Next Lesson - Gastrointestinal Malignancy
Core
An anal fissure is a linear tear in the anal mucosa, usually following the posterior midline. It occurs due to high internal anal sphincter tone and decreased blood flow to the anal mucosa. Patients typically present with very painful defaecation (pain when opening the bowels) and a small amount of haematochezia (bright red blood in the stool).
Conservative management (simple measures without drugs or surgery) involves increasing hydration (drinking enough fluid), regular exercise and increasing fibre intake to reduce constipation alongside taking warm baths to help relax the anal sphincter tone. Medical treatment is analgesia (simple painkillers such as paracetamol or ibuprofen; opioids, the strong morphine-like painkillers, are avoided because they cause constipation and make fissures worse) and topical medications (ointments applied to the anus) to relax anal sphincter tone. The usual first choice is rectal glyceryl trinitrate (GTN) 0.4% ointment, although headache is a common side effect. Topical diltiazem (a calcium-channel blocker ointment that relaxes the sphincter) is an alternative, for example if GTN is not tolerated. Surgery is considered when a fissure has not healed after 6 to 8 weeks of proper treatment, and the person is then referred to a surgeon. Specialist options include botulinum toxin injection and lateral internal sphincterotomy (a small cut in the internal anal sphincter to reduce its tone). Surgery is more effective than medical treatment at achieving lasting healing, but it carries a small risk of incontinence (loss of bowel control).
Image - Posterior Anal Fissure
Public Domain Source by Jonathanlund [Public domain]
Perianal (around the anus) abscesses are common. They occur in different locations: superficial (most common), intersphincteric (between the internal and external anal sphincters), ischiorectal (in the space beside the anal canal, below the levator ani muscle) and supralevator (above the levator ani muscle, the muscle sheet of the pelvic floor; rare, and often arising from diverticulitis, which is inflammation of pouches in the bowel wall, or from pelvic inflammatory disease, which is infection of the female pelvic organs).
Risk factors include male sex (men account for about 70% of cases), middle-aged, inflammatory bowel disease (IBD), smoking, HIV and diabetes mellitus. Most abscesses start when a small gland just inside the anus becomes infected, and many occur in otherwise healthy people.
A superficial perianal abscess typically causes a painful, tender, erythematous swelling (a red, sore lump) near the anus. Deeper abscesses around the anus and rectum (anorectal abscesses) may cause fever or systemic illness, sometimes with no visible swelling. Further reading: Leicester NHS guidance; MSD Manual page on anorectal abscess.
Management is prompt incision and drainage (cutting the abscess open to let the pus out), and it should not wait until the abscess points (comes to a head under the skin). Between about 15% and 50% of people with an anorectal abscess go on to develop an anal fistula (an abnormal channel between the anal canal and the skin), so it is important to treat the fistula if present to prevent abscess recurrence.
Diagram - Locations of perianal abscesses
Creative commons source by McortNGHH [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Haemorrhoids (also called piles) are enlarged anal cushions, the normal pads of blood vessels and tissue that line the anal canal. They can be divided into internal haemorrhoids and external haemorrhoids depending on their location.
Internal haemorrhoids are the most common. They are enlarged venous anal cushions caused by a loss of connective tissue support. They form above the dentate line (the junction between the upper and lower anal canal) so are relatively painless, but they can prolapse (slip down and protrude outside the anal canal) and cause haematochezia (bright red bleeding) and pruritus (itching). Conservative management (simple measures without drugs or surgery) involves increasing hydration (drinking enough fluid), increasing fibre intake and avoiding straining. If these measures are insufficient, rubber band ligation is the best available outpatient treatment: a small band is placed around the base of the haemorrhoid so that it loses its blood supply and drops off. Injection of a chemical to shrink the haemorrhoid (sclerotherapy) and infrared coagulation are other options. Surgery to remove the haemorrhoids may be required in severe cases. Rectal bleeding should not be assumed to be haemorrhoids without assessment, because bowel cancer can cause the same symptom. People are referred urgently if cancer is suspected.
