Blood in Stool and Diarrhoea: Common Colorectal Causes

Blood in the stool and diarrhoea are common symptoms that can indicate a variety of colorectal conditions. These symptoms may result from minor issues, like haemorrhoids, or more serious conditions, such as inflammatory bowel disease (IBD) or colorectal cancer. Recognising potential causes is necessary for timely diagnosis and treatment, as some conditions necessitate immediate medical care. This guide outlines the most common colorectal causes of blood in stool and diarrhoea to help patients know when to seek professional advice.

Why Blood in Stool and Diarrhoea Occur Together

Blood in stool and diarrhoea often co-occur when there is inflammation, infection, or damage to the colon or rectal tissues. Inflammatory processes, such as those seen in IBD, can irritate and damage the colon’s lining, leading to diarrhoea and bleeding. Infections that irritate the colon may also cause both symptoms. Recognising the connection between these symptoms helps explain why they are commonly seen together.

Common Causes of Blood in Stool and Diarrhoea

Haemorrhoids

Haemorrhoids are swollen blood vessels in the rectum or anus that can cause bright red blood in the stool, often due to straining or prolonged sitting. While haemorrhoids themselves do not typically cause diarrhoea, irritation from the swollen blood vessels may affect bowel habits. Bleeding from haemorrhoids usually appears as small streaks of blood on toilet paper or stool.

Anal Fissures

Anal fissures are small tears in the anus lining, often caused by passing hard or large stools, frequent diarrhoea, or chronic constipation. These tears can lead to bright red blood in the stool and pain during bowel movements. Although anal fissures do not directly cause diarrhoea, irritation from a fissure may contribute to looser stools as the body tries to avoid discomfort.

Diverticulosis and Diverticulitis

Diverticulosis involves the formation of small pouches (diverticula) in the colon wall. If these pouches become inflamed or infected, a condition known as diverticulitis develops, which can cause bleeding and diarrhoea along with abdominal pain and fever. Bleeding from diverticular disease is often darker and may appear mixed with stool.

Inflammatory Bowel Disease (IBD)

IBD, which includes Crohn’s disease and ulcerative colitis, causes chronic inflammation of the gastrointestinal tract. Crohn’s disease can affect any part of the gastrointestinal tract, while ulcerative colitis mainly affects the colon and rectum. Inflammation can lead to diarrhoea and blood in the stool, often with additional symptoms such as abdominal pain, weight loss, and fatigue.

Colorectal Polyps and Cancer

Colorectal polyps are abnormal growths in the colon or rectum lining. While most polyps are benign, some may develop into cancer. Both polyps and colorectal cancer can cause bleeding, and cancer can also lead to changes in bowel habits, including diarrhoea or constipation. 

Infectious Colitis

Infectious colitis is inflammation of the colon caused by bacterial, viral, or parasitic infections. Common pathogens include Salmonella, E. coli, and Shigella. Infections irritate the colon lining, leading to diarrhoea with blood or mucus, along with symptoms such as abdominal cramps, fever, and dehydration. 

Diagnostic Methods

To determine the cause of blood in stool and diarrhoea, a specialist will use a combination of medical history, physical examination, and diagnostic tests:

Physical Examination

The specialist often begins with a physical examination to identify any visible causes of blood in stool, such as haemorrhoids or anal fissures, which are common sources of rectal bleeding. This initial step helps rule out or confirm some external causes of bleeding and can provide valuable information for further testing.

Colonoscopy

A colonoscopy allows the specialist to examine the entire colon and rectum in detail using a flexible tube with a camera. During the procedure, the specialist can look for conditions such as polyps, diverticulosis, inflammatory lesions, and signs of colorectal cancer. If any suspicious areas are found, the specialist may take biopsies (small tissue samples) to send for laboratory analysis, which helps in confirming a diagnosis.

Imaging Tests

Imaging tests, such as CT scans or MRI, provide detailed images of the colon and surrounding abdominal structures. These tests are especially useful when conditions like diverticulitis, colorectal cancer, or other structural complications are suspected. A CT scan can show inflammation, abscesses, and other changes in the colon, while an MRI provides high-resolution images that can help in assessing tumour involvement and spread in cancer cases. 

Laboratory Tests

Blood tests may check for anaemia, which can result from chronic blood loss, while stool tests can identify pathogens in cases of infectious colitis. Stool samples may also be analysed for signs of inflammation or occult (hidden) blood, which can aid in diagnosis.

