Digital rectal examination is a simple and very important method. Digital rectal examination can help diagnose certain anorectal diseases. For example, 75% of rectal cancer can be found during digital rectal examination. Digital rectal examination has important guiding significance for the treatment of some anorectal diseases, including the treatment of low rectal cancer.
1 Understand the applied anatomy of the surgical anal canal and surgical rectum to facilitate digital rectal examination
1.1 Surgical anal canal
According to embryonic development and tissue morphology, from below the dentate line to the anal margin, the anal canal is called anatomical canal, and the anal canal is approximately 1.5-2 cm long. From the clinical application and surgical point of view, from the upper edge of the anorectal ring to the anal edge (that is, the lowest point of the levator ani muscle plane to the anal edge) is called the surgical anal canal . The surgical anal canal is approximately twice as long as the anatomical anal canal. The surgical anal canal is mainly composed of involuntary muscles and voluntary muscles.
The involuntary muscle is the internal sphincter, a thickened circular muscle at the lower end of the rectum, located in the inner layer of the surgical anal canal. There is a white line between the lower edge of the internal sphincter muscle and the lower part of the skin of the external sphincter. The white line is invisible. This groove can be palpated by digital rectal examination. It is located at the junction of the lower 1/3 of the surgical anal canal. The voluntary muscles are arranged from top to bottom: the pubococcygeus muscle (part of the levator ani muscle), the puborectalis muscle, and the external anal sphincter (deep, superficial, and subcutaneous). The upper 1/3 of the surgical anal canal is divided into anorectal ring.
Abdominal pressure increases during defecation, and the surgical anal canal is enlarged, which is conducive to stool discharge. According to this principle, the patient is instructed to do defecation during the digital rectal examination. At this time, the index finger enters the rectum, and the patient generally has no obvious pain. On digital rectal examination, it is obvious that the muscular-tube surgical anal tube with a length of about 3-4 cm surrounds the index finger.
The essence of anal preservation surgery is to retain the surgical anal canal. The surgical anal canal not only has the function of defecation control, but also has the function of defecation feeling. Recently, it is believed that there are defecation reflex receptors in the skin, submucosa and puborectalis muscle in the surgical anal canal[ 2].
1.2 Surgical rectum
The upper part of the surgical upper rectum is defined as the sacral scapular level, so the rectum is about 12cm in length, and the rectal stroke is not linear. There are 2 curvatures in the sagittal plane, namely the rectal perineal curvature of about 4cm and the rectal sacral curvature of about 8cm. . China and Europe and the United States divide the rectum into three segments. The surgical anal canal is 3-4cm, the rectum below 8cm from the anal margin is called low rectum (lower rectum), 8-12cm is called median rectum (middle rectum), and 12-16cm is called high rectum. (Upper rectum) . The rectal perineal flexure is equivalent to the lower rectum. Digital rectal examination can clearly feel that there is a low slope-like flexure of the rectum and perineum above the muscular surgical anal canal.
2 Digital rectal examination method
2.1 Position of the patient
We don't often put the patient in the chest-knee or squat position. It is inconvenient for the patient to be in the chest-knee position, and the patient is in the squatting position, which is inconvenient for the doctor to check. We first let the patient empty the stool, instruct the patient to lie on the left side, bend the hips upward, hug the knees with both hands, and keep the knees as close to the abdomen as possible so that the anus is fully exposed.
2.2 Examination around the anus before digital examination
First check the skin around the patient's anal margin. If there is tenderness or pulsation, it often indicates a perianal infection; there is a cord under the skin and connected to the external anus, indicating an anal fistula.
2.3 Ways to advance
The examiner wears finger cots, and the index finger is coated with lubricating liquid paraffin to facilitate examination and reduce patient discomfort. The conventional method of finger feeding is: lightly massage the anus with the index finger of the right hand, and ask the patient to relax the anus. The patient often backfires, and the anus becomes tense. At this time, the index finger enters the rectum, and the patient often has obvious pain. If you do a digital rectal examination in the future, the patient often feels fear. The author's method is: in order to allow the patient to use the index finger to gently massage the anus, and then instruct the patient to do defecation movements, tell the patient not to worry about the defecation, because the index finger has been against the anus. When the patient performs defecation, the pelvic floor drops and the anal sphincter expands. At this time, the index finger naturally enters the rectum, and the patient generally has no pain.
