrition is cheaper than parenteral nutrition, and has fewer operational complications and more comprehensive nutrient absorption. However, parenteral nutrition also has its own advantages and characteristics. In some cases, parenteral nutrition is necessary, for example, if a tubular fistula is to be glued and blocked, the amount of gastrointestinal fluid needs to be reduced, which requires complete parenteral nutrition, so when to choose what kind of nutrition to give needs to be considered in conjunction with the patient’s condition, disease development and treatment needs.
5. Maintenance of important organ functions: Among the causes of treatment failure or death of patients with parenteral fistula, multi-organ failure due to infection is the main cause at present, in which infection is often the first cause of deterioration, and malnutrition is often another cause of deterioration, infection and malnutrition are often causal, vicious circle, if the patient has other organs originally have underlying disease, or If the patient has underlying disease in other organs or is old and frail, the likelihood of multi-organ failure is even greater. The lungs and liver are the most commonly involved organs, and coagulation disorders are not uncommon in clinical practice. Clinically, it is important to control the infection and correct the nutritional status on the one hand, and to protect the other organs, especially the liver and lungs, from the very beginning.
6. Surgical treatment: Surgery for extraintestinal fistula can be divided into two main categories, namely adjuvant surgery and definitive surgery. However, the timing of definitive surgery such as intestinal repair and resection and reconstruction to eliminate intestinal fistula depends on the control of abdominal infection and improvement of the patient’s nutritional status. However, early definitive surgery must be performed with great caution because of the possibility of releakage and because there is still little experience in individual centers. Commonly used surgical approaches include.
(1) partial resection anastomosis of intestinal collaterals for intestinal fistula;
(2) partial resection anastomosis of the intestinal canal;
(3) Plasma membrane repair of intestinal collaterals;
(4) repair of intestinal fistula with tipped intestinal plasma layer coverage;
(5) External stoma for intestinal fistula;
(6) intestinal open stoma. Among them, partial bowel resection, butt-end anastomosis and tipped intestinal plasma layer coverage are the more commonly used procedures with more satisfactory results. The specific surgical procedures have been described in detail in surgical monographs and will not be repeated here.
The author believes that the following points require special attention to prevent the risk of parenteral fistula treatment.
1. Patients with transintestinal fistula require a high degree of responsibility on the part of the physician. In order to facilitate the reader’s understanding, I cite a case in which the author once managed a male patient with an extra-intestinal fistula who was referred from a famous tertiary hospital in China, the patient had a traumatic injury to the duodenum and developed an extra-intestinal fistula after surgery, which was treated in the hospital for more than 3 months. The patient was discharged from the hospital with a self-healing extra-intestinal fistula after withdrawal of the tube, parenteral nutrition, suppression of digestive juice secretion, and adhesive blockage. If the physician at the original hospital had carefully evaluated the patient’s condition, I believe this patient would have been cured at that hospital as well, which is why the author puts responsibility first. In addition, the condition of patients with parenteral fistula changes rapidly because the organism reserves of patients with parenteral fistula are often used to the limit, and a few medical errors or untimely or unexpected situations such as infection or bleeding can make the condition deteriorate rapidly, so it is necessary for the physician in charge to check the patient diligently to understand the changes in condition and the implementation of treatment, and to detect and deal with changes in condition early. This is another reason for the author to emphasize responsibility.
This is the principle to be followed not only for extra-intestinal fistula, but also for the treatment of most other diseases. In cases of extra-intestinal fistula with abdominal infection and abscess formation, efficient and adequate drainage is the key to resolving the abdominal abscess, but not always an exploratory abdominal surgery is required, as most patients can be resolved by ultrasound or CT-guided puncture and drainage. Before surgery, one should ask oneself whether there is no other way to proceed. This is also true for definitive surgery, where every effort should be made to achieve spontaneous healing of the fistula before deciding to perform definitive surgery, and surgery should only be considered if there is no possibility of spontaneous healing. Common causes of fistulas include obstruction of the intestine distal to the fistula, local infection or foreign bodies, sinus tracts shorter than 1.5 cm, radiological injury, and labyrinthine fistulas, etc. If these factors cannot be removed, reoperation for fistula removal should be considered.
3. Meticulous and comprehensive preoperative evaluation is the basis for determining the treatment plan and the first step in preventing parenteral fistula. Before performing definitive surgery, be sure to ask yourself these questions: Why did this patient leak during the last surgery? How can I be sure that this surgery will not leak again? What were the triggers for the fistula that occurred during the last surgery? Have these causes been corrected prior to this definitive surgery? Previous studies have shown that abdominal infection, peritonitis, malnutrition, glucocorticoid use, intestinal obstruction, chronic obstructive pulmonary disease, Crohn’s disease, and radiation therapy are high-risk factors for postoperative extra-intestinal fistula. Were these risk factors well evaluated and corrected prior to this surgery? Through history taking, physical examination and related tests, we can make a preliminary judgment on the expected risk of extra-intestinal fistula, and we can always be vigilant in the follow-up treatment of high-risk cases and actively take preventive measures.
