General information
It is a chronic granulomatous inflammatory disease that can involve the entire gastrointestinal tract and progresses with remissions and relapses.
• The most important gene mutation in the development of Crohn's disease is NOD2 (CARD15).
• Different from ulcerative colitis, it has been suggested that various microorganisms may play a role in the etiology or exacerbation of the disease.
• It is more common in smokers and relapses more frequently.
Pathology
• Biopsy shows lymphoid aggregates and sometimes non-caseating granulomas.
• Any part from the mouth to the anus can be involved (most often in the form of ileocolitis - distal ileum and proximal colon are involved).
• Involvement is segmental and transmural, the earliest macroscopic lesion is aphthous ulcers. These ulcers progress linearly to form the cobblestone landscape.
• Strictures are common during healing. Sausage-like intestinal loops may occur.
Clinic
• Clinical symptoms, signs and complications may vary depending on the affected area (such as ileo-colitis, jejuno-ileitis or colitis-perianal).
• Common symptoms in Crohn's disease are abdominal pain and diarrhea.
• Especially since the small intestines are involved, malabsorption (element, vitamin, etc. deficiencies) and related secondary systemic symptoms are evident.
• Weight loss is more common than ulcerative colitis.
• Since the involvement is transmural, fistula, stricture, obstruction, intra-abdominal abscess may be seen.
• Perianal region pathologies are common.
• Extraintestinal symptoms
It is generally similar to ulcerative colitis.
Erythema nodosum, peripheral arthritis, and ankylosing spondylitis are more common in Crohn's disease.
Gallstones, osteomalacia, vitamin deficiencies, calcium-oxalate stones, and obstructive uropathy are specific to Crohn's disease and are not expected in ulcerative colitis.
- Primary sclerosing cholangitis and pyoderma gangrenosum are less common than ulcerative colitis.
Complications
• Especially stricture, obstruction, perianal diseases, fistulization between intestinal segments or other adjacent tissues (such as rectovesical, rectovaginal), intra-abdominal abscess are very important and common complications.
• There may be signs of malnutrition and malabsorption.
• Cancer development
In cases involving the entire colon, the risk of colon cancer is close to ulcerative colitis.
However, the risk of colon cancer in segmental or localized cases was not as increased as ulcerative colitis, although it is higher than in the normal population.
The risk of developing small bowel adenocarcinoma also increases.
Diagnosis
• Clinical, laboratory, endoscopic and pathological findings are combined.
• Acute phase reactants in serum, especially CRP, are high and reflect the activity of the disease. Fecal lactoferrin and calprotectin in stool are helpful in differential diagnosis, determination of activity and follow-up.
• Laboratory anomalies are more prominent due to small intestine involvement and malabsorption (iron, vitamin B12 and folate deficiency, protein loss, hypocalcemia, ADEK vitamin deficiency, magnesium and zinc deficiency).
• Small bowel imaging is helpful in diagnosis in some cases. CT or MR enterography is primarily requested. However, capsule endoscopy is superior to radiological methods in demonstrating small bowel involvement.
• Colonoscopy is very valuable in diagnosis in cases with colon and terminal ileum involvement.
Hyperemic and edematous mucosa is seen in the involved segments, but this image is not diffuse.
Deep linear ulcers and coarse mucosa (cobblestone appearance) can be detected between the edematous areas.
Erosion and ulcers may be seen, surrounded by normal mucosa (skip area).
• Endoscopy is the most valuable in diagnosis when upper GI involvement is suspected.
• Barium small intestine and colon radiographs are not widely used today, but very useful findings such as segmental changes, ulcers, fistulas, narrowed segments (rope sign), enlargement behind the narrow segment (sausage sign) can be detected in the diagnosis and follow-up.
Treatment
• Medical treatment is similar to ulcerative colitis and the same drugs are used.
• 5-ASA preparations: Their effectiveness in ileal disease is limited. It is given if there is colon involvement.
• Corticosteroids: They are used to achieve remission in almost all cases requiring treatment. Budesonide, which is released in the terminal ileum and has a topical effect, is preferred in cases with ileum involvement because its systemic side effects are minimal. The efficacy of budesonide in colon involvement is weak, it is not recommended.
• Azathioprine or 6-mercaptopurine: They are widely used to maintain remission.
They are not effective in inducing remission. They are also effective in the treatment of fistula.
• TNF-alpha antagonists (infliximab, adalimumab, golimumab,certolizumab): They are widely used in steroid-resistant or relapsing cases to both achieve remission and maintain maintenance. These drugs are also effective and preferred in fistulizing cases.
• Monoclonal antibodies
Used in anti-TNF resistant cases
Natalizumab and vedolizumab (anti integrin)
Ustekinumab (anti-IL12/23)
• Antibiotics: Metronidazole and ciprofloxacin are effective in suppressing active inflammation, perianal disease and fistulizing cases. They reduce recurrences after ileal resection.
• Elemental diet: It defines a liquid diet consisting of amino acids and small nutrient molecules. They are effective in achieving remission.
• Surgical treatment: Often for complications. Primary curative treatment
Purposeful surgery should be avoided because the disease can recur in any part of the GIS.