Treatment Options

Non-Surgical Approaches

For many colorectal conditions that cause blood in stool and diarrhoea, non-surgical approaches are the first line of management. These methods focus on relieving symptoms, addressing underlying causes, and supporting digestive health.

Lifestyle and Dietary Adjustments

Dietary modifications are often a first step for mild cases, particularly for conditions like haemorrhoids, diverticulosis, and mild IBD. Increasing fibre intake through fruits, vegetables, and whole grains can support regular bowel movements and reduce straining, which helps prevent and manage haemorrhoids and diverticular issues. Staying well-hydrated and avoiding irritants, such as processed foods, alcohol, and caffeine, may also reduce irritation in the digestive tract.

Medications

Medications help manage conditions that cause blood in stool and diarrhoea depending on the underlying cause. For IBD, anti-inflammatory drugs, such as corticosteroids and aminosalicylates, help reduce colon inflammation and manage symptoms. Antibiotics are commonly used to treat infections causing colitis by eliminating bacteria like E. coli or Salmonella. 

In cases where constipation or hard stools aggravate symptoms, stool softeners or fibre supplements may aid smoother bowel movements, reducing strain and the risk of bleeding, especially in haemorrhoids and anal fissures. Pain relief options may also be provided but are used cautiously, especially in IBD, to avoid exacerbating symptoms.

Topical Treatments

In cases of haemorrhoids or anal fissures, topical creams and ointments may provide relief. For example, haemorrhoidal creams can reduce inflammation and swelling, while medicated ointments for anal fissures promote healing and reduce discomfort during bowel movements.

Surgical Treatment

Surgical interventions may be necessary when non-surgical treatments are insufficient or when the underlying condition is advanced or severe. Common surgical options include:

Haemorrhoidectomy

In cases of severe or recurring haemorrhoids that do not respond to lifestyle changes or topical treatments, a haemorrhoidectomy may be performed. This procedure involves the surgical removal of haemorrhoids, providing long-term relief from bleeding and discomfort.

Polypectomy

For patients with colorectal polyps, a polypectomy (removal of polyps) is often performed during a colonoscopy. This procedure prevents polyps from growing larger or potentially turning cancerous. Polypectomy is generally a quick and minimally invasive procedure.

Colectomy

For severe IBD, diverticulitis complications, or colorectal cancer, a colectomy may be necessary. This surgery involves removing a portion (or, in some cases, the entirety) of the colon. In IBD, a colectomy may help manage symptoms when other treatments have failed, while in colorectal cancer, it can be life-saving by removing cancerous tissue.

Resection for Colorectal Cancer

In cases of colorectal cancer, a section of the colon or rectum containing the tumour may be surgically removed. This procedure often involves removing nearby lymph nodes to prevent cancer spread. Depending on the tumour’s location and stage, resection may be combined with other treatments, such as chemotherapy or radiation therapy.

Abscess Drainage

For diverticulitis patients who develop an abscess (a collection of infected fluid), surgical drainage may be required. This procedure helps remove infected material and reduce inflammation, preventing further complications.

When Should You See a Specialist?

Not all cases of blood in the stool and diarrhoea necessitate immediate medical attention, but some symptoms may indicate a serious underlying problem and necessitate a prompt consultation with a specialist. Seek medical advice if you experience:

• Persistent or worsening symptoms that do not improve within a few days.
• Dark (black or tarry) blood in the stool, or bright red blood that appears consistently.
• Severe abdominal pain, fever, or unintentional weight loss along with these symptoms.
• A personal or family history of colorectal cancer, polyps, or gastrointestinal disorders.

In these instances, consulting a colorectal specialist is recommended to help determine the cause and ensure appropriate treatment.

Conclusion

Blood in stool and diarrhoea can be symptoms of various colorectal conditions, some of which require timely medical attention. Recognising common causes helps patients determine when to seek evaluation from a specialist. Consulting with a colorectal surgeon is advisable if these symptoms persist, worsen, or are accompanied by other warning signs. Early diagnosis and treatment are key to managing underlying conditions and promoting long-term gastrointestinal health.

If you have blood in your stool, persistent diarrhoea, or other digestive issues, schedule a consultation today to discuss your symptoms and explore personalised diagnostic and treatment options.