Rectal/perianal mass and colorectal cancer

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22 Rectal/perianal mass and colorectal cancer

Colorectal cancer is the third most common cause of cancer mortality in most developed countries. Screening and early endoscopic intervention form the crux of management strategy.

Rectal or Perianal Mass

There are three ways a patient with a perianal or rectal mass may present:

The causes of a lump in the rectum are listed in Box 22.1.


Establish when the lump was first recognised and whether it has changed over time. An intermittent nature suggests that the lump relates to prolapse of a lesion from the rectum (e.g. haemorrhoids or rectal prolapse). Determine if the lump could be manually reduced when the lump is external to the anus. Haemorrhoids are a classic example of a potentially reducible lump, but the differential diagnosis includes rectal prolapse and hypertrophied anal papilla. An acute time course favours conditions such as thrombosed internal or external haemorrhoids. Tenderness suggests an infective process such as an ischiorectal abscess (Chapter 12).

If a rectal lump is found, ask about painful straining or feeling of incomplete rectal evacuation. The sense of faecal urgency associated with these symptoms is referred to as tenesmus; these complaints may occur with any irritating lesion of the rectum.

Another key symptom is rectal bleeding. Never ignore rectal bleeding and never assume it has a benign cause; bleeding should raise the suspicion of colorectal cancer. Ask about a family history of gastrointestinal disease and, in particular, colon cancer or polyps. Less commonly, a solitary rectal ulcer secondary to prolapse of the rectum can cause bleeding and tenesmus. The passage of mucus may occur with benign or malignant tumours as well as ulceration. Systemic symptoms such as weight loss (e.g. with malignancy) or fever (e.g. with an abscess) may also help point towards the correct diagnosis. A history of menstrual bleeding associated with a tender lump may suggest a perineal endometrial deposit that rarely occurs.

Physical examination


Careful inspection is crucial (see Chapter 12) but, importantly, one must expect to find an abnormality. Place the patient in the left lateral position with the buttocks well over the edge of the couch. Part the buttocks, looking for perianal skin tags, which may be associated with pruritus due to suboptimal hygiene. These are usually haemorrhoidal remnants, but they can occasionally be an indicator of a systemic process such as Crohn’s disease (Chapter 15). A perianal haematoma may be visible, which is usually small (under 1 cm). Rectal prolapse can occur at any age; suspect this if the anus is patulous or gaping. Ask the patient to strain; perineal descent may be seen and sometimes rectal prolapse (circumferential folds of red mucosa) may be demonstrated.


To begin digital rectal examination, warn the patient, then apply gentle but firm pressure to the anal verge with the flat of the well lubricated right index fingertip. The initial contraction of the sphincter will relax after several moments and allow the finger in. The examination will be uncomfortable for the patient; if it is painful, desist. Note the resting muscle tone of the sphincter, and ask the patient to squeeze down on the examining finger to evaluate active tone. Note the anorectal ring where the external anal sphincter spreads out to become pelvic floor and the narrow anal canal (3 cm long) gives way to the spacious rectum. Palpate the coccyx between finger and thumb. This will lead you onto the pelvic floor; feel one side, then the other. Pronation and supination of the forearm may not give sufficient ‘degrees of freedom’ to the pulp of the index finger; change your angle of approach by squatting or sitting beside the examination couch to better feel the smooth mobility of normal mucosa over the midline groove of the prostate (in males).

Expect to feel a mass. If you feel a mass, determine its size, shape (e.g. polypoid, plaque or ulcer), consistency (soft, firm or hard; it may indent like faeces), surface texture (smooth or granular) and mobility. Tenderness of the lesion suggests an inflammatory process. Decide whether the lesion is mobile or fixed to surrounding structures, such as the prostate, pelvic floor or sacrum. Tethering implies that the pathological process has extended beyond the limits of the muscularis propria to involve the adjacent structure or organ. Fixation may occur as a result of fibrosis, but usually indicates malignant infiltration.

Ask yourself: ‘Will I be able to describe this mass in my notes or referral letter?’ An example is: ‘On the left lateral wall of the rectum about 2 cm from the anorectal ring is a hard, fixed mass, 3 cm in diameter that does not indent’.

Occasionally you may feel a mass through the rectal wall; these arise most commonly in the sigmoid colon (e.g. a diverticular mass). Alternatively, there may be a hard, relatively immobile mass anterior to the rectum near the tip of the finger on deep palpation associated with a tumour that has spread from a primary elsewhere (such as in the stomach); this is termed a Blumer’s shelf. Other masses that might be felt include a tampon or a pessary lying in the vagina, or lateral lumps from enlarged lymph nodes infiltrated with tumour from a primary rectal carcinoma.

