Intestinal fistulas are not uncommon in clinical work in abdominal surgery. Advances in surgical techniques have led to an expansion of the scope of surgery and the frequent application of multiple therapies such as surgery, chemotherapy, and radiation therapy to the same patient, all of which have increased the incidence of enterocutaneous fistulas.
There are many causes of intestinal fistulas, which can be broadly classified as surgical, injury, disease-induced, and congenital. Most of them are caused by surgery.
1. Surgery is the most common cause of intestinal fistula
(1) Duodenal fistula. Because only part of the peritoneum is covered, the duodenum is prone to fistula after anastomosis or suturing. Fistulas can be divided into terminal fistulas and lateral fistulas according to whether they occur at the stump closure or at the intestinal wall incision suture.
(2) Gastrointestinal anastomotic leak. It is a common cause of enterocutaneous fistula. Many anastomotic leaks are due to technical shortcomings of the operation. , the
For example, the difference in diameter of the gastrointestinal tract between the two ends of the anastomosis is too great, and the anastomosis is not evenly matched so that there is a large gap in one place; the anastomosis is too dense or too sparse; the anastomosis has insufficient blood supply or too high tension; the intestinal wall of the anastomosis is edematous, scarred or infiltrated with cancer, etc. Post-operative intestinal obstruction at the distal end of the anastomosis or poor decompression of the proximal gastrointestinal tract are also causes of anastomotic fistula.
(3) Surgical injury. Poorly exposed or extensive intestinal adhesions during abdominal surgery, or inexperienced operators and rough movements can damage the intestinal wall or its blood supply and cause intestinal fistula. In particular, the surgical separation of extensive intestinal adhesions is most likely to damage the intestinal wall and requires special attention.
(4) Foreign bodies such as gauze or improperly placed drainage tubes and wire sutures are left behind after surgery. Most of the gauze left in the abdominal cavity causes intestinal perforation and abdominal abscess, and the abscess either penetrates the incision by itself or forms an external fistula after surgical drainage. The improper placement of drainage tubes after abdominal surgery (tubes too hard, catheters pressed against the intestinal wall) can compress and wear the intestinal wall and form a fistula.
2, disease caused by intestinal fistula. Acute appendicitis perforation often forms a periappendiceal abscess, which often forms an appendiceal stump fistula after drainage. Inflammatory bowel diseases such as Crohn’s disease, intestinal tuberculosis, and intestinal tumors can form intestinal perforations and fistulas. Another common type of fistula is that between the gallbladder or bile duct and the intestinal segment.
When the gallbladder adheres to the duodenum due to inflammation, stones in the gallbladder can compress the adhesions causing ischemia and necrosis and then become an internal fistula (cholecystoduodenal fistula). Gallbladder fistulas can also pass into the stomach or colon. The ulcer in the duodenal bulb can also be combined with gallbladder or bile duct duodenal fistula. Acute necrotizing pancreatitis with abscess can also break into the intestine and form an intestinal fistula.
3, trauma abdominal sharp or blunt trauma may damage the intestinal canal and become intestinal fistula. In particular, part of the retroperitoneum of the duodenum is vulnerable to crushing injuries due to fixation. Intestinal penetration generally into the free abdominal cavity, resulting in diffuse peritonitis; posterior wall penetration to form a retroperitoneal abscess, which can later break into the free abdominal cavity.
4, congenital anomalous yolk duct non-closure can cause congenital umbilical intestinal fistula.
The pathophysiology caused by intestinal fistula can vary depending on the height of the fistula site. Generally, the physiological disturbances of high intestinal fistula are more severe than those of low fistula. The following pathophysiologic changes are generally observed.
(1) Disturbance of water loss and electrolyte, acid-base balance: The daily gastrointestinal fluid secretion in adults is estimated to be 7000-10000 ml, most of which is reabsorbed in the ileum and proximal part of the colon. Therefore, high intestinal fistulas in the upper duodenum and jejunum lose more intestinal fluid daily, which can be as high as 7000ml.
Therefore, if not replenished in time, it can quickly cause dehydration, hypovolemia, peripheral circulatory failure, and shock.
(2) Infection: A few fistulas are formed when the surgical drainage does not heal. These fistulas are formed without significant local or systemic infection. However, most fistulas are complicated by limited or diffuse peritonitis and abscesses, single or multiple, during their formation. Patients have fever, abdominal pain, abdominal distension, gastrointestinal dysfunction such as nausea, vomiting, poor nausea, diarrhea or absence of defecation and exhaustion, wasting, toxic symptoms, and even sepsis, shock, and death; they can also be complicated by stress ulcers, gastrointestinal bleeding, toxic hepatitis, ARDS, and renal failure.
Malnutrition: With the loss of intestinal fluid and loss of digestive enzymes and proteins, digestion and absorption are impaired, resulting in negative nitrogen balance, vitamin deficiency, dramatic weight loss, anemia, hypoproteinemia, and even death due to the formation of cachexia.
