The Best Way to Painless Colonoscopy

“Colonoscopy hurts” [1] is the opening sentence of an article reporting a study in England in which the forces exhibited during colonoscopy were measured. In contrast to it is the statement, “Many patients undergoing colonoscopy do not experience significant discomfort during the procedure and may not require any premedication,” made by a group in Germany [2]. Colonoscopists are taking sides as to whether sedation should or should not be a routine part of the examination.

Why is the world of endoscopists and patients so divided on the question of whether colonoscopy is or is not a painful experience? The answer is multifactorial and certainly not straightforward. The actual degree of pain experienced during colonoscopy varies from person to person. Older persons tolerate colonoscopy better than younger persons, males tend to tolerate colonoscopy better than females, and the degree of pain during colonoscopy is associated with the duration of the examination (longer examinations are associated with increased pain). My own experience in New York is that patients are quite aware of the value of colonoscopy for discovering polyps and preventing colon cancer, and are almost universally informed (by friends and colleagues) that it is a painful experience. Whether the patients are male or female, young or old, executives or laborers, the vast majority of my patients want to be “put out” and they strongly express the desire “not to feel anything.”

There is no doubt that visceral pain occurs during colonoscopy. In this issue of Endoscopy, Shah et al. [3] focus on an explanation of those colonoscopic maneuvers associated with painful stimuli. Most of the pain and discomfort is related to stretching of the mesenteric attachments and, to a lesser extent, the pressure of air distension on the colon wall. Another important part of the equation is the individual's perception of pain. Almost all the patients that I see for colonoscopy quite happily receive some sort of sedation-analgesia immediately prior to the endoscopic examination. Although this alters the pain threshold, I find it quite gratifying that many patients are awake and apparently coherent, able to converse fairly normally, during the course of the colonoscopic examination, inquiring appropriately as to the endoscopic picture, and are quite content not to be totally “knocked out” in spite of their initially expressed desire to be unconscious during it.

All human beings are born with essentially the same autonomic nervous system and a very similar set of large intestines. The enteric neuronal system of the colon is connected to the autonomic system, which transmits signals via the spinal cord to the brain. This being the case, why do patients undergoing colonoscopy in Korea [4], Norway [5], Finland [6], Greece [7] and Germany [8] appear able to tolerate colonoscopy without sedation in the vast majority of instances, while most patients in the United States [8] [9], Great Britain [10], and Australia [11] have their colonoscopy with sedation/anesthesia? Some of the physiological, but not geographical, answers are provided by anatomical and neurological differences. The reason why the elderly are more tolerant of loops, twists, and bends caused by the colonoscope is because the elasticity of the mesentery increases with age; the younger person experiences small amounts of mesenteric traction as a painful stimulus, but older patients having the same degree of looping in the colonoscope will not have the same degree of pain. Similarly, women - who arguably have a slightly longer large intestine than men - have the colon confined in a smaller abdominal package, necessitating more folding, bends, and twists than in the male colon, which is in a larger abdominal cavity. In addition, the female sigmoid colon is draped over the uterus, and as the sigmoid colon descends toward the left inguinal area, having coursed over the uterus, an acute angulation is often present that is difficult to overcome without considerable manipulation and thus an increase in the degree of mesenteric traction - a hazard not present in the male colon. Because of the anatomic difference, young, slender women are the most difficult of all patients to colonoscope and have the most discomfort during the procedure. However, heavier women of any age are considerably more tolerant of colonoscopy, since fat pushes the sigmoid up and out of the pelvis, changing the angulation (caused by the “V” descent and then ascent from the left pelvis) from acute to obtuse and creating an undulating sigmoid curve more similar to that found in men.

However, none of this explains the vast differences in the acceptance of nonsedated colonoscopy in several parts of the world among patients of all ages and of both sexes. Among the people in the various countries in which sedation is not routine, the colons are no shorter or less tortuous than are the colons of persons who live in English-speaking countries; the uterus is the same size and in the same location in women all over the world. The answer cannot be that endoscopists in English-speaking countries are more heavy-handed, or push more forcefully on the instrument.

