10Most (15-20%) colorectal cancers develop in people with either a positive family history or a personal history of colorectal cancer or polyps.
11The remaining cases occur in people with certain genetic predispositions, such as hereditary nonpolyposis colorectal cancer (HNPCC, 4-7%) or familial adinomatous polyposis (FAP, 1%) or in people with inflammatory bowel disease (IBD, 1%).
16- Approximately 75% of colorectal cancers are sporadic and develop in people with no specific risk factors. The remaining 25% of cases occur in people with significant risk factors.
17Race: - Western nations tend to have a higher incidence than Asian and African countries; however, within the United States, little difference in incidence exists among whites, African Ameicans, and Asian Americans.
18- Among religious denominations, colorectal cancer occurs more frequently in the Jewish population.
19Sex: The incidence of colorectal malignancy is slightly higher in males than in females. Age: Incidence peaks in the seventh decade; however, cases have been reported in young children
24History: - Bleeding - This is the most common symptom of rectal cancer and occurs in 60% of patients Bleeding often is attributed to other causes (eg, hemorrhoids), especially if the patient has a history of other problems.
25- Profuse bleeding and anemia are rare - Profuse bleeding and anemia are rare Bleeding may be accompanie by the passage of mucus, which warrants further investigation.
26- Occult bleeding: This is detected on screening fecal occult blood test (FOBT) in 26% of cases
27- Change in bowel habits - Change in bowel habits Present in 43% of patients, this symptom has several different presentations. Often, it occurs in the form of diarrhea, particularly if the tumor has a large villous component.
28- These patients may have hypokalemia on laboratory studies - These patients may have hypokalemia on laboratory studies The capacity of the rectal reservoir may mask the presence of a small lesion Some patients experience a change in caliber of the stool.
29- Large tumors can cause obstructive symptoms - Large tumors can cause obstructive symptoms Tumors located low in the rectum can cause a feeling of incomplete evacuation and tenesmus.
30Abdominal pain - Partial large bowel obstruc- tion may cause colicky abdominal pain and bloating , present in 20% of cases.
31- Back pain is usually a late sign caused by a tumor invading or compressing nerve trunks. - Urinary symptoms may occur if the tumor is invading or compressing the bladder or prostate.
32- Malaise: This nonspecific entity is the presenting symptom in 9% of cases. - Bowel obstruction: Complete obstruction of the large bowel is rare and is the presenting symptom in 9% of cases.
33- Pelvic pain: This late symptom usually indicates nerve trunk involvement and is present in 5% of cases. - Other presentations include emergencies such as peritonitis from perforation(3%) or jaundice, which may occur with liver metastases (<1%).
34Physical: - Physical examination is performed with specific attention to possible metastatic lesions, including enlarged lymph nodes or hepatomegaly. The remainder of the colon is also examined.
35Digital rectal examination Digital rectal examination - The easy accessibility of the rectum provides an opportunity to readily detect abnormal lesions via digital rectal examination (DRE). The average finger can reach approximately 8 cm above the dentate line.
36- Tumors can be assessed for size, ulceration, and presence of any pararectal lymph nodes. Fixation of the tumor to surrounding strctures (eg. Sphincters, prostate, vagina) also can be assessed.
37- DRE also permits a cursory evaluation of the patient’s sphincter function. This information is necessary when determining whether a patient is a candidate for a sphincter-sparing procedure.
40- Chest radiograph: Obtain a chest radiograph to rule out pulmonary metastases and to determine whether the patient has any gross underlying pulmonary disease, including emphysema.
41CT scan : This study is generally used to determine the presence or absence of metastases. - CT scans can identify lesions in the liver, adrenals, ovaries, lymph nodes, and other organs.
42- In 10% of patients, the CT scan misses small liver lesions - In 10% of patients, the CT scan misses small liver lesions. - When combined with an angiogram, a CT scan is 95% accurate in identifying liver metastases.
43- Some information can be gleaned from a CT scan regarding depth of penetration of the primary rectal tumor. When performed with rectal contrast given as an enema, accurately in 84% of cases.
44- CT scan detects lymph nodes larger than 1 cm in 75% of cases - CT scan detects lymph nodes larger than 1 cm in 75% of cases - CT scans are helpful in determining whether patients require preoperative chemoradiation therapy.
45MRI actually is the most sensitive test for determining the presence of liver metastases and often is used if liver resection is considered.MRI
50- The accuracy of detection of lymph node involvement ranges from 73-86%. Most of these nodes are larger than 1 cm. Smaller nodes can be detected, but the accuracy of determining tumor involvement is substantially lower.
52- Positron emission tomography: The major advantage of a positron emission tomography (PET) scan is to differentiate between recurrent tumor and scar tissue by measuring tissue metabolism of an injected glucose-based substance. Scar tissue is inactive, whereas tumor generally is hypermetabolic. This test generally is not used in a routine preoperative metastatic workup.
87TME involves sharp dissection in the avascular plane that is created by the envelope that separates the mesorectum from the surrounding structure. This includes the anterior peritoneal reflection and Denovillers fascia anteriorly and preserves the inferior hypogastric plexus posteriorly and laterally.
88TME yields a lower local recurrence rate (4%) than transanal excision (20%) ,but it is associated with a higher rate of anastomic leak (11%).