2.4 Inspection method
After the index finger enters the rectum, stick the fingertips parallel to the intestinal wall, turn it clockwise for 2 turns and then turn it counterclockwise for 2 turns, and touch it up and down. Digital rectal examination can understand the anorectal lesions within 8cm from the anus.
2.5 Recording method
If the digital rectal examination touches the lesion, the location, size, shape, texture, distance from the anus, distance from the upper edge of the surgical anal canal, and fraction of the intestinal wall should be recorded. Professor Zhou Xigeng, a well-known Chinese anorectal surgery expert, does not like to use the hour hand to indicate the location of the lesion, because the hour hand varies with the patient's position. For example, the lithotomy position is changed from 6 o'clock to the thoracic knee position at 12 o'clock. Professor Zhou Xigeng advocated using the patient's left, right, front, and back to mark the location of the mass. For example, a raised mass was touched 6cm from the anus, located in the left front of the rectum, with a size of 3x3cm, occupying 1/4 of the intestinal wall.
3 Digital rectal examination is of great significance in the diagnosis and treatment of the following diseases.
3.1 Internal hemorrhoids
Patients often seek treatment for fresh blood or moisture or itching around the anus. Digital rectal examination generally does not detect internal hemorrhoids. Occasionally, a large, soft, and elastic mass can be felt on the tooth line. At this time, internal hemorrhoids are usually accompanied by bleeding or prolapse during defecation. The diagnosis depends on anoscopy. Under the anoscope, it can be seen that the internal hemorrhoids appear as dark purple bulges in the front of the anoscope, or the pink masses fall out of the anoscope.
Sometimes a hard mass is felt as a tumor, but if the mucous membrane is smooth, the base runs along the rectal column, and the base moves, mostly internal hemorrhoids form thrombus. The diagnosis depends on surgical resection and medical examination.
3.2 Anal fissure
Patients often see a doctor with anal pain or with fresh blood in the stool. Digital rectal examination is usually not used because of sphincter contracture and tight anal contraction, which will aggravate the pain. Diagnosis depends on inspection: open the anal opening, you can find a 0.5-1.0cm gap behind or in front of the anal opening, and sometimes sentinel hemorrhoids are seen outside the opening.
3.3 Anal fistula
Patients often see a doctor with secretions outside the anus and itching. Perianal digital examination often touches the subcutaneous cord that leads from the external mouth to the anus. In digital rectal examination, small depressions or indurations are sometimes felt near the tooth line, which is mostly the internal opening of anal fistula. Sometimes, above the surgical anal canal, the coronal surface feels arc-shaped, uneven cords located under the mucosa, and most of them are submucosal horseshoe-shaped anal fistulas. The diagnosis depends on medical history, clinical manifestations, and digital rectal examination. Generally, there is no probe inspection before surgery.
3.4 Perirectal abscess
At the beginning of the disease, the patient may have perineal swelling, or tenesmus, or incomplete defecation, or anal pain. At the beginning of the disease, there may be no positive findings or only the patient’s anal sphincter is tight. Digital rectal examination sometimes finds tenderness on the affected side, and the patient sometimes refuses to undergo digital rectal examination because of fear of pain.
When the disease develops to a certain stage, the affected side can be palpable uplift or fluctuation: (1) Subcutaneous uplift or fluctuation around the anus: subcutaneous abscess around the anus. (2) The anal canal on the affected side is raised or fluctuated or lengthened: internal and external sphincter abscess or ischial anal space abscess. (3) Uplift or fluctuation on the levator ani muscle: pelvic and rectal space abscess or submucosal abscess. The diagnosis relies on B-ultrasound to find liquid dark areas or pus from puncture.
3.5 Anal sinusitis
The diagnosis is mainly based on digital rectal examination or anoscopy. When checking the tooth line for a week, there is obvious local tenderness and sometimes local hotness. Anoscopy sometimes reveals local congestion or secretions in the affected area.
3.6 Anal Papilloma
Patients often see a doctor with small nodules protruding outside the anus. The digital rectal examination touched soybean-sized nodules at the tooth line, and the nodules were often pedicled.
