Introduction

Have you ever wondered if that uncomfortable, urgent feeling to defecate could be more than just a fleeting issue? This sensation, known as tenesmus, involves a feeling of incomplete emptying of the bowel, normally with a sense of needing to defecate urgently but ineffectively. Tenesmus is commonly present with rectal and colonic diseases, such as inflammatory, infectious, and neoplastic diseases (conditions characterised by uncontrolled, abnormal cell growth, resulting in tumours). One such neoplastic condition is colorectal cancer (CRC), a malignancy of the rectum or colon that usually begins as a benign polyp that becomes malignant over time. As one of the leading causes of cancer-related deaths worldwide, CRC has various risk factors, including age, heredity, diet, inflammatory bowel disease, and lifestyle factors such as smoking and obesity. Symptoms of CRC are multifarious and may involve rectal bleeding, altered bowel habits, abdominal cramps, and weight loss. Tenesmus can be an early warning sign of CRC, especially obstructive rectal tumours. Early detection of symptoms can lead to prompt medical assessment, speedy diagnosis, and better outcomes in management.

Understanding tenesmus

Pathophysiology and mechanisms

Tenesmus is the persistent sensation of incomplete bowel emptying, usually caused by inflammation, obstruction, or neuromuscular dysfunction. Inflammation triggers rectal nerve endings, leading to urgency. Additionally, tumours or masses in the rectum result in mechanical obstruction, hence emptying is felt as incomplete. Neuromuscular dysfunction, as in colorectal cancer and other conditions, further disrupts bowel coordination, while mucosal damage from infections or chronic inflammation enhances rectal sensitivity, thus worsening tenesmus.¹

Common causes other than colorectal cancer

Tenesmus can also be caused by:

• Inflammatory bowel disease (IBD), such as ulcerative colitis and Crohn's disease
  •  Produces chronic rectal inflammation and a sense of urgency
• Infection, such as bacterial colitis (Shigella, Salmonella) or parasitic infection (Entamoeba histolytica)
  •  Causes irritation of the rectum and excessive passage of stool
• Rectal illness like haemorrhoids, fissure of the anus, or proctitis can mimic tenesmus
• Pelvic floor or spinal cord neurological illness may compromise bowel control
• Irritable bowel syndrome (subtype IBS-D)
  • Causes rectal urgency and hypersensitivity

Correlation between tenesmus and CRC

CRC causes tenesmus due to obstruction, inflammation, and neural involvement.² Colonic or rectal neoplasms block the defecation route, leading to an ongoing need for a bowel movement. Inflammation also stimulates the mucosa of the rectum and produces repetitive impulses. Additionally, pelvic nerves are compressed by tumours, thus increasing tenesmus.

Rectal cancer is the most common and direct cause of tenesmus since tumours in this area have an effect on both stool storage and removal. These tumours create discomfort and a persistent sensation of needing to pass stool. In contrast, colonic cancer usually leads to symptoms such as constipation and abdominal pain.¹ However, tenesmus only appears in the advanced stages of CRC, when the tumour has grown large enough to compress the rectum, obstructing normal defecation and causing the uncomfortable and constant sensation of needing to pass stool.

Symptoms of CRC

Rectal bleeding:

• Bright red (rectal tumours) or dark/tarry (higher tumours)
• Often mistaken for haemorrhoids
• Chronic bleeding can cause iron-deficiency anaemia (fatigue and pallor)

Altered bowel habits:

• Constipation secondary to tumour obstruction
• Diarrhoea is secondary to tumour irritation or bowel incompleteness

Abdominal pain and weight loss:

• Obstruction, inflammation, or metastasis pain (cramping, bloating and gas)
• Unintentional weight loss due to metabolic alteration, loss of appetite, or malabsorption

Persistent symptoms require medical evaluation for CRC.

Diagnostic approach

Clinical assessment

History: 

• Assess symptoms of tenesmus, change in bowel habit, rectal bleeding, and pain
• Enquire about duration, pattern, and risk factors such as family history or IBD³

Digital Rectal Exam (DRE): 

• Detects palpable masses, irregularity, or tenderness of the rectum, especially useful for rectal cancers

Imaging

Colonoscopy: 

• Visualises the colon and rectum for tumours, polyps, or abnormalities, and allows biopsy collection³

CT scan: 

• Aids in the assessment of tumour site, size, and potential metastasis to nodes or distant organs³

MRI: 

• Beneficial for rectal cancer staging, determining local extension (the growth and spread of a tumour directly into surrounding structures), and planning treatment³

Biopsy and histopathology

If an abnormal growth is found during a colonoscopy, a biopsy (where cells are examined to determine whether they are cancerous) may be performed. Biopsy samples can be used to define malignancy and the type of cancer, allowing a prognosis to be established and a treatment plan to be developed. Targeted therapy may be guided by molecular analysis.

