Key clinical syndromes of shigellosis
The disease has an acute onset and is characterized by two leading syndromes. Intoxication syndrome includes high fever, chills, general weakness, and headache. Distal spastic colitis syndrome is specific to shigellosis. Patients complain of lower abdominal pain and painful false urges to defecate (tenesmus).
Physical examination reveals an indurated, tender, and spastic cord-like sigmoid colon. Early appearance of hemocolitis symptoms (from the first day) is characteristic: frequent loose stools contain clear admixtures of mucus and blood. Dehydration frequently acts as a complication that determines the severity of the patient's condition (dry tongue, thirst, decreased tissue turgor, hypotension).
Differences from foodborne toxicoinfections (FTI)
The gastroenterocolitic variant of FTI also has an acute onset, but the clinical picture differs by a number of features:
- Nature of pain: in FTI, pain is localized throughout the abdomen rather than solely along the course of the large intestine.
- Dyspepsia: repeated vomiting often comes to the forefront.
- Stool: in FTI, it is frequent and copious, with a distinct fecal character, despite the possible presence of pathological admixtures.
Important clinical rule: if shigellosis presents as a gastroenteritic variant (frequent loose stools without mucus and blood admixtures) and there is a lack of clear epidemiological history data (e.g., contact with dysentery), making a definitive diagnosis based on clinical presentation alone is impossible. Mandatory laboratory verification—isolation of Shigella serovars—is required.
Differentiation from ulcerative colitis (UC)
Acute forms and initial manifestations of UC can mimic dysentery. UC should be suspected in the absence of a full response to standard antibacterial therapy (e.g., nitrofuran derivatives)—the patient continues to have frequent stools with copious blood and mucus admixtures, and fever persists.
Extraintestinal symptoms and systemic manifestations characteristic of autoimmune inflammation are of decisive importance in differential diagnosis:
- Periodic arthralgia and myalgia.
- Pallor of the skin and skin rash.
- Progressive weight loss.
- Anemic syndrome (decreased hemoglobin and red blood cells).
- Sharp increase in ESR (e.g., up to 40 mm/h).
Differences from amebiasis
Amebiasis has a more protracted course (the patient may consider themselves ill for about a month) and does not respond to standard antibiotic therapy such as ciprofloxacin.
Unlike shigellosis, in amebiasis intoxication is mild: body temperature remains normal or reaches only low-grade subfebrile values. The pain syndrome gradually increases and is localized predominantly in the right iliac region (affecting the right colon and cecum). Palpation often reveals a moderately enlarged and tender liver (hepatomegaly). Stools are loose, while admixtures of mucus and blood do not lie on the surface but are evenly mixed with fecal masses.
Algorithm for laboratory diagnostics and therapy
The diagnosis of shigellosis is made by exclusion. The following are used for etiological confirmation:
- Bacteriological examination: stool culture on selective media (gold standard).
- Rapid diagnostics: co-agglutination reaction to detect antigens in saliva, blood, or coprofiltrate.
- Serology: indirect hemagglutination assay (IHA) with dysentery diagnosticum (indicated from the end of the first week).
Etiotropic therapy (e.g., Ciprofloxacin 0.5 g twice daily for a 5–7 day course) is prescribed for moderately severe cases. The main rule: material for bacteriological examination must be collected strictly before starting antibiotics. Oral glucose-electrolyte solutions (Regidron) or intravenous infusions (polyionic solutions) are used to restore water-electrolyte balance. Restoration of microflora with probiotics is allowed only after completing the course of etiopatogenetic therapy.
Briefly: answers to topical questions
When and how is serological diagnostics of shigellosis performed?
Serological diagnostics of shigellosis is performed starting from the first hours of the disease using rapid methods and from the end of the first week using classical reactions.
- Co-agglutination reaction allows the detection of Shigella antigens from the first hours (or day) of the disease. Test material: coprofiltrate, saliva, blood (as part of circulating immune complexes), and urine.
- IHA and agglutination reaction detect antibodies to Shigella in blood serum. A positive result is noted from the end of the 1st week (or 5th–7th day), and an increase in antibody titer by the end of the 2nd week.
- ELISA (enzyme-linked immunosorbent assay) is used to detect antibodies at earlier stages.
How does shigellosis differ from salmonellosis?
Shigellosis differs from salmonellosis in the character of the stool, the presence of tenesmus, and changes in peripheral blood.
| Sign | Salmonellosis | Shigellosis |
|---|---|---|
| Stool | Copious, watery, greenish/dark brown color ("bog mud" appearance) | Scanty, with streaks of mucus and blood |
| Frequency of defecation | Up to 10 times/day, rarely more | Often more than 10 times a day |
| False urges (tenesmus) | Not characteristic | Characteristic |
| Blood | Leukocytosis, possible increase in hematocrit (hemoconcentration) | Minor leukocytosis |
| Pathogen (culture) | Salmonella enterica | Shigella spp. |
What diseases are included in the differential diagnosis of shigellosis?
Differential diagnosis of shigellosis is carried out with diseases having a similar clinical course.
- Amebiasis / amebic dysentery is necessarily included in the differential diagnostic panel when shigellosis is suspected.
- Ulcerative colitis (UC)—its initial manifestations and acute forms are excluded.
- Balantidiasis.
- Foodborne toxicoinfections (FTI), especially the gastroenterocolitic variant.
- Salmonellosis.
- Escherichiosis, including diseases associated with EIEC.
How to clinically distinguish shigellosis from balantidiasis?
Clinically, shigellosis differs from balantidiasis in the localization of tenderness upon palpation and the palpable features of the large intestine.
- In shigellosis, pronounced tenderness on palpation is determined predominantly along the course of the large intestine; the sigmoid colon is tender, indurated, and spastic, and may be palpated as a dense cord.
- In balantidiasis, tenderness is noted in the right iliac region; thickening and induration of a spastic, tender large intestine are palpated in isolated areas.
- For balantidiasis, watery stools mixed with mucus and blood up to 20 times a day with a putrid odor, rapid weight loss, and hepatomegaly with tenderness are also described.
Class and exam questions
At what point is it necessary to prescribe antibiotics when shigellosis is suspected?
Antibacterial drugs are prescribed for moderate severity of the colitic variant, but strictly after stool collection for bacteriological examination.
How to distinguish shigellosis from amebiasis based on stool characteristics?
In shigellosis, admixtures of mucus and blood are usually clearly visible, whereas in amebiasis, blood and mucus are evenly mixed with the fecal masses.
What are the criteria for discharging a patient with shigellosis from the hospital?
Discharge is possible after two consecutive negative bacteriological stool tests. The first control is performed 2 days after the completion of the antibiotic course, and the next one at an interval of 1–2 days.
What else to study on this topic
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