Symptoms of Infectious Colitis
Infectious colitis presents with bloody, purulent, and mucoid diarrhea accompanied by fever, severe abdominal pain, and tenesmus. 1
Cardinal Symptoms
The hallmark presentation includes:
- Bloody diarrhea with purulent and mucoid stool – this inflammatory-type diarrhea distinguishes infectious colitis from non-inflammatory causes 1, 2
- Fever – typically present in invasive bacterial infections such as Shigella, Salmonella, and Campylobacter 3, 1
- Severe abdominal pain and cramping – colicky in nature, often accompanied by urgency 3
- Tenesmus – painful straining with bowel movements, reflecting rectal inflammation 1, 2
- Blood and mucus in stool – indicates mucosal invasion and inflammation 3
Associated Clinical Features
Additional symptoms that commonly occur include:
- Increased stool frequency – watery diarrhea with multiple bowel movements per day above baseline 3
- Urgency and nocturnal bowel movements – disruption of normal bowel patterns 3
- Nausea and vomiting – may accompany the gastrointestinal inflammation 3
- Systemic symptoms – headache, myalgias, and malaise can occur 3
Signs of Volume Depletion
Watch for indicators of dehydration, which can develop rapidly:
- Thirst, tachycardia, and orthostatic hypotension – early signs requiring fluid resuscitation 3
- Decreased urination and lethargy – progression of volume depletion 3
- Dry mucous membranes and decreased skin turgor – physical examination findings 3
- Hemodynamic instability – indicates severe disease requiring urgent intervention 3, 4
Stool Characteristics to Assess
The nature of diarrhea provides diagnostic clues:
- Watery versus bloody – helps distinguish inflammatory from non-inflammatory causes 3
- Presence of pus – suggests invasive bacterial pathogens 3, 1
- Greasy appearance – less common in infectious colitis, more suggestive of malabsorption 3
Important Clinical Pitfalls
Do not assume all bloody diarrhea is infectious colitis – inflammatory bowel disease, ischemic colitis, and other causes must be excluded through stool cultures and endoscopy 4, 2. The key distinguishing feature is that infectious colitis typically has acute onset (days to weeks) rather than the chronic, relapsing pattern seen in IBD 5.
Shiga toxin-producing E. coli (STEC) may present with only low-grade or absent fever despite causing severe dysentery, making it an important exception to the typical febrile presentation 2. This pathogen requires specific testing beyond standard stool culture 2.