Introductory Chapter: The Actual State of Colonoscopy

1. Introduction

Before dealing with the characteristics and indications of colonoscopy, let us briefly refer to its younger sister, flexible sigmoidoscopy, which, as its name indicates, is used only for the distal exploration of the colon, including the rectum and sigmoid, which is also interesting to know in its applications that are complementary in some cases, with the complete exploration of the entire colon.

2. Flexible sigmoidoscopy: indications and contraindications

It has been at least two decades since flexible sigmoidoscopy has replaced conventional rectoscopy, and the reasons must be sought independently of the limited associated discomfort and in a better general acceptance of the use of a flexible instrument instead of the introduction of a rigid tube, as well as obtaining greater diagnostic performance in the detection of polyps and/or rectal tumors.

However, with the introduction and progressive development of colonoscopy worldwide, which allows the entire colon and terminal ileum to be adequately explored, sigmoidoscopy has been losing prominence in most clinical centers. However, it still has some indications, which are summarized: 1. Study of the distal pathology of the colon (ano-rectal). 2. Evaluation of cases of acute diarrhea. 3. Monitoring and control of ulcerative colitis. 4. Periodic control of ileo-anal reservoirs. 5. In patients with low tumor risk in asymptomatic patients. 6. In those over 50 years of age, without a family history. 7. In relatives of patients with familial adenomatous polyposis from the age of 10 and annually. 8. In surveillance of the excluded rectal stump in cases of inflammatory bowel disease.

Two absolute contraindications are included: 1. Severe acute diverticulitis. 2. Suspected intestinal perforation.

In United States and some other countries, sigmoidoscopy is usually performed by specialized nurses under the direct supervision and occasional help of expert endoscopists [1].

3. Colonoscopy: indications and contraindications

The development of colonoscopy in recent decades worldwide has followed a course parallel to advances in knowledge of the sequence of changes from polyp to carcinoma in the colon. Malignant colon and rectal tumors are often associated with certain conditions that are considered premalignant. In colorectal carcinoma, the most common premalignant lesion consists of the presence of adenomatous polyps. Therefore, the development of an early diagnosis plan is based on the periodic and careful surveillance of patients with premalignant lesions in order to detect the presence of cancers at an early (pre-symptomatic) stage, when endoscopic or surgical cure is still possible. It is possible…

Although there is any conclusive evidence in controlled studies to support that endoscopic surveillance reduces the mortality rate, some data suggest improved survival of patients included in surveillance programs.

Consequently, colonoscopy has acquired maximum notoriety, as has the close control of the evolution of adenomatous polyps. The advance in colonoscopy knowledge regarding the possibility of detecting the presence of premalignant lesions and at the same time, being able to remove them, replacing the opaque enema due to its greater capacity for the diagnosis and treatment of these lesions.

The indications for colonoscopy can be divided into two categories: diagnostic and therapeutic (Tables 1 and 2). The contraindications and complications of this technique are also described (Tables 3–5) [2, 3, 4, 5].

For the evaluation of repletion defects and/or stenosis, visualized in the Opaque Enema

First of all, Iron Deficiency Anemia of unexplained origin

In the evaluation of Gastrointestinal Bleeding of unclear origin

Melenas with previous normal Esophago-Gastro-Duodenoscopy study

Confirmed presence of Occult Blood in Feces

Hematochezia that does not clearly come from the rectum or perianal region

To rule out synchronous lesions (Cancer and/or Polyps) in patients with these suspicious findings

Post-resection follow-up of CRC or neoplastic polyps at periodic intervals

In family screening for hereditary CRC and subsequent follow-up

Table 1.

Indications for diagnostic colonoscopy.

Treatment of all types of bleeding lesions of the colon (post-polypectomy, angiomas, neoplasms, diverticula, vascular anomalies)

Removal of foreign bodies from the colon and rectum

Decompression of acute non-toxic megacolon, or sigmoid volvulus

Balloon dilation of stenotic lesions

Removal of colon polyps

Palliative treatment of tumorous, stenotic, or bleeding lesions

Bridging treatment prior to surgery of colonic obstructions secondary to malignant lesions

Table 2.

Indications for therapeutic colonoscopy.

Chronic Abdominal Pain and Irritable Bowel Syndrome that does not present diagnostic doubts

Acute self-limited diarrhea

Routine monitoring of inflammatory bowel disease

Digestive bleeding of known cause in the upper digestive tract

Acute fulminant colitis

Acute diverticulitis

Acute pancreatitis

Recent postoperative colonic surgery

Second and third trimester of pregnancy

When the risks to the patient’s health and/or life are greater than the benefits of the examination

Suspected perforation of a hollow viscus

In patients with recent pulmonary embolism

When there is no collaboration on the part of the patient

Table 3.

Contraindications of colonoscopy.

Bacteremia

Drilling

Pneumatic drilling

Hemorrhage

Volvulus

Cardiac and/or ECG alterations

Aortic aneurysm dissection

Post-colonoscopy distention syndrome

Vaso-vagal reflex

Incarceration of an inguinal hernia

Impaction of the endoscope into the hernial sac

Table 4.

Complications of diagnostic colonoscopy.

Hemorrhage

Drilling

Incomplete polypectomy

Post-polypectomy syndrome (suffering of the colon wall due to excess coagulation)

Exitus

Table 5.

Complications of therapeutic colonoscopy.

