61. Colonic polyps and cancer. Diverticulosis and diverticulitis of the colon

Page created on April 11, 2022. Not updated since.

Colonic polyps

Introduction and epidemiology

Colonic polyps are elevated protruding lesions of the colon into the colon lumen. They may be hyperplastic, inflammatory, hamartomatous, or neoplastic. These polyps may cause symptoms or develop into cancer. >90% of colorectal cancers develop from an adenomatous polyp, but only 3 – 5% of adenomatous polyps progress to cancer.

Colon polyps are very common, affecting 30% of adults >50 years.

For types of colon polyps and etiology, see the corresponding pathology 2 topic.

Clinical features

Colonic polyps are mostly asymptomatic, detecting during routine screening for colorectal cancer. If they cause symptoms, they cause:

  • Haematochezia or occult blood loss
  • Change in bowel habits

Diagnosis and evaluation

Some have occult blood which can be demonstrated in the faeces.

Colonoscopy is the best examination for polyps, as it allows for visualisation of even small polyps and for biopsy. Virtual colonoscopy, a CT examination of the colorectum insufflated with air and contrast, can be used as an alternative, but biopsies can not be made, and small (<1 cm) polyps cannot be visualised.


If polyps are symptomatic or have significant malignant potential (e.g. in case of many large adenomatous polyps), removal is indicated. This can be performed by endoscopic or surgical resection. Some hereditary polyposis syndromes like FAP require prophylactic colectomy to avoid development of colorectal cancer.

Following polypectomy, regular surveillance colonoscopy is indicated based on the pre-treatment risk for malignant transformation, and whether removal was complete or not.

Colorectal cancer

Colorectal carcinoma (CRC) refers to all cancers that can affect the colon and rectum. Carcinomas in the colon are the most common malignancy in the GI-tract, accounting for 95% of all GI cancers.

CRC is the third most common type of cancer, but it’s the second most common cause of cancer-related death. It accounts for 10% of the world’s cancers. It’s mostly a disease of elderly, affecting those in their 60s and 70s. >90% of colorectal cancers develop from adenomatous polyps of the colon.

For etiology, and pathomechanism, see the corresponding pathology 2 topic. For surgical treatment, see the corresponding surgery topic.

Clinical features

The most important symptoms are those of lower GI bleeding (haematochezia, melena, iron-deficiency anaemia) or altered bowel habits. Altered bowel habits is more common for left-sided cancers compared to right-sided, due to the smaller lumen of the left-sided colon. Abdominal pain is also a common symptom. Rectal cancers cause tenesmus and incomplete defecation.

Metastases are present at presentation in 20% of cases. Distal rectal cancers may be palpated on DRE.

Diagnosis and evaluation

Colonoscopy is the gold standard investigation for CRC, as it not only allows for diagnosis but also for biopsy (and sometimes complete removal) of the lesion. If a suspicious lesion is found, the whole colon must still be examined, because of the relatively high chance of synchronous primary tumours.

CT colonography (virtual colonoscopy) is an alternative to colonoscopy, but it does not allow for biopsy or removal.

Once the diagnosis of colon cancer has been made, a CT of the chest, abdomen, and pelvis is required for staging. For rectal cancers, MRI is used.

CEA should be measured upon diagnosis. Elevated CEA is associated with a worse prognosis, and CEA which doesn’t normalise postoperatively is indicative of persistent disease.


Screening is important to reduce the incidence of CRC, as most CRCs develop from adenomatous polyps which take years to develop into cancer. In Europe, screening programs for CRC are in development or recently launched. Generally, people above 50/55 should be screened with colonoscopy, or alternatively, with a faecal occult blood test.

Diverticulosis and diverticulitis

Introduction and epidemiology

A colonic diverticulum is a sac-like protrusion of the colonic wall. The presence of many diverticula is called diverticulosis. In some cases, the diverticula may become inflamed, in which case the condition is called diverticulitis and occurs in approx. 10% of people with diverticulosis.

Diverticulosis is usually asymptomatic, but it may cause symptoms like abdominal pain or lower GI tract bleeding. Diverticular disease refers to symptomatic diverticulosis or diverticulitis.

Diverticular disease is mostly a disease of elderly. 60% of people at the age of 60 have diverticulosis. Diverticulosis and diverticular disease are more common in the West, likely due to our eating habits. In the Western world, diverticulosis predominantly affects the left colon, while in Asia, it predominantly affects the right colon.

For etiology, and pathomechanism, see the corresponding pathology 2 topic.

Clinical features

Diverticular bleeding is one manifestation of diverticular disease. This bleeding may be occult (discovered by a screening test) or acute, manifesting as haematochezia. See topic A26.

Diverticulitis typically presents with left sided abdominal pain, especially in the left lower quadrant (the location of the sigmoid), and low-grade fever. The pain usually lasts for multiple days. Patients may also have nausea/vomiting or recent change in bowel habits.

Patients with complicated diverticulitis may present with ileus, colovesical fistula, haemodynamic instability, or downright shock. The patient will be peritonitic in the left lower quadrant.

Patients with diverticulitis have a high risk of recurrent bouts of diverticulitis.

Diagnosis and evaluation

CRP and WBC may be elevated in diverticulitis, but not always.

Abdominal CT with contrast is the first choice for imaging and to establish the diagnosis. CT will also show any complications of diverticulitis.

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