Colon Infection (Colitis, Diverticulitis)

What is a colon infection?

A colon infection refers to inflammation or irritation of the large intestine caused by bacteria, viruses or other underlying conditions that disturb its normal function. The colon, which forms the final part of the digestive tract, is responsible for absorbing water and nutrients and removing waste from the body. When its lining becomes infected or inflamed, the result can be abdominal pain, bloating, diarrhoea and other digestive symptoms.

Colon infections may occur suddenly (acute) or develop over time (chronic), depending on the cause. They range from mild infections that clear on their own to more serious forms that can lead to complications if untreated. Infections may arise after food contamination, antibiotic use or immune disturbances that weaken the natural defences of the gut.

Two of the most common conditions associated with colon infection are colitis and diverticulitis. Although both involve inflammation of the colon, they differ in how and where the inflammation occurs. Colitis affects the inner lining of the colon, whereas diverticulitis results from infection or inflammation of small pouches (diverticula) that form along the colon wall.

Early recognition and treatment of colon infections are essential to prevent complications such as dehydration, abscess formation, or perforation of the bowel. Persistent abdominal pain, fever or blood in the stool should always be evaluated by a doctor.

Types of colon infections

Colon infections can take different forms depending on which part of the large intestine is affected and what causes the inflammation. The two main types are colitis and diverticulitis. Both conditions involve inflammation but differ in their underlying mechanisms, symptoms, and treatment approaches.

• Colitis — this refers to inflammation of the inner lining of the colon. It can be caused by infections, reduced blood flow (ischaemic colitis) or autoimmune diseases that trigger the immune system to attack the colon (inflammatory bowel diseases such as ulcerative colitis and Crohn’s disease). Infectious colitis is often due to bacteria like Clostridioides difficile, Salmonella, Shigella, or Escherichia coli, and may occur after consuming contaminated food or water or following antibiotic use.

• Diverticulitis — this occurs when small bulging pouches, known as diverticula, form along the walls of the colon and become infected or inflamed. These pouches are common in older adults and are often harmless until bacteria become trapped within them. The condition is more frequent in the sigmoid colon, the section of the large intestine closest to the rectum.

What causes colon infections? 

Colon infections can develop due to various factors that disrupt the natural balance of bacteria and the normal function of the large intestine. These causes may be infectious, arising from bacteria, viruses or parasites, or non-infectious, related to inflammation, poor blood flow or structural changes in the colon.

• Bacterial infection — one of the most common causes of colon inflammation, bacterial infections occur when harmful organisms invade the intestinal lining and release toxins. Common culprits include Clostridioides difficile (C. difficile), Salmonella, Shigella, Campylobacter, and toxin-producing Escherichia coli. C. difficile often develops after antibiotic use, which disturbs the gut’s normal flora and allows the bacteria to multiply. Foodborne infections may also occur after consuming undercooked meat, unpasteurised dairy, or contaminated water.

• Viral and parasitic infection — certain viruses, such as norovirus and cytomegalovirus (CMV), can inflame the colon, especially in people with weakened immune systems. Parasitic infections like Entamoeba histolytica (which causes amoebic colitis) and Giardia lamblia can also lead to persistent diarrhoea and abdominal discomfort, particularly in areas where clean water and sanitation are inadequate.

• Diverticulitis — in diverticulitis, bacteria become trapped inside small pouches (diverticula) that form along the colon wall. When these pouches are blocked by stool or debris, infection and inflammation occur. This process is often linked to increased pressure in the colon and changes in bowel habits.

What are the symptoms of colon infections? 

The symptoms of a colon infection can vary depending on its cause and severity. Some infections cause mild discomfort that resolves quickly, while others may lead to more serious inflammation requiring medical attention. Recognising the symptoms early helps prevent complications and ensures timely treatment.

• Abdominal pain and cramping — pain is the most common symptom of colon infection and may range from mild discomfort to sharp, persistent cramps. The pain is often felt in the lower abdomen, especially in cases of diverticulitis, where it typically occurs on the left side.

• Diarrhoea — loose, watery stools are a hallmark of most colon infections. In infectious or inflammatory colitis, diarrhoea may contain mucus, pus or traces of blood. Persistent diarrhoea can lead to dehydration and electrolyte loss if not properly managed.

• Fever and chills — the body’s immune response to infection may cause fever, chills or general fatigue. A high or persistent fever can indicate a more serious infection that may need antibiotics or hospital care.

• Nausea and vomiting — some patients experience nausea, loss of appetite or vomiting due to intestinal irritation or inflammation. These symptoms can worsen if dehydration develops.