As a general rule, benign processes are soft, whereas malignant processes are hard. Fixed, irregular lesions with friable mucosa are more often malignant. Blood on the examining finger is an important sign of friable mucosa.

Sigmoidoscopy and proctoscopy

A sigmoidoscope or proctoscope may allow you to see the lesion that you have felt, exclude other impalpable lesions (e.g. multiple rectal polyps, or areas of ulceration that might be suggestive of inflammatory bowel disease) and take a biopsy of the lesion for histological examination.

The examination is most commonly performed with the patient in the left lateral decubitus position. In some centres, particularly those equipped with specialised tables, the examination is performed with the patient in the jack-knife position resting on the knees. Usually, adequate clinical information can be achieved without rectal preparation. When the rectum is totally loaded, it can be cleared by inserting an enema; full mechanical bowel preparation is not needed for this examination. Most patients will be anxious about proctoscopy or sigmoidoscopy. They need not see the instrument (Figs 22.1 and 22.2). The examiner needs to reassure the patient, pointing out that the diameter of the instrument is less than the diameter of a large stool and that the examination will be discontinued if there is excessive discomfort.

With the patient in position, lift the uppermost buttock upwards and gently insert the lubricated instrument with the obturator in place in the line of the anal canal. Note that the line of the anal canal is toward the patient’s umbilicus for the first 3–4 cm, then angles posteriorly. Once the instrument has been inserted into the lower rectum, remove the obturator. The sigmoidoscope can usually be passed with deft insufflation (reassure the patient that you are putting air in and tell them not to be embarrassed) and minor deviations to the level of the rectosigmoid junction at about 15 cm from the anal verge. At the rectosigmoid junction there is usually acute angulation, which can make progression into the sigmoid colon more difficult. In older patients who are likely to have diverticulosis, it is always best to stop at this point if there is any degree of difficulty. It is important to realise that the rectum is covered with peritoneum to a greater extent anteriorly than laterally or posteriorly. The limit of peritonealisation anteriorly is usually about 7–10 cm from the anal verge so you need to be more careful with the depth of biopsy above the level of the peritoneal reflection to minimise the risk of rectal perforation. Biopsy may be best left to the specialist.

If further examination is required (e.g. colon cancer is confirmed), full colonoscopy should be performed at a later stage (see below).

Tumours of the Colon and Rectum


A colorectal tumour can present with any symptom referable to the gastrointestinal tract; such symptoms include a recent change in bowel habit (constipation or diarrhoea), abdominal pain, bleeding (occult or major) or, rarely, an abdominal catastrophe (perforation or bowel obstruction). Other symptoms include weight loss, lethargy and those of disseminated metastatic disease (e.g. bone pain, jaundice, pathological fracture and, uncommonly, thrombophlebitis migrans, skin nodules or acanthosis nigricans).

The classic right-sided colon cancer is soft, protuberant and located where the lumen is large and the contents semisolid; anaemia is therefore more likely than obstruction. The classic left-sided colon cancer is annular, stenosing and located where the lumen is narrow and contents are firm; consequently, obstruction is more likely (Fig 22.3). Cancers may form a fistula into the bladder or elsewhere. Advanced cancers may be asymptomatic, while a very early caecal cancer may occasionally present with appendicitis, having obstructed the appendiceal opening.

History taking should include any family history of colon polyps, and colorectal or breast cancer, and past history of screening or surgery for bowel cancer. Weight loss, recent change of bowel habit, rectal bleeding, abdominal pain and tenesmus are all indications for further investigation.

Rarely, infective endocarditis caused by Streptococcus bovis or Clostridium septicus is the first manifestation of colon cancer.


Diagnosis is made on the basis of history, physical examination and special investigation (Table 22.1).

Table 22.1 Preoperative assessment of patients with colorectal carcinoma

Investigation Comment
Blood count, electrolytes, creatinine and liver function tests Results probably will be normal; useful base-line assessment if major surgery planned
Carcinoembryonic antigen (CEA)

Chest x-ray Useful—not necessary if patient is healthy or if CT chest is contemplated together with the CT abdomen/pelvis Colonoscopy with biopsy of tumour Essential unless patient presents acutely with bowel obstruction/perforation Abdominopelvic CT Essential especially if a laparoscopic colectomy is being considered Transrectal ultrasonography (TRUS) Essential for staging of rectal cancer which determines the course of management

Note: Intravenous pyelogram, abdominal ultrasound and MRI may be indicated in special circumstances.

Preoperative investigations should include a full blood count, electrolyte tests and liver function tests. Baseline carcinoembryonic antigen can be sought to aid follow-up, although the benefit of this is controversial (Ch 17). A chest x‑ray examination may detect metastatic disease. If advanced disease is suspected, computed tomography (CT) scanning of the abdomen may be useful; surgery may still be needed for palliation.

Colorectal cancer