External haemorrhoids are less common and are swollen anal cushions that may then thrombose (form a blood clot). These haemorrhoids form below the dentate line, where the skin has many pain fibres, so they can be itchy and painful. They are usually painless unless thrombosis occurs, which causes an acutely painful lump. They can also cause haematochezia. Initial treatment is usually conservative (simple painkillers such as paracetamol, keeping the stools soft and easy to pass, and topical preparations applied to the anus). Anyone with an extremely painful thrombosed external haemorrhoid who presents within 72 hours of onset may need admission or referral, because the clot or haemorrhoid may need to be removed. Surgery is otherwise reserved for severe cases or those that do not respond to simple measures.
Diagram - Internal vs external haemorrhoid locations
Creative commons source by https://www.myupchar.com/en, edited by Dr. Laura Hansell [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Diarrhoea is a sign/symptom, not a condition. It is defined as the passage of three or more loose or liquid stools per day (or more frequent passage than is normal for the person).
There are four main mechanisms: secretory, osmotic, inflammatory and increased gut movement (motility). More than one can act at once. In secretory dysfunction (the gut releases too much fluid) there is reduced absorption of Na+ (sodium) ions and an increased net secretion of Cl- (chloride) ions into the gut lumen. In osmotic dysfunction the gut lumen contains too much osmotic material (e.g. unabsorbed lactose due to lactase deficiency), which draws water into the bowel. Lactase is the brush-border enzyme (found on the microscopic surface folds of the small intestine lining) that digests lactose; undigested lactose retains water in the bowel by osmosis. Further reading: MSD Manual page on carbohydrate intolerance.
Diarrhoea is often self-limiting (it gets better on its own), but management focuses on preventing dehydration. Healthy adults should drink fluids regularly. Oral rehydration solutions (special salt and sugar drinks that replace fluid and electrolyte losses) are the first treatment to try in people who are dehydrated or at higher risk of dehydration, such as older people, people with a weakened immune system and people with other medical conditions. Medical assessment is advised if symptoms persist or if there are red flags (warning signs) such as dehydration, fever, blood in the stool, weight loss, vomiting that stops fluids being kept down, or recent antibiotic treatment or a recent hospital stay. Loperamide (an anti-diarrhoeal drug that slows the gut) is not routinely recommended, but it can relieve symptoms in adults with mild to moderate diarrhoea. It should not be used if there is blood, mucus or pus in the stool or a high fever (which suggest dysentery, a severe bowel infection), or in active ulcerative colitis or antibiotic-associated colitis. It is not recommended for children under 12 years. Treatment should address the underlying cause. Antibiotics are not routinely prescribed for adults with gastroenteritis (infection of the gut). Treatment of a confirmed bacterial cause is arranged where appropriate, guided by stool culture and sensitivity testing.
Constipation is a sign/symptom, not a condition. It is defined as hard stools, difficulty passing stools (often with straining), a feeling of incomplete emptying, infrequent stools (fewer than three bowel movements a week) or the complete inability to pass stools.
Risk factors include female sex (constipation is about twice as common in women as in men), an inactive lifestyle (low levels of physical activity), a family history of constipation and certain medicines (many drug classes can cause constipation). Constipation is also common in children, with a peak around toilet training (typically 2 to 3 years of age).
Conservative management (simple measures without drugs) involves drinking an adequate amount of fluid, increasing fibre intake gradually (adults should aim for about 30 g a day) and regular exercise. If these measures are not enough, laxatives (medicines that help the bowels to open) are used in steps. A bulk-forming laxative such as ispaghula (which swells in the gut and makes the stool bulkier) is offered first. If stools stay hard, an osmotic laxative such as a macrogol (which holds water in the stool) is added or used instead, with lactulose as the second choice. If stools are soft but still difficult to pass, a stimulant laxative (which makes the bowel contract more) is added. Any underlying cause, including a medicine that may be responsible, should also be looked for and treated.
Image - Abdominal x-ray showing significant constipation
Creative commons source by James Heilman, MD [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Edited by: Dr. Maddie Swannack
Reviewed by: Dr. Thomas Burnell and Dr. Marcus Judge
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