3.7 Anorectal stenosis
Patients often see a doctor with difficulty defecation. Anal stenosis after annular hemorrhoids is mostly membranous stenosis, sometimes it cannot pass the index finger, and the stenosis is close to the anus, generally not more than 4cm away. Anastomotic stenosis after rectal cancer is generally located above the surgical anal canal, which can be a circular stenosis. Rectal cancer can also be palpable before surgery for intestinal stenosis, bumpy masses, and finger cuffs often stained with blood. Rectal stenosis caused by endometriosis can be palpable outside the mucosa (usually located in the uterine rectum depression) with single or several indurations of varying sizes, fixed and tender. Rectal stenosis caused by prostate cancer can cause the prostate to become larger and harder. Diagnosis mainly depends on medical history, digital rectal examination, and sometimes pathological biopsy is needed to help confirm the diagnosis.
3.8 Protruding rectal constipation
Digital rectal examination is an important method for diagnosing rectal protrusion. In the upper end of the surgical anal canal, the front wall of the rectum, and the round or oval weakened area that is easy to sink, the patient is asked to do vigorous defecation movements. The concave area shows varying degrees Deepen, protruding into the vagina. The diagnosis depends on defecography.
3.9 Puborectal hypertrophy constipation
Puborectal muscle hypertrophy can be felt during digital rectal examination. When the patient is instructed to do defecation, the puborectal muscle is not easy to expand. The diagnosis depends on defecography.
3.10 Internal anal sphincter constipation
Digital rectal examination can feel that the lower end of the internal sphincter is obviously thickened, and the intersphincteric groove is deeper than normal. Sometimes the intersphincteric groove is located at the anus or outside the anus. When the patient is asked to defecate, the internal sphincter is not easy to expand. The diagnosis depends on electromyography.
3.11 Prolapse of intestinal mucosa
Patients often see a doctor with anal bulging feeling. Digital rectal examination can be palpable and the rectal mucosa is loose and circular folds. The diagnosis depends on defecography.
3.11 Hirschsprung's disease
Sick children often see a doctor with difficulty defecation. The cause is the absence of nerve node cells between the muscles of the intestinal wall and the submucosal nerve plexus. When a child is instructed to do defecation by the digital rectal examination, if the surgical anal canal is not easy to expand, it indicates that the patient is ultra-short segment Hirschsprung's disease; such as the surgical anal canal It can be expanded to exclude ultra-short Hirschsprung. The diagnosis mainly depends on barium enema.
3.12 Stool incarceration
Patients often have a history of constipation. When they go to the hospital for treatment, they often show irritability, abdominal pain or perineal pain, and the rectum is full of dry stool during digital rectal examination. The treatment took out the incarcerated stool by hand.
3.13 Intestinal obstruction
In patients with intestinal obstruction, perform a digital rectal examination, such as finger cuff stained blood, indicating intestinal strangulation or intestinal tumor ulceration and bleeding, such as touching an uneven mass, indicating rectal cancer with obstruction, such as touching a hard mass outside the mucosa. Most abdominal tumors have pelvic implantation and metastasis.
3.14 Rectal villous adenoma
Patients often see a doctor for blood or mucus. Digital rectal examination can palpate soft masses, and diagnosis depends on medical examination. If there is a harder nodule in a soft lump, it often indicates cancer.
3.15 rectal cancer
Patients often see a doctor with purple or dark red blood. Digital rectal examination can palpate hard, ulcerated, or infiltrating masses. The diagnosis mainly depends on pathological biopsy.
3.16 Rectal foreign body
It can be swallowed by the mouth or inserted into the anus. The types and shapes of foreign bodies can be varied.
3.17 Gastric cancer
The patient must do a digital rectal examination before the operation. If the digital rectal examination touches an uneven hard mass outside the mucosa, it indicates that the gastric cancer is in the advanced stage.
4 Digital rectal examination is of great significance in the preoperative planning of surgical methods for low rectal cancer.
Surgeons consider the condition of patients with low rectal cancer, tumor disease examination, digital rectal examination, pelvic CT, intracavitary ultrasound and other conditions before the operation, so as to formulate the surgical method for rectal cancer. Preoperative digital rectal examination can understand the distance between the base of rectal cancer and the anus, the depth of invasion of the base of rectal cancer, the gross pathological type of rectal cancer, the distribution of rectal cancer, etc., and provide the most basic information to the operator. Digital rectal examination has an irreplaceable role in helping to determine the surgical method for rectal cancer before surgery. Of course, the final decision on the surgical method used during the operation is still based on the specific conditions during the operation.
