A colonoscopy cannot detect gallstones because the procedures examine two entirely separate organ systems. A colonoscopy inspects the large intestine, or colon, using a long, flexible viewing tube. Gallstones are solid, hardened deposits of digestive fluid that form within the gallbladder. Due to the vast anatomical distance, a colonoscopy is not a suitable tool for diagnosis.
The Scope of a Colonoscopy
The primary objective of a colonoscopy is to examine the inner lining of the large bowel and the rectum. During the procedure, a doctor inserts a flexible tube, called a colonoscope, through the rectum and advances it through the entire length of the colon. This instrument is equipped with a small camera that transmits images to a monitor, allowing for a thorough visual inspection of the intestinal wall.
The main purposes of this exam are to screen for colorectal cancer, investigate the causes of symptoms such as rectal bleeding or chronic diarrhea, and locate and remove precancerous growths called polyps. The colon is a part of the lower digestive tract, a hollow, muscular tube approximately five to six feet in length. The procedure is entirely confined to this lower portion of the gastrointestinal system.
The gallbladder is located in the upper right quadrant of the abdomen, situated beneath the liver, far removed from the colon. The colonoscope does not travel near the gallbladder or the biliary system. Attempting to diagnose a problem in the biliary system with a colonoscopy is ineffective, as the anatomical pathways are completely separate. Specialists must rely on different imaging techniques to visualize the gallbladder and its contents.
Diagnostic Tools for Gallstones
To effectively detect gallstones, medical professionals primarily use imaging tests that visualize the soft tissues and fluid-filled organs of the upper abdomen. The most common initial test for diagnosing gallstones is an abdominal ultrasound. This non-invasive procedure uses sound waves to create real-time images of the gallbladder, allowing doctors to clearly see the size and number of any solid deposits present.
The ultrasound can also assess if the gallbladder wall is thickened or inflamed, suggesting a complication known as cholecystitis. While ultrasound is the gold standard, other imaging modalities investigate complications. A Computed Tomography (CT) scan uses X-rays to create cross-sectional images, which are helpful for identifying complications like infection or blockage. CT scans can sometimes miss gallstones composed purely of cholesterol.
Specialized Imaging Techniques
The Hepatobiliary Iminodiacetic Acid (HIDA) scan, also known as cholescintigraphy, evaluates the function of the gallbladder and bile ducts. This scan involves injecting a radioactive tracer, which the liver absorbs and secretes into the bile. The path of the bile flow is then tracked with a special camera.
For issues involving stones that have moved into the bile ducts, procedures like Magnetic Resonance Cholangiopancreatography (MRCP) or Endoscopic Retrograde Cholangiopancreatography (ERCP) may be used. MRCP is a non-invasive MRI technique that creates detailed images of the biliary tree. The more invasive ERCP combines endoscopy and X-rays to visualize and often remove stones directly from the bile duct.
Understanding Gallstones and Their Symptoms
Gallstones form when components of bile, a digestive fluid, crystallize and harden into pebble-like deposits. The two main types are cholesterol stones (about 80% of cases) and pigment stones, which form from excess bilirubin. These stones develop inside the gallbladder, a small, pear-shaped organ beneath the liver that stores and concentrates bile.
Many people have “silent” gallstones that cause no symptoms and do not require treatment. Symptoms arise when a stone blocks one of the ducts leading out of the gallbladder, causing a painful episode known as biliary colic. This pain is experienced as a sudden, rapidly intensifying discomfort in the upper right or center part of the abdomen.
The pain can last from minutes to several hours and may radiate to the back between the shoulder blades or to the right shoulder. These episodes are often triggered after eating a fatty meal, which stimulates the gallbladder to contract and release bile. Other accompanying symptoms include nausea and vomiting.