Virtual colonoscopy (VC, also called CT Colonography or CT
Pneumocolon) is a medical imaging procedure which uses x-rays and computers to
produce two- and three-dimensional images of the colon (large intestine) from
the lowest part, the rectum, all the way to the lower end of the small intestine
and display them on a screen. The procedure is used to diagnose colon and bowel
disease, including polyps, diverticulosis and cancer. VC is performed via
computed tomography (CT), sometimes called a CAT scan, or with magnetic
resonance imaging (MRI). A virtual colonoscopy can provide 3D reconstructed
endoluminal views of the bowel.
This video shows a virtual colonoscopy of the rectosigmoid colon
performed in a retrograde fashion. There is a 10-mm colonoscopically-proven
polyp in the sigmoid colon seen at the top of the frame at the midpoint of the
movie. The movie concludes at the tip of the rectal tube which was used to
insufflate the colon.
While preparations for VC vary, the patient will usually be
asked to take laxatives or other oral agents at home the day before the
procedure to clear stool from the colon. A suppository is also used to cleanse
the rectum of any remaining fecal matter. The patient may also given a solution
designed to coat any residual feces which may not have been cleared by the
laxative. This is called 'fecal tagging'. This allows the user (usually a
consultant radiologist), viewing the 3D images to effectively subtract the left
over faeces, which may otherwise give false positive results.
VC takes place in the radiology department of a hospital or
medical center. The examination takes about 10 minutes and does not require
During the procedure:
The patient is placed in a supine position on the examination
The patient may be given a dosage of Butylscopolamine
intravenously to minimize muscle activity in the area.
A thin tube is inserted into the rectum, so that air can be
pumped through the tube in order to inflate the colon for better viewing.
The table moves through the scanner to produce a series of
two-dimensional cross-sections along the length of the colon. A computer program
puts these images together to create a three-dimensional picture that can be
viewed on the video screen.
The patient is asked to hold his/her breath during the scan to
avoid distortion on the images.
The scan is then repeated with the patient lying in a prone
After the examination, the images produced by the scanner must
be processed into a 3D image, +/- a fly through (a cine program which allows the
user move through the bowel as if performing a normal colonoscopy). A
radiologist evaluates the results to identify any abnormalities.
The patient may resume normal activity after the procedure, but
if abnormalities are found and the patient needs conventional colonoscopy, it
may be performed the same day.
VC is more comfortable than conventional colonoscopy for some
people because it does not use a colonoscope. As a result, no sedation is
needed, and the patient can return to his/her usual activities or go home after
the procedure without the aid of another person. The lack of sedation also
lowers the risk of the procedure since some people may have adverse reactions to
sedative medications used during conventional colonoscopy. VC provides clearer,
more detailed images than a conventional x-ray using a barium enema, sometimes
called a lower gastrointestinal (GI) series. Further, about 1 in 10 patients
will not have a complete right colon (cecum) evaluation completed with
conventional colonoscopy. It also takes less time than either a conventional
colonoscopy or a lower GI series.
VC provides a secondary benefit of revealing diseases or
abnormalities outside the colon.
According to an article on niddk.nih.gov, the main disadvantage
to VC is that a radiologist cannot take tissue samples (biopsy) or remove polyps
during VC, so a conventional colonoscopy must be performed if abnormalities are
found. Also, VC does not show as much detail as a conventional colonoscopy, so
polyps smaller than between 2 and 10 millimeters in diameter may not show up on
the images. Furthermore Virtual Colonoscopy performed with CT exposes the
patient to ionizing radiation, however some research has demonstrated that
ultra-low dose VC can be just as effective in demonstrating colon and bowel
disease due to the great difference in x-ray absorption between air and the
tissue comprising the inner wall of the colon.
Optical colonoscopy is taken as the "gold standard" for
colorectal cancer screening by the vast majority of the medical and research
communities. Some radiologists recommend VC as a preferred approach to
colorectal screening. However, virtual colonoscopy is considered the gold
standard by some professionals because it permits complete visualization of the
entire colon, hence providing the opportunity to identify precancerous polyps
and cancer, and then to do diagnostic biopsies or therapeutic removal of these
lesions, as soon as possible.
