Most people who have a flexible sigmoidoscopy without sedation rate the pain somewhere between mild and moderate. In studies using a 0-to-10 scale, average scores tend to land around 3 to 5, and the majority of patients report they would willingly have the procedure again. That said, the experience varies widely from person to person, and certain factors, from your sex to who holds the scope, can shift your pain level considerably.
What the Numbers Look Like
Pain research on unsedated flexible sigmoidoscopy gives a surprisingly broad range of results, partly because different studies measure discomfort in different ways and recruit different populations. One study of 45 patients undergoing unsedated flexible sigmoidoscopy reported an average pain score of about 5 out of 10 on a visual analogue scale.1中華民國大腸直腸外科醫學會雜誌. Patient Factors Affecting the Pain Perception of Sedation-free Flexible Sigmoidoscopy A larger screening study found the picture was rosier: roughly seven in ten men and more than half of women scored their pain below 3 on an 11-point scale.2PubMed. Acceptance of flexible sigmoidoscopy and colonoscopy for screening and surveillance in colorectal cancer prevention A major screening dataset of over 23,000 sigmoidoscopies found that only about 5% of men and roughly 14% of women reported pain at all, though the threshold for “pain” in that study may have been higher than in others.3PubMed. Endoscopist as a key determinant of patient pain: a sigmoidoscopy screening model for unbiased assessment
The takeaway from these numbers is that flexible sigmoidoscopy lands in an awkward middle ground. It is not painless for everyone, but it is rarely agonizing. Most people describe a feeling of pressure, bloating, or cramping that comes and goes as the scope navigates the lower colon. The moments of sharpest discomfort tend to be brief, occurring when the scope rounds a bend or when air is pumped in to open up the view.
Why Women Tend to Have a Harder Time
Across nearly every study on this topic, women report more pain than men during unsedated sigmoidoscopy. The screening study noted above found that women were almost three times as likely as men to experience significant discomfort, even after controlling for age, race, and anxiety level.4JAMA Internal Medicine. Patient Satisfaction With Screening Flexible Sigmoidoscopy The large 23,000-patient dataset confirmed the same pattern, listing female sex as an independent predictor of pain.3PubMed. Endoscopist as a key determinant of patient pain: a sigmoidoscopy screening model for unbiased assessment
The reasons are partly anatomical. Women on average have a longer and more mobile sigmoid colon, which means the scope has more twists to negotiate. The pelvis in women is also wider, allowing more colon to dip down and form redundant loops that can be painful when the scope pushes through them. Prior abdominal or pelvic surgery compounds the problem, because adhesions from surgery can tether the bowel in place, making it less flexible and more sensitive to stretching.
Hysterectomy history is a particularly strong predictor of trouble. One study found that women under 70 who had previously had a hysterectomy were nearly seven times more likely to have an incomplete examination compared to women the same age without that history.5The Journal of the American Board of Family Practice. Predictors of Incomplete Flexible Sigmoidoscopy The scar tissue from pelvic surgery can fix the sigmoid colon in awkward positions, making scope advancement painful enough to abort the procedure. Older women in general also face higher rates of incomplete exams, with those over 80 at roughly two and a half times the risk of an inadequate examination compared to people in their fifties.6PubMed Central. Incomplete screening flexible sigmoidoscopy associated with female sex, age, and increased risk of colorectal cancer
Your Endoscopist Matters More Than You Might Think
One of the most striking findings in the pain research is how much variation exists between individual endoscopists. The large screening study of over 23,000 procedures found that pain rates ranged from about 4% to 21% depending on which endoscopist performed the exam, and that each additional year of endoscopy experience was associated with roughly an 18% reduction in the odds of patient pain.3PubMed. Endoscopist as a key determinant of patient pain: a sigmoidoscopy screening model for unbiased assessment Pain during the procedure was also linked to lower completion rates and a trend toward lower polyp detection, meaning that a less-skilled operator could simultaneously cause you more discomfort and give you a less thorough exam.
What makes one endoscopist gentler than another? Experience teaches subtle techniques: using the scope’s torque rather than pushing force to round bends, minimizing the amount of air pumped into the bowel, pulling back and repositioning rather than powering through resistance, and reading the patient’s responses in real time. These are skills that develop over hundreds of procedures. If you have any say in who performs your sigmoidoscopy, asking about volume and experience is reasonable.
A related finding involves the willingness to return for a future procedure. A Canadian study of endoscopy patients found that perceived technical skill of the endoscopist and absence of pain were both independently associated with whether people said they would come back. Having had a previous endoscopy also helped, presumably because those patients knew what to expect.7PubMed Central. Patient satisfaction with the endoscopy experience and willingness to return in a central Canadian health region
Other Factors That Predict More or Less Pain
Beyond sex and endoscopist skill, a few other variables influence how much a sigmoidoscopy hurts. Younger patients tend to report more pain than older ones in some datasets, possibly because older colons lose some of their tone and are easier to navigate (though advanced age brings its own challenges with angulation and diverticula).3PubMed. Endoscopist as a key determinant of patient pain: a sigmoidoscopy screening model for unbiased assessment Diverticula, the small pouches that form in the colon wall, and inflammatory bowel disease were also independent predictors of pain in the same study.
