Anamnesis collection and risk factor assessment
The initial stage of diagnosis is a thorough collection of epidemiological history. The incubation period of the infection is relatively short, so it is important to find out the events of the last 2–7 days. The physician should clarify contact with individuals suffering from intestinal disorders and stays in endemic areas.
Key transmission factors for shigellosis:
- Alimentary: consumption of raw milk, salads, unwashed fruits, and vegetables without heat treatment.
- Waterborne: drinking unboiled water, especially from open water bodies.
- Sanitary and hygienic: lack of sewage systems, abundance of flies, and violation of basic hygiene rules.
The course of the disease is often exacerbated by reduced gastrointestinal resistance. This is facilitated by previous intestinal infections (salmonellosis, foodborne toxic infections), helminthiases, protozoan infestations (amebiasis, giardiasis), as well as chronic gastrointestinal pathology (gastritis, enterocolitis, cholecystitis).
Clinical presentation of the colitic variant
Classic acute shigellosis presents as the colitic variant. The onset of the disease can be typical, flu-like, or with spasmodic pain. In the first three days, pronounced intoxication with subfebrile or high fever is observed.
Main clinical markers:
- Pain syndrome: cramping pains localized predominantly in the lower abdomen.
- Signs of distal colon damage: painful false urges to defecate and tenesmus.
- Character of stool: frequent and liquid. Over time, feces become scanty (down to fecal-free excreta — "rectal spit"), and a significant amount of pathological impurities appear — mucus and blood.
- Physical examination: abdominal palpation clearly defines a dense, painful, and spastic sigmoid colon.
Laboratory and instrumental diagnostics
Laboratory and, less commonly, instrumental methods are used to confirm the clinical diagnosis. Differential diagnosis is carried out with other gastrointestinal diseases presenting with a similar picture.
- Bacteriological examination: the "gold standard". It consists of culturing feces on special diagnostic media to isolate the Shigella culture.
- Serological diagnostics:
- Coagglutination test: allows the detection of Shigella antigens in the blood (as part of circulating immune complexes), saliva, urine, and coprofiltrates. The result is positive as early as day 1 of the disease.
- IHA (indirect hemagglutination assay): detects specific antibodies in blood serum. They appear from the end of the first week, and a reliable titer increase is recorded by the end of the second week.
- Instrumental methods (sigmoidoscopy): play an auxiliary role. Endoscopy visualizes a picture of catarrhal, catarrhal-hemorrhagic, erosive, or ulcerative proctosigmoiditis.
Formulation of diagnosis and discharge rules
The detailed clinical diagnosis must reflect the type of pathogen (based on analysis results), clinical variant (colitic, gastroenterocolitic, or gastroenteritic), and severity level. Severity is assessed by the level of fever, toxicosis, pain intensity, stool frequency, impurities in the stool, and degree of dehydration. Example: Acute Sonne shigellosis, gastroenterocolitic variant, mild course (Sh. sonnei in analysis No. 33 dated 11.01.2015).
Discharge criteria: Clinically, a patient can be discharged no earlier than 3 days after sustained normalization of temperature and stool. The bacteriological criterion is one negative stool culture collected no earlier than 2 days after the end of antibiotic therapy.
Special rules apply to food service workers, water supply workers, and children in childcare facilities:
- In case of a bacteriologically unconfirmed diagnosis, one control test is submitted before discharge.
- In case of a confirmed diagnosis, two tests with an interval of 1–2 days. Subsequently, such convalescents are under outpatient observation for 3 months to monitor work clearance.
Briefly: answers to topical questions
What specific elective nutrient media are used for the bacteriological culture of feces for Shigella?
In the cited sources for shigellosis, it is confirmed: etiological confirmation is carried out by bacteriological examination of feces — culture on selective/diagnostic nutrient media.
Among the specific media directly associated with Shigella in the sources, Ploskirev agar is named: bile salts inhibit E. coli, while lactose differentiates Shigella/Salmonella (colorless colonies) from E. coli (dark red colonies).
With which infectious and non-infectious bowel diseases is differential diagnosis of shigellosis performed?
Differential diagnosis of shigellosis (acute dysentery) is performed with a wide range of pathologies.
Infectious and parasitic diseases:
- Amebiasis
- Balantidiasis
- Campylobacteriosis
- Yersiniosis
- Pseudomembranous colitis
- Helminthiases
Non-infectious and surgical pathology:
- Ulcerative colitis
- Crohn's disease
- Irritable bowel syndrome
- Colonic neoplasms
- Mesenteric thrombosis (mesenteric arterial thrombosis)
- Acute intestinal obstruction
- Heavy metal salt poisoning
To remember the clinical presentation of typical shigellosis, use the rule of three "S"s: Sigmoid colon spasm, Scanty stool, Slime (and blood) in stool.
Class and exam questions
When do antibodies to Shigella appear in the patient's blood?
When using IHA, antibodies begin to be detected only from the end of the first week of the disease, and their maximum increase is noted by the end of the second week.
When should the follow-up stool culture be taken before discharge?
Material for control bacteriological examination is taken no earlier than 2 days after the complete completion of the course of antibiotic treatment.
How long does dispensary follow-up for food industry workers last?
Observation of convalescents of decreed groups is carried out on an outpatient basis for 3 months after discharge from the hospital.
What else to study on this topic
- Severity criteria and assessment of dehydration in shigellosis
- Specifics of the gastroenteritic and gastroenterocolitic variants of the course
- Differential diagnosis of shigellosis with amebiasis and salmonellosis
- Management tactics for patients with acute dysentery
Master the complete topic in the «Infectious Diseases» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Diagnosis of shigellosis" and 3,312 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 41 video lessons on the subject
Other topics in the "Acute Intestinal Infections" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.