Colonoscopy or coloscopy is the endoscopic examination of the
large bowel and the distal part of the small bowel with a CCD camera or a fiber
optic camera on a flexible tube passed through the anus. It may provide a visual
diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or
removal of suspected colorectal cancer lesions.
Colonoscopy can remove polyps as small as one millimetre or
less. Once polyps are removed, they can be studied with the aid of a microscope
to determine if they are precancerous or not.
Colonoscopy is similar to sigmoidoscopy—the difference being
related to which parts of the colon each can examine. A colonoscopy allows an
examination of the entire colon (1200–1500 mm in length). A sigmoidoscopy allows
an examination of the distal portion (about 600 mm) of the colon, which may be
sufficient because benefits to cancer survival of colonoscopy have been limited
to the detection of lesions in the distal portion of the colon.
The American Cancer Society "Guidelines for the Early Detection
of Cancer" recommend, beginning at age 50, both men and women follow one of
these testing schedules for screening to find colon polyps and cancer: 1.
Flexible sigmoidoscopy every 5 years, or 2. Colonoscopy every 10 years, or 3.
Double-contrast barium enema every 5 years, or 4. CT colonography (virtual
colonoscopy) every 5 years.
A sigmoidoscopy is often used as a screening procedure for a
full colonoscopy, often done in conjunction with a fecal occult blood test (FOBT).
About 5% of these screened patients are referred to colonoscopy.
Virtual colonoscopy, which uses 2D and 3D imagery reconstructed
from computed tomography (CT) scans or from nuclear magnetic resonance (MR)
scans, is also possible, as a totally non-invasive medical test, although it is
not standard and still under investigation regarding its diagnostic abilities.
Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such
as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5
millimetres. If a growth or polyp is detected using CT colonography, a standard
colonoscopy would still need to be performed.
Colonoscopy is not recommended for patients having an active
flare of ulcerative colitis or Crohn's disease to avoid a perforation of the
colon. Additionally, surgeons have lately been using the term pouchoscopy to
refer to a colonoscopy of the ileo-anal pouch.
Conditions that call for colonoscopies include gastrointestinal
hemorrhage, unexplained changes in bowel habit and suspicion of malignancy.
Colonoscopies are often used to diagnose colon cancer, but are also frequently
used to diagnose inflammatory bowel disease. In older patients (sometimes even
younger ones) an unexplained drop in hematocrit (one sign of anemia) is an
indication that calls for a colonoscopy, usually along with an
esophagogastroduodenoscopy (EGD), even if no obvious blood has been seen in the
Fecal occult blood is a quick test which can be done to test for
microscopic traces of blood in the stool. A positive test is almost always an
indication to do a colonoscopy. In most cases the positive result is just due to
hemorrhoids; however, it can also be due to diverticulosis, inflammatory bowel
disease (Crohn's disease, ulcerative colitis), colon cancer, or polyps.
However—since its development by Dr. Hiromi Shinya and Dr. William I. Wolff in
the 1960s—polypectomy has become a routine part of colonoscopy, allowing for
quick and simple removal of polyps without invasive surgery.
Colonoscopy has become a primary routine screening test for
people in the US who are over 50 years of age, but flexible sigmoidoscopy every
5 years, or colonoscopy every 10 years, or double-contrast barium enema every 5
years, or CT colonography (virtual colonoscopy) every 5 years are all equally
recommended.; Subsequent rescreenings are then scheduled based on the initial
results found, with a five- or ten-year recall being common for colonoscopies
that produce normal results. Patients with a family history of colon cancer are
often first screened during their teenage years. Among people who have had an
initial colonoscopy that found no polyps, the risk of developing colorectal
cancer within five years is extremely low. Therefore, there is no need for those
people to have another colonoscopy sooner than five years after the first
Medical societies recommend a screening colonoscopy every 10
years beginning at age 50 for adults without increased risk for colorectal
cancer. Research shows that the risk of cancer is low for 10 years if a
high-quality colonoscopy does not detect cancer, so tests for this purpose are
indicated every ten years.
The colon must be free of solid matter for the test to be
performed properly. For one to three days, the patient is required to follow a
low fiber or clear-liquid only diet. Examples of clear fluids are apple juice,
chicken and/or beef broth or bouillon, lemon-lime soda, lemonade, sports drink,
and water. It is very important that the patient remain hydrated. Sports drinks
contain electrolytes which are depleted during the purging of the bowel. Orange
juice, prune juice, and milk containing fiber should not be consumed, nor should
liquids dyed red, purple, orange, or sometimes brown; however, cola is allowed.