• Changes in bowel habits — a colon infection can alter normal bowel rhythm, leading to constipation alternating with diarrhoea. In diverticulitis, constipation is more common due to inflammation or blockage of the colon.

• Bloating and abdominal fullness — gas accumulation and swelling of the intestinal wall can cause a sensation of fullness or bloating. This may worsen after eating or during flare-ups of inflammation.

• Blood in the stool — visible blood or dark, tarry stools suggest bleeding within the colon. This symptom is more common in moderate to severe infections or inflammatory conditions and requires medical evaluation.

• Fatigue and weakness — ongoing infection, fluid loss and reduced nutrient absorption can cause tiredness and general weakness, especially if symptoms persist over several days.

Who is at risk of colon infections in Singapore? 

Colon infections can affect anyone, but certain groups of people are more likely to develop them due to weakened immunity, underlying health conditions or lifestyle factors. Understanding these risks can help with prevention and early detection.

• Older adults — ageing weakens the immune system and slows intestinal movement, increasing the likelihood of infections and diverticular disease. Older adults are also more prone to ischaemic colitis due to reduced blood flow in the colon.

• People with weakened immunity — individuals with weakened immune systems, such as those undergoing chemotherapy, taking immunosuppressive medication or living with HIV are more susceptible to bacterial, viral and parasitic infections that affect the colon.

• People who recently used antibiotics — antibiotics can disturb the balance of healthy bacteria in the gut, allowing harmful organisms like Clostridioides difficile (C. difficile) to overgrow and cause severe inflammation.

• Individuals with inflammatory bowel disease (IBD) — conditions like ulcerative colitis or Crohn’s disease cause chronic inflammation that makes the colon lining more vulnerable to infection. Flare-ups are also more frequent in those with poorly controlled disease.

• Those with poor dietary habits — a low-fibre diet increases the risk of diverticulitis by contributing to constipation and increased pressure in the colon. On the other hand, consumption of contaminated food or water raises the risk of bacterial and parasitic infections.

• People with poor circulation or vascular disease — reduced blood flow from heart disease, diabetes or arterial narrowing can lead to ischaemic colitis and make the colon more prone to infection.

• Frequent travellers — travelling to areas with unsafe water or poor hygiene increases the risk of foodborne and parasitic infections that cause colitis or infectious diarrhoea.

How are colon infections diagnosed?

Accurate diagnosis is essential to determine the cause of a colon infection and guide proper treatment. Doctors use a combination of medical history, physical examination, laboratory tests and imaging studies to identify the source and extent of inflammation.

• Medical history and physical examination — the doctor will begin by reviewing symptoms such as abdominal pain, bowel changes and fever. They may also ask about recent antibiotic use, travel history or dietary habits. During the physical examination, gentle pressure is applied to the abdomen to identify areas of tenderness or swelling.

• Stool tests — a stool sample is analysed to detect bacteria, viruses or parasites responsible for the infection. It can also reveal traces of blood, mucus or white blood cells that indicate inflammation. Special tests can confirm infections like Clostridioides difficile (C. difficile) or E. coli.

• Blood tests — blood tests help assess overall health and detect signs of infection such as raised white blood cell count, inflammation markers or dehydration. Electrolyte levels may also be checked in patients with prolonged diarrhoea or vomiting.

• Imaging studies — imaging such as an abdominal X-ray, ultrasound or CT scan may be performed to identify inflammation, thickening of the colon wall or complications like abscesses or perforations, especially in cases of diverticulitis.

• Colonoscopy or sigmoidoscopy — these procedures use a thin, flexible tube with a camera to view the inside of the colon directly. They allow the doctor to identify inflamed or infected areas and, if needed, take small tissue samples (biopsies) for further analysis. Colonoscopy is especially useful when the diagnosis remains unclear or when inflammatory bowel disease is suspected.

What are the treatment options for colon infections in Singapore? 

Treatment for colon infections depends on the underlying cause, severity and overall health of the patient. The main goals are to control the infection, relieve symptoms and prevent complications such as dehydration or perforation of the colon.

• Antibiotic or antiviral therapy — when a bacterial or viral cause is confirmed, specific medications are prescribed to eliminate the infection. For example, Clostridioides difficile (C. difficile) infections are often treated with antibiotics such as vancomycin or fidaxomicin. Antiviral medicines may be used for cytomegalovirus (CMV) infections, particularly in immunocompromised patients.

• Hydration and electrolyte replacement — maintaining proper hydration is crucial, especially in patients with diarrhoea or vomiting. Oral rehydration solutions may be recommended, while severe dehydration might require intravenous fluids in a hospital setting.

