Therapeutics/Abdominal Abscesses and Gastrointestinal Fistula

Case

A 60-year-old male presents with a 2-day history of crampy left lower abdominal pain. The day of presentation he has a fever to 102°F. He has no change in his bowel habits and currently has two to three bowel movements per day. He denies hematochezia, melena, nausea, and vomiting. He is otherwise healthy, takes no medications, and has no medication allergies.

He denies tobacco, drinks alcohol occasionally, and denies illicit drug use. He has no family history of gastrointestinal diseases. His physical exam was remarkable for mild tenderness to palpation in the left lower quadrant of the abdomen, and mild voluntary guarding in the left lower quadrant without rebound tenderness.

Therapeutics

Abdominal Abscess

Management of an abdominal abscess depends on the location and cause. Initial treatment requires removal of the abscess by percutaneous and/or surgical drainage and adjunctive antimicrobial therapy. Feasibility of percutaneous drainage needs to be assessed based on the clinic scenario and location of the abscess.

In the setting of multiple, complex, multiloculated abscesses, percutaneous drainage may not be beneficial. If possible, a catheter is placed to aspirate an abscess, fluid sent for Gram stain and culture, and the catheter is left in place, followed for daily output and clinical response. If clinical response (continued fever and/or leukocytosis) is poor, repeat cross-sectional imaging may be needed to monitor the abscess site. Once there is minimal drainage, less than 15-20 mL/day, and appropriate clinical response, the catheter may be removed.

Peridiverticular Abscesses

For abscesses less than 4 cm, patients may be treated conservatively with antibiotics and bowel rest. Larger abscesses require drainage and computed tomography-guided percutaneous drainage is an option, based on the location of the abscess and the clinical condition of the patient. Drainage may prevent urgent surgery that may require a two-stage operation (temporary stoma) and allow for elective surgery leading to a one-stage operation. Treatment also entails antimicrobial therapy, with aerobic and anaerobic coverage.

Periappendical Abscesses

When a periappendiceal abscess is detected preopera-tively, patients have better long-term outcome if managed initially by percutaneous drainage and antimicrobial therapy followed by elective surgery.

Gastrointestinal Fistulae

Spontaneous closure of a fistula is more likely to occur if drainage output is low (<500mL/day), located in the proximal small bowel, secondary to anastomotic breakdown, a long fistulous tract, a new fistula, and in a young (<40 years of age) patient that is well nourished (Table 52.3). Otherwise, surgical closure and/or therapy is directed at the underlying cause.

Initial management of gastrointestinal fistula involves volume repletion and electrolyte and acid/base correction. If patients are malnourished, total parenteral nutrition (total parenteral nutrition) is needed. For high-output proximal fistulae, nasogastric tube suction, gastric acid suppression, total parenteral nutrition, and bowel rest including avoidance of enteral feeds proximal to the fistula is warranted.

Table Factors influencing spontaneous closure of fistulae

Octreotide, a somatostatin analogue, may also help in decreasing fistula output but controlled studies have failed to verify this. In the setting of sepsis, therapy is directed at assuring adequate drainage of the fistula (surgical or percutaneous) and treating with antimicrobials. Endoscopic or percutaneous fibrin glue injection into a fistulous track may also be attempted in patients that fail conservative management. Short tracts tend to have poor outcomes. Fistulae that persist for more than 4-6 weeks, sepsis or abscess formation, distal intestinal obstruction, or bleeding are indications for surgery.

Surgical Emergencies

Esophageal fistulae tend to require urgent evaluation due to the surrounding organs, such as the respiratory system and aorta. Malignant esophagorespiratory fistulae can often be palliated with self-expanding metallic stents. Benign esophagorespiratory fistulae, including postoperative, anastomotic leaks, can often be treated with temporary placement of a self-expanding, removable, plastic stent. Chest tube drainage is often needed as these are frequently associated with infected pleural effusions or empyema.

Additionally, aortoenteric fistula may occur in the setting of aortic vascular grafts that erode into the gastrointestinal tract. The most frequent location in the gastrointestinal tract affected is the duodenum. Suspected aortoenteric fistula is a surgical emergency. Any fistula in the setting of sepsis and/or abscess requires urgent antimicrobial therapy and drainage.

Fistulizing Crohn disease

Fistulae occur in a third of Crohn disease patients with the most common location in the perianal region. Treatment of fistulae include medical therapy with antibiotics, immunomodulators (azathioprine, methotrexate, or cyclosporine), and/or antitumor necrosis factor alpha (anti-tumor necrosis factor-a) therapy (infliximab, adalimumab, or certolizumab).