4. Preparation and cleaning of the colon for performing the colonoscopy

It is carried out through the ingestion of an electrolyte solution of polyethylene glycol (PEG) with electrolyte solution at a rate of 250 cc orally every 15 minutes, up to a total of 2-3 liters. It can be used safely in patients with heart, kidney, and liver diseases, as it prevents dehydration and significant loss of electrolytes, its main disadvantage being the large amount of liquid that the patient has to drink and its salty taste, which can induce vomiting, in up to 10% of cases. It is possible to administer a prokinetic such as cisapride at a dose of 20 mg. Thirty minutes before starting to take the preparation, reduce the chances of nausea and/or vomiting.

The Fleet preparation is also recommended, which obtains similar results to the PEG/electrolyte solution preparation, probably with greater acceptance by patients, since the volume of the solution to be ingested is smaller, only 90 ml., followed by abundant amount of liquid to choose for each patient. Its main drawback is the risk of dehydration and the appearance of hydroelectrolyte alterations, being contraindicated in patients with associated diseases. Another possible side effect of this preparation is the appearance of thrush-type mucosal lesions in the colon, which can be misleading and appear in up to 15% of cases [6, 7, 8].

5. Preparation in special situations

5.1 Persistent constipation

If there is evidence of chronic constipation, it is suggested to always indicate intense bowel preparation. It is advisable to administer an effective oral purgative the day before, along with the intake of large quantities of liquids.

5.2 Colostomy wearers

It is as difficult to prepare as normal colon, so the usual preparation should not be modified.

5.3 Ileal reservoirs

These patients should be prepared with saline enemas and repeated until they come out completely clean.

5.4 Conventional ileostomy

They do not require preparation.

5.5 Ileorectal anastomosis

Administration of a saline enema is usually sufficient.

5.6 “Shotgun barrel” colostomy

The distal loop of a shotgun colostomy usually contains a considerable amount of viscous mucus and some thick debris that can block the colonoscope. For all these reasons, it is recommended to introduce a water/saline enema or lavage through the colostomy, before examining an intestine devoid of function.

5.7 Inflammatory bowel disease

Patients with severe colitis rarely need a colonoscopy, since a simple abdominal X-ray usually provides sufficient information, making its performance largely contraindicated.

In cases of moderate or mild colitis, the preparation should be the usual one with PEG solutions, balanced with electrolytes.

5.8 Treatment with oral iron preparations

Its administration must be suspended at least 7 days before performing the examination.

5.9 Antiplatelet or anticoagulated patients

There is no evidence that continued low-dose aspirin may increase the risk of bleeding after polypectomy, and therefore, this medication does not need to be discontinued.

In anticoagulated with warfarin due to risk of embolism, the medication can be safely suspended 3-4 days before the test, while if the risk is high, due to the presence of metallic heart valves, prior admission of the patient and conversion to heparin, at least 3 hours before the examination.

5.10 Technical aspects related to colonoscopy

The insertion of the colonoscope is a technique that is difficult to teach because, in essence, it consists of introducing a flexible tube, which is the endoscope, through a long and flexible duct, which is the colon.

The latter is characterized by having a variable length, mobility, and fixation, its movements being unpredictable after the introduction of the endoscope inside.

Since the colon is an elastic tube, it becomes arduous and tortuous with air insufflation, with the frequent formation of loops and angulations after its dilation. However, when deflated, it is much shorter. The following principles must be observed when performing a colonoscopy:

1. Insufflate the minimum amount of air throughout the entire examination and aspirate it whenever possible.

2. Avoid the formation of loops (for which you have to push as little as possible).

3. Move the endoscope back, with the aim of shortening the colon whenever possible, inserting it according to the anatomical position in which the viewer is located, 40 cm in the descending colon and inserted, in the splenic angle of 50 cm, transverse colon of about 60 cm, being at the level of the cecum, 70-80 cm.

4. Monitor at all times the presence of discomfort that the patient presents, which indicates excessive insufflation, or the formation of loops, trying to rectify the position of the endoscope if this occurs.

5. If the tip of the endoscope does not advance, try different combinations of changes, including patient posture, instrument pressure, and tube rotation.

Unassisted colonoscopy is recommended as the ideal method and is performed by most experienced endoscopists. This method requires discipline of the hands, and it is recommended that each hand have a certain task. Thus, while the left hand is in charge of holding the colonoscope and manages the air, water and aspiration controls and the up-down control and only on some occasions in the lateral control. The right hand is used to twist the instrument and becomes an essential part of the exploration [9, 10].

There are three different kinds of rotational effects:

1. Rotation with the endoscope and the straight tip is done by rotating the instrument on its axis. This movement can be used to orient the biopsy forceps, adhere the polypectomy loop to a specific lesion, or to position the aspiration channel precisely over a fluid accumulator.

2. Rotation with the endoscope straight and the tip angled and directed upwards, clockwise twisting deviates it to the right, while with the tip directed downwards, the same clockwise movement produces a deviation to the left.

3. Rotation with a loop is usually formed at the sigmoid level. To try to resolve it, it is advisable to perform a clockwise rotation, so that the mobile sigmoid is shortened above the endoscope, while the end of the latter will ascend toward the fixed ascending colon.

6. Colonoscopy with magnification and chromography

In recent years, a very important development has been achieved in video image quality, since chips (> 400,000 pixels) have been incorporated into colonoscopes that produce high-resolution images that are digitally treated, thus achieving greater definition (similar to that obtained using low-power microscopes with 100× image magnification) [11].

This technique, together with the staining of the mucosa using dyes, allows us to better visualize its surface and thus differentiate between those neoplastic polyps and those that are not.

Furthermore, Chromography and Endoscopic Magnification are also useful when applied to follow-up [12].

For patients with long-standing ulcerative colitis, since staining the mucosa with dyes such as methylene blue allows us to detect areas of possible dysplasia and direct biopsy taking toward them.