Intervention
CT-guided therapy
CT has become the procedure of choice, not only in diagnosing Crohn disease but also in managing abscesses. A growing body of literature shows that CT-guided percutaneous abscess drainage may obviate surgery. In recent studies, CT percutaneous abscess drainage has shown great success either as a temporizing measure or as definitive therapy with a decreased rate of recurrence, as compared with that of surgery. Because about 70-90% of patients with regional enteritis eventually require surgery, avoiding an operation to treat an abscess is a tangible benefit of CT.
Medical therapy
The medical management of Crohn disease can be divided into the treatment of an acute exacerbation and the maintenance of remission. In acute exacerbation, triggers such as underlying infection, fistula, perforation, and other pathology must be ruled out prior to the intravenous administration of glucocorticoids.
Intravenous hydrocortisone or methylprednisolone is often used, in addition to metronidazole and bowel rest, as main acute therapy. The use of steroid therapy is limited for short burst response because of its various long-term adverse effects, including osteonecrosis, myopathy, osteoporosis, and growth retardation. A potent inhibitor of cell-mediated immunity, intravenous cyclosporine may be used for further immune modulation if the response to corticosteroids is poor. Many studies have established that cyclosporine is effective in the short term, but it fails as long-term therapy.
The goal of chronic therapy is the remission of bowel inflammation. Aminosalicylates has been the mainstay of therapy because of its anti-inflammatory activities. Several formulations have been introduced, each with a different carrier molecule for targeting a specific region of the bowel. Sulfasalazine and balsalazide are primarily released in the colon. Dipentum and Asacol are formulations for targeted release in the distal ileum and colon. Pentasa can be released in the duodenum to the distal colon, whereas Rowasa is specific for the rectum and distal colon.
Methotrexate, azathioprine, and 6-mercaptopurine are other nonsteroidal immune modulators that are well tolerated. Azathioprine, which is nonenzymatically converted in the body to 6-mercaptopurine, is metabolized to thioinosinic acid, which is a purine synthesis inhibitor. Adverse effects of azathioprine and 6-mercaptopurine are less common, as compared with those of steroids. Nevertheless, a 3% incidence of pancreatitis, allergic reactions, infections, and marrow toxicity is associated with their use. The main drawback to the use of azathioprine and 6-mercaptopurine is their slow onset of action. The effect of therapy is noted after 3-6 months of treatment.
Methotrexate, the long-standing folic acid antagonist, is effective in many patients with disease refractory to azathioprine and 6-mercaptopurine. It has the well-known adverse effects of leukopenia, GI upset, and hypersensitivity pneumonitis.
New therapies target tumor necrosis factor-alpha. Agents such as infliximab, Etanercept and CDP571 are becoming available and showing promising results, with an increased remission rate in 48% at 4 weeks and with complete fistula closure in 55% of patients at 80 days for infliximab. Other agents such as mycophenolate have been developed to inhibit guanine nucleotide synthesis and thereby inhibit B and T lymphocytes. Randomized clinical trials are underway to compare mycophenolate with azathioprine. So far, mycophenolate has shown a greater rate of improvement at 1 month.
Surgical therapy
More than 70% of patients with Crohn disease undergo surgery within 20 years of the diagnosis. Indications for surgery in Crohn disease include stricture, intractable or fulminant disease, anorectal disease and intra-abdominal abscess. The basic tenant in Crohn surgery is to limit small-bowel resection to grossly diseased segment. When stricture is present, the small bowel can often be preserved with stricturoplasty. This involves incising a stricture longitudinally and then suturing it transversely to widen the lumen.
The recurrence rate has been reported to be 34% at 7-year follow-up (Dietz, 2001), and it is comparable with that of surgical resection, namely, 25% at 5 years and 50% at 10 years. The procedure also has the additional benefit of preventing short-bowel syndrome. The morbidity rate of 18% and the lack of perioperative deaths with stricturoplasty are favorable features (Dietz, 2001), as compared with surgical resection. The site of recurrence in stricturoplasty is similar to that of resection, ie, perianastomotic, with the highest rate of recurrence in younger patients. Recurrence is often defined as detectable active disease, as depicted with radiography or endoscopy, with a return of symptoms.
Medicolegal Pitfalls
- The oral administration of contrast material is to be avoided when moderate- or high-grade colonic obstruction is present.
- Double-contrast (air contrast) barium enema examination is contraindicated in patients with severe colitis because injection of air with contrast agent may precipitate toxic megacolon or colonic perforation.
- Barium studies are contraindicated when signs and symptoms of peritonitis or when radiographic signs of gas in the bowel wall or pneumoperitoneum are present.
- The intravenous injection of contrast material for CT studies should be avoided when chronic renal insufficiency, continued use of Glucophage, or signs and symptoms of acute renal failure are present.
- CT and barium studies use ionizing radiation, which may result in considerable radiation burden. This exposure is a relative contraindication in pregnancy and childhood. Sonography and MRI may prove to be useful alternative imaging modalities.
See also the Medscape topic Medical Malpractice and Legal Issues.
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Further Reading
Keywords
Crohn's disease, regional enteritis, inflammatory bowel disease, HLA-DR1 gene, DQw5 gene