4.1 Digital rectal examination should understand the height of the base of the low rectal cancer.
The upper edge of the surgical anal canal is at the junction of the muscular surgical anal canal and the empty rectal perineal flexure. Digital rectal examination should not only understand the distance between the base of rectal cancer and the anus, but also the distance between the base of rectal cancer and the upper edge of the surgical anal canal.
Assume that the patient’s surgical anal canal is 4cm long and the tumor is a limited type of rectal adenocarcinoma with a certain degree of mobility. Preoperative digital examination shows that the base of the tumor is 6 cm away from the anus (that is, the distance from the upper edge of the surgical anal canal is 2 cm) In general, an ultra-low double anastomosis technique can be considered to preserve anus; if the base is 5 cm away from the anus (that is, 1 cm away from the upper edge of the surgical anal canal), modified Bacon surgery (colon transanal pulling Out surgery), Parks surgery (colon anal canal anastomosis) [5, 6].
4.2 Digital rectal examination should understand the depth of invasion of the base of low rectal cancer
Understanding the depth of the basal invasion of low rectal cancer is more important than knowing the height. The most accurate determination of the depth of invasion depends on intraluminal B-ultrasound. Of course, the basal orientation of low rectal cancer can still be roughly determined based on the activity of the tumor basal during digital rectal examination. The depth of external invasion: (1) The tumor basal activity is large, and the intestinal wall does not move with the tumor basal activity, indicating that the tumor is located in the submucosa. (2) The base of the tumor has a certain degree of activity, and the intestinal wall often moves with the activity of the tumor base, indicating that the rectal tumor is within the mesentery. (3) The base of the tumor is fixed, indicating that the tumor has invaded the pelvic wall.
Suppose a rectal cancer located in the submucosal layer, if the pathology is well-differentiated or moderately differentiated, the mass is a localized protuberance or superficial ulcer type, the diameter of the mass is less than 3cm, although the mass is 3cm from the anus, it can still be transanal or coccosacral Local resection [5, 6], Mason surgery can also be performed to preserve the anus .
Assuming a rectal cancer located within the mesentery of the rectum, such as a distance of 2cm or more than 1cm from the upper edge of the surgical anal canal, and the mass is a localized lesion, it is generally feasible to double anastomosis technique to preserve the anus  or modified Bacon surgery (colon Transanal pull-out surgery), Parks surgery (colon anal canal anastomosis) [5, 6]. Assuming that a tumor has invaded the pelvic wall, although the tumor can be removed, this type of surgery is often non-radical. It is best to do an abdominal intestinal stoma after resection to avoid local recurrence of the tumor and compress the intestinal duct in the pelvic cavity and cause obstruction.
4.3 Digital rectal examination should understand the general pathological types of low rectal cancer
Digital rectal examination for low rectal cancer can be judged to be a localized lesion (protruding or ulcer) or a diffuse lesion. The tumor biology of the latter is worse than the former, so it should be cautious to do anal-saving surgery , and the Miles surgery should not be too condemned.
4.4 Digital rectal examination should understand the distribution of low rectal cancer and rectal cancer
Assume that two female patients are both localized rectal cancers with a certain degree of basal activity. Patient A rectal cancer is located on the front wall of the rectum, and patient B rectal cancer is located on the back wall of the rectum. A patient should undergo a rectal cavity B-ultrasound or vaginal B-ultrasound to determine whether the tumor has infiltrated the rectovaginal diaphragm. If the tumor has infiltrated the rectovaginal diaphragm, the patient should undergo a posterior pelvic resection. Patient B does not need to consider a posterior pelvic resection because the tumor is located on the back wall of the rectum.
4.5 Digital rectal examination has important guiding significance in evaluating whether the anus can be preserved before rectal cancer surgery
Digital rectal examination can determine whether the low rectal cancer involves the surgical anal canal. If the low rectal cancer involves the surgical anal canal, the principle is to go through abdominal perineal resection, and the tumor and the anus will be removed during the operation; if the low rectal cancer is located in the surgical anal canal For a certain distance and the base is not fixed, anal sparing surgery can be considered.
Generally speaking: (1) The base of rectal cancer is >2cm or >1cm from the upper edge of the surgical anal canal, the base is not fixed, the mass is a localized raised or ulcerated lesion, and the pathology is high, medium, or poorly differentiated adenocarcinoma, which can be considered Double anastomosis technique anus preservation surgery or modified Bacon surgery, Parks surgery. (2) The base of rectal cancer is less than 1cm from the upper edge of the surgical anal canal, or