In most cases, tea (no milk) or black coffee (no milk) are allowed.
The day before the colonoscopy, the patient is either given a
laxative preparation (such as Picosalax, Bisacodyl, phospho soda, sodium
picosulfate, or sodium phosphate and/or magnesium citrate) and large quantities
of fluid, or whole bowel irrigation is performed using a solution of
polyethylene glycol and electrolytes. Often, the procedure involves both a
pill-form laxative and a bowel irrigation preparation with the polyethylene
glycol powder dissolved into any clear liquid, preferably a sports drink which
In this case, a typical procedure regimen then would be as
follows: in the morning of the day before the procedure, a 238 g bottle of
polyethylene glycol powder should be poured into 64 oz. of the chosen clear
liquid, which then should be mixed and refrigerated. Two (2) bisacodyl 5 mg
tablets are taken 3 pm; at 5 pm, the patient starts drinking the mixture
(approx. 8 oz. each 15-30 min. until finished); at 8 pm, take two (2) bisacodyl
5 mg tablets; continue drinking/hydrating into the evening until bedtime with
clear permitted fluids. A common brand name of bisacodyl is Dulcolax, and store
brands are available. A common brand name of polyethylene glycol powder is
MiraLAX. It may be advisable to schedule the procedure early on a given day so
the patient need not go without food and only limited fluids the morning of the
procedure on top of having to go through the foregoing preparation procedures
the preceding day.
Since the goal of the preparation is to clear the colon of solid
matter, the patient should plan to spend the day at home in comfortable
surroundings with ready access to toilet facilities. The patient may also want
to have at hand moist towelettes or a bidet for cleaning the anus. A soothing
salve such as petroleum jelly applied after cleaning the anus will improve
The patient may be asked to skip aspirin and aspirin-like
products such as salicylate, ibuprofen, and similar medications for up to ten
days before the procedure to avoid the risk of bleeding if a polypectomy is
performed during the procedure. A blood test may be performed before the
During the procedure the patient is often given sedation
intravenously, employing agents such as fentanyl or midazolam. Although
meperidine (Demerol) may be used as an alternative to fentanyl, the concern of
seizures has relegated this agent to second choice for sedation behind the
combination of fentanyl and midazolam. The average person will receive a
combination of these two drugs, usually between 25 to 100 µg IV fentanyl and 1–4
mg IV midazolam. Sedation practices vary between practitioners and nations; in
some clinics in Norway, sedation is rarely administered.
Some endoscopists are experimenting with, or routinely use,
alternative or additional methods such as nitrous oxide and propofol, which have
advantages and disadvantages relating to recovery time (particularly the
duration of amnesia after the procedure is complete), patient experience, and
the degree of supervision needed for safe administration. This sedation is
called "twilight anesthesia." For some patients it is not fully effective, so
they are indeed awake for the procedure and can watch the inside of their colon
on the colour monitor. Substituting propofol for midazolam, which gives the
patient quicker recovery, is gaining wider use, but requires closer monitoring
A meta-analysis found that playing music improves patient
tolerability of the procedure.
The first step is usually a digital rectal examination, to
examine the tone of the sphincter and to determine if preparation has been
adequate. The endoscope is then passed through the anus up the rectum, the colon
(sigmoid, descending, transverse and ascending colon, the cecum), and ultimately
the terminal ileum. The endoscope has a movable tip and multiple channels for
instrumentation, air, suction and light. The bowel is occasionally insufflated
with air to maximize visibility (a procedure which gives one the false sensation
of needing to take a bowel movement). Biopsies are frequently taken for
histology. Additionally in a procedure known as "Chromoscopy", a contrast-dye
(such as Indigo carmine) may be sprayed via the endoscope onto the bowel wall to
help visualise any abnormalities in the mucosal morphology.
