Pain while passing stool and spontaneous, bright-red hemorrhages during defecation are the most common symptoms of hemorrhoidal disorders. Of note, painless hemorrhages are frequently reported and may delay medical examination. However, pain may also be very intense and interfere with sitting and walking.
With regards to TH, the skin covering the affected vessel is usually very tender and may take on a bluish color. The lesion itself is mostly hard and protruding. TH may rupture and start to bleed during medical examination. If they ruptured before, ulceration or tissue necrosis may be observed at the site of lesion. Even though this has not occurred, signs of inflammation, i.e., erythema and swelling, may be noted in its surroundings. Most TH affect external hemorrhoids. Internal hemorrhoids don't usually occlude with thrombi unless prolapse and strangulation by the anal sphincter occurs.
Contrary to enlargement of hemorrhoids, TH symptom onset is rather sudden. However, since TH are generally related to enlarged hemorrhoidal vessels, a medical history of hemorrhoidal issues is not uncommon. Additionally, patients often report to suffer from recurrent or chronic constipation, diarrhea or other conditions described as potential etiological factors.
Macroscopic examination, anoscopy and - if considered necessary - sigmoidoscopy or colonoscopy are the methods of choice to assess the condition of squamous epithelium covering the anal canal and large intestinal mucosa. The latter are applied to evaluate the source of painless hemorrhages if hemorrhoidal disorders like TH cannot be detected by means of simple inspection of anus and rectum. Of note, severe colonopathies may be overlooked if symptoms are prematurely ascribed to hemorrhoidal disorders. Thus, if any doubt remains, patients should be submitted to more extensive endoscopic exams. The patient's medical history should be considered when taking this decision. Some experts recommend to perform sigmoidoscopy in every patient presenting with anal bleeding .
Uncomplicated cases of TH do not require additional laboratory analysis. However, recurrent thrombosis of hemorrhoids and/or other vessels should prompt coagulation studies. Additionally, blood cell counts may reveal anemia due to blood loss and infection.
Most cases of TH are self-limiting and symptoms subside spontaneously after thrombolysis. While pain typically eases within a few days, tissue swelling may persist for longer periods of time. Because even "a few days" may be a considerable time span when suffering from intense pain and hemorrhages during defecation, many patients request symptomatic treatment.
In this context, stool softeners like linseed, psyllium and wheat bran may significantly facilitate passage of stool. At the same time, such treatment prevents constipation and prolonged straining and thus reduces the risk of hemorrhages, ulceration and possible formation of new thrombi in adjacent vessels. Sitz baths are often found to be particularly pleasant. They should be carried out after defecation. Soothing ointments, e.g., those containing lidocaine or hamamelis, may provide immediate relief. Moderate pain may also be treated with systemic application of non-steroidal anti-inflammatory drugs.
Spontaneous remission is less likely if greatly enlarged hemorrhoids are occluded by thrombi. Here, the treatment of choice consists in excision of thrombus and the affected section of the vessel under local anesthesia.
If thrombosis affects prolapsed and strangulated internal hemorrhoids, treatment primarily aims at remedying the condition of hemorrhoidal prolapse. Injection sclerotherapy and rubber band ligation are possible therapeutic approaches.
Prognosis is usually very good. TH generally resolve without provision of any treatment although the latter may relieve symptoms. In most cases, thrombolysis occurs within several days after symptom onset and pain, hemorrhages and production of mucus subside. The probability of spontaneous remission may be lower if greatly enlarged hemorrhoids are affected by thrombosis. Recently, it has been reported that thrombosis of very large hemorrhoids may lead to gangrene and death .
With regards to pregnancy-associated hemorrhoidal disorders, symptoms generally resolve after delivery .
The precise causes of hemorrhoidal disorders are unknown. Most studies conducted so far have focused on enlarged hemorrhoids, a very common condition among adults. The latter is assumed to be a major risk factor for TH, so etiological factors contributing to expansion of hemorrhoids may also be considered possible triggers of TH.
Results of previously conducted studies imply an increased risk of hemorrhoidal illness in those patients suffering from problems regarding bowel evacuation, i.e., from either constipation or diarrhea  These may be provoked by dietary habits. Fibers support intestinal motility and digestion, and therefore, a diet rich in fibers may prevent digestive disorders. Consequently, low fiber intake may cause constipation, obstipation or diarrhea and hemorrhoidal issues.
Furthermore, a sedentary lifestyle and lack of exercise may contribute to the latter.
Any physiological or pathological condition associated with an increased intraabdominal pressure, e.g., pregnancy, prolonged straining, obesity, chronic cough, ascites, an intraabdominal mass, may trigger enlargement of hemorrhoidal vessels. With regards to pregnancy, hormonal changes may further exacerbate hemorrhoidal disorders that do, however, resolve after giving birth .
Gene variants may predispose to any of the above described conditions that augment the risk for hemorrhoidal disorders, or may directly contribute to the latter.
Of note, scientific evidence to support the aforementioned relations between (suspected) etiological factors and hemorrhoids is scarce. In fact, some of them have even been refuted in single studies . The difficulty to distinguish between cause, effect and incidental comorbidity may serve as an explanation for some of those apparent contradictions.
Hemorrhoidal disorders are known to be a very common condition. All races and both genders are affected. Although age is considered a risk factor, even pediatric patients may present with hemorrhoidal problems  . Still, precise epidemiological data cannot be provided because many patients never develop any symptoms and because those that do may nevertheless choose not to consult their physician.
