INTRODUCTION
A 22-year-old woman has had recurrent episodes of diarrhea, crampy abdominal pain, and slight fever over the last 2 years. At first the episodes, which usually last 1 or 2 weeks, were several months apart, but recently they have occurred more frequently. Other symptoms have included mild joint pain and sometimes red skin lesions. On at least one occasion, her stool has been guaiac-positive, indicating the presence of occult blood. Colonoscopy reveals several sharply delineated areas with thickening of the bowel wall and mucosal ulceration. Areas adjacent to these lesions appear normal. Biopsies of the affected areas show full-thickness inflammation of the bowel wall and several noncaseating granulomas.
· What is the most likely diagnosis?
· What are the common complications of this disease?
Summary: A 22-year-old woman has a 2-year history of recurrent diarrhea, abdominal pain, slight fever, joint pain, and red skin lesions. Colonoscopy reveals several sharply delineated areas with thickening of the bowel wall and mucosal ulceration, which on biopsy show full-thickness inflammation of the bowel wall and several noncaseating granulomas.
· Most likely diagnosis: Crohn disease.
· Common complications of this disease: Malabsorption and malnutrition, fibrous strictures of the intestine, and fistulae to other organs, such as from bowel to skin or bowel to bladder.
CLINICAL CORRELATION
Introduction
The patient's presentation is very characteristic for inflammatory bowel disease, that is, a several-year history of diarrhea and abdominal pain. Additionally, the colonoscopy revealing full-thickness inflammation with noncaseating granulomas is consistent with Crohn disease. Crohn disease is a chronic inflammatory condition that is ubiquitous in its distribution in the gastrointestinal tract. It most commonly manifests in the small intestine, in particular the terminal ileum. The disease exhibits aggressive activity of the gastrointestinal immune system, but the exact cause is unknown. Published studies in the United States report incidence rates that vary between 1.2 and 8.8 per 100,000 population; the prevalence is 44 to 106 per 100,000. The condition is more common in the cold climates of the northeastern United States than in the south. Those of Jewish ethnicity have a high incidence. The disorder, which is slightly more common in females, has a bimodal age distribution, peaking in the early twenties and again emerging in the mid-sixties. Theories regarding pathogenesis have referred to genetics, infection, autoimmune or allergic processes, thromboembolic disorders, and dietary disorders.
Approach to Inflammatory Bowel Disease
Discussion
The predominant symptoms of Crohn disease are diarrhea, abdominal pain, and weight loss. These symptoms may be widely variable, depending on the distribution of the inflammatory lesions in the patient's intestines. The principal stimulus for diarrhea is the mucosal immune response in association with cytokine release. If the colon is involved, diarrhea may be more marked and tenesmus may occur. Abdominal pain may be due to local inflammation or obstruction if it is experienced in the central abdomen or right lower quadrant. Abscesses or fistulae also may produce pain. Secondary causes of abdominal pain in relation to Crohn disease are gallstones and renal colic. Malabsorption leading to weight loss and failure to thrive may occur in children. Fat, protein, mineral, and vitamin deficiencies may be associated with extensive or recurrent disease. About one-third of patients develop perineal symptoms or signs such as anal fistulae or fissures.
Nongastrointestinal symptoms of Crohn disease involve the skin, joints, or eyes. Skin lesions include erythema nodosum, pyoderma gangrenosa, aphthous stomatitis, and finger clubbing. The rheumatologic manifestations often present as a large joint polyarthropathy resembling ankylosing spondylitis or a small joint fleeting polyarthropathy that is like rheumatoid arthritis. The human lymphocyte antigen B-27 (HLA-B27) may be present. Inflammatory eye lesions are confined to the anterior chamber, such as uveitis, iritis, episcleritis, and conjunctivitis. A chronic active hepatitis may develop; more seriously, sclerosing cholangitis can progress to cirrhosis. There is a predisposition to gallstones when terminal ileal disease is present.
Physical Examination
Physical examination may reveal a nutritional deficiency. The extraintestinal manifestations may be apparent. Abdominal examination may suggest partial bowel obstruction, an inflammatory mass, focal areas of tenderness, or enterocutaneous fistulae. Perineal examination may reveal fistulae or abscesses. Perianal skin tags with bluish discoloration may be present. On rectal examination there may be a stricture, a palpable ulcer, or perirectal abscesses. Bloody diarrhea may be detectable. Clinical features compatible with anemia or hypoalbuminemia may be present. Hypoalbuminemia may manifest with peripheral edema.
Approach to Inflammatory Bowel Disease
Plain abdominal radiographs provide important information in the acute presentation of symptoms, as they may demonstrate intestinal obstruction or evidence of perforation. Biliary or renal calculi, arthropathy, or osteoporosis also may be detected. Endoscopy of the lower and upper gastrointestinal tract is used to identify disease and provide biopsy evidence. Barium follow-through examination or small bowel enteroclysis may demonstrate discrete lesions in the small intestine. Fistulograms are helpful to surgeons by providing information about the site of the fistula and the presence of obstruction or abscess cavity in association with it.