In most experienced hands, the endoscope is advanced to the
junction of where the colon and small bowel join up (cecum) in under 10 minutes
in 95% of cases. Due to tight turns and redundancy in areas of the colon that
are not "fixed", loops may form in which advancement of the endoscope creates a
"bowing" effect that causes the tip to actually retract. These loops often
result in discomfort due to stretching of the colon and its associated
mesentery. Manoeuvres to "reduce" or remove the loop include pulling the
endoscope backwards while torquing the instrument. Alternatively, body position
changes and abdominal support from external hand pressure can often "straighten"
the endoscope to allow the scope to move forward. In a minority of patients,
looping is often cited as a cause for an incomplete examination. Usage of
alternative instruments leading to completion of the examination has been
investigated, including use of pediatric colonoscope, push enteroscope and upper
GI endoscope variants.
For screening purposes, a closer visual inspection is then often
performed upon withdrawal of the endoscope over the course of 20 to 25 minutes.
Lawsuits over missed cancerous lesions have recently prompted some institutions
to better document withdrawal time as rapid withdrawal times may be a source of
potential medical legal liability. This is often a real concern in clinical
settings where high caseloads could provide financial incentive to complete
colonoscopies as quickly as possible.
Suspicious lesions may be cauterized, treated with laser light
or cut with an electric wire for purposes of biopsy or complete removal
polypectomy. Medication can be injected, e.g. to control bleeding lesions. On
average, the procedure takes 20–30 minutes, depending on the indication and
findings. With multiple polypectomies or biopsies, procedure times may be
longer. As mentioned above, anatomic considerations may also affect procedure
After the procedure, some recovery time is usually allowed to
let the sedative wear off. Outpatient recovery time can take an estimate of
30–60 minutes. Most facilities require that patients have a person with them to
help them home afterwards (again, depending on the sedation method used).
One very common aftereffect from the procedure is a bout of
flatulence and minor wind pain caused by air insufflation into the colon during
An advantage of colonoscopy over x-ray imaging or other, less
invasive tests, is the ability to perform therapeutic interventions during the
test. A polyp is a growth of excess of tissue that can develop into cancer. If a
polyp is found, for example, it can be removed by one of several techniques. A
snare device can be placed around a polyp for removal. Even if the polyp is flat
on the surface it can often be removed. For example, the following shows a polyp
removed in stages:
The pain associated with the procedure is not caused by the
insertion of the scope but rather by the inflation of the colon in order to do
the inspection. The scope itself is essentially a long, flexible tube about a
centimetre in diameter, i.e. as big around as the little finger, which is less
than the diameter of an average stool. The pain is said to be very uncomfortable
and also burning.
The colon is wrinkled and corrugated, somewhat like an accordion
or a clothes-dryer exhaust tube, which gives it the large surface area needed
for digestion. In order to inspect this surface thoroughly the physician blows
it up like a balloon, using an air compressor, in order to get the creases out.
The stomach, intestines and colon have a so-called "second brain" wrapped around
them, which autonomously runs the chemical factory of digestion. It uses complex
hormone signals and nerve signals to communicate with the brain and the rest of
the body. Normally a colon's job is to digest food and regulate the intestinal
flora. The harmful bacteria in rancid food, for example, creates gas. The colon
has distension sensors that can tell when there is unexpected gas pushing the
colon walls out —thus the "second brain" tells the person that he or she is
having intestinal difficulties by way of the sensation of nausea. Doctors
typically recommend either total anaesthesia or a partial "twilight" sedative to
either preclude or to lessen the patient's awareness of pain or discomfort, or
just the unusual sensations of the procedure. Once the colon has been inflated,
the doctor inspects it with the scope as it is slowly pulled backwards. If any
polyps are found they are then cut out for later biopsy.
Some doctors prefer to work with totally anesthetized patients
inasmuch as the lack of any perceived pain or discomfort allows for a leisurely
examination. Twilight sedation is, however, inherently safer than general
anesthesia; it also allows the patients to follow simple commands and even to
watch the procedure on a closed-circuit monitor. For these reasons it is
generally best to request twilight sedation and ask the doctor to take his or
her time despite any discomfort which the procedure may entail. Tens of millions
of adults annually need to have colonoscopies, and yet many don't because of
concerns about the procedure.
It is worth noting that in many hospitals (for instance St.
