Rectal bleeding: The warning sign of hemorrhoids and colorectal cancer

8 minute(s) read
Rectal bleeding: The warning sign of hemorrhoids and colorectal cancer


Rectal bleeding is not only the common sign of hemorrhoids, but colorectal cancer. Due to the similarity of clinical manifestations, colorectal cancer is often mistaken for hemorrhoids, leading to delayed diagnosis and ineffective treatments. Therefore being aware of the specific warning signs and symptoms of these diseases results in early detection and appropriate treatments. If suspected signs of hemorrhoids or colorectal cancer exhibit, especially rectal bleeding, immediate medical attention must be sought as soon as possible.  


Get to know “hemorrhoids”

Hemorrhoids are swollen veins in lower part of the anus and rectum. The veins around the anus tend to stretch due to additional pressure, causing bulge or swelling. This condition can develop from increased pressure in the lower rectum. Hemorrhoids can be classified into 2 types:

  1. Internal hemorrhoids: Internal hemorrhoids lie inside the rectum and are covered with cells that line the rest of the intestines. Internal hemorrhoids cannot be typically seen or felt. It does not typically cause rectal pain, discomfort or irritation if complications are absent. The hemorrhoids might protrude through the rectum with strain during defecation. 
  2. External hemorrhoids: External hemorrhoids are hemorrhoids that affect veins outside the anus. External bulges can be seen and touched around the anal area. They are covered with cells that resemble skin, typically slightly less pink than the surrounding skin. Symptoms might include itching or irritation in the anal region, pain or discomfort, swelling around the anus and rectal bleeding that might be found during defecation. 


Get to know “rectal cancer”

Rectal cancer is a disease in which cancer cells form in the tissues of the rectum. Sometimes cancerous tumors develop relatively close to the anal canal, a short tube at the end of the rectum through which stool leaves the body. It is commonly found in both male and female. Major contributing factor to develop rectal cancer is related to the family history of cancer, especially first-degree relatives. A wide range of signs and symptoms of rectal cancer might include rectal bleeding or blood in the stool, irregular stool patterns such separate hard lumps, a feeling of incomplete defecation, persistent changes in bowel habits including diarrhea or constipation, or alternating bouts of diarrhea and constipation, abdominal discomfort such as cramps or pain, fatigue or weakness and unintentional weight loss. In addition, manifestations are determined by disease severity, location and its stage.

Hemorrhoids have certainly shared similarities with rectal cancer. If these warning signs and symptoms exhibit, immediate medical attention must be sought in order to receive appropriate and timely treatments. The differences involve: 

  • Hemorrhoids: Hemorrhoids with bulge might be palpable inside the anus. It might protrude through the rectum and spontaneously returns to their original position inside the rectum. Common symptoms are swelling, pain or discomfort, itching or irritation in the anal region and straining during bowel movements with frequent defecation.
  • Rectal cancer: Masses are discovered inside the anus by the specialists and cannot be seen externally. There is no presence of protruding mass. Pain in the anal region is rarely found. Symptoms include frequent bowel movements with a feeling of incomplete defecation and stool with mucus or blood stains.


ถ่ายเป็นเลือด, ริดสีดวง, มะเร็งลำไส้ใหญ่ส่วนปลาย



Suspected signs and symptoms of rectal cancer include rectal bleeding during defecation and abdominal abnormalities that might be caused by other diseases such as an anal fistula (an infection near the anus due to chronic constipation), diverticulitis (inflammation or infection of small pouches called diverticula that develop along the walls of the intestines) or an angiodysplasia defined as an abnormality with the blood vessels in the lining of the intestine.

Potential risk factors for developing rectal cancer might involve genetics or family history of cancer, age over 45, being obese or overweight and unhealthy lifestyle habits e.g. regular eating of high-fat foods or red meat, fermented or processed foods as well as alcohol drinking and smoking. 

If signs and symptoms present, especially in a combination with risk factors, diagnostic tests must be performed by highly experienced specialists. Early diagnosis plays a major role to increase the chances of successful treatments. Diagnostic tests and procedures involve: 

  • Medical history taking and full physical examination. 
  • Laboratory tests. 
  • Barium swallow to view and access the abnormalities of the intestine and rectum. 
  • Computed tomography (CT)-colonoscopy uses special X-ray to examine the large intestine and rectum.
  • Colonoscopy: Using a scope to examine the inside of the colon and rectum. A long, flexible and slender tube attached to a video camera and monitor is inserted through the anus to view the entire colon and rectum. 
  • Blood test to determine carcinoembryonic antigen (CEA), tumor marker used for disease prognosis and follow-up after receiving treatment. 
  • Biopsy: If any suspicious areas are found during colonoscopy, the specialists pass surgical tools through the tube to take tissue samples (biopsy) for analysis and remove polyps.