4. Timing of surgery. For patients with elective surgery, surgery should be scheduled after correction of malnutrition and improvement of general condition in order to minimize the risk of extra-intestinal fistula. Patients with mechanical intestinal obstruction in many cases develop rapidly, and a relatively aggressive attitude should be adopted for caesarean operation in such patients to release the obstruction before the occurrence of intestinal strangulation and peritonitis and to reduce the risk of intestinal fistula due to abdominal contamination and intestinal segment removal. In contrast, early postoperative intestinal obstruction is mostly dynamic intestinal obstruction and extensive inflammatory adhesions exist in the abdominal cavity, so conservative treatment should be the main focus.
Second-stage surgery is mostly chosen to be performed after 3 months postoperatively, when inflammatory adhesions gradually transform into membranous adhesions, and separation is relatively easy. Generally speaking, the longer the waiting time, the lighter the adhesions, the easier the surgery is to separate them, and during physical examination, palpation of the abdominal cavity becomes significantly softer as an important sign of adhesion release, and the convexity of the intestinal canal through the fistula opening is also a sign of adhesion release near the fistula opening, and CT examination can also provide information on intestinal adhesions; meanwhile The patient’s malnutrition was also corrected by more than 3 months of clinical nutritional support; the implementation of enteral nutrition led to the decreasing of intestinal edema and a healthier intestine, creating conditions for intestinal reconstruction; by flushing and draining the sinus tract of the extraintestinal fistula, the sinus tract became more mature and infection was more limited, avoiding the innocent removal of more intestine and tissue. In addition, during the waiting period for definitive surgery, the patient’s functional exercise is a very important aspect, according to Professor Ren Jian’an of Nanjing General Hospital of Nanjing Military Region, generally adult patients with intestinal fistula, the smoothest recovery from surgery can climb 16 flights of stairs on foot in about 6 min, even for patients with intestinal fistula over 80 years old, who can climb 4 to 6 flights of stairs before surgery, have excellent postoperative recovery, while long-term bed-ridden cannot get out of bed This is one of the contraindications to definitive surgery.
Intraoperative exploration is a comprehensive and in-depth visual assessment of the patient, which can often lead to unexpected information and correction of preoperative errors, and cannot be done hastily, wasting an opportunity to see the lesion directly with the naked eye. Intraoperative exploration strives to be comprehensive and careful. For patients with closed upper abdominal injuries, attention should be paid to the possibility of duodenal injury, and exploration requires opening the lateral peritoneum of the duodenum; for open abdominal injuries, especially when the site of intestinal injury cannot be found, the lateral peritoneum should be opened and attention should be paid to the presence of injury to the posterior wall of the colon; for extra-intestinal fistulas that occur after appendectomy, especially when the history is atypical, attention should be paid to ileal exploration to determine whether there is an ileal tumor or Crohn’s disease, etc.
6. Based on the preoperative evaluation and intraoperative exploration, we can fully and accurately grasp the condition and formulate a reasonable surgical approach. Before surgery, the operator must have a mature surgical plan, at least three sets of upper, middle and lower surgical plans for patients with complex intestinal fistula, and a corresponding plan for the possible situations that may occur during surgery. For example, for adhesional intestinal obstruction, adhesion release and restoration of intestinal patency is the preferred approach, but when it is difficult to separate intestinal adhesions into clusters, the pursuit of separating adhesions can cause extensive damage to the intestinal wall and even affect the intestinal blood supply, increasing the risk of intestinal fistula. If intra-abdominal contamination is serious during colon and rectal surgery, the incidence of enterocutaneous fistula is high after the first-stage anastomosis, and second-stage surgery after stoma is recommended.
The incidence of anastomotic fistula after TME for rectal cancer is 10-20%, and this rate is higher in low-grade rectal cancer, so for patients with unsatisfactory anastomosis or high-risk patients treated with preoperative radiotherapy, a prophylactic proximal enterostomy can be performed. The terminal ileum 10-15 cm from the ileocecal valve is affected by the blood supply and the ileocecal valve, and the incidence of anastomotic fistula here is high. The second operation occurs in the early postoperative period, when the abdomen needs to be dissected again due to bleeding or poor drainage, when there are extensive inflammatory adhesions in the abdominal cavity and edema and thickening of the intestinal canal, which are easily damaged during separation and difficult to repair. The success rate of simple repair of Crohn’s disease perforation is very low, requiring anastomosis after resection to the normal intestinal wall, but even then the incidence of postoperative intestinal fistula is still very high, and multiple operations are likely to cause short bowel syndrome, which is still a major surgical problem.
7. Patients with extra-intestinal fistula have had abdominal infections and extensive intra-abdominal adhesions, and it is inevitable to perform extensive intestinal adhesion release during surgery. For the prevention of adhesive intestinal obstruction, on the one hand, patients should be encouraged to get out of bed as early as possible and given enteral nutrition as early as possible, and on the other hand, intestinal alignment can be added after parenteral fistula surgery.