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The Diagnostic Journey: Tests for Unexplained Blood in Stools

blood in the toilet bowl

Finding blood in your stools can be a distressing and concerning experience. While it may sometimes be due to harmless causes like hemorrhoids or minor gastrointestinal issues, it can also be a sign of more serious underlying conditions.

When blood in stools is unexplained, it is essential to undergo a thorough diagnostic journey to identify the root cause. In this article, we will explore the various tests and procedures involved in diagnosing unexplained blood in stools and the importance of seeking timely medical attention.

Understanding Unexplained Blood in Stools

Blood in stools, also known as rectal bleeding, can appear as bright red blood or tarry, black stools. Unexplained rectal bleeding occurs when the source of bleeding cannot be easily determined based on symptoms or medical history. In such cases, it is crucial to undergo a series of diagnostic tests to determine the cause and develop an appropriate treatment plan.

Medical History and Physical Examination

The diagnostic journey begins with your healthcare provider taking a detailed medical history and performing a thorough physical examination. During this stage, the healthcare professional will ask about your symptoms, duration of blood in stools, any associated pain, changes in bowel habits, and family history of gastrointestinal conditions.

The physical examination may include an external examination of the anus and rectum to check for any visible abnormalities or signs of hemorrhoids.

Stool Tests

Stool tests are commonly used to assess the presence of blood in stools and identify potential underlying causes. Two common stool tests are:

  • Fecal Occult Blood Test (FOBT): This test detects tiny amounts of blood in the stool that may not be visible to the naked eye. It is a simple and non-invasive test that can be performed at home or in a healthcare setting. A positive FOBT result may indicate the need for further investigation.
  • Stool Culture: A stool culture is used to identify any bacterial, viral, or parasitic infections that may be causing the blood in stools. The sample is sent to a laboratory, where it is cultured and tested for various pathogens.

Digital Rectal Examination (DRE)

A digital rectal examination is a procedure in which a gloved and lubricated finger is inserted into the rectum to feel for any abnormalities, such as growths, hemorrhoids, or fissures. While not a definitive test, DRE can provide valuable information to guide further diagnostic steps.


Colonoscopy is a crucial procedure in the diagnostic journey for unexplained blood in stools. During a colonoscopy, a long, flexible tube with a camera at its tip (colonoscope) is inserted into the rectum and advanced through the colon.

This allows the healthcare provider to visualize the entire colon and rectum, looking for any abnormalities, polyps, or tumors that may be causing the bleeding. If any suspicious areas are identified, the healthcare provider may take biopsies for further analysis.

Flexible Sigmoidoscopy

Similar to a colonoscopy, a flexible sigmoidoscopy involves using a flexible tube with a camera to examine the lower portion of the colon (sigmoid colon) and rectum. It is particularly useful for evaluating the left side of the colon and can help identify potential sources of bleeding.

Imaging Studies

In some cases, imaging studies may be recommended to evaluate the gastrointestinal tract further. Two common imaging tests are:

  • Barium Enema: In this test, a liquid containing barium is introduced into the colon through the rectum, and X-rays are taken. The barium highlights the colon’s shape and allows the healthcare provider to identify any abnormalities.
  • Computed Tomography (CT) Scan: A CT scan provides detailed cross-sectional images of the abdomen and pelvis, enabling healthcare professionals to assess the extent of any abnormality and detect potential causes of unexplained blood in stools.

Endoscopic Ultrasound (EUS)

Endoscopic ultrasound combines endoscopy and ultrasound technology to produce detailed images of the gastrointestinal tract and nearby organs. It is particularly useful for assessing the depth of tumors or growths and can aid in staging the disease and guiding treatment decisions.

Capsule Endoscopy

Capsule endoscopy involves swallowing a small capsule containing a camera that captures images of the digestive tract as it passes through. The images are transmitted to a recording device worn by the patient and later reviewed by the healthcare provider. Capsule endoscopy is primarily used to evaluate the small intestine, where traditional endoscopic procedures may be challenging.

Double Balloon Endoscopy

Double balloon endoscopy is a specialized procedure that allows the healthcare provider to examine the small intestine in greater detail. It involves using a long endoscope with two inflatable balloons to navigate through the small intestine, enabling visualization and biopsy of suspicious areas.

Biopsies and Pathology

Throughout the diagnostic journey, biopsies may be taken during endoscopic procedures to obtain tissue samples for further examination under a microscope. These samples are sent to a pathology laboratory, where they are analyzed to determine the presence of any abnormal cells or conditions.


Unexplained blood in stools can be an alarming symptom that requires a comprehensive diagnostic journey to identify the underlying cause. Medical history, physical examinations, stool tests, and endoscopic procedures like colonoscopy and flexible sigmoidoscopy are essential steps in the evaluation process.

Imaging studies, capsule endoscopy, and double balloon endoscopy provide additional information to guide treatment decisions. Biopsies and pathology analysis play a critical role in identifying specific conditions that may be causing the bleeding.

Prompt medical attention and cooperation with healthcare providers throughout the diagnostic journey are essential in achieving an accurate diagnosis and developing an appropriate treatment plan for unexplained blood in stools.

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