After receiving all investigational results including cancer staging, customized treatments are collectively planned by multidisciplinary team consisting of colorectal surgeons, diagnostic radiologists, radiation oncologists, medical oncologists and pathologists. The ultimate aim is to provide the treatment with the best possible outcomes while taking into consideration of patient’s physical and mental aspects.



Selected treatment options for hemorrhoids entirely depend on presenting symptoms and disease severity as well as individual conditions of the patients. Treatment options include non-surgical treatments (e.g. medications, injections or sclerotherapy and rubber band ligation) and surgical treatments. 

In case that rectal cancer is strongly suspected, colonoscopy will be used for confirmatory diagnosis. Normally, the rectum regulates the defecation process. It is consisted of an anal sphincter, a group of muscles at the end of the rectum that controls the release of stool, thereby maintaining continence. Furthermore, sphincter muscles are regularly controlled by nervous systems.  If polyps or tumors are found in the rectum fairly close to the anal canal, it usually requires rectal surgery that the entire rectum and sphincter muscles must be removed, causing difficulties in defecation. After surgery, patients have to undergo “permanent colostomy” to make a permanent opening called a stoma for passing the stool out of the body. 

Treatment of colorectal cancer must be given by highly specialized multidisciplinary team consisting of colorectal surgeons, diagnostic radiologists, radiation oncologists, medical oncologists and pathologists. Supported by cutting-edge surgical technology, minimally invasive colorectal surgery with sphincter-saving technique significantly increases chances of being cured, resulting in preserved sphincter functions required for bowel movements and improved quality of life. Superior advantages might include less pain, fewer complications and faster recovery time that leads to a quick return to daily life and activities.


Roles of radiation treatment

The major treatment option of rectal cancer is surgery, often in a combination with radiation treatment and chemotherapy. After the diagnosis of cancer is confirmed on tissue pathology, cancer staging must be additionally performed in order to examine the metastasis of cancer cells to other organs in the body. Imaging tests for cancer staging are CT (computed tomography) scan, MRI (magnetic resonance imaging) scan and PET/CT (positron emission tomography–computed tomography) scan. Staging and pathological results determine the most appropriate treatment plan. If rectal cancer has been found in its early stage (stage 1-2), surgery as a single treatment might be considered. Nevertheless, if cancerous cells have invaded to the outer membrane (serosa layer) or have spread to lymph nodes in the pelvic floor areas, combined treatments of surgery, radiation treatment and chemotherapy must be collectively given. In the past, radiation treatment was initiated after surgery. However, a number of recent clinical researches review that administration of radiation treatment and chemotherapy prior to  surgery can significantly help to reduce the size of the tumors as well as the stage of cancer (down-staging). This largely helps enhancing chances to surgically remove all cancerous cells while increasing chances to successfully perform colorectal surgery with sphincter-saving technique. In addition, radiation treatment combined with chemotherapy and minimally invasive surgery with sphincter-saving technique results in fewer complications affecting bladder and small intestine located in the pelvic floor area.

The advancements in radiotherapy has been dramatically evolved, including the utilization of CT scan, MRI scan or PET/CT scan for radiation treatment planning in order to determine appropriate treatment plans with the optimal radiation doses. In the past, conventional 2D technique might cause undesired effects to adjacent organs such as bladder, small intestine and bone marrow. Three-dimensional conformal radiation therapy or 3D-CRT is an advanced technique that incorporates the use of imaging technologies to generate 3D images of a patient’s tumor and nearby organs and tissues. Several techniques can be used such as IMRT (intensity-modulated radiation therapy) and VMAT (volumetric-modulated arc therapy) which is combined with image-guided radiation therapy (IGRT) to improve the precision and accuracy of treatment delivery. Due to advanced technology, it results in accurate and precise treatments with patient’s comfort and convenience as well as enhanced safety degree due to fewer complications to organs located in the pelvic floor area, leading to improved quality of life. 


If there is the presence of rectal bleeding during bowel movement, immediate medical care must be provided in order to get it accurately diagnosed, resulting in timely and effective treatments. 



Prof. Dr. Art Hiranyakas

Colorectal surgeon and Director of Colorectal Clinic, Surgery Center, Bangkok Hospital.

Dr. Panida Thong u-thaisri

Gastroenterologist, GI and Liver Center, Bangkok Hospital.

Assoc. Prof. Dr. Prasert Lertsanguansinchai

Radiation oncologist and Director of Radiotherapy Center, Bangkok Cancer Hospital Wattanosoth. 

For more information, please contact:

Surgery Center, Bangkok Hospital.

1st floor, D-Building, Bangkok Hospital.

Tel: +662-310-3000 or 1719 (local call only)


For more information, please contact