الفهرس 
Anatomy of the rectumOnly 14 pages are availabe for public view
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Abstract
The rectum is the final straight portion of the large intestine, terminating in the anus. The human rectum is about 12 cm long. The rectum hooks up with the sigmoid colon superiorly and with the anal canal inferiorly.
Estimated new cases from rectal cancer in the United States in 2007 are 41,420. Incidence rate of rectal cancer in 1993- 1997 according to sex per 100.000 populations, in Canada: 15.8 new cases in males and 8.8 new cases in females. In China (Shanghai): 9 in males and 7.5 in females. In Japan (Osaka):15.1 in males and 7.3 in females. In Denmark: 17.6 in males and 11.2 in females. In Egypt: 2.3 new cases in males and 1.8 new cases in females.
The incidence is slightly higher in males than in females. Western nations tend to have a higher incidence than Asian and African countries. Incidence peaks in the seventh decade;
however, cases have been reported in young children. Adenocarcinoma is the most common type of cancer rectum. It accounts for over 90-95% of cancers originating in the rectum.
The exact cause of rectal cancer is unknown, but rectal cancer appears to be multifactorial in origin and studies showing concentration in areas of higher economic development suggest a relationship to diet (excess saturated animal fat). Causes of rectal cancer are probably environmental in the sporadic cases (80%), and genetic in the hereditary − predisposed (20%) cases.
All patients should undergo a complete history, including a family history and assessment of risk factors for the development of rectal cancer. Many rectal cancers produce no symptoms and are discovered during digital or proctoscopic screening examinations. Bleeding per rectum is the most common symptom of rectal cancer and occurs in 60% of patients. Change in bowel habits present in 43% of patients. Partial large-bowel obstruction may cause colicky abdominal pain and bloating and is present in 20% of cases. Also unexplained weight loss and malaise.
General and local physical examination is performed including digital rectal examination, routine laboratory studies, CEA, fecal occult blood test and imaging Studies, such as, double contrast barium enema, CT scan, endorectal ultrasound, proctosigmoidoscopy, biopsy and metastatic workup for Staging which is an important part of diagnosis, treatment planning, and predictions of long term survival. Surgeons and oncologists are increasingly using the unified TNM stage system.
Neoadjuvant therapy: This can be defined as any form of treatment (chemotherapy, radiotherapy or targeted therapy) the patient receives prior to definitive surgical intervention, with the aim of limiting the scope of surgery required.
Preoperative radiation therapy among the potential advantages of the preoperative approach are downstaging and downsizing effects that possibly enhance curative surgery in locally advanced, e.g. T4-rectal cancer, and sphincter preservation in low-lying rectal cancer. Moreover, neoadjuvant therapy may be advantageous also in resectable rectal cancer as sterilization of the tumor cells prior to surgery may reduce the risk of tumor cell spillage during surgery. Technically, there are two approaches to preoperative radiation therapy. The first one is an intensive short-course radiation, for one week & the second includes 5 to 6 weeks of conventional fractionation.
Neoadjuvant therapy used in locally advanced rectal cancer is neoadjuvant CRT that consisted of 50.4 Gy in 28 fractions to the tumor and pelvic lymph nodes and concomitant 5-FU continuous infusion during weeks 1 and 5. All patients also received 4 additional cycles of 5-FU adjuvant chemotherapy and a 5.4 Gy small-volume boost. Neoadjuvant XELOX-RT 50.4 Gy consists of preoperative radiation therapy with concomitant Xeloda and Eloxatin.
Several institutions have applied preoperative radiation in conventional fractionation in the treatment of fixed (T4) rectal lesions. The goal is to convert („downsize“) the tumor, which is clinically not amenable to a curative resection at presentation, to a resectable status. Minsky et al.,2000 compared preoperative radiotherapy (50.4 Gy) with or without 5-FU/high-dose folinic acid and showed that 90% of the patients with initially „unresectable“ tumors were converted to resectable lesions by preoperative combined therapy as compared with only 64% of those who received radiation therapy alone. Moreover, a complete pathologic response was found in 20% of patients receiving combined modality therapy as compared to 6% receiving radiotherapy alone, indicating an enhancement of radiation-induced downstaging by concomitant 5-FU-based chemotherapy. Several phase II trials of preoperative radiochemotherapy confirmed overall and complete resectability rates between 79 and 100% and 62 and 94%, respectively, and overall-survival rates in the range of 69% at 3 years and 51% at 5 years .All these studies demonstrate the feasibility of tumor shrinkage in T4 rectal cancer with preoperative multimodality regimen, allowing for potential curative resections. Thus there is no real controversy about this type of treatment, although there are still few evidence-based data with regard to the optimal doses of radiation and chemotherapy as well as the type of 5-FU administration and combination with other cytotoxic agents. In a subset of patients, even more aggressive attempts to achieve a local tumor control, including preoperative radiochemo- thermotherapy or intraoperative radiation boost techniques may be indicated.
Enhancing Sphincter preservation another major goal of neoadjuvant therapy is the conversion of a low-lying tumor, that was declared by the surgeon to require an abdominoperineal resection (APR), into a lesion amenable to sphincter-preserving procedures (SPP).Technically, two surgical approaches have been used after preoperative therapy: local excision and a low anterior resection with or without a coloanal anastomosis.
The prognosis and treatment options depend on the stage of the cancer (whether it affects the inner lining of the rectum only, involves the whole rectum, or has spread to other places in the body), the patient’s general health and whether the cancer has just been diagnosed or has recurred.