The cause of rectal cancer is still not well understood, and its development is related to social environment, dietary habits, genetic factors, etc. Rectal polyps are also a high risk factor for rectal cancer. 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, shortness of breath, constipation and diarrhea will appear.
3.The stool will gradually become thinner, and in advanced stage, there will be obstruction of defecation, wasting 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.
Examination
1.Rectal finger examination
It is the necessary examination step to diagnose rectal cancer. About 80% of patients with rectal cancer can be detected through rectal finger examination when they visit the doctor. Hard and uneven masses can be palpated; in advanced stage, narrowing of intestinal lumen 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
To understand whether there is metastasis in lung, pleura, mediastinal lymph nodes, etc.
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.
Treatment
The treatment of rectal cancer needs to be mainly surgical, supplemented by chemotherapy and radiotherapy.
(I) Surgical treatment
There are two kinds: radical and palliative.
1.Radical surgery
(1) Combined transabdominal perineal resection (Miles surgery) is suitable for cancer of the lower rectum less than 7cm from the anal verge, and the scope of resection includes sigmoid colon and its mesentery, rectum, anal canal, anal raphe, sciatic rectal fossa and skin around the anus, and blood vessels are ligated and cut 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), is suitable for upper rectal cancer that is more than 12 cm 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 is suitable for early rectal cancer of 7-11 cm 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 combined resection 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 the cancer is serious or the metastasis is extensive and cannot be cured, in order to relieve the obstruction and reduce the patient’s pain, palliative resection is feasible by making limited resection of the intestinal segment with cancer, sewing up the distal rectum and taking the sigmoid colon for stoma (Hartma surgery). If this is not possible, only sigmoidostomy will be performed, especially in patients with intestinal obstruction.
(ii) Radiation therapy
Radiotherapy plays an important role in the treatment of rectal cancer. At present, 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 medium rectal cancer with late local staging.
(iii) Chemotherapy
For patients with postoperative pathological stage II and III of rectal cancer, postoperative chemotherapy is recommended, with a total chemotherapy duration of six months.
(IV) 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, the recurrent lesions in the pelvis 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 removed, systemic chemotherapy can be used first to shrink the tumor to the extent that it can be surgically removed 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.