Diagnosis of colorectal carcinoma (Colon Cancer) is based on history, physical examination (abdominal and rectal examination). The most important diagnostic procedures for colon cancer are the fecal occult blood test (FOBT), barium enema, proctosigmoidoscopy, and colonoscopy. These checks should be performed every three years for ages 40 and above. As many as 60% of colorectal cancer cases can be identified by sigmoidoscopy, biopsy, or cytology smear.

A. Physical examinations

Physical examinations are important in identifying metastases and detecting other organ systems that play a role in treatment. Palpate the supraclavicular area to check for metastatic glands.

1. Inspection

On examination of the abdomen, inspect for surgical marks, protrusion of the mass, and bowel contours visible (darm contour, darm steifung).

2. Palpation

Palpation is feeling for mass, enlargement of the liver, ascites, or tenderness in the abdomen. If a mass is palpable, determine the location, consistency, diameter, mobility, adhering to the tissue, and clear boundaries.

3. Percussion

Tympanic is the normal percussion sound on the abdomen. If there is mass, there is a change in the sound to become dim.

4. Auscultation

Auscultation is for assessing bowel sounds. In distal rectal cancer, a flat, hard, oval, or circular mass may be felt with central depression. If expanded, the size and degree of tissue attachment must be determined. On the RT examination, blood can be obtained on the gloves.

5. Digital Rectal Examination

For this examination, palpate the lateral, posterior, and anterior walls and the ischial spine, sacrum, and coccygeus. Intraperitoneal metastases may be palpable anterior to the rectum, corresponding to the Douglas pouch's anatomical position due to neoplastic cell infiltration.

Although 10 cm is the limit for finger exploration possible, it has long been known that the fingers can reach 50% of colon cancers. Hence, the Rectal examination is a good way to diagnose colon cancer that cannot be ignored.
Rectal toucher for grading:
  • Anal sphincter tone: strong or weak
  • Rectal ampulla: collapsed, bloated, or filled with feces
  • Mucosa: rough, lumpy, stiff tumor: palpable or not, location, lumen that can be penetrated by fingers, easy to bleed or not, upper border and surrounding tissue, distance from the anorectal line to the tumor.


1. Biopsy

Confirmation of malignancy by biopsy is essential. If there is an obstruction to prevent a biopsy, cytology is very useful.

2. Carcinoembryonic Antigen (CEA) Screening

CEA is a glycoprotein found on the cell surface that enters the bloodstream and is used as a serological marker to monitor colorectal cancer status and detect early recurrence and liver metastases. CEA is too insensitive and nonspecific to be used as a screening for colorectal cancer. Increased serum CEA values, however, are associated with several parameters.

High CEA values ​​are associated with grade 1 and 2 tumors, advanced stage of the disease, and metastases to internal organs. However, serum CEA concentration is an independent prognostic factor. The new serum CEA value can be said to be significant in continuous monitoring after surgery. Despite the CEA test's limited specificity and sensitivity, it is often proposed to recognize early recurrences. The preoperative CEA test is very useful as a prognostic factor and whether the primary tumor is associated with increased CEA values. Increasing the preoperative CEA value helps identify metastases because metastasized tumor cells often result in an elevated CEA value.

3. Fecal Occult Blood Test

The colorless phenol in guaiac gum is turned blue by oxidation. This reaction indicates the presence of a catalytic peroxidase; the oxidase is complete in the presence of a catalyst, for example, hemoglobin. But unfortunately, there are various catalysts in the diet. For example, red meat, therefore special attention is needed to avoid this.

This test will detect 20 mg HB / g of feces. The immunofluorescence test of occult blood converts the HB to fluorescent porphyrin, which will detect 5-10 mg HB / g of feces. The false-negative result of this test is very high. Various problems need to be considered using the occult blood test because all bleeding sources will produce positive results. Cancer may only bleed intermittently or not at all and will result in a false-negative test. Processing, diet manipulation, aspirin, number of tests, test interval are all factors that will influence the accuracy of the occult blood test.

The occult blood test's direct effect in reducing mortality from various causes is unclear, and the efficacy of this test as a screening for colorectal cancer requires further evaluation.

