Are Colonoscopies Safe?

Table of Contents

    Colonoscopies are one of the most commonly ordered screening procedures for men and women over the age of 50. In fact, 19 million colonoscopies are performed each year in the United States alone. This number reflects the work of cancer awareness groups, government bodies, and public awareness media campaigns to increase colon cancer screenings to battle colorectal cancer. 

    If you are one of the millions who have been asked to get a colonoscopy by your physician, you may be concerned with the risk of complications. You may also be worried about the side effects of the bowel preparation and the procedure itself. To assure you, colonoscopies are considered safe. The overall risk of complications for a routine colonoscopy is 1.6%. Compared to the risk of developing colorectal cancer being between 4-5%, the benefits of getting a colonoscopy outweigh the risk of having a complication. 

    Despite the rare occurrence of complications, they still occur especially in older populations and in those with preexisting conditions. The goal of this article is to inform you about the complications associated with a colonoscopy, how often these complications occur, and to explain the side effects that may follow the preparation and procedure. 

    Risks and Complications of a Colonoscopy: Types and Frequency

    Complications during a colonoscopy are rare but can be serious if they happen. If you are healthy and not of an advanced age your risk is very low for developing a complication. In terms of gender, women have a slightly higher risk of developing a complication because they have longer and more bendy bowels. 

    Complications and longer-lasting side effects after a colonoscopy occur more frequently in the following groups of people:

    • Women
    • Patients who are elderly or weak
    • Patients with history of stroke, diabetes, and/or heart disease
    • Patients with a history of COPD (chronic obstructive pulmonary disease)
    • Patients who are on blood thinners
    • Patients who undergo a polypectomy (removal of a polyp)
    • Patients with inflammatory bowel disease
    • Patients with a history of colon cancer

    The rIsks associated with colonoscopy include infection, bleeding, and a perforation (tear or hole) of the colon. The bowel cleanse preparation before a colonoscopy can cause complications such as dehydration and heart-related issues in those with a history of heart disease. Any concern you have about a complication during any part of your colonoscopy, including the preparation, should be discussed with your physician. 

    Complications From Colonoscopy Preparation 

    Before a colonoscopy, you will be asked to avoid certain foods and medication and to cleanse your bowels completely. Complications from the preparation stage – that is, from the time before a colonoscopy is actually performed – usually occur because an at-risk patient becomes dehydrated or suffers from electrolyte imbalance. Patients who are are a high risk for developing complications from the bowel preparation include:

    • Pregnant women
    • People with kidney, liver, or heart problems
    • Older adults
    • People with inflammatory bowel disease (IBD)

    Complications Arising During a Colonoscopy

    While your risk for a complication during a colonoscopy is relatively low, you may still be concerned about what may happen if a complication does occur. Common complications that occur during or after a colonoscopy include: 

    Perforation. 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. 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. 

    GI bleed. 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. If the bleeding is severe, you will need immediate treatment. 

    Cardiovascular event. Patients who have a history of cardiovascular disease or high blood pressure are at a higher risk for complication during a colonoscopy. The loss of potassium from the bowel cleanse can cause heart-related issues such as atrial fibrillation or tachycardia (rapid heart rate). The sedation used during the procedure can also put extra pressure on the heart, especially in older patients and cause a heart attack, stroke, or slowed heart rate. 

    Respiratory distress. Sedation that involves anesthesia can cause low oxygen levels,slowed breathing, and respiratory distress. For this reason, many nurses and anesthesiologists will give oxygen to patients during a colonoscopy.

    Postpolypectomy electrocoagulation syndrome (PES). This complication occurs when a patient suffers an electrical burn to the intestinal lining caused by a removal of a polyp or polyps. It is known as an electrocoagulation burn and causes the lining of the intestines to become inflamed and causes a lesion. Symptoms of PES include abdominal pain, fever, and a rapid heart rate (tachycardia). 

    Allergic reaction. Allergic reactions to sedation are very rare, but do occur in patients during a colonoscopy. If an allergic reaction occurs during the colonoscopy the patient is treated immediately. Be sure to tell your medical team about any allergies you have, including food (for example egg and soybean), so they are prepared to give you the proper medication. 

    Bacterial infection. If the colonoscopy tools are not completely clean or disinfected they may harbor bacteria like E. coli that can be transmitted during a routine colonoscopy. Bacterial infections from these instruments are very rare due to strict sterilization practices of healthcare centers. 

    Common Side Effects 

    The most common side effects from a colonoscopy are minor in nature, and consist of the following: 

    • Abdominal pain
    • Gas or wind
    • Nausea and lightheadedness
    • Soreness around the anal region
    • Diarrhea

    When to Call the Doctor 

    Call your physician immediately or seek emergency medical attention if you have any of the following symptoms after your colonoscopy:

    • Fever
    • Dizziness or extreme lightheadedness
    • Vomiting
    • A hard belly
    • Constipation or trouble passing gas
    • Many or severe bloody bowel movements
    • Rectal bleeding that does not stop
    • Rectal bleeding more than 1-2 tablespoons

    Colonoscopies: Risk of Complications vs. Benefits

    A colonoscopy is often referred to as the gold standard of cancer screening methods for colorectal cancer and millions of colonoscopies are performed each year. You may be concerned, however, about a complication during or after your colonoscopy and want to weigh the risk of a complication compared to the benefit of screening for colorectal cancer. 

    Important statistics to consider when weighing the balance of the risk of a colonoscopy complication versus the risk of colorectal cancer:

    • The second leading cause of death due to cancer is colorectal cancer
    • Approximately 1 in 23 men and 1 in 25 women have a lifetime risk for developing colorectal cancer
    • Early regular colorectal cancer screenings is associated with a 65-75% reduced risk in dying from colorectal cancer
    • At least three of every 1000 colonoscopy procedures are associated with a serious complication
    • 1.6% of all colonoscopies are associated with a complication – that is, 2 out of every 125 patients
    • 4 out of 10,000 patients are at risk for a perforation during a colonoscopy
    • 8 out of 10,000 patients are at risk for a major hemorrhage during surgery

    Other factors that influence your risk for a complication include the training of your gastroenterologist, the number of patients your gastroenterologist has at one time, and the quality of technique your physician uses when removing a polyp. 

    If you are concerned about complications or side effects before, during, or after your procedure, be sure to contact your physician and make an appointment to discuss all your worries and your questions. 


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