Computerized tomography is the mainstay in terms of providing information about thickened loops of bowel, abscesses, and fistulous tracts. Magnetic resonance imaging, including cholangiography, may be helpful. Ultrasound may reveal thickened terminal ileum, abscesses, and evidence of bilary tract disease. Ultrasound examination of the renal tract may reveal obstruction or stone formation. Endoscopic ultrasound may be useful in assessing bowel wall involvement and the extent of the disease process. Studies of bone density may be required.
Endoscopy allows detailed examination of the mucosa of the upper and lower intestines, with the added advantage of allowing biopsies of abnormal areas to be taken. Capsule endoscopy is an innovation that permits detailed photography of the small intestinal lumen. There may be eletrolyte abnormalities in Crohn disease. The erythrocyte sedimentation rate (ESR) frequently is elevated above 30 mm/h, and the serum vitamin B12 level may be reduced.
Crohn Disease Versus Ulcerative Colitis
These inflammatory bowel diseases share certain features, but there are fundamental and often distinguishing features. On occasion it may be very difficult to determine whether a patient has Crohn disease or ulcerative colitis, and in these circumstances the condition often is designated indeterminate colitis. The fundamental differences between Crohn disease and ulcerative colitis are that Crohn disease begins in the submucosa and ulcerative colitis begins in the mucosa of the gut. Ulcerative colitis, as its name suggests, is a disease confined to the colon and rectum, whereas, as was stated above, Crohn disease is ubiquitous throughout the bowel. Full-thickness involvement of the bowel, although more common in Crohn disease, may occur in both disorders. Fibrosis cicatrization and fistula formation are confined almost exclusively to patients with Crohn disease. The histopathologic feature that differentiates the two conditions is the presence of granulomas in Crohn disease. Aphthoid ulcers are more likely to occur in patients with Crohn disease. Both conditions are associated with an increased incidence of colon cancer, which, however, is more likely to develop in long-standing ulcerative colitis than in Crohn disease. The incidence of malignant change in the colon or rectum of ulcerative colitis is about 20 percent after 25 years of disease activity. Many patients develop ulcerative colitis at a young age and therefore may develop cancerous changes in the colon in their forties or fifties. A further important consideration is that patients with inflammatory bowel disease live with episodes of diarrhea and occasional rectal bleeding so that the heralding features of malignancy may be observed by referring to the underlying inflammatory disease.
Treatment
Pain Control and Anti-Inflammatory Agents
The treatment of Crohn disease can be divided into four areas of management: dealing with symptoms, treating mucosal inflammation, nutritional management, and surgery. Abdominal pain and diarrhea are dealt with mostly by addressing intestinal inflammation. Pain may be due to the stretching of nerve endings as a result of distention from obstruction or inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs) should be avoided, and narcotics lead to addiction in this chronic condition. Acetominophen, Tramadol and Darvocet are used most frequently for pain control. 5-Aminosalicylic acid derivatives such as Azulfidine, Asacol, Pentasa, and Rowasa are used widely and have some effect. They are more effective in ulcerative colitis than in Crohn disease.
Steroids
Corticosteroids have been the mainstay in the acute treatment of Crohn disease for many years. Steroids should be used only when more conservative measures fail. The strategy employed is to induce remission by using high doses (prednisolone 60 mg per day) in the short term, followed by a temporary regime as soon as remission is induced. Maintenance therapy should employ the lowest dose possible. About 20 percent of patients require long-term steroids.
Second-Line Agents
Steroid sparing in long-term management can be achieved with 6-mercaptopurine. This drug is slow to act and unpredictable in terms of achieving a therapeutic response. In doses of 50 to 125 mg daily, bone marrow suppression and other side effects are rare. The antibiotic metronidazole is also used as second-line therapy with a degree of success, particularly in treating fistulae. In addition to its properties as an antibiotic, the drug has an effect on the immune system. Other antibiotics that have been used to some effect are ciprofloxacin and clarithromycin.
Immune Suppressants
The immune suppressants methorexate and cyclosporine have been shown to confer some benefit in the short term. The latest, still experimental, strategy in the treatment of Crohn disease involves the role of cytokines. Anti-tumor necrosis factor has been shown to be effective. Other cytokine therapies, such as the use of interleukin-11 (IL-11) and IL-10, have been reported to be efficacious in about 30 percent of cases.
Surgery
The cumulative risk of undergoing surgery sometime in their lives for patients with Crohn disease is nearly 90 percent, and the cumulative risk of recurrent disease at 20 years is 70 percent. Many recurrences may be asymptomatic, however. The major indication for surgery is failed medical therapy, usually in the presence of obstruction, fistula formation, and electrolyte or nutritional problems.