• Anti-inflammatory and pain-relief medication — for conditions like ulcerative colitis or Crohn’s disease, anti-inflammatory drugs or corticosteroids help reduce inflammation and ease discomfort. Pain-relief medication may also be used, but non-steroidal anti-inflammatory drugs (NSAIDs) are usually avoided as they can worsen intestinal irritation.

• Dietary management — during recovery, a soft or low-fibre diet may be recommended to reduce bowel strain. Once symptoms improve, patients are encouraged to gradually reintroduce high-fibre foods to support healthy digestion and prevent recurrence of diverticulitis.

• Hospital treatment — severe infections, abscess formation or complications such as bowel perforation may require hospitalisation. Intravenous antibiotics, bowel rest, and close monitoring are often necessary until inflammation subsides.

• Surgical intervention — surgery may be needed in recurrent or complicated cases of diverticulitis, chronic colitis with severe bleeding, or when parts of the colon become damaged or blocked. The affected section of the colon may be removed to prevent further infection.

How to prevent colon infections? 

Preventing colon infections involves maintaining good digestive health, practising proper hygiene and managing any underlying conditions that increase risk. Simple lifestyle measures can significantly lower the likelihood of infection and inflammation in the colon.

• Eat a balanced, high-fibre diet — a diet rich in fruits, vegetables and whole grains helps keep bowel movements regular and reduces pressure in the colon, lowering the risk of diverticulitis. Fibre also supports healthy gut bacteria, which protect against infection.

• Stay hydrated — drinking enough water supports digestion and prevents constipation, which can strain the colon and contribute to inflammation.

• Practise good food hygiene — wash fruits and vegetables thoroughly, cook meat properly and avoid unpasteurised dairy products. These steps reduce exposure to bacteria and parasites that cause infectious colitis.

• Use antibiotics responsibly — only take antibiotics when prescribed by a doctor and complete the full course. Overuse or misuse can disrupt the balance of healthy gut bacteria, increasing the risk of Clostridioides difficile (C. difficile) infection.

• Exercise regularly — physical activity promotes healthy bowel movement and improves blood circulation, reducing the risk of ischaemic colitis and diverticular disease.

• Manage chronic conditions — conditions such as diabetes, vascular disease or inflammatory bowel disease should be well controlled under medical supervision to minimise the risk of colon-related complications.

• Practise safe food and water habits while travelling — Avoid untreated water, raw foods and street-prepared meals in areas where sanitation is uncertain to prevent bacterial or parasitic infections.

When to see a doctor for colon infection 

While mild colon infections may improve with rest and hydration, certain symptoms require prompt medical attention. Early assessment helps prevent serious complications and ensures timely treatment.

• Persistent abdominal pain — ongoing or severe abdominal pain, especially in the lower left side, can indicate diverticulitis or another serious infection that needs medical evaluation.

• High fever or chills — a fever above 38°C (100.4°F) or chills that do not subside may signal that the infection is spreading or worsening.

• Blood or mucus in stool — the presence of blood, mucus or dark stools suggests inflammation or bleeding inside the colon and should always be investigated.

• Frequent or severe diarrhoea — diarrhoea lasting more than two or three days, or accompanied by dehydration, dizziness or weakness, may require medical treatment and laboratory testing.

• Nausea and vomiting — persistent vomiting can cause dehydration and electrolyte imbalance and may point to an intestinal obstruction or severe inflammation.

• Unexplained weight loss or fatigue — ongoing weight loss, tiredness or reduced appetite can be signs of chronic colitis or another underlying digestive condition that needs further investigation.

If you experience any of these symptoms, seek prompt evaluation by a colorectal specialist. Early diagnosis and treatment can prevent complications and help restore healthy bowel function.

Summary 

Colon infections, including colitis and diverticulitis, occur when the large intestine becomes inflamed or infected. They can cause abdominal pain, diarrhoea, bloating or fever, and may result from bacteria, viruses, reduced blood flow or chronic inflammatory conditions. Diagnosis typically involves stool and blood tests, imaging studies, or colonoscopy to identify the cause and extent of inflammation.

Treatment depends on the severity and underlying condition and may include antibiotics, anti-inflammatory medication, hydration support or dietary changes. Preventive care focuses on a balanced, high-fibre diet, good food hygiene and responsible antibiotic use. If you are experiencing persistent abdominal discomfort or changes in bowel habits, schedule a consultation with Tan Siong San Surgery for an accurate diagnosis and personalised treatment plan.