Morphology of the Ulceration Stage (Week 3)
In the pathogenesis of the disease, the third week is marked by the onset of active rejection of necrotic masses within the intestinal mucosa. During this period, so-called 'dirty' ulcers are formed. Their geometric shape is not random—it precisely mirrors the contours of the affected lymphoid follicles, known as Peyer's patches (noduli lymphatici aggregati).
Upon macroscopic examination, the surface of these ulcer defects appears dull, rough, and uneven. The edges of the ulcers characteristically overhang the base, which in turn is densely covered with necrotic detritus. It is important to note the strict topographical pattern of the pathological process: ulceration initially manifests in the distal ileum (ileum), after which it steadily spreads upward, involving its proximal section.
Stage of Clean Ulcers and Complication Risks (Week 4)
By the beginning of the fourth week, the pathological process naturally transitions into the next morphological phase: the stage of clean ulcers. Pathogenetically, this stage is characterized by the complete and final cessation of necrotic mass rejection from the lesion zone.
The morphological picture of the intestinal wall undergoes significant visual changes: the ulcer defects acquire a regular oval or round shape. The edges of the defects become smooth and slightly rounded, and the base of the ulcer is completely cleared of detritus, becoming entirely smooth.
It is at this stage that the most formidable and life-threatening complication arises. In some cases, the destructive pathological process penetrates so deeply into the wall that only a thin serous membrane of the intestine remains as the base of the ulcer. This creates a critically high risk of intestinal wall perforation, which inevitably leads to the leakage of contents into the abdominal cavity and the development of severe peritonitis (peritonitis).
Healing Stage and Clinical-Morphological Dissonance (Week 5)
The fifth week of the disease is characterized by the long-awaited onset of reparative processes in the gastrointestinal tract. At the site of the deep, cleaned ulcer defects, thin, delicate scars gradually form. Simultaneously with scarring, a complex process of restoring the pool of intestinal lymphoid tissue takes place.
An essential histological characteristic of this stage is that tissue repair proceeds via restitution (restitutio), meaning a complete and adequate restoration of the original damaged structures occurs without coarse connective tissue replacement.
However, in clinical practice, this harbors an important clinical-morphological feature: during the healing stage, a pronounced mismatch (dissonance) is often observed between the patient's subjective state and the objective morphological picture. Despite the patient clinically reporting a good general condition and absence of complaints, residual morphological changes are still present in the intestinal wall, requiring additional time for complete tissue regeneration.
Pathomorphology of Mesenteric Lymph Nodes
Pathological changes in the mesenteric lymph nodes occur absolutely synchronously and morphologically analogously to the intestinal manifestations. This process is clearly divided into several sequential stages:
- Initial stage: Mesenteric lymph nodes become sharply enlarged and hyperemic. At the microscopic level (clearly visualized with standard hematoxylin and eosin staining), a paradoxical decrease in the number of lymphocytes is noted. Their place is taken by active proliferation of monocytes and reticular cells, which literally crowd out normal lymphoid elements from the node tissue.
- Granulomatous stage: Specific typhoid granulomas form. The main effector role here is played by specific macrophages (macrophagocytus)—so-called typhoid cells, which accumulate and form granulomatous foci.
- Outcomes: The pathological process concludes with the predictable necrosis of the formed granulomas. Subsequently, their gradual tissue organization and petrification (calcification of the remaining necrotic masses) occur, marking the final point of morphological changes in the lymphatic system.