Introduction
Background
Hemorrhoids are one of the most common causes of anal pathology. Subsequently, hemorrhoids are blamed for virtually any anorectal complaint by patients and medical professionals alike. Confusion often arises because the term "hemorrhoid" has been used to refer to both normal anatomical structures and pathological structures. In the context of this article, "hemorrhoids" refers to the pathological presentation of hemorrhoidal venous cushions.
Hemorrhoidal venous cushions are normal structures of the anorectum and are universally present unless a prior intervention has taken place. Because of their rich vascular supply, highly sensitive location, and tendency to engorge and prolapse, they are common causes of anal pathology.1 Symptoms can range from mildly bothersome, such as pruritus, to quite concerning, such as rectal bleeding, and while it is a common condition diagnosed in clinical practice, many patients are too embarrassed to ever seek treatment. Consequently, the true prevalence of pathologic hemorrhoids is not known.2
Even though hemorrhoids are responsible for a large portion of anorectal complaints, it is important to rule out more serious conditions, such as other causes of GI bleeding, before reflexively attributing symptoms to hemorrhoids.3
Pathophysiology
Hemorrhoidal venous cushions are a normal part of the human anorectum and arise from subepithelial connective tissue within the anal canal.
Present in utero, these cushions surround and support distal anastomoses between the superior rectal arteries and the superior, middle, and inferior rectal veins. They also contain a subepithelial smooth muscle layer, contributing to the bulk of the cushions. Normal hemorrhoidal tissue accounts for approximately 15-20% of resting anal pressure and provides important sensory information, enabling the differentiation between solid, liquid, and gas.
Most people contain 3 of these cushions. Although classically described as lying in the right posterior (most common), right anterior, and left lateral positions, this combination is found in only 19% of patients. Hemorrhoids can be found at any position within the rectum.
Hemorrhoids are classified by their anatomic origin within the anal canal and by their position relative to the dentate line.
- Internal hemorrhoids develop above the dentate line from embryonic endoderm. They are covered by the simple columnar epithelium of anal mucosa and lack somatic sensory innervation and are therefore painless.
- External hemorrhoids develop from ectoderm and arise distal to the dentate line. They are covered by stratified squamous epithelium and receive somatic sensory innervation from the inferior rectal nerve rendering them painful when irritated.
Anatomy of external hemorrhoid. Image courtesy of MedicineNet, Inc.
- Mixed hemorrhoids are confluent internal and external hemorrhoids.
Venous drainage of hemorrhoidal tissue mirrors embryologic origin:
- Internal hemorrhoids drain through the superior rectal vein into the portal system.
- External hemorrhoids drain through the inferior rectal vein into the inferior vena cava.
- Rich anastomoses exist between these 2 and the middle rectal vein, connecting the portal and systemic circulations.
Most symptoms arise from enlarged internal hemorrhoids. Abnormal swelling of the anal cushions causes dilatation and engorgement of the arteriovenous plexuses. This leads to stretching of the suspensory muscles and eventual prolapse of rectal tissue through the anal canal. The engorged anal mucosa is easily traumatized, leading to rectal bleeding that is typically bright red due to high blood oxygen content within the arteriovenous anastomoses. Prolapse leads to soiling and mucus discharge (triggering pruritus) and predisposes to incarceration and strangulation.
Most clinicians use the grading system proposed by Banov et al in 1985, which classifies internal hemorrhoids by their degree of prolapse into the anal canal. This system both correlates with symptoms and guides therapeutic approaches.
- Grade I hemorrhoids project into the anal canal and often bleed but do not prolapse.
- Grade II hemorrhoids may protrude beyond the anal verge with straining or defecating but reduce spontaneously when straining ceases.
- Grade III hemorrhoids protrude spontaneously or with straining and require manual reduction.
- Grade IV hemorrhoids chronically prolapse and cannot be reduced. They usually contain both internal and external components and may present with acute thrombosis or strangulation.
Frequency
United States
Prevalence of symptomatic hemorrhoids is estimated at 4.4% in the general population.
Race
Patients presenting with hemorrhoidal disease are more frequently Caucasian, from higher socioeconomic status, and from rural areas.
Sex
No predilection is known, although men are more likely to seek treatment. However, pregnancy causes physiologic changes that predispose women to developing symptomatic hemorrhoids. As the gravid uterus expands, it compresses the inferior vena cava, causing decreased venous return and distal engorgement.