Controversy still exists over how radical the surgeon should be in treating Crohn disease. Some studies show that the more disease-free the margins are after the resection, the less likely there is to be recurrent disease. Conversely, there is a danger that overly radical resections will leave the patient with the short bowel syndrome and its nutritional consequences. Conservative surgery in the form of stricturoplasty for short stenotic lesions that are producing obstructions can be helpful without the loss of any bowel. For longer diseased segments, resection is preferred to bypass. For colonic Crohn disease with severe rectal and anal involvement, a proctocolectomy with ileostomy may be required. Meticulous care is required in performing anastomoses in patients with Crohn disease, as healing is often impaired and the risk of anastomotic leakage therefore is increased.
COMPREHENSION QUESTIONS
[6.1] A 44-year-old man presents with multiple episodes of bloody diarrhea accompanied by cramping abdominal pain. A colonoscopy reveals the rectum and distal colon to be unremarkable, but x-ray studies find areas of focal thickening of the wall of the proximal colon, producing a characteristic "string sign." Biopsies from the abnormal portions of the colon revealed histologic features that were diagnostic of Crohn disease. Which of the following histologic features is most characteristic of Crohn disease?
A. Dilated submucosal blood vessels with focal thrombosis
B. Increased thickness of the subepithelial collagen layer
C. Noncaseating granulomas with scattered giant cells
D. Numerous eosinophils within the lamina propria
E. Small curved bacteria identified with special silver stains
[6.2] Which one of the therapies listed below is used most often to treat an individual with a history of Crohn disease who acutely develops abdominal pain and bloody diarrhea but has no clinical evidence of obstruction or fistula formation?
A. Aspirin
B. Interleukin-10
C. Metronidazole
D. Prednisolone
E. Surgery
[6.3] What is the fundamental distinguishing feature between Crohn disease and ulcerative colitis?
A. Crohn disease begins in the rectum; ulcerative colitis may have "skip lesions."
B. Crohn disease begins in the submucosa; ulcerative colitis begins in the mucosa.
C. Crohn disease has an increased risk of malignancy; ulcerative colitis has a very low association with malignancy.
D. Crohn disease is associated with crypt abscesses; ulcerative colitis, with pericolonic abscesses.
E. Crohn disease is associated with the formation of inflammatory polyps; ulcerative colitis, with hamartomatous polyps.
ANSWERS
[6.1] C. Microscopic examination of the abnormal bowel from an individual with Crohn disease will reveal transmural inflammation with fibrosis, but the histologic feature that is most diagnostic of Crohn disease is the presence of noncaseating granulomas. This characteristic histologic feature, however, may be present in only about 50 percent of patients; however, the diagnosis of Crohn disease can still be made without finding granulomas by the characteristic clinical presentation, which includes the production of fissures, fistulae, and bowel obstruction by the transmural inflammation.
[6.2] D. In the absence of bowel obstruction or fistula formation, several types of medical therapies have been used to treat the acute inflammation associated with Crohn disease. Corticosteroids, such as high-dose prednisolone, have been used commonly to treat the acute symptoms and induce remissions. In contrast, the antibiotic metronidazole may be used to treat patients with fistula formation, whereas the use of cytokines such as interleukin-10 is experimental. Surgical resection of bowel usually is done to treat problems such as obstruction.
[6.3] B. Crohn disease and ulcerative colitis are both inflammatory bowel diseases characterized by marked acute inflammation, but the fundamental difference is that with Crohn disease the inflammation begins in the submucosa and may involve the entire bowel wall, whereas ulcerative colitis begins in the mucosa and the inflammatory response remains superficial in location. Another important difference is that the inflammation in ulcerative colitis begins in the rectum and distal portions of the colon and precedes proximally without "skip lesions," whereas the inflammation in Crohn disease can be found throughout the gastrointestinal tract.
PATHOLOGY PEARLS
· Crohn disease is transmural (full thickness) and can occur anywhere along the gastrointestinal tract.
· Intestinal strictures and fistulae are complications of Crohn disease.
· Individuals with Crohn disease have an increased risk of colon cancer, but the risk is lower than that with ulcerative colitis.
· Nongastrointestinal symptoms of Crohn disease involve the skin, joints, and eyes. Skin lesions include erythema nodosum, pyoderma gangrenosa, aphthous stomatitis, and finger clubbing.
REFERENCES
Friedman S, Blumberg RS. Inflammatory bowel disease. In: Kasper DL, Fauci AS, Longo DL, et al. Harrison's principles of internal medicine, 16th ed. New York: McGraw-Hill, 2004:1776-1788.
Liu C, Crawford JM. The gastrointestinal tract. In: Kumar V, Assas AK, Fausto N, eds. Robbins and Cotran pathologic basis of disease, 7th ed. Philadelphia: Elsevier Saunders, 2004:846-849.
Copyright © 2006 by the McGraw-Hill Companies, Inc. All rights reserved.
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