Infectious Colitis

Overview

Infectious colitis is inflammation of the colon, or large intestine, caused by an infection. A range of germs can be responsible, including bacteria, viruses, and parasites, which irritate and inflame the lining of the bowel. This inflammation interferes with the colon's normal job of absorbing water and forming stool, leading to diarrhea and other symptoms.

Most cases are short-lived and improve on their own with rest and fluids, much like other forms of gastroenteritis. However, some infections can be more serious, causing bloody diarrhea, dehydration, or complications, particularly in young children, older adults, and people with weakened immune systems. Knowing the warning signs helps distinguish a routine illness from one needing prompt care.

Symptoms

Symptoms usually begin within hours to a few days of infection and may include:

• Diarrhea, which may be watery or contain blood or mucus
• Abdominal cramping and pain
• An urgent or frequent need to pass stool
• Fever and chills
• Nausea and sometimes vomiting
• Feeling generally unwell and tired

Signs of dehydration, such as marked thirst, dizziness, reduced urination, and dry mouth, are important to watch for. Bloody diarrhea, high fever, or severe abdominal pain suggest a more serious infection that needs medical evaluation.

Causes

Many different germs can cause infectious colitis. Common culprits include:

• Bacteria: Such as Salmonella, Shigella, Campylobacter, certain types of E. coli, and Clostridioides difficile (often after antibiotic use).
• Viruses: Such as norovirus and rotavirus, which more often cause general gastroenteritis but can inflame the colon.
• Parasites: Such as Entamoeba histolytica and Giardia.

Infection usually spreads through contaminated food or water, or by contact with an infected person or surface. Poor hand hygiene and undercooked foods are common routes of transmission.

Risk Factors

• Eating undercooked meat, eggs, or unpasteurized foods
• Drinking untreated or contaminated water
• Recent travel to areas with poor sanitation
• Recent antibiotic use (a risk for C. difficile)
• A weakened immune system
• Close contact with someone who has a gastrointestinal infection

Diagnosis

Diagnosis is based on symptoms and tests to identify the cause and rule out other conditions:

• Stool tests: To detect bacteria, parasites, or their toxins, including testing for C. difficile.
• Blood tests: To check for signs of infection, inflammation, and dehydration.
• Colonoscopy: Occasionally needed to view the colon lining and distinguish infection from other causes such as ulcerative colitis or Crohn's disease.

Identifying the specific germ helps guide treatment, especially for infections that require targeted therapy.

Treatment

Most cases improve with supportive care, but some need specific treatment:

• Fluids: Drinking plenty of fluids, or using oral rehydration solutions, is the cornerstone of care to prevent dehydration. Severe dehydration may need intravenous fluids.
• Rest and gradual eating: Returning to a normal diet as tolerated.
• Antibiotics: Used selectively for certain bacterial or parasitic infections, but not for every case, since some infections clear on their own and antibiotics can sometimes worsen the illness.
• Treating C. difficile: Requires specific antibiotics and often stopping the antibiotic that triggered it.

Anti-diarrheal medicines are used cautiously, as they can be harmful in certain bacterial infections.

For most healthy adults with mild illness, careful attention to fluids and gradual return to normal eating is enough, and the body clears the infection on its own. People at higher risk, including infants, older adults, pregnant people, and those with weakened immune systems, may need closer monitoring and sometimes hospital care to manage dehydration and prevent complications. Resting and avoiding preparing food for others while ill also helps limit the spread of infection.

Prevention

• Wash hands thoroughly with soap, especially before eating and after using the toilet
• Cook meat and eggs fully and avoid unpasteurized products
• Drink safe water and avoid untreated water when traveling
• Wash fruits and vegetables and avoid cross-contamination when preparing food
• Use antibiotics only when prescribed to reduce the risk of C. difficile

When to See a Doctor

See a doctor if diarrhea lasts more than a few days, or sooner if symptoms are severe. Seek urgent or emergency care for:

• Blood in the stool or black, tarry stools
• High fever
• Signs of dehydration such as dizziness, very little urine, or confusion
• Severe or worsening abdominal pain
• Diarrhea in a baby, older adult, or person with a weak immune system

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Foodborne illnesses.
2. MedlinePlus, U.S. National Library of Medicine. Gastroenteritis.
3. Mayo Clinic. Diarrhea.
4. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Digestive diseases.