④ Skin erosion around the fistula: Due to the prolonged erosion of digestive juices, the skin around the fistula is prone to erosion and the patient complains of severe pain. Especially high intestinal fistulas are rich in digestive enzymes and are more likely to produce skin damage. The granulation tissue next to the fistula in the abdominal cavity can also be corroded by digestive juices and bleed.
I. Clinical manifestations
The clinical manifestations of enterocutaneous fistula vary from site to site and from etiology to etiology, as well as from time to time in the formation of enterocutaneous fistula.
Duodenal fistulas contain bile and pancreatic juice. The jejuno-intestinal fistula has a yellow, dilute, egg-like fluid. The higher the location of the fistula, the larger the fistula, or the more obstructed the distal end of the fistula, the more digestive fluid will flow. Without proper treatment, dehydration, acidosis, acute renal failure, and cachexia will quickly appear. The skin around the fistula or surgical incision is often eroded.
II. Principles of treatment
Any intestinal fistula that occurs due to a lesion in the intestinal wall or an obstruction in the intestinal cavity below the fistula is difficult to heal on its own. Once an external fistula occurs, it should be considered a serious condition and must be treated aggressively, including maintaining nutrition and hydration, protecting the skin around the fistula and controlling infection. If, after a period of treatment, the fistula does not tend to heal spontaneously, an enterocutaneous fistula or fistula repair should be considered.
Endenteric fistulas do not tend to heal on their own and often cause recurrent infections in the organs connected to the intestine, so surgery should be used as soon as possible.
The treatment of endenteric fistula should first address the primary lesion, such as intestinal Crohn’s disease or other intra-abdominal inflammatory lesions, should first control the acute lesion of the primary disease, and then perform surgical treatment.
2, the treatment of extra-intestinal fistula varies according to the stage of the disease.
(1) Early stage: the peritonitis stage, roughly within 2 to 4 weeks after the onset of the disease. The key to treatment is early and unobstructed drainage, control of infection, correction of hypovolemia and water-electrolyte disorders, and attention to protection of the skin around the fistula.
①Drain the abdominal abscess thoroughly if found;
②Correct hypovolemia and water-electrolyte disorders;
③Apply antibiotics to control the spread of infection;
④Control the intestinal fistula and prevent skin erosion.
(2) Middle stage: roughly the second or third month after the disease. The intra-abdominal infection has been basically controlled and external fistula has been formed. In this period, in addition to continuing to pay attention to maintaining good drainage and controlling infection, continue to protect the skin next to the fistula. It is more important to replenish nutrition and strengthen the body so that the fistula can close on its own. There are various methods of nutrition, which should be chosen according to the specific situation.
(1) Intravenous nutrition;
(2) Feeding through catheter or mouth.
(3) Late stage: 3 months after the occurrence of intestinal fistula. At this time, nutrition is maintained satisfactorily and the gastrointestinal function has been restored. The stump is either sutured closed or a laparostomy is made, and after the fistula heals, a second-stage surgery is performed to remove the adherent intestinal mass. In the immediate aftermath of an intestinal fistula, the results are infection caused by spillage of intestinal fluid, bleeding caused by digestion of tissue by intestinal fluid, malnutrition due to intestinal dysfunction, and biliary sludge and biliary cholecystitis caused by prolonged fasting.
Some of these complications can be cured by non-surgical methods, while others need to be addressed by another caesarean section.
For abdominal infections in combination with enterocutaneous fistulae, the original drainage site can be evaluated by trans-fistulography and CT to see if the drainage is reasonable and adequate. Whether the infection can be resolved by improving drainage, such as switching to negative pressure double cannula drainage or adding local irrigation on top of drainage. If an undrained abscess does exist, it should be managed by ultrasound or CT-guided percutaneous abscess puncture and drainage if possible.
In patients with severe abdominal infection and combined organ compromise, direct drainage of the abdominal cavity can also be performed by opening the incision at the bedside. Only if all means have been used and the infection still cannot be drained is another dissection considered to remove the infection and drain the abscess cavity.
Bleeding is a common complication in patients with extra-intestinal fistulae. In the case of bleeding in combination with parenteral fistula, it is important to analyze whether the bleeding is due to stress-induced gastrointestinal mucosal erosion, mucosal bleeding from the fistula, or bleeding from rupture of the abdominal vessels due to digestive decay of intestinal fluid. The healing of bleeding due to extensive gastrointestinal mucosal erosion can be improved by improving ischemia and hypoxia and providing mucosal nutrition. Mucosal bleeding from fistulas can be reduced and eliminated by improving drainage and controlling the spillage of intestinal fluid.
If necessary, DSA angiography can be used to identify the site of bleeding and vascular embolization can be used to stop the bleeding. Only if all measures fail should a repeat dissection be considered to stop the hemorrhage.