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Carcinoma of the Colon, Rectum and Anus

Carcinoma of the colon and Rectum are the most common malignancies and generally a disease of old individuals with equal incidence in men and women. The pathogenesis of colorectal cancer is unclear but certainly, there is almost strong environmental influence, which is suggestive of the individuals who migrate from the areas of low incidence such as Japan to an area of high incidence as USA. Dietary influence is also encountered as western diet (high in animal fat and low in fibres). In addition, group of familial polyposis have high incidence of colorectal cancers suggesting genetic influence as well. Patient with long term Ulcerative Colitis, Crohn’s disease, previous colorectal carcinoma, familial colon cancers, Gardener’s syndrome have high risk of cancer.

Signs and Symptoms:
Right sided
Lesions are clinically associated with:
  • Dull abdominal pain
  • Occult bleeding, bleeding per rectum
  • Alterations in bowel habits (not prominent in left side)
  • Anorexia and weight loss
  • Vomiting
  • Lump in right iliac fossa
Signs:
Weight loss, pallor, supraclavicular lymph nodes palpable, palpable liver, hyperactive bowel sounds and a firm irregular mass may be palpable in right iliac fossa, which may be fixed or mobile.

Left sided
Lesions are associated with:
  • Abdominal pain
  • Alteration I bowel habits
  • Abdominal distension
  • Feeling of lump in abdomen
  • Weight loss
  • Vomiting
Signs:
Weight loss, pallor (if chronic blood loss occurs), and a palpable mass in the left iliac fossa (due to presence of hard faeces above tumour), liver may be palpable, hyperactive abdominal sounds in case of chronic obstruction

Diagnosis:
  • Proctosigmoidoscopy identifies as many as half of colonic malignancies
  • Flexible sigmoidoscopy allows examination of distal 40 -60 cm of colon
  • Colonoscopy
  • Barium enema for mucosal details in whole colon
  • Abdominal CT
Gregren’s test: is used to indicate occult blood in faeces (to examine occult bleeding). Faeces are brownish black because of ferrus (Fe) in RBC mixed with H2S
FeS + H2S -------------> FeS (black colour stool)

H2S in colon is released from bacterial action.

Staging:
The true extent of the disease can be determined by after resection of specimen and staging. Carcinoma of colon and rectum exist by six routes.
  • Intramural extension
  • Direct invasion of adjacent structures
  • Lymphatic spread
  • Haematogenous spread
  • Intraperitoneal spread
  • Anastomotic implantation
Localization:
  • Sigmoid part – 50%
  • Descending colon – 5%
  • Left angle of splenic flexure – 5%
  • Transverse colon – 5%
  • Cecum - 15%
  • Right angle – 12%
  • Ascending colon - 8%
Histological types:
  • Adenocarcinoma – 90%
  • Rest are like mucous membrane and squamosal type of cancers
Clinical Forms:
There are six clinical forms of colon cancer:
  • Toxic anaemic type
  • Dyspeptic like form
  • Pseudo-inflammatory form
  • Tumour forms
  • Enterocolic forms
  • Obstructive forms
The Pseudo-inflammatory, enterocolic, dyspeptic, toxic anaemic forms are characteristic for left colon but tumours and obstructive forms are for the right colon.

Treatment:
  • Preoperatively the patient undergoes bowel preparation including whole gut lavage with polyethylene-glycol electrolyte solution and oral erythromycin. Intravenous antibiotics are administered before operation and continued for two days post-operatively
  • Lesions in the right colon are treated with a right hemicolectomy with lymph node excision and cutting the arteries nearby its origin (superior mesenteric artery) and after the creation of ileotransverse anastomosis is indicated
  • If the cancer is located in the transverse colon then we make the En-Block resection and after the creation transverse-transverse anastomosis is indicated. Lesions in the left colon are treated with left hemicolectomy with transversosigmoidal anastomosis
  • If the bowel obstruction occurs it must be treated with the Hartmann’s type of operation. In case of rectal cancer we perform Kenumiles type of operation or wide removal of abdominoperineal part of the rectum
  • Associated radiotherapy in patients with rectal lesions had been shown improved by the local control but not overall survival. Some patients have improved survival with combined radiation therapy and chemotherapy. Associated therapy is recommended for those patients who are at higher risk of recurrence mainly for those with the transmural spread of disease
  • Colonoscopy and barium enema for the examination of entire colon, examination of complete blood count, liver function tests, chest film and carcinoembryonic antigen level should be recommended regularly in the post-operative period


    • Removal of Abdominoperineal part of Rectum:
    In this operation, two groups of surgeons are active. Patient lies in the gynaecological position. The abdominal group of surgeons dissect from proximal to distal end. Perineal group dissect from distal to proximal and then they meet at one point.

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    This article has been written by Dr. M. Javed Abbas.
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    21:06 21/12/2002