Rectal cancer is cancer between the dentate line and the junction of the rectosigmoid colon, and is one of the most common malignant tumors of the gastrointestinal tract. The location of rectal cancer is low, so it can be easily diagnosed by rectal finger diagnosis and sigmoidoscopy. However, because of its location deep into the pelvic cavity and complex anatomical relationship, surgery is not easy to be complete and the recurrence rate after surgery is high. The proximity of lower and middle rectal cancer to the anal sphincter makes it difficult to preserve the anus and its function during surgery, which is a difficult problem in surgery and is also the most debated disease in terms of surgical methods. The median age of rectal cancer incidence in China is around 45 years old. There is a trend of increasing incidence in young people.
I. Etiology
The etiology of rectal cancer is still not very clear, and its development is related to social environment, dietary habits, genetic factors and so on. Rectal polyp is also a high risk factor for rectal cancer. At present, it is basically recognized that high intake of animal fat and protein and insufficient intake of dietary fiber are the high-risk factors for rectal cancer.
Clinical manifestations
1.Most early rectal cancers are asymptomatic.
2. When rectal cancer grows to a certain extent, change in bowel habit, bloody stool, pus-blood stool, urgency, constipation, diarrhea, etc. will appear.
3.The stool will gradually become thinner, and in the advanced stage, there will be obstruction of defecation, emaciation and even cachexia.
4. When the tumor invades the bladder, urethra, vagina and other surrounding organs, symptoms of urinary tract irritation, vaginal discharge of fecal fluid, pain in the sacral and perineal areas, edema of lower limbs, etc. may appear.
3.Examination
1.rectal finger examination
It is the necessary examination step to diagnose rectal cancer. About 80% of rectal cancer patients can be detected through rectal finger examination. Hard and uneven masses can be palpated; in advanced stage, narrow intestinal cavity and fixed masses can be palpated. The finger sleeve can see the dirty pus and blood containing feces.
2.Proctoscopy
Proctoscopy should be performed after rectal finger examination to assist diagnosis under direct vision, observe the shape, upper and lower edges and distance from the anal edge of the mass, and take the mass tissue for pathological section to determine the nature of the mass and its differentiation degree. If the cancer is located in the middle or upper rectum and cannot be touched by fingers, sigmoidoscopy is a better method.
3.Barium enema and fiberoptic colonoscopy
It is not very helpful to the diagnosis of rectal cancer, so it is not listed as routine examination, but only used to exclude multiple tumors of colon and rectum.
4.Pelvic magnetic resonance examination (MRI)
To understand the location of tumor and the relationship with the surrounding adjacent structures, which helps to make preoperative clinically accurate staging and formulate reasonable comprehensive treatment strategy, for example: surgery or radiotherapy first?
5.CT of abdominopelvic cavity
It can understand the location of tumor, its relationship with adjacent structures, and whether there are metastases around rectum and other parts of abdominopelvic cavity. It is important for the staging of rectal cancer.
6.CT of chest or chest X-ray examination
It can understand whether there is metastasis in lung, pleura, mediastinal lymph nodes, etc.
IV. Diagnosis
In general, patients with bleeding stools should be highly alert clinically and should not be rashly diagnosed as “dysentery”, “internal hemorrhoids”, etc. Further examination is necessary to exclude the possibility of cancer. For the early diagnosis of rectal cancer, we must pay attention to the application of examination methods such as rectal finger examination, proctoscopy or sigmoidoscopy. Pathological diagnosis can be obtained through microscopic examination.
V. Treatment
The treatment of rectal cancer needs to be mainly surgical, supplemented by chemotherapy and radiotherapy.
Surgical treatment
There are two kinds: radical and palliative.
1.Radical surgery
(1) Combined transabdominal perineal resection: it is applicable to cancer of the lower rectum less than 175px from the anal verge, and the resection area includes sigmoid colon and its lining, rectum, anal canal, anal raphe, sciatic rectal fossa and skin around the anus, and the blood vessels are cut off by ligation at the root of the inferior mesenteric artery or below the left colonic artery division, and the corresponding para-arterial lymph nodes are cleared. A permanent colostomy (artificial anus) is made in the abdomen. This procedure has a complete resection and high cure rate.
(2) Transabdominal low resection and extraperitoneal one-stage anastomosis: also called anterolateral resection of rectal cancer (Dixon operation), it is suitable for upper rectal cancer more than 300 px from the anal verge, in which the sigmoid colon and most of the rectum are resected in the abdominal cavity, the rectum below the peritoneal reflex is freed, and the sigmoid colon and the rectum are anastomosed extraperitoneally. This operation is less damaging and can preserve the original anus, which is more ideal. If the cancer is large in size and has infiltrated the surrounding tissues, it is not suitable.
(3) Rectal cancer resection with preservation of anal sphincter: it is suitable for early rectal cancer of 7-275px from the anal verge. If the cancer is large, poorly differentiated, or the main lymphatic vessels upward have been obstructed by cancer cells and there are transverse lymphatic vessels metastasis, the resection by this operation is not complete, and transabdominal perineal colectomy is still better. The existing anastomosis for rectal cancer with preserved anal sphincter includes anastomosis by anastomosis, transabdominal low resection – transanal exenteration anastomosis, transabdominal free – transanal drag-out resection anastomosis, and transabdominal transsacral resection, etc., which can be chosen according to specific conditions.
2.Palliative surgery
If the local infiltration of cancer is serious or the metastasis is extensive and cannot be cured, in order to relieve obstruction and reduce the patient’s pain, palliative resection is feasible, with limited resection of the cancerous intestinal segment, suture closure of the distal rectum, and sigmoid colon as stoma. If this is not possible, only sigmoidostomy is performed, especially in patients with intestinal obstruction.
Radiation therapy
Radiotherapy plays an important role in the treatment of rectal cancer. Currently, it is believed that the survival period of preoperative radiotherapy followed by surgery is longer than that of surgery followed by radiotherapy for low to intermediate rectal cancer with late local staging.
Chemotherapy
Postoperative chemotherapy is recommended for patients with postoperative pathological stage II and III rectal cancer, with a total chemotherapy duration of six months.
Treatment for patients with metastasis and recurrence
1.Treatment of local recurrence
If the local recurrence lesion is limited in scope and there is no recurrence or metastasis in other sites, surgical exploration can be performed for resection. For patients who have not undergone pelvic radiotherapy before, the recurrent lesions in the pelvic cavity can be treated with radiation therapy, which can temporarily relieve the pain symptoms.
2.Treatment of liver metastasis
In recent years, many studies have confirmed that the effect of surgical resection of liver metastases from rectal cancer is not as pessimistic as originally imagined. If liver metastases occur in rectal cancer patients, whether they exist at the same time with the primary foci or occur only after the primary foci are removed, the survival rate can be improved if the liver metastases can be completely removed. For a single metastasis, liver segment or wedge resection is feasible. In case of multiple liver metastases that cannot be surgically resected, systemic chemotherapy can be administered first to shrink the tumor to the point where it can be surgically resected before resection, which can achieve the same effect. For some patients, even intense chemotherapy cannot shrink the liver metastases to the extent that they can be surgically resected, palliative chemotherapy is administered.
Systemic chemotherapy is used for patients who have no chance of surgical resection. If there is pain and bleeding obstruction due to the metastatic site, appropriate palliative measures such as radiotherapy, pain medication, and fistula are used.