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.

Palpation

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.

Figure 22.1 Disposable rigid sigmoidoscope with bellows.

Figure 22.2 Plastic disposable and metallic reusable proctoscopes. Note the oblique working end to visualise, inject or band haemorrhoids.

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

History

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.

Physical examination

Physical examination is directed towards making a diagnosis, assessing for metastases and detection of other medical or surgical conditions likely to influence treatment.

General examination should include evidence of muscle wasting, malnutrition or anaemia. Jaundice suggests hepatic metastases. Subcutaneous metastatic nodules may rarely be present. A left supraclavicular lymph node should be sought, but it is rare. Lung consolidation or pleural effusion will suggest lung metastases.

Abdominal examination may reveal distension due to ascites or bowel obstruction; there may be hepatomegaly due to secondary spread. A tumour mass may be palpable.

On digital rectal examination, a middle or lower-third rectal tumour or polyp will usually be palpable, but a higher cancer will not be unless it has prolapsed into the pouch of Douglas. The cervix, uterus, pubic bone and even a tampon may cause diagnostic confusion for the beginner.

The rectum may be evaluated with a rigid ‘sigmoidoscope’—a misnomer in that the sigmoid is not adequately seen with this 30-cm instrument. Full evaluation of the colon is necessary with a colonoscopy to identify any tumours (Fig 22.3) and to rule out synchronous cancers. The bowel must be prepared (emptied of all stool) to see the wall clearly. Colonoscopy has the advantage of allowing biopsies and/or therapeutic intervention, and the disadvantage that it can cause rare bowel perforation.

Figure 22.3 Colonic adenocarcinoma.

Investigation

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)	Useful—optional CEA is of no value in the preoperative diagnosis of colonic cancer or as a prognostic indicator CEA is of value in the follow-up of resected colonic cancer; a consistently rising titre suggests metastatic disease and further diagnostic evaluation is indicated

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.