Thrombosis of hemorrhoids is assumed to be related to an increased pressure in the respective vessels, particularly if they are enlarged and considerable amounts of blood remains within them . The precise trigger of coagulation has not yet been identified, but TH are an acute condition induced by a single, specific event. Clot formation leads to further distension of the affected hemorrhoidal vessel. Consequent activation of nociceptors located in the epithelium that covers external hemorrhoids makes this a painful process. TH are tender and rupture easily during defecation, which explains why hemorrhages while passing stool are commonly observed. Subsequent inflammation of the surrounding skin may further aggravate pain.
Thrombolysis occurs within a few days and allows for the wound to heal. However, vascular structures may not be reconstructed to their physiological state. The risk of thrombosis remains increased and recurrences are very frequent unless the thrombus and the damaged vessel are excised. Additionally, dilated skin may not revert completely and may disturb during defecation and cleansing. Removal may be indicated.
Although the causal relation between the above mentioned etiologic factors and hemorrhoidal disorders has not yet been unequivocally proven, maintenance of a healthy diet rich in fibers, avoidance of prolonged sitting and regular exercise may be recommended as preventive measures against TH.
The term "hemorrhoids" is colloquially used to describe a painful disease of the anal region. However, from a professional point of view, it merely refers to a physiological structure to be found within the wall of the anal canal. Hemorrhoids are vascular elements that form a cushioning ring, the rectal corpus cavernosum, which fulfills an important function in the maintenance of anal continence. Most of the time, i.e., when a person doesn't attempt to pass stool, hemorrhoids are filled with arterial blood and serve as a seal. They are emptied upon defecation, allow passage of stool, and refill afterwards.
Since hemorrhoids form part of the vascular system, they may be affected by a variety of vascular disorders. It has been estimated that the majority of the world's adult population suffers from some type of hemorrhoidal disease, but only part of them becomes symptomatic. Most commonly, hemorrhoids are enlarged, and this condition is associated with anal pain that aggravates during defecation, with hemorrhages and production of mucus. Thrombosed hemorrhoids (TH) are less frequently observed but are associated with similar symptoms. Both conditions - enlarged hemorrhoids and TH - may be observed concurrently and a causal relation is very likely. Blood pooling within expanded hemorrhoids presumably contributes to coagulation and formation of thrombi. Thrombosis of healthy hemorrhoidal vessels has not yet been described but can't be ruled out either.
According to their precise location, thrombosed external hemorrhoids and thrombosed internal hemorrhoids may be distinguished. The former are located distal of the pectate line, i.e., within the outer part of the anal canal. They are covered by squamous epithelium and account for the majority of TH cases. Thrombosed internal hemorrhoids are located proximal of the pectate line and are therefore coated by rectal mucosa. Thrombus formation within internal hemorrhoids is rare unless protrusion and strangulation by the anal sphincter occur .
Although supportive treatment may be provided to relieve symptoms, TH are usually self-limiting within a few days. Complications may arise if greatly enlarged hemorrhoids are affected by thrombosis. In these cases, surgical intervention may be indicated to remove the thrombus under local anesthesia.
Because most patients suffering from TH or other hemorrhoidal disorders never consult their physicians, it is difficult to deduce etiologic factors and to provide epidemiological information. In general, constipation, diarrhea, prolonged sitting, augmented intraabdominal pressure due to pregnancy or pathological conditions, as well as dietary habits are assumed to be associated with an increased risk of hemorrhoidal disorders. Data regarding TH in particular have not been collected.
Hemorrhoids are vascular structures that form a cushioning ring that fulfills an important function in maintenance of anal continence. Most of the time, i.e., when a person doesn't attempt to pass stool, hemorrhoids are filled with blood and serve as a seal. They are emptied while using the toilet, allow passage of stool, and refill afterwards.
Because hemorrhoids are blood vessels, they are susceptible to vascular disorders like thrombosis. If a blood clot forms within a hemorrhoidal vessel, the patient will be diagnosed with thrombosed hemorrhoids (TH).
Despite hemorrhoidal disorders being a very common condition, little is known about their precise causes. It has been estimated that the majority of the world's population suffers from enlarged hemorrhoids, although this condition does not necessarily become symptomatic. However, it has been assumed that blood pooling in large hemorrhoids may predispose for TH.
Pain that aggravates while passing stool and rectal bleedings are the most common symptoms. However, painless bleedings have also been observed and the absence of pain does not rule out TH.
The affected vessel expands, forms a hard, tender protrusion that is further irritated during defecation. It may rupture, which explains the rectal bleeding, and ulcerate or become infected.
Macroscopic examination of anus and rectum are usually sufficient to diagnose TH. If a patient reports anal bleedings and no alterations can be found in close proximity to the anus, endoscopic examinations of the large intestine are indicated to identify their source.
TH are usually self-limiting. Pain subsides within a few days, swelling a little bit later. To relieve symptoms during that time, soothing ointments may be applied. They may contain local anesthetics or herbal compounds. Many patients find considerable relieve in taking sitz baths after using the toilet. Additionally, consumption of linseed, psyllium or wheat bran should soften the stool and facilitate its excretion.
In rare cases and if thrombosis affects greatly enlarged hemorrhoids, surgical removal of thrombus and affected vessel is necessary to prevent recurrence. This procedure is carried out under local anesthesia.