Shah et al. [3] studied the location of the colonoscope tip and its configuration in relation to the use of self-administered sedation by using a continuous display from a magnetic imager in a double-channel colonoscope. Most of the demands occurred when the colonoscope tip was in the sigmoid colon, and only 4 - 7 % of the demands occurred when the tip was in the descending colon, splenic flexure, transverse colon, or proximal colon. Ninety percent of all pain episodes coincided with either looping or pulling back on the shaft in a straightening maneuver. The authors found that over-insufflation was an infrequent cause of abdominal pain. The loops described in the paper by Shah et al. are present, to a very similar degree, in all patients undergoing colonoscopy. What is the difference, then?

The difference between the success of sedation and nonsedation for colonoscopy must lie in the patient’s outlook on the examination. The difference is in the patient’s perception of pain. Patients in nonsedation studies expect to have some discomfort during the colonoscopic examination, and indeed do report discomfort during it. However, these patients accept the possibility of some discomfort as a part of the procedure, and consider it to be a “normal” part of the examination. Patients do have pain when having unsedated colonoscopy, but it seems that the patient's “suffering threshold” (willingness to tolerate some degree of suffering) is higher in some countries than others. In the United States, patients have a relatively low “suffering threshold,” and when faced with a potentially painful procedure that can be made more comfortable by sedation and analgesia, they opt for medication to increase their “suffering threshold.”

Everything involved in the procedure is easier when unsedated colonoscopy is performed. Patients are not drowsy, and they can dress and leave immediately, resuming their normal daily activities and driving a vehicle. The addition of “conscious sedation” adds the necessity and cost of the drugs, the use of a recovery room, requirement for a companion to collect the patient after the examination and accompany him or her home, as well as loss of work and inability to drive a vehicle. On the other hand, some colonoscopic examinations are performed under propofol anesthesia given by an anesthesiologist. In these cases, there is no pain during the procedure, but the cost of having two physicians present for the examination is inordinate and, certainly according to most reports in the literature, not necessary.

Studies such as that by Shah et al. [3] should make it possible to identify the parts of the examination in which pain or discomfort are encountered, perhaps providing an ability to alter the procedure prior to a painful maneuver in such a way as to decrease the level of discomfort. The alteration might involve external abdominal pressure, or use of an external stent or sedation/analgesia in the United States [8]. With meticulous attention to detail, maneuvers can be developed to decrease the “peak force” applied during colonoscopy [1].

There is evidence that visceral pain declines with aging [12]. Pain can also be significantly modulated by cognitive, emotional, and environmental factors, since with the same stimulus [13] in persons of similar habitus, age, and sex, there may be completely different responses. One person may complain severely, while another may claim to have experienced only mild discomfort. I would bet that the complaining person is from the United States, and the non-complainer from Scandinavia, where sedation/analgesia is not routinely given. The actual level of pain for both patients may be the same, but it is their perception and their response to pain that makes the difference. Changing the outlook of a patient toward pain is a difficult task, and takes time. However, colonoscopy is less painful when the endoscopist strives to maintain a straight scope configuration during the examination. On the basis of my experience - and having seen many patients undergo a difficult colonoscopic examination that was described as “impossibly painful” elsewhere, with the same patients tolerating a repeat procedure with light sedation (when using a “straight scope” technique) - I am inclined to accept that Shah’s observations are correct, and to believe in the concept that an individual’s pain perception plays a large role in the ability to tolerate a colonoscopic examination without sedation. Loops in the colonoscope do cause pain, and with a technique of frequent shaft withdrawal to keep the instrument as straight as possible, heeding the observation by Shah et al. [3], the likelihood of severe pain is markedly diminished. Some patients do request unsedated colonoscopy, and I am pleased to oblige. These examinations are relatively quick, and although patients may have some discomfort during them, those who request no sedation rarely ask for medication during the examination. Changing a basic attitude, developing a higher “suffering threshold,” and perhaps overcoming the fear of an examination is a daunting task. Until methods are developed that can make colonoscopy more gentle and patients more stoical, I believe that American doctors will continue to give sedation/analgesia for colonoscopy - since even in the best of hands, colonoscopy hurts.

References

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