Treatment considerations

Surgical treatment

Resection is usually performed on localised colon cancer, where the tumour with the surrounding attached tissue is removed to offer an opportunity for cure. Abdominoperineal resection (APR) or a low anterior resection (LAR) can be performed depending on the location of the tumour.⁴ Surgical resection can provide immediate relief from tenesmus if the tumour is obstructive or compresses the rectum.⁴

A colostomy, which provides an opening in the abdomen to re-route stool from the rectum through an opening in the abdominal wall, may be performed if:

• The colon needs time to heal after surgery
• A colostomy would lower the risk of bowel obstruction during treatment (e.g., chemotherapy) before or after surgery 
• A large part of the colon has to be removed, and the remaining section cannot be rejoined
• Complete tumour removal is not possible. Re-routing stool from the rectum relieves tenesmus, but is typically only used as a last resort for symptom relief

Adjuvant therapies

Chemotherapy is usually used after surgery for stage III or high-risk stage II colon cancer to avoid recurrence. While chemotherapy decreases tumour size, it does not treat tenesmus.⁵

Radiation therapy may be used either before surgery to shrink rectal cancers and reduce obstruction or after surgery to kill lingering cancer cells. Radiation serves to prevent tenesmus by shrinking the tumour.⁵

Palliative care

For palliative management of advanced CRC, symptom control is the goal, i.e., tenesmus. Constipation and spasm of the bowel are eased by medications like antispasmodics (e.g., hyoscine) and laxatives. Relief of pain is also essential, and administration of opioids should be balanced against bowel function to prevent worsening of constipation and tenesmus.¹ In some cases, rectal stenting can be used to decompress and reduce tenesmus temporarily. If the cancer is at an advanced stage, a colostomy may be performed to bypass the bowel around the rectum and relieve the symptoms.

Support groups or psychological counselling also help patients cope with the emotional stress of long-term symptoms like tenesmus.

Prognosis and outcomes

Impact of early detection on survival rates

Early detection of CRC greatly improves survival rates, with a survival rate above 90% in early stages (stages 1-2) due to localised tumours and successful surgery. In contrast, late-stage CRC (stage 3-4), where cancer has spread, has a 5-year survival rate of only 14-15%. Early screening examinations (e.g., colonoscopies) are critical for detecting CRC early and improving outcomes, especially in high-risk patients.⁴

Long-term management and quality of life

After treatment, long-term management includes surveillance for recurrence and management of complications:⁴

• Follow-up care involves regular colonoscopy and imaging to detect recurrence
• Complications after treatment, like colostomy care, chemotherapy side effects, and long-term bowel issues, require ongoing management
• Psychosocial care helps with anxiety, depression, and lifestyle adjustment
• Survivors need to prioritise a healthy lifestyle, such as nutrition, exercise, and regular screening, to manage long-term health.

FAQs

Why is tenesmus a red flag?

Tenesmus is often associated with other clinical signs of colonic disease. 

What is the fastest way to cure tenesmus?

Treatment for tenesmus will depend on the underlying cause. Treatment options include lifestyle changes like eating more fibre, drinking more water, and getting regular exercise. Medical treatments range from taking over-the-counter stool softeners to prescription drugs and surgery.

What is the number one cause of colorectal cancer?

The exact cause of colorectal cancer is unknown, but it is thought that the primary cause is environmental factors, such as a diet high in fat and low in fibre, tobacco consumption, and alcohol misuse.⁶ 

Who is at high risk for colorectal cancer?

The risk of developing colorectal cancer increases with age. Other risk factors include having inflammatory bowel disease, such as Crohn's disease or ulcerative colitis. A personal or family history of colorectal cancer or colorectal polyps also increases risk.

Summary

• Tenesmus, the sensation of not having completely emptied the bowel, is related to CRC, especially when rectal or sigmoid colon tumours are present
• This is due to blockage, inflammation, or nerve involvement caused by the tumour and can be linked with other symptoms of CRC, like rectal bleeding and abdominal pain
• Diagnosis is by clinical evaluation, imaging, and biopsy, and treatment may be by surgery, chemotherapy, and radiotherapy
• Early detection of CRC improves survival and quality of life, and thus, timely medical consultation is crucial