Mark's Hospital, London, which specialises in intestinal and colorectal
medicine) colonoscopies are carried out without any sedation. This allows the
patient to shift his or her body position to help the doctor carry out the
procedure and significantly reduces recovery time and side-effects. Although
there is some discomfort when the colon is distended with air, this is not
usually particularly painful and it passes relatively quickly. Patients can then
be released from hospital on their own very swiftly without any feelings of
Duodenography and colonography are performed like a standard
abdominal examination using B-mode and color flow Doppler ultrasonography using
a low frequency transducer — for example a 2.5 MHz — and a high frequency
transducer, for example a 7.5 MHz probe. Detailed examination of duodenal walls
and folds, colonic walls and haustra was performed using a 7.5 MHz probe. Deeply
located abdominal structures were examined using 2.5 MHz probe. All ultrasound
examinations are performed after overnight fasting (for at least 16 hours) using
standard scanning procedure. Subjects are examined with and without water
contrast. Water contrast imaging is performed by having adult subjects take at
least one liter of water prior to examination. Patients are examined in the
supine, left posterior oblique, and left lateral decubitus positions using the
intercostal and subcostal approaches. The liver, gall bladder, spleen, pancreas,
duodenum, colon, and kidneys are routinely evaluated in all patients. With
patient lying supine, the examination of the duodenum with high frequency
ultrasound duodenography is performed with 7.5 MHz probe placed in the right
upper abdomen, and central epigastric successively; for high frequency
ultrasound colonography, the ascending colon, is examined with starting point
usually midway of an imaginary line running from the iliac crest to the
umbilicus and proceeding cephalid through the right mid abdomen; for the
descending colon, the examination begins from the left upper abdomen proceeding
caudally and traversing the left mid abdomen and left lower abdomen, terminating
at the sigmoid colon in the lower pelvic region. Color flow Doppler sonography
is used to examine the localization of lesions in relation to vessels. All
measurements of diameter and wall thickness are performed with built-in
software. Measurements are taken between peristaltic waves.
A 2009 study published in the Annals of Internal Medicine
implies that colonoscopy screening prevents approximately two thirds of the
deaths due to colorectal cancers on the left side of the colon, and is not
associated with a significant reduction in deaths from right-sided disease. This
study examined people with colon cancer diagnosed between 1996 and 2001 in
Ontario who died of colon cancer by 2003, and hence studied colonoscopies done
in the early to mid 1990s. (Since the procedure continues to evolve, more recent
colonoscopies may be more effective). The summary result, according to table 3
of the report, show approximately a 37% reduction in the death rate from
colorectal cancer, with a significantly lower reduction in death for
A 2011 study published in Annals of Internal Medicine, on the
other hand, showed that in people who had colonoscopy in the previous 10 years
"the risks for early and more advanced stages of cancer were reduced by more
than 50%. A lower risk for CRC colorectal cancer] was seen for both cancer on
the left side of the colon (closer to the anus and thus easier to reach during
colonoscopy) and for cancer on the right side (which is harder to reach)."
This procedure has a low (0.35%) risk of serious complications.
In a 2006 study of colonoscopies done from 1994 to 2002, Levin et al., found
serious complications occurred in 5.0 of 1000 colonoscopies, comprising 0.8 in
1000 colonoscopies without biopsy or polypectomy, and a rate of 7.0 per 1000 for
colonoscopies with biopsy or polypectomy; although McDonell and Loura criticize
this rate as being unacceptably high.
The rate of complications varies with the practitioner and
institution performing the procedure, as well as a function of other variables.
The most serious complication generally is the gastrointestinal
perforation, which is life-threatening and requires immediate major surgery for
repair. A 2003 summary study of 25,000 patients showed a perforation rate of
0.2%, and a death rate of 0.006% on a total of 84,000 patients. The 2006 study
by Levin et al. showed a perforation rate of 0.09%; while a 2009 study quoted a
similar perforation rate of 0.082%. Appendicitis, has been associated with
either perforation or colonoscopy, in case reports in Korean, Italian and
According to a study published in the Annals of Internal
Medicine, for which researchers reviewed colon cancer screening data from 1966
to 2001, the most severe complications from colonoscopy are perforation (that
occurred in 0.029% to 0.72% of cases), heavy bleeding (occurring in 0.2% to
2.67% of colonoscopies) and death (occurring in 0.003% to 0.03% of colonoscopy
A 2003 analysis of the relative risks of sigmoidoscopy and
colonoscopy, brought into attention that the risk of perforation after
colonoscopy is approximately double that after sigmoidoscopy (consistent with
the fact that colonoscopy examines a longer section of the colon), even though
this difference appeared to be decreasing.