A concomitant abscess needs to be excluded prior to initiating immunosuppressants. Surgery may also be needed based on the type and severity of disease. Asymptomatic internal fistulae rarely require therapy.

Enterocutaneous Fistulae

High-output fistulae occur in the setting of proximal small bowel involvement (>500 mL/day) and cause severe volume depletion. Initial management of these patients involves volume repletion. In the postoperative setting, a fistulous opening is usually in the area of a wound and it is imperative to protect the healing skin from infection due to the drainage either by an ostomy bag or a catheter for high-output fistula. High-output fistulae will rarely close spontaneously and will require surgical closure.

Fistulae that are low output and arising from Crohn disease may be treated initially medically with azathioprine (or 6-mercaptopurine), methotrexate, or anti-tumor necrosis factor-a therapy (infliximab, adalimumab, or certolizumab).

Perianal Fistulae

Treatment of perianal fistula is based on several factors. The first factor is the understanding of the anatomy of the fistulous track in relation to the anal sphincter. Anal fistula anatomic location, based on the Parks classification, is divided into superficial (or submucosal), intersphincteric, trans-sphincteric, suprasphincteric, and extrasphincteric.

For Crohn disease-related perianal fistulae, classification is divided into simple and complex fistula. Simple fistulae are located below most of the anal sphincter (superficial or intersphincteric (low track) location) and have one track. Complex fistulae go through the intersphincteric (high track), trans-sphincteric, and supra-sphincteric region and may have multiple tracks.

Simple fistulae respond well to therapy. Initial therapy is an antibiotic, metronidazole with or without ciprofloxacin for the fistula, and treating mucosal Crohn disease if present. Patients without rectal mucosal Crohn disease may respond well to fistulotomy, whereas patients with mucosal involvement may benefit from seton placement rather than fistulotomy due to poor wound healing. Treatment with immunomodulators (azathioprine or methotrexate) or anti-tumor necrosis factor-a therapy may also be considered.

Treatment of complex fistulae usually entails a combination of surgical and medical therapy. Complex fistulae may be associated with concomitant perianal abscess. In the setting of intractable disease, colonic or Heal diversion may allow for rectal/perianal healing and in severe cases proctocolectomy may be necessary.

Rectovaginal Fistulae

The decision for surgical or medical therapy depends on the clinical scenario. Surgical therapy such as fistulotomy and mucosal flap may be considered. For Crohn disease-related fistula, medical therapy may be considered prior to surgery.

Enterovesical and Colovesical Fistula

Initial Crohn disease-related fistulae may be treated with medical therapy, but recurrent urinary tract infection is an indication for surgery. Surgery usually involves resection of bowel involved and closure of the bladder defect. Colovesicular fistulae are more commonly a consequence of diverticular disease and require surgical intervention.

Internal Fistula

Asymptomatic internal fistulae, such as enteroenteric fistulae, do not require surgical intervention and may be observed as long as the cause has been identified. If the fistula is a consequence of Crohn disease, then treatment with an immunomodulator may be considered. Internal fistulae, such as cologastric and coloduodenal, may cause significant symptoms due to bypass of intestine. These fistulae may be treated medically if a consequence of Crohn disease. If medical management fails, surgery is recommended. Internal fistulae that are associated with sepsis and abscess should be surgically treated.

Case continued

Intravenous ampicillin/sulbactam and bowel rest was initiated. Interventional radiology was consulted and ultrasound-guided perirectal drainage with catheter placement was completed. Antibiotics and total parenteral nutrition were continued and 2 weeks later fluoroscopic assessment and computed tomography scan of the abdomen and pelvis revealed resolution of the complex abscess. A colonoscopy 6 weeks later revealed sigmoid diverticula and diverticulitis as the likely cause for the abscess.

Most gastrointestinal fistulae are iatrogenic, postoperative.

Crohn disease is the most common cause for spontaneous gastrointestinal fistulae in the developed world.

If an abdominal abscess is suspected, then cross-sectional imaging, preferably computed tomography, scan should be completed for diagnosis.

The cornerstone of treatment of an abdominal abscess is drainage, surgical or percutaneous, along with antimicrobial therapy.

The cause, location, and duration of fistulae are predictors of healing.

Jennifer Bowles

Jennifer is a clinical pharmacologist. She helps doctors of all medical specialties choose medications. Jennifer consults about drug dosage, interactions, and side effects.