Anxiety plays a complicated role. You might assume that more anxious patients would have more pain, and that is partly true, but one study found an unexpected U-shaped relationship: people with the lowest and the highest levels of pre-test anxiety actually reported less pain and higher satisfaction than those with moderate anxiety.4JAMA Internal Medicine. Patient Satisfaction With Screening Flexible Sigmoidoscopy The highly anxious patients may have mentally prepared more thoroughly, while the least anxious simply weren’t bothered. It was the middle group, apprehensive but not braced, who seemed to be caught off guard. Women were also found to have higher anxiety scores before endoscopy procedures in general.8PubMed Central. Does music reduce anxiety and discomfort during flexible sigmoidoscopy? A systematic review and meta-analysis
Techniques That Reduce Discomfort
Several methods can make unsedated sigmoidoscopy more bearable, falling into three broad categories: what gas is used, what you breathe, and what distracts you.
During any endoscopy of the lower bowel, gas has to be pumped in to inflate the colon so the camera can see the lining. Traditionally this was room air, but carbon dioxide (CO₂) is now widely used because the body absorbs it far more quickly. One randomized trial found that CO₂ insufflation did not change discomfort during the sigmoidoscopy itself, but made a clear difference afterward: 84% of patients in the CO₂ group reported no discomfort an hour after the exam, versus 64% in the air group.9PubMed. Carbon dioxide insufflation reduces discomfort due to flexible sigmoidoscopy in colorectal cancer screening The bloating and cramping that linger after a sigmoidoscopy are mostly caused by trapped gas, so using CO₂ addresses that problem effectively. A large UK bowel screening trial also compared water-assisted sigmoidoscopy to the standard CO₂ method and found no difference in pain, with roughly 14 to 15% of patients in both groups reporting moderate or severe discomfort.10Gut. WASh multicentre randomised controlled trial: water-assisted sigmoidoscopy in English NHS bowel scope screening
Inhaled nitrous oxide, the same gas used in dental offices, has also shown benefit. A placebo-controlled trial found that patients who breathed nitrous oxide during flexible sigmoidoscopy reported significantly less discomfort and were more willing to have the procedure again compared to those given a placebo gas.11PubMed. The use of inhaled nitrous oxide for flexible sigmoidoscopy: a placebo-controlled trial One more recent trial explored patient-controlled Entonox (a 50/50 mix of nitrous oxide and oxygen) alongside a familiarization video for sigmoidoscopy patients, acknowledging that the procedure without any analgesia or sedation can be unpleasant enough to compromise the quality of the exam.12PubMed. Randomized controlled trial of effects of a familiarization video and patient-controlled Entonox inhalation on patient stress levels and clinical efficacy of flexible sigmoidoscopy without analgesia or sedation for investigation of fresh rectal bleeding Nitrous oxide wears off within minutes, so it preserves one of the main advantages of skipping sedation: you can drive yourself home and return to normal activity immediately.
Distraction techniques are a growing area of interest. A systematic review and meta-analysis found that music during colonoscopy (the evidence translates well to sigmoidoscopy) reduced pain scores by an average of about 1.5 points on a 10-point scale, and other forms of distraction had a similar effect on pain while producing an even larger drop in anxiety.13PubMed Central. The effect of music and distraction on pain and anxiety during colonoscopy: a systematic review and meta-analysis Virtual reality headsets have also been tested: a randomized trial found that VR significantly reduced both pain and anxiety during colonoscopy.14PubMed Central. The Effect of Virtual Reality on Pain and Anxiety During Colonoscopy: A Randomized Controlled Trial These approaches are low-cost, carry no pharmacological risks, and can be combined with each other.
Scope design itself has also evolved. Reviews of discomfort-reduction methods mention that thinner scopes, including pediatric colonoscopes and variable-stiffness models, can reduce pain, particularly in patients with challenging anatomy.15SpringerLink (Digestive Diseases and Sciences). Methods of reducing discomfort during colonoscopy
When the Procedure Has to Be Stopped
In a small percentage of cases, pain during unsedated sigmoidoscopy becomes severe enough that the endoscopist has to stop before reaching full insertion depth. The large dataset of over 23,000 procedures found that pain was associated with a roughly threefold reduction in the odds of completing the exam.3PubMed. Endoscopist as a key determinant of patient pain: a sigmoidoscopy screening model for unbiased assessment Poor bowel preparation, severe diverticular disease, and post-surgical adhesions are the usual culprits alongside pain. One study that attempted to extend a sigmoidoscope to the cecum (essentially trying to do a colonoscopy with a shorter scope) found that patient discomfort was the reason for stopping in over 40% of cases where full insertion was not achieved.16Gastrointestinal Endoscopy. Use of a colonoscope instead of a sigmoidoscope to screen asymptomatic adults for colorectal cancer That study, though, was pushing the scope well beyond what a standard sigmoidoscopy requires.
