Brucellosis

Morphology of the ulceration stage (3rd week)

In the pathogenesis of the disease, the third week is marked by the onset of active rejection of necrotic masses in the intestinal mucosa. During this period, so-called "dirty" ulcers are formed. Their geometric shape is not random—it precisely repeats the contours of the affected lymphoid follicles known as Peyer's patches (noduli lymphatici aggregati).

Upon macroscopic examination, the surface of such ulcer defects appears dull, rough, and uneven. The edges of the ulcers characteristically overhang the floor, which, in turn, is densely covered with necrotic detritus. It is important to note the strict topographical regularity of the pathological process's spread: ulceration manifests initially in the distal ileum (ileum), and then steadily spreads upward, involving its proximal section.

Stage of clean ulcers and complication risks (4th week)

By the beginning of the fourth week, the pathological process logically 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 affected area.

The morphological picture of the intestinal wall undergoes significant visual changes: the ulcer defects acquire a regular oval or rounded shape. The edges of the defects become smooth and slightly rounded, and the floor of the ulcer is completely cleared of detritus and becomes absolutely smooth.

It is at this stage that the most formidable and life-threatening complication arises. In some cases, the pathological destructive process penetrates so deeply into the wall that only a thin serous membrane of the intestine remains as the floor of the ulcer. This creates a critically high risk of intestinal wall perforation, which inevitably leads to the release of contents into the abdominal cavity and the development of severe peritonitis (peritonitis).

Stage of healing and clinical-morphological dissonance (5th week)

The fifth week of the disease is characterized by the long-awaited onset of reparative processes in the gastrointestinal tract. Thin, delicate scars gradually form at the site of the deep, cleansed ulcer defects. In parallel with scarring, the complex process of restoring the pool of intestinal lymphoid tissue takes place.

The most important histological characteristic of this stage is that tissue repair proceeds via restitutio (restitutio), meaning that a complete and adequate restoration of the original damaged structures occurs without coarse connective tissue replacement.

However, in clinical practice, an important clinical-morphological feature lies here: at the healing stage, there is often a marked discrepancy (dissonance) between the patient's subjective condition and the objective morphological picture. Despite the fact that clinically the patient may note a good state of health and the absence of complaints, clear 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 consecutive stages:

1. Initial stage: Mesenteric lymph nodes become sharply enlarged in size and hyperemic. At the microscopic level (which is well visualized with standard hematoxylin and eosin staining), there is a paradoxical decrease in the number of lymphocytes. Their place is taken by the active proliferation of monocytes and reticular cells, which literally crowd out normal lymphoid elements from the node tissue.
2. Granulomatous stage: Specific typhoid granulomas are formed. The main effector role here is played by specific macrophages (macrophagocytus)—the so-called typhoid cells, which accumulate and form granulomatous foci.
3. Outcomes: The pathological process ends with the predictable necrosis of the formed granulomas. Subsequently, their gradual tissue organization and petrification (calcification) of the remaining necrotic masses occur, which is the final point of morphological changes in the lymphatic system.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Microscopic structure of a solitary follicle stained with hematoxylin and eosin
• Mechanisms of lymphoid element displacement by monocytes and reticular cells
• Pathogenesis of peritonitis development upon perforation of the intestinal serous membrane
• The process of petrification of necrotic masses in mesenteric lymph nodes
• Differences between restitution and substitution in the healing of intestinal ulcers

Other topics in "Chapter 16. Infectious and Parasitic Diseases"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.