Crohn's Disease - Diagnosis

Laboratory and instrumental data

1. Complete blood count: anemia, leukocytosis, increased ESR. These changes are most pronounced in the active phase of the disease.
2. General urine analysis: no significant changes. In the active phase, proteinuria and microhematuria may appear.
3. Biochemical blood test: decreased albumin and iron levels, increased O2- and gamma-globulins, alanine aminotransferase, and sometimes bilirubin.
4. Immunological blood test: increased amount of immunoglobulins, circulating immune complexes, decreased amount of T-lymphocytes - suppressors.
5. Coprological analysis: blood and mucus impurities are determined macroscopically; in the absence of clearly visible blood, there is an increased number of erythrocytes, a always positive reaction to occult blood (Gregersen's reaction) and soluble protein (Triboulet's reaction), many epithelial cells and leukocytes.
6. FEGDS: allows to detect lesions of the upper gastrointestinal tract. Esophageal lesions are extremely rare, manifested by a picture of inflammation of the esophageal mucosa, sometimes its ulceration. The diagnosis is clarified by histological examination of biopsy samples of the esophageal mucosa. Stomach lesions are observed in only 5-6.5% of patients, and the most typical is isolated lesion of the antral part of the stomach or a combination of lesions of the stomach and the initial part of the duodenum. However, it is possible that the stomach is not initially affected, but is involved in the pathological process with advanced intestinal damage (terminal stage of the disease). Stomach lesions are manifested by an infiltrative inflammatory process with ulceration in the center. The diagnosis is clarified by histological examination of biopsy samples of the gastric mucosa.
7. Endoscopic examination of the intestine (rectoscopy, colonoscopy). Rectosigmoidoscopy is informative in cases where the rectum is involved in the pathological process (in 20% of patients). The most significant is fibrocolonoscopy with biopsy of the intestinal mucosa. The endoscopic picture depends on the period and activity of the process.

In the initial stage of the disease, against the background of a dull (not shiny) mucous membrane, erosions-aphthae surrounded by whitish granulations are visible. Mucus and pus are visible in the lumen of the intestinal walls. As the disease progresses and the activity of the process increases, the mucous membrane unevenly thickens, acquires a whitish appearance, large ulcers (superficial or deep) appear, often longitudinally located, and a narrowing of the intestinal lumen is noted (a picture of a cobblestone pavement). During the period of greatest activity, the inflammatory process spreads to all layers of the intestinal wall, including the serous membrane, and fistulas are formed.

Later, cicatricial constrictions form at the site of the ulcers and cracks.

8. Microscopic examination of mucosal biopsies: the biopsy should be performed so that the biopsy includes a section of the submucosal layer, because in Crohn's disease the process begins there and then spreads transmurally. The following features of the pathological process are revealed microscopically:
   • the submucosal layer is affected to the greatest extent, and the mucous membrane to a lesser extent;
   • The inflammatory cell infiltrate is represented by lymphocytes, plasma cells, histiocytes, eosinophils, against the background of which sarcoid-like granulomas with giant Langers cells are determined.
9. X-ray examination of the intestine: irrigoscopy is performed in the absence of rectal bleeding. Characteristic signs of Crohn's disease are:
   • segmental nature of colon lesion;
   • the presence of normal intestinal areas between the affected segments;
   • uneven intestinal contour;
   • longitudinal ulcers and a mucosal texture reminiscent of a “cobblestone pavement”;
   • narrowing of the affected areas of the intestine in the form of a “cord”;

It is most appropriate to conduct an X-ray examination of the small intestine by introducing barium through a probe behind the Treitz ligament (P. Ya. Grigoriev, A. V. Yakovenko, 1998). The X-ray signs of damage to the small intestine are the same as those of the large intestine.

10. Laparoscopy: performed primarily for differential diagnostic purposes. The affected sections of the intestine, primarily the terminal ileum, appear hyperemic, thinned, edematous; compaction and enlargement of the mesenteric lymph nodes are also noted.

Differential diagnosis of Crohn's disease

Crohn's disease must be differentiated from almost all diseases that occur with abdominal pain, bloody diarrhea and weight loss, as well as amebiasis, dysentery, pseudomembranous and ischemic colitis, tuberculosis and intestinal cancer.

The form of Crohn's disease with predominant damage to the terminal ileum requires differential diagnostics with yersiniosis. In this case, the most important diagnostic test is the dynamics of titers of specific anti-yersiniosis antibodies; titers of at least 1:160 are considered diagnostically significant (antibodies are usually detected in the blood serum on the 7-14th day).

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