Colonoscopy Complications: Signs and Symptoms

Table of Contents

    There are between 15 to 19 million colonoscopies performed every year in the United States. The sheer number of colonoscopies performed signify the medical movement to screen for colorectal cancer in order to prevent unnecessary deaths from a cancer that is highly treatable when caught in its earlier stages. Nearly 40% of these colonoscopies are performed on patients who have no presenting symptoms nor gastrointestinal disturbances and conditions. Approximately 4% of patients who have had a colonoscopy will suffer from a complication from the procedure. The complications associated with colonoscopies are typically related to three different categories:

    • Sedation-related complications
    • Biopsy and polypectomy-related bleeding complications
    • Colonoscopy-related perforation of the colon

    Other rarer complications that can also be caused by a colonoscopy include bacterial infections and postpolypectomy electrocoagulation syndrome. Colonoscopy complications can arise during the procedure, within several hours after the surgery, and, in rare cases, up to a few weeks after a colonoscopy. 

    There are between 15 to 19 million colonoscopies performed every year in the United States. Of these, approximately 4% of patients will experience a complication.

    In this article, you will learn about the symptoms associated with colonoscopy complications and when to seek emergency care to treat the complications.

    Polyp removal during a colonoscopy
    Removal of a polyp during a colonoscopy is a common cause of bleeding-related complications

    Signs and Symptoms of Colonoscopy Complications

    Sedation-related complications

    People who have a complication related to sedation medications or anesthesia will often experience these symptoms while sedated without the realization that they are occurring. Your healthcare team will closely monitor your vitals during the procedure and address any complication you are having immediately. There are some complications that may occur after the procedure when you are in the recovery room or at home. Again, all of these complications must be addressed immediately and require emergency care. Common sedation-related complications include:

    • Low oxygen levels
    • Respiratory arrest
    • Tachycardia (fast heart rate) or bradycardia (slow heart rate)
    • Cardiac arrhythmias (irregular heart beat)
    • Myocardial infarction (heart attack)
    • Stroke
    • Seizures
    • Shock

    Biopsy and Polypectomy-related Bleeding Complications

    People who are on anticoagulant medications are at a high-risk for a hemorrhage, especially after the procedure when they begin taking their medications again. 

    Hemorrhages occur in 1-6 patients per 1,000 of colonoscopies. A hemorrhage can occur during the procedure or within a few hours after the colonoscopy. In some cases, a delayed hemorrhage can occur up to several weeks after the procedure.  A polypectomy is the medical term for removal of a polyp during a colonoscopy. Many hemorrhages are caused by a knick or cut in the lining by the tip of the colonoscope or instrument used to remove the polyp. The unintentional knick may cut a blood vessel and it continues to bleed after the procedure without the physician’s knowledge. People who are on anticoagulant medications are at a high-risk for a hemorrhage, especially after the procedure when they begin taking their medications again. 

    Colonoscopy-related Perforation of the Colon

    If you have a polyp removed during a colonoscopy, you are at a higher risk for getting a perforation, or a tear or hole in the lining of the intestine. Perforations are typically caused by the following: 

    • Mechanical forces ( caused by tip of colonoscope or  biopsy forceps) cause trauma
    • Barotrauma from the air inserted into rectum and colon during the procedure

    You are at a much lower risk for a perforation if you did not have a polyp removed. There are cases where an instrument may puncture a thin section of the intestinal wall and cause a tear or hole. If your examiner introduces too much air in the colon during the procedure, the distention of the abdomen can also cause a perforation. Some patients who have a perforation will look like their abdomen is sticking out more than normal and the abdomen feels hard when palpated. Symptoms of a perforation include: 

    • Severe and unremitting abdominal pain
    • Tenderness to touch on the area where the perforation is located
    • Fever
    • Chills
    • Nausea
    • Vomiting

    Postpolypectomy Electrocoagulation Syndrome

    A polyp that is found in the intestinal lining of the colon will usually be removed immediately upon recognition by your gastroenterologist during a colonoscopy. Polyps are typically small in size and the wound left behind is generally small enough that it does not need to be stitched close. Instead, a tool attached to the colonoscope uses an electrical current to cauterize or seal off the area left behind. Rarely, this electrical current can reach deeper layers of the lining and cause a serious burn. This is known as postpolypectomy electrocoagulation syndrome and it often mimics the same symptoms as someone who has a colonic perforation. The signs and symptoms of postpolypectomy electrocoagulation syndrome include:

    • Abdominal pain (often described as sharp)
    • Fever
    • Tachycardia (fast heart rate)
    • Leukocytosis (high white blood cell count)

    A person with an electrical burn caused by cauterization can present symptoms within a few hours of the procedure or several days following the colonoscopy. 

    Symptoms of Serious and Life-threatening Complications

    If you or a loved one are experiencing any of the following complications call 911 and seek immediate medical attention. 

    Stroke. Caused by a clot in the brain that blocks oxygen supply to the brain, a stroke is a rare but very serious complication from sedation. Symptoms of a stroke include:

    • Paralysis, weakness, or numbness of one side of the body involving the face, arm, or leg
    • Trouble seeing in one or both eyes
    • Sudden and severe headaches
    • Trouble with balance and walking

    Heart attack. A heart attack, also known as an acute myocardial infarction, is the blockage of blood supply and oxygen to the heart muscle causing irreversible tissue damage. Common symptoms of a heart attack include: 

    • Chest pain
    • Shortness of breath
    • Dizziness, nausea, and/or vomiting
    • Radiating pain in neck, jaw, arm, and/or abdomen
    • Cold sweats

    Seizure. Also rare, a medication-related seizure is caused by neurological disturbances in the electrical pathways of the brain. People who are having a seizure will sometimes appear confused, lose consciousness and awareness,  or they will have a staring spell. Outward signs of a seizure are uncontrollable jerking movements of the arms and legs and emotional symptoms such as anxiety or fear. If you have never experienced a seizure before and are concerned you are having symptoms, seek medical care immediately.

    Infection. Despite rigorous sanitation and sterilization of equipment used during a colonoscopy, some instruments may harbor infectious bacteria such as E. coli and Salmonella spp. These infections occur in more than 1 out of 1000 screening colonoscopies. Bacterial infections are easily treated with antibiotic therapy.. Symptoms of an infection include:

    • Fever
    • Abdominal pain and tenderness
    • Chills
    • Constipation
    • Diarrhea
    • Nausea and/or vomiting

    Some patients, especially the very elderly and immuno-compromised, are susceptible to developing sepsis, a life-threatening condition caused by the immune system’s response to an infection. Symptoms of sepsis include:

    • Change in mental status
    • Low blood pressure
    • Rapid breathing

    Hemorrhage. Many patients will bleed a small amount after their colonoscopy, especially if they had a polyp removed or a biopsy taken of abnormal tissue. Bleeding occurs during a colonoscopy in approximately 1 in every 1,000 patients. The bleed is typically treated immediately as it occurs during the procedure. Often the bleeding goes away naturally without any treatment intervention. In some cases, the bleeding does not go away on it’s own or the volume increases and this requires a medical intervention. Signs and symptoms of a colonoscopy-related hemorrhage include:

    • Many or severe bloody bowel movements
    • Rectal bleeding that does not stop
    • Rectal bleeding more than 1-2 tablespoons
    • Light-headedness, dizziness, and/or fainting

    Shock can occur if you begin to lose blood abruptly or if you lose a lot at one time. SIgns and symptoms of shock include:

    • Unconsciousness
    • Pale, cold, and clammy skin
    • Fast heart rate
    • Drop in blood pressure
    • Not urinating or infrequent urination 


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