Bleeding complications may be treated immediately during the
procedure by cauterization via the instrument. Delayed bleeding may also occur
at the site of polyp removal up to a week after the procedure and a repeat
procedure can then be performed to treat the bleeding site. Even more rarely,
splenic rupture can occur after colonoscopy because of adhesions between the
colon and the spleen.
As with any procedure involving anaesthesia, other complications
would include cardiopulmonary complications such as a temporary drop in blood
pressure, and oxygen saturation usually the result of overmedication, and are
easily reversed. Anesthesia can also increase the risk of developing blood clots
and lead to pulmonary embolism or deep venous thrombosis. (DVT) In rare cases,
more serious cardiopulmonary events such as a heart attack, stroke, or even
death may occur; these are extremely rare except in critically ill patients with
multiple risk factors. In very rare cases, coma associated with anesthesia may
Virtual colonoscopies carry risks that are associated with
Severe dehydration caused by the laxatives that are usually
administered during the bowel preparation for colonoscopy also may occur.
Therefore, patients must drink large amounts of fluids during the days of
colonoscopy preparation to prevent dehydration. Loss of electrolytes or
dehydration is potential risk that can even prove deadly. In rare cases, severe
dehydration can lead to kidney damage or renal dysfunction under the form of
Colonoscopy preparation and colonoscopy procedure can cause
inflammation of the bowels and diarrhea or even bowel obstruction.
During colonoscopies where a polyp is removed (a polypectomy),
the risk of complications has been higher, although still very uncommon, at
about 2.3 percent. One of the most serious complications that may arise after
colonoscopy is the postpolypectomy syndrome. This syndrome occurs due to
potential burns to the bowel wall when the polyp is removed. It is however a
very rare complication and as a result patients may experience fever and
abdominal pain. The condition is treated with intravenous fluids and antibiotics
while the patient is recommended to rest.
Bowel infections are a potential colonoscopy risk, although very
rare. The colon is not a sterile environment as many bacteria live in the colon
to assure the well-functioning of the bowel and therefore the risk of infections
is very low. Infections can occur during biopsies when too much tissue is
removed and bacteria protrude in areas they do not belong to or in cases when
the lining of the colon is perforated and the bacteria get into the abdominal
cavity. Infection may also be transmitted between patients if the colonoscope is
not cleaned and sterilized properly between tests, although the risk of this
happening is very low.
Minor colonoscopy risks may include nausea, vomiting or
allergies to the sedatives that are used. If medication is given intravenously,
the vein may become irritated. Most localized irritations to the vein leave a
tender lump lasting a number of days but going away eventually. The incidence of
these complications is less than 1%.
On very rare occasions, intracolonic explosion may occur. High
frequency ultrasound duodenography and colonography do not carry the risks
associated with a traditional colonoscopy. Although complications after
colonoscopy are uncommon, it is important for patients to recognize early signs
of any possible complications. They include severe abdominal pain, fevers and
chills, or rectal bleeding (more than half a cup).
Colonoscopy reduces cancer rates by preventing some colon
cancers on the left side of the colon; these colon polyps and early cancers
would have been treated during a safer sigmoidoscopy procedure. Colonoscopy is
relatively risky, with 5 in 1000 patients facing serious complications. To
prevent one cancer death, 1,250 colonoscopies need to be performed, but
perforation of the colon occurs at a rate of about 1 in 1000 procedures.
Since polyps often take 10 to 15 years to transform into cancer,
in someone at average risk of colorectal cancer, guidelines recommend 10 years
after a normal screening colonoscopy before the next colonoscopy. (This interval
does not apply to people at high risk of colorectal cancer, or to those who
experience symptoms of colorectal cancer.)
Colonoscopy is not recommended for patients over 75, and the
procedure has been "considerably overused" among elderly patients. Researchers
found that older patients with three or more significant health problems, like
dementia or heart failure, had high rates of repeat colonoscopies without
medical indications. These patients are less likely to live long enough to
develop colon cancer. Gordon states, "At about $1,000 per procedure, there’s
clearly an economic incentive".
An Old Fashioned Proctoscope Exam