Age
External hemorrhoids occur more commonly in young and middle-aged adults than in older adults. The prevalence of hemorrhoids increases with age, with a peak in persons aged 45-65 years.
Clinical
History
The most common presentation of hemorrhoids is rectal bleeding, pain, pruritus, or prolapse. However, these symptoms are extremely nonspecific and may be seen in a number of anorectal diseases. The physician must therefore rely on a thorough history to help narrow the differential and must perform an adequate physical examination (including anoscopy when indicated) to confirm the diagnosis.
- An adequate history should include the onset and duration of symptoms. In addition to characterizing any pain, bleeding, protrusion, or change in bowel habits, special attention should be placed on the patient's coagulation history and immune status.
- Bleeding is the most common presenting symptom. Blood is usually bright red and may drip, squirt into the toilet bowl, or appear as streaks on the toilet paper. The physician should inquire about the quantity, color, and timing of any rectal bleeding. Darker blood or blood mixed with stool should raise suspicion of a more proximal cause of bleeding.
- A patient with a thrombosed external hemorrhoid may present with complaints of an acutely painful mass at the rectum (see Media file 1). Pain truly caused by hemorrhoids usually arises only with acute thrombus formation. This pain peaks at 48-72 hours and begins to decline by the fourth day as the thrombus organizes. New-onset anal pain in the absence of a thrombosed hemorrhoid should prompt investigation for an alternate cause, such as an intersphincteric abscess or anal fissure. As many as 20% of patients with hemorrhoids will have concomitant anal fissures.
Thrombosed hemorrhoid. This hemorrhoid was treated by incision and removal of clot.
- The presence, timing, and reducibility of prolapse, when present, will help classify the grade of internal hemorrhoids and guide the therapeutic approach.
- Grade I internal hemorrhoids are usually asymptomatic but, at times, may cause minimal bleeding.
- Grades II, III, or IV internal hemorrhoids usually present with painless bleeding but also may present with complaints of a dull aching pain, pruritus, or other symptoms due to prolapse.
- Familial predisposition, diet, history of constipation or diarrhea, and history of prolonged sitting or heavy lifting are also relevant, as are weight loss, abdominal pain, or any change in appetite or bowel habits. Presence of pruritus or any discharge should also be noted.
Physical
In addition to the general physical examination, physicians should also perform visual inspection of the rectum, digital rectal examination, and anoscopy or proctosigmoidoscopy when appropriate.
The preferred position for the digital rectal examination is the left lateral decubitus with the patient's knees flexed toward the chest. Topical anesthetics (eg, 20% benzocaine or 5% lidocaine ointment) may help to reduce any discomfort caused by examination.
- External findings important to note include any of the following:
- Redundant tissue
- Skin tags from old thrombosed external hemorrhoids
- Fissures
- Fistulas
- Signs of infection or abscess formation
- Rectal or hemorrhoidal prolapse, appearing as a bluish, tender perianal mass
- During the digital rectal examination, assess for any masses, tenderness, mucoid discharge or blood, and rectal tone. Internal hemorrhoids are usually not palpable unless thrombosed.
- Current guidelines from most gastrointestinal and surgical societies advocate anoscopy and/or flexible sigmoidoscopy to evaluate any bright-red rectal bleeding. Colonoscopy should be considered in the evaluation of any rectal bleeding that is not typical of hemorrhoids such as in the presence of strong risk factors for colonic malignancy or in the setting of rectal bleeding with a negative anorectal examination.
Causes
Although many patients and clinicians believe that hemorrhoids are caused by chronic constipation, prolonged sitting, and vigorous straining, little evidence to support a causative link exists.
- Other risk factors historically associated with the development of hemorrhoids include the following:
- Pregnancy
- Lack of erect posture
- Familial tendency
- Higher socioeconomic status
- Chronic diarrhea
- Colon malignancy
- Hepatic disease
- Obesity
- Elevated anal resting pressure
- Spinal cord injury
- Loss of rectal muscle tone
- Rectal surgery
- Episiotomy
- Anal intercourse
- Varicosities caused from portal hypertension are a distinct entity from hemorrhoids.
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References
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Further Reading
Keywords
hemorrhoids, hemorrhoid treatment, hemorrhoid causes, hemorrhoid symptoms, anus swellings, piles, cutaneous hemorrhoids, external hemorrhoids, internal hemorrhoids, hemorrhoidal venous plexus, hematochezia, varicosities of the hemorrhoidal venous plexus, thrombosed external hemorrhoid, rectal bleeding, prolapsed hemorrhoid, rectal prolapse
