Excerpt from Crohn Disease: Surgical Perspective

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Crohn disease is a chronic disease that primarily affects young individuals. Although its etiology is unknown, recent findings regarding the genetic and immunologic features of Crohn disease have provided insight into the possible mechanisms of pathogenesis. Corticosteroids have been the mainstay of medical treatment in patients with active inflammation, but salicylates, antibiotics, and immunosuppressants have also shown benefit. Biologic therapies involving antibodies, antisense oligonucleotides, and cytokines are promising new medical therapies. Surgical treatment has been reserved for refractory disease and complications. Minimally invasive surgery has provided an alternative to the traditional open surgical approach.

History of the Procedure

In 1932, the article "Regional Ileitis" by Crohn, Ginzburn, and Oppenheimer appeared in the Journal of the American Medical Association. This landmark article described findings in a series of 14 patients with a disease of the terminal ileum characterized by subacute or chronic necrotizing and cicatrizing inflammation. Since then, Crohn disease has been found to occur in all parts of the gastrointestinal tract and to have widespread extraintestinal manifestations. The pathologic criteria to distinguish Crohn disease from other forms of inflammatory bowel disease were not established until 1960.

Problem

Crohn disease predominantly affects a young population and is a chronic incurable condition. It requires ongoing medical management and causes long-term pain and disability. Frequent surgical interventions are often required to treat complications. The understanding of this disease in incomplete, but advances in medical therapies and surgical techniques have led to an improvement in patients' quality of life.

Frequency

The incidence of Crohn disease in the general population is approximately 5.3 cases per 100,000 persons. The onset of the disease peaks in older adolescents and young adults. However, approximately 5% of new cases occur in children younger than 5 years. Crohn disease affects persons of every ethnic origin, but it is most common in the Ashkenazi Jewish and Caucasian populations. Male and female individuals are affected with equal frequency.

Etiology

The etiology of Crohn disease is unknown. Its pathogenesis is likely multifactorial, involving a combination of infectious agents and environmental exposures that activate an immune response in a genetically susceptible host. Familial clustering of Crohn disease suggests a genetic etiology. A positive family history is found in 10-15% of patients. The relative risk for first-degree relatives of these patients is estimated to be 10-21 times that of the general population. Disease locations and types (eg, stricturing, inflammatory, perforating) tend to be similar among family members. Other genetic abnormalities linked with Crohn disease include hereditary conditions such as glycogen storage disease type 1b and dysfunction of the complement pathway.

Bacterial agents have long been thought to be involved in the pathogenesis of Crohn disease, though no bacteria have been definitively identified. Therefore, in the multifactorial model, the interaction of bacteria, immune mechanisms, and genetic susceptibility may be necessary for the development of the disease.

Environmental factors, such as smoking and exposure to second-hand smoke, have been linked to Crohn disease. Concerns about the measles vaccine in the development of Crohn disease have been unfounded. Although appendectomy has been suggested to be protective in ulcerative colitis, it is not a protective in Crohn disease.

Pathophysiology

Crohn disease can affect any part of the alimentary tract from the mouth to the anus. The most common site is the terminal ileum. The appendix is often involved as well. The disease is often segmental (unlike ulcerative colitis), and the rectum is frequently spared.

On endoscopy, Crohn disease typically appears as patchy areas of inflammation separated by uninvolved bowel. The earliest lesions are aphthous ulcers, ie, tiny, discrete erosions that typically occur over lymphoid follicles. As the disease progresses, interconnecting rows of aphthous ulcers create linear ulcers. These linear ulcers cross transverse folds, contributing to a cobblestone appearance.

On gross examination, surgical specimens are rigid and thickened as a result of chronic inflammation and fibrosis during healing periods. The mesentery is typically thickened and foreshortened and may partly surround the bowel wall in a phenomenon known as creeping fat (see Image 1). The transmural nature of inflammation contributes to possible fistulous connections between segments of bowel or other organs.

Clinical

The differential diagnosis of Crohn disease includes infections, such as bacterial enteritis, giardiasis, amoebiasis, viral gastroenteritis, and granulomatous disease, or other inflammatory conditions, such as ulcerative colitis.

Crohn disease most commonly presents in an adolescent or young adult with chronic abdominal pain, diarrhea, and weight loss. Patients presenting with Crohn colitis may additionally have bloody diarrhea, tenesmus, or incontinence. A small group of children initially present for treatment because of secondary amenorrhea or a delayed onset of puberty.

Approximately 5% of patients present with only perianal symptoms. Anal fissures are the most common finding in perianal disease. They are often located eccentrically rather than in the classic posterior midline position of most benign fissures. Skin tags, anal stenosis, fecal incontinence, fistula, and perianal abscesses are also common signs and symptoms of perianal disease.

On occasion, a patient's initial presentation is for the treatment of a complication of Crohn disease. Although more common in ulcerative colitis, toxic megacolon can be a life-threatening manifestation of Crohn disease. Small-bowel obstruction, intestinal perforation, intra-abdominal abscess, or enteric fistulas can also be part of the initial presentation. Because symptoms of ileitis may mimic those of appendicitis, the diagnosis may be made at the time of appendectomy.

Of interest, extraintestinal manifestations of Crohn disease may develop first. Many of these extraintestinal signs overlap with those of ulcerative colitis. Aphthous ulcerations of the buccal mucosa, lips, or tongue should alert the clinician to assess for intestinal involvement. Skin manifestations, such as erythema nodosum and pyoderma gangrenosum, occur more commonly in Crohn disease then in ulcerative colitis. These occur predominantly on the lower legs over the tibia.

Ankylosing spondylitis is more common in men with Crohn disease than in women. Ocular symptoms, such as iritis and uveitis, and hepatic involvement with chronic hepatitis or sclerosing cholangitis may be observed, though these are most commonly associated with ulcerative colitis than with Crohn disease. Renal calculi and cholelithiasis are complications of long-standing ileal disease.

Children commonly have growth failure as an extraintestinal manifestation of inflammatory bowel disease. This growth failure results from both decreased caloric intake and circulating inflammatory cytokines. Growth failure is defined by using several parameters, including height below the third percentile, a shift to a lower height percentile, or reduced growth velocity. Enteral feeding is the first-line treatment. However, achieving remission of the inflammation is critical to maintaining growth. If intensive medical treatment does not result in remission, surgical intervention may be warranted, particularly for isolated small-bowel disease.

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