The etiology of Crohn's disease remains unclear. It is more commonly observed in developed countries, particularly in Europe and North America.
Pathology
Crohn's disease can affect any part of the gastrointestinal tract, with the terminal ileum being the most common site. Both the small intestine and colon are frequently involved simultaneously, while disease confined solely to the colon is less common. Lesions may be present in one or multiple segments of the intestine, exhibiting a segmental distribution. The inflammation affects the entire thickness of the intestinal wall, with serosal surfaces showing congestion, edema, and fibrinous exudation. Thickening of the mucosa is accompanied by deep fissural ulcers, which give the mucosal surface a cobblestone appearance due to prominent edema. The intestinal wall undergoes thickening and granuloma formation, leading to luminal narrowing. The affected mesentery often shows edema, thickening, and inflammatory lymphadenopathy, along with shortening of the mesentery and encasement of the intestine by fat. Diseased intestinal loops often adhere to each other or nearby tissues and organs, and ulcers may penetrate the intestinal wall, resulting in the formation of internal or external fistulas.
Clinical Presentation
The disease typically has a slow onset with a long clinical course. Common symptoms include diarrhea, abdominal pain, and weight loss, occasionally accompanied by mucus and blood in stools. Abdominal pain is usually located in the right lower quadrant or periumbilical region, is often cramp-like, mild in severity, and may be accompanied by localized tenderness. Chronic ulcer perforation, formation of intestinal fistulas, and adhesions may lead to abdominal mass development. Symptoms of intestinal obstruction, usually partial, may occur in some patients. A minority of individuals initially present with perianal disease as their primary symptom.
Diagnosis and Differential Diagnosis
Diagnosis of Crohn's disease requires integration of clinical findings with results from endoscopy, pathology, imaging, and biochemical tests. Colonoscopy with pathological biopsy, CT enterography (CTE), or MRI enterography (MRE) are particularly useful for confirming the diagnosis. Additional diagnostic tools, such as capsule endoscopy or enteroscopy, may be considered when necessary.
Differential diagnosis includes intestinal tuberculosis, Behçet's syndrome, intestinal lymphoma, and ulcerative colitis. Acute presentations of Crohn's disease may sometimes be misdiagnosed as acute appendicitis. However, acute appendicitis is typically distinguished by the absence of a history of recurrent low-grade fever or diarrhea, more localized and fixed tenderness in the right lower quadrant, and significantly elevated white blood cell counts.
Treatment
Medical treatment is the primary approach, though approximately 70% of patients undergo surgery during their lifetime due to disease-related complications. Surgical intervention is primarily aimed at managing complications such as intestinal stricture and obstruction, intra-abdominal abscesses, internal or external fistulas, free perforation, uncontrollable intestinal bleeding, malignancy, perianal disease, refractory cases, or delayed growth and development in pediatric patients.
Surgical resection involves removing the affected segment along with 2 cm of visibly normal proximal and distal bowel. Side-to-side anastomosis is often recommended. Recent approaches also advocate removal of the diseased mesentery to reduce postoperative recurrence of the disease. In cases of recurrent disease after multiple bowel resections, stricturoplasty may be performed for single or multiple short fibrotic strictures in the small intestine.
If Crohn's disease is suspected intraoperatively during appendectomy, simple appendectomy alone may lead to a stump leak. In cases of stump leakage following acute appendicitis surgery, consideration of Crohn's disease as the underlying cause should be undertaken. Perioperative care is critical, as many patients suffer from malnutrition and have long-term corticosteroid or immunosuppressant use. Postoperative recurrence rates are high, and patients with high-risk disease should receive pharmacological therapy following surgery to prevent recurrence.