Etiology and clinical presentation
Whipple's disease is among rare infectious conditions. The causative agent is the gram-positive bacillus Tropheryma whipplei.
Clinical manifestations of the disease are quite diverse, but symptoms of gastrointestinal tract involvement and systemic reactions usually come to the fore. The classic picture includes:
- Abdominal pain of varying intensity.
- Chronic diarrhea.
- Malabsorption syndrome (impaired nutrient absorption in the small intestine).
- Enlarged lymph nodes (lymphadenopathy).
- Polyarthritis (multiple joint inflammation).
Radiological signs of small bowel involvement
During radiological imaging, the main focus is on the state of the small intestine. Whipple's disease is characterized by specific changes in its mucosa and the bowel wall as a whole.
The most typical sign is thickening of the circular mucosal folds (so-called valvulae conniventes). In the proximal small intestine, these altered folds often acquire a prominent nodular appearance. The bowel wall itself demonstrates non-specific thickening visualized on computed tomography (CT).
Specific CT findings and lymphadenopathy
Abdominal computed tomography plays a key role in identifying characteristic complications of Whipple's disease associated with involvement of the lymphatic system and mesentery.
The main diagnostic finding on CT is intestinal lipodystrophy with the development of specific lymphadenopathy. Enlarged lymph nodes are visualized in the small bowel mesentery (mesenteric) and retroperitoneal space (retroperitoneal).
Their main distinguishing feature is low X-ray attenuation (low-attenuation). This decrease in attenuation is caused by the pathological process: increased deposition of fat and fatty acids directly within the lymph node tissue. Upon intravenous contrast administration, these low-attenuation lymph nodes do not enhance, which serves as a crucial criterion when describing tomograms.
Differential diagnosis based on CT data
When bowel wall thickening and mesenteric lymphadenopathy are detected, Whipple's disease must be differentiated from other infectious and neoplastic processes affecting the small intestine:
- MAI infection (Mycobacterium avium-intracellulare): also affects the proximal segment and causes mesenteric lymphadenopathy (frequently found in AIDS patients).
- Yersiniosis (Yersinia): changes are strictly limited to the distal 20 cm of the ileum, mucosal folds are tortuous, and small nodular filling defects (lymphoid hyperplasia) are present.
- Neoplastic lesions (AIDS-related lymphomas, Kaposi's sarcoma): can form massive conglomerates of retroperitoneal and mesenteric lymph nodes resembling severe infections.
Briefly: answers to topical questions
What radiological signs are detected during a small bowel barium follow-through examination in patients with Whipple's disease?
Imaging of patients with Whipple's disease reveals specific pathological changes in the mucosal relief.
- Thickening of circular folds (valvulae conniventes) — the altered folds often acquire a characteristic nodular appearance.
These pathological changes are predominantly localized in the proximal small intestine.
What specific markers are found during histological examination of intestinal mucosal biopsies in Whipple's disease?
Histological examination of the biopsy reveals infiltration of the lamina propria of the mucosa by specific cells.
- Macrophages — large, polygonal (foamy) cells that accumulate due to incomplete phagocytosis.
- PAS-positive material (PAS-positive) — granules inside macrophages representing Tropheryma whipplei bacteria.
On electron microscopy, the pathogen itself is found inside macrophages, individual enterocytes, and in intercellular spaces.
How do CT attenuation and lymph node structure in MAI infection differ from those in Whipple's disease?
MAI infection reveals mesenteric lymphadenopathy; the source does not specify its attenuation or structure. Whipple's disease shows mesenteric and retroperitoneal lymphadenopathy with low-attenuation lymph nodes that do not enhance with contrast. The low attenuation is associated with increased deposition of fat and fatty acids.
Class and exam questions
What microorganism is the causative agent of Whipple's disease?
The disease is associated with an infection caused by the gram-positive bacillus Tropheryma whipplei.
Why do lymph nodes have low attenuation on CT in Whipple's disease?
The low X-ray attenuation of lymph nodes is caused by intestinal lipodystrophy—increased deposition of fat and fatty acids within their structure.
How do affected lymph nodes behave upon contrast enhancement?
During contrast-enhanced CT, the altered low-attenuation lymph nodes in the mesentery do not enhance.
Which parts of the intestine are most commonly affected?
Characteristic changes in the form of nodular thickening of circular folds (valvulae conniventes) are most often detected in the proximal small intestine.
What else to study on this topic
- Mechanical small bowel obstruction: searching for the "transition zone" on CT
- Strangulation obstruction: CT signs of threatened bowel viability
- Opportunistic GI infections in HIV (Cryptosporidiosis, MAI, CMV)
- CT enterography in assessing partial bowel obstruction
- Radiological manifestations of yersiniosis and ileocecal tuberculosis
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