Crohn disease (CD) is a chronic disorder that primarily affects young individuals. Although its etiology is unknown, recent findings regarding the genetic and immunologic features of CD 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 immune therapies have also shown benefit. Surgical treatment has been reserved for refractory disease and complications. Minimally invasive surgery provides an alternative to the traditional open surgical approach.
History of the Procedure
In 1932, the article “Regional Ileitis” 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, CD has been found to occur in all parts of the gastrointestinal tract (GI) and to have widespread extraintestinal manifestations. The pathologic criteria to distinguish CD from other forms of inflammatory bowel disease (IBD) were not established until 1960. [2, 3]
CD predominantly affects young individuals 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 CD is incomplete, but advances in medical therapies and surgical techniques have led to an improvement in patient quality of life.
The incidence of CD in the general population is approximately 6.3-7.9 cases per 100,000 persons, with a reported prevalence of 43-174 per 100,000. [3, 4, 5, 6] 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. CD affects persons of every ethnic origin but is more common in the Ashkenazi Jewish and Caucasian populations.  The disease has no sexual predilection.
The etiology of CD 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 CD 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, or perforating) tend to be similar among family members. Other genetic abnormalities linked with CD include hereditary conditions such as glycogen storage disease type 1b and complement pathway dysfunction. [7, 8, 9]
Bacterial agents have long been thought to be involved in the pathogenesis of CD, though no bacteria have been definitively identified. Thus, in this multifactorial model, the interaction of bacteria, immune mechanisms, and genetic susceptibility may be necessary for the development of the disease. [7, 8, 9]
Environmental factors such as smoking and second-hand smoke have been linked to the development of CD.  There has been a suggestion that a diet high in fatty foods may increase the risk for the disease.  Concerns about the measles vaccine and the development of the disease have proved unfounded.  Although appendectomy has been suggested to be protective in ulcerative colitis (UC), it is not a protective factor in CD. 
CD 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 also often involved. The disease is often segmental (unlike ulcerative colitis), and the rectum is frequently spared.
Endoscopically, CD typically appears as patchy areas of inflammation separated by uninvolved bowel. The earliest lesions are aphthous ulcers—tiny discrete erosions that typically develop 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. 
Grossly, surgical specimens are rigid and thickened owing to 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 the image below). The transmural nature of inflammation contributes to possible fistulous connections between segments of bowel or other organs.
The differential diagnoses of CD include infectious diseases such as bacterial enteritis, giardiasis, amebiasis, viral gastroenteritis, and granulomatous disease or other inflammatory conditions (eg, UC).
CD most commonly presents in an adolescent or young adult as chronic abdominal pain, diarrhea, and weight loss. Patients who present with Crohn colitis may also have bloody diarrhea, tenesmus, or incontinence. In some cases, CD is diagnosed in children who are undergoing evaluation for delayed puberty onset or secondary amenorrhea.
Five percent of patients with CD present with only perianal symptoms. Anal fissures, the most common finding in perianal disease, often develop 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.
In some cases, CD is discovered during treatment of one of its complications. Although more common in patients with UC, toxic megacolon can be a life-threatening manifestation of CD. Small-bowel obstruction, intestinal perforation, intra-abdominal abscess, and 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.
Interestingly, the extraintestinal manifestations of CD may develop first. Many of these extraintestinal signs overlap with those of UC. 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 association with CD than in UC. These occur predominantly on the lower legs, over the tibia. [15, 16]
Ankylosing spondylitis is more common in men with CD 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 more commonly associated with UC than with CD. Renal calculi and cholelithiasis are complications of long-standing ileal disease. 
Children with CD commonly experience growth failure as an extraintestinal manifestation of IBD. This growth failure results from both decreased caloric intake and the presence of circulating inflammatory cytokines. Growth failure is defined by several parameters, including height below the third percentile, a shift to a lower height percentile, or reduction in 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. 
Characteristics distinguishing CD from UC are listed in Table 1 below.
Table 1. Differentiating Characteristics of Crohn Disease and Ulcerative Colitis (Open Table in a new window)
|Characteristic||Crohn Disease||Ulcerative Colitis|
|Distribution||Entire gastrointestinal tract||Colon only|
|Skip lesions||Continuous involvement proximally from rectum|
|Pathology||Full thickness||Mucosa only|
|Granulomas (50%)||No granulomas|
|Radiology||Entire gastrointestinal tract||Colon only|
|Skip lesions||Continuous involvement proximally from rectum|
|Fistulas, abscesses, fibrotic strictures||Mucosal disease only|
|Cancer risk||Controversial||1% per year starting 10 years after diagnosis (estimated)|
Because CD cannot be cured with surgical intervention, the goal is palliation of active symptoms and disease remission. Indications for surgery include intractable disease, growth retardation, cancer, perianal disease, and complications of intestinal disease, such as stricture, intestinal obstruction, and enteric, colonic, or vesicular fistulas (see below). In children with recurrent acute episodes, the potential for further bowel loss must be weighed against the risks of long-term steroid therapy and failure to thrive.
Indications for surgical intervention in patients with CD include the following:
Failure of medical therapy
Complications of steroid or other medical therapy (eg, growth failure)
Complications of the disease process - Intestinal obstruction (especially terminal ileum), intestinal perforation, intestinal bleeding, recalcitrant sepsis
The operative management of CD remains one of the most challenging areas of surgery. Surgery is generally reserved for refractory disease or intestinal complications. Resection of asymptomatic disease is not warranted, because disease recurrence is the rule.
Although surgical options are expanding, CD is an important contraindication for creation of a Kock pouch. Patients with CD who receive a Kock pouch ultimately require resection of the pouch or continuing treatment for severe pouchitis.
What would you like to print?