4. Barium Enema

A frequently used technique is to use a double-contrast barium enema, which has a sensitivity of up to 90% in detecting polyps> 1 cm in size. When used in conjunction with flexible sigmoidoscopy, this technique is a cost-effective alternative to colonoscopy for patients who cannot tolerate colonoscopy or is used as long-term monitoring in patients with a history of excised polyps or cancer. The risk of perforation using a barium enema is very low, at 0.02%. If the perforation is possible, a water-soluble contrast should be used instead of a barium enema. Barium peritonitis is a severe complication that can lead to multiple infections and peritoneal fibrosis. Unfortunately, a water-soluble contrast could not provide the necessary detail to show the small colonic mucosal lesions.

a. Colon in Loop Carcinoma Overview
Colon carcinoma radiologically provides the following features:
- Protruding into the lumen. The classic form of this type is the polyp. Polyps can be peduncle (pedunculated and sessile. Colon walls are often good.
- Colonic wall deformity can be symmetrical (napkin ring) or asymmetrical (apple core). The colonic lumen is narrow and irregular. It is often difficult to distinguish this from Crohn's colitis
- Rigidity colonic wall is segmental, and sometimes the mucosa is still good. The lumen of the colon may not narrow. This form is difficult to distinguish from ulcerative colitis.

5. Endoscopy

The indication for carrying out this test is to assess the entire colonic mucosa because 3% of patients have synchronous cancer and are likely to have premalignant polyps.

6. Proktosigmoidoscopy

 This examination can reach 20-25 cm from the dentate line. But, the rectosigmoid junction's acute angulation will prevent instrument entry. This examination can detect 20-25% of colon cancers. Rigid proctosigmoidoscopy is safe and effective for evaluating a low-risk person under 40 years of age when used in conjunction with an occult blood test.

7. Flexible Sigmoidoscopy

 A flexible sigmoidoscopy can reach 60 cm into the colonic lumen and reach the left colon's proximal part. Fifty percent of colon cancers can be detected using this tool. Flexible sigmoidoscopy is not recommended for therapeutic indications for polypectomy, cautery, and the like, except in special circumstances, such as ileorectal anastomosis.

Flexible sigmoidoscopy every five years (starting at age 50 years old) is the recommended method for screening an asymptomatic person at an intermediate risk level for colon cancer. An adenomatous polyp found on flexible sigmoidoscopy is an indication of the colonoscopy. Although it is small (<10 mm), adenoma distal to the colon is usually associated with a proximal neoplasm in 6-10% of patients.

8. Colonoscopy

 Colonoscopy can be used to show an overview of the entire mucosa of the colon and rectum. Standard colonoscopy can be up to 160 cm long. Colonoscopy is the most accurate way to show polyps with a size of less than 1 cm, and the accuracy of colonoscopy is 94%, better than barium enema, which is only 67% accurate.

A colonoscopy can also be used for biopsy, polypectomy, control of bleeding, and strictures. Colonoscopy is a very safe procedure where the main complications (bleeding, complications of anesthesia, and perforation) occur in less than 0.2% of patients.

Colonoscopy is an advantageous method to diagnose and manage:
  • inflammatory bowel disease,
  • non-acute diverticulitis,
  • sigmoid volvulus,
  • gastrointestinal bleeding,
  • non-toxic megacolon colonic strictures,
  • and neoplasms.

Complications are more common in therapeutic colonoscopy than in diagnostic colonoscopy; bleeding is the main complication of therapeutic colonoscopy, whereas perforation is the main complication of diagnostic colonoscopy. 

9. Imaging Techniques

 MRI, CT scan, and transrectal ultrasound are part of the imaging techniques used to evaluate, staging, and follow-up patients with colon cancer, but these techniques are not a screening test.

a. CT scan
 CT scan can evaluate the abdominal cavity of colon cancer patients preoperatively. CT scans can detect metastases to the liver, adrenal glands, ovaries, lymph glands, and other pelvis organs. CT scan is beneficial for detecting recurrence in patients whose CEA values ​​are elevated after colon cancer surgery. The sensitivity of the CT scan reaches 55%. CT scan plays a vital role in colon cancer patients because of the difficulty in determining the lesion stage before surgery. A pelvic CT scan can identify the intestinal wall's tumor invasion with an accuracy of up to 90% and detect lymph node enlargement> 1 cm in 75% of patients.

The use of contrast-enhanced CT of the abdomen and pelvis can identify metastases in the liver and intraperitoneal areas.

b. MRI
  MRI is more specific for the liver's tumors than the CT scan and is often used to clarify lesions that are not identified using CT scanning. Because of its higher sensitivity than CT scan, MRI is used to identify metastases to the liver.

c. UltraSound Endoscopy (EUS)
  EUS significantly enhanced the directal33e assessment of the depth of tumor invasion, especially for rectal tumors. The accuracy of the EUS is 95%, 70% for CT, and 60% for the digital rectal examination. In rectal cancer, the combination of using EUS to look for tumors and digital rectal examination to assess tumor mobility should improve the accuracy of planning for surgical therapy.