For standard-length sigmoidoscopy, incomplete exams due to pain are uncommon in men, with one analysis showing less than 5% risk.17PubMed. Selecting patients for flexible sigmoidoscopy. Determinants of incomplete depth of insertion The risk is higher in older women and women with prior pelvic surgery, as noted earlier. If your exam is stopped for pain, the typical next step is to schedule a full colonoscopy with sedation, where the issue is much less likely to recur.
Would People Do It Again?
Willingness to repeat the procedure is arguably the most meaningful measure of how tolerable it really is. Here, the data is reassuring for most people. In the study with an average pain score of 5 out of 10, over 90% of patients still said they would undergo unsedated sigmoidoscopy again if needed.1中華民國大腸直腸外科醫學會雜誌. Patient Factors Affecting the Pain Perception of Sedation-free Flexible Sigmoidoscopy Even in a pilot study where 46% of patients reported moderate to severe discomfort, about three-quarters said they would probably or definitely repeat the procedure.18PubMed. Extended flexible sigmoidoscopy performed by colonoscopists for colorectal cancer screening: a pilot study
People seem to distinguish between “that was unpleasant” and “I would not do that again.” The discomfort is real but short-lived, usually lasting only 5 to 15 minutes during the exam, and the payoff of colorectal screening is clear to most patients. The absence of sedation also means no recovery time, no need for a driver, and no grogginess, all of which contribute to the sense that the tradeoff was worthwhile.
Flexible Versus Rigid Sigmoidoscopy
If you have seen older references to sigmoidoscopy that describe it as extremely painful, those may reflect experiences with the rigid sigmoidoscope, a straight metal or plastic tube that was once the standard instrument for examining the rectum and lower colon. A systematic review and meta-analysis comparing rigid and flexible sigmoidoscopy found that the rigid scope caused significantly more discomfort.19PubMed. Rigid or flexible sigmoidoscopy in colorectal clinics? Appraisal through a systematic review and meta-analysis The flexible scope also detected more cancers and abnormalities overall.20PubMed. Comparison of rigid vs flexible sigmoidoscopy in detection of significant anorectal lesions Rigid sigmoidoscopy is still used in some settings for quick rectal exams, but if you are being scheduled for a screening or diagnostic sigmoidoscopy today, it will almost certainly be with a flexible scope.
How Sedation Practices Vary Around the World
Whether you are offered sedation for a sigmoidoscopy depends heavily on where you live. In the United States, sedation has traditionally been the default for most lower endoscopy procedures, driven in part by patient expectations and by a healthcare system that absorbs the added cost. In much of Europe, unsedated sigmoidoscopy and even unsedated colonoscopy remain routine, particularly in screening programs. The UK’s bowel scope screening program, for instance, performed hundreds of thousands of unsedated sigmoidoscopies as standard practice. In parts of Asia, unsedated colonoscopy has also been common for decades.21PubMed Central. Unsedated colonoscopy: A neverending story
This variation reflects cultural expectations as much as medical evidence. The clinical argument for skipping sedation during sigmoidoscopy is strong: sedation carries its own risks (respiratory depression, allergic reactions, rare but real cardiovascular events), requires monitoring equipment and recovery time, costs more, and forces you to arrange for someone to drive you home. For a procedure that typically examines only the last 60 centimeters of the colon and lasts well under 20 minutes, many clinicians outside the US consider sedation an unnecessary escalation.22PubMed Central. Sedation-risk-free colonoscopy for minimizing the burden of colorectal cancer screening The fact that over 80% of patients who are offered on-demand sedation for full colonoscopy end up not needing it suggests that for the shorter sigmoidoscopy, most patients can manage without pharmacological help.15SpringerLink (Digestive Diseases and Sciences). Methods of reducing discomfort during colonoscopy
What the Bowel Prep Feels Like by Comparison
A detail that catches many first-timers off guard: the bowel preparation before a sigmoidoscopy is often described as worse than the procedure itself. For sigmoidoscopy, prep is usually limited to one or two enemas administered at home or in the clinic shortly before the exam, which is far lighter than the full-day liquid diet and large-volume laxative solutions required before colonoscopy. Still, the cramping and urgency caused by the enema can be genuinely unpleasant and can set the stage for heightened anxiety heading into the exam room. Poor prep was identified as a significant predictor of incomplete examinations in women, with roughly three and a half times the odds of an incomplete exam compared to women with adequate preparation.5The Journal of the American Board of Family Practice. Predictors of Incomplete Flexible Sigmoidoscopy If stool remains in the colon, the endoscopist has to push through it, inject more air, and spend more time navigating, all of which increase discomfort. Following the prep instructions closely is one of the simplest things you can do to minimize pain during the actual exam.
After the procedure, most discomfort clears within an hour or two. The bloating and gas pains that follow are the main complaint, and as noted earlier, facilities that use CO₂ instead of air for insufflation can shorten this phase considerably. There is no recovery period in the sedation sense: you can eat, drive, and return to your normal routine immediately. Some people feel mildly sore in the lower abdomen for the rest of the day, but this is the exception rather than the rule.