NARRATIVE REVIEWS Fasiha Kanwal, Section Editor Rethinking What We Know About Hemorrhoids Robert S. Sandler and Anne F. Peery Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina Although hemorrhoids are responsible for considerable economic cost and personal suffering, they have received surprisingly little research attention. In the United States, hemorrhoids are the third most common outpatient gastrointestinal diagnosis with nearly 4 million office and emergency department visits annually. The etiology of hemorrhoids is speculative. A low-fiber diet and con- stipation have historically been thought to increase the risk for hemorrhoids, but not proven. Symptoms commonly attributed to hemorrhoids include bleeding, pain, pruritus, fecal seepage, prolapse, and mucus discharge. Research has found that these symptoms were equally reported by patients with and without hemorrhoids. Medical therapies for hemorrhoids have not been formally studied except for fiber where the results have been inconsistent. A number of office-based interventions such as rubber band ligation and infrared coagulation are widely used and economically favorable for practitioners. Surgical procedures are effec- tive at eliminating hemorrhoids but may be painful. Given the burden of disease and numerous gaps in our under- standing, the time has come for targeted research to understand the cause, symptoms, and best treatment for patients with symptomatic hemorrhoids. Keywords: Hemorrhoids; Prevalence; Patient-Reported Outcome; Review. O ne in 3 Americans has hemorrhoids on screening colonoscopy. 1 Office-based treatment of hemor- rhoids is a growing and lucrative business practice. Despite being prevalent and increasingly treated, symp- tomatic hemorrhoids are poorly understood with little evidence to guide treatment. To date, there has been no high-quality study of hemorrhoids in the United States. Given the potential for overtreatment, hemor- rhoids deserve more attention. The purpose of this perspective is to summarize what is known about hem- orrhoids and to outline an agenda for future research. Hemorrhoids are clusters of vascular tissue, smooth muscle, and connective tissue arranged in 3 columns along the anal canal. 2 They are present in healthy individuals as cushions that help to maintain conti- nence. 3 Although hemorrhoids are normal structures, 4 the term hemorrhoid has come to refer to a pathologic or symptomatic process. 2 Internal hemorrhoids are located above the dentate line (Figure 1). They are covered by columnar epithelium innervated by visceral nerve fibers that are not associated with pain. Internal hemorrhoids are graded based on the extent of prolapse. External hemorrhoids lie below the dentate line. They are covered with squamous epithelium and are innervated by somatic nerves that can produce pain. External hem- orrhoids generally are asymptomatic unless they throm- bose. Thrombosed hemorrhoids are acutely painful. 5 When external hemorrhoids resolve, skin tags may persist that can become irritated or create problems with hygiene. The remainder of this article focuses on internal hemorrhoids. The Burden of Hemorrhoids There has only been one national survey of hemorrhoids in the United States and that survey was conducted in 1989. In a digestive disease supplement to the National Health Interview Survey, participants were asked if a doctor had ever diagnosed them with hemor- rhoids. 6 The survey data were extrapolated to the US population. An estimated 23 million adults (13% of the US population) were diagnosed with hemorrhoids in the prior year. An estimated 36 million adults (20% of the US population) were ever diagnosed with hemorrhoids. 6 Women were more likely to report hemorrhoids than men (24% vs 16%). Overall, 21% (7.7 million) reported having had surgery for their hemorrhoids. The number of US citizens with hemorrhoids in 2018 is not known. Information on physician and hospital encounters for hemorrhoids can be found in published sources as a measure of burden. In 2004, there were 306,000 hospital discharges for hemorrhoids. 1 Demand for hemorrhoid therapy has been predicted to increase 23% over the next 20 years. 7 Data from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey from 2010 show that hemorrhoids were the third most common outpatient gastrointestinal diagnosis with nearly 4 million office and emergency department visits annu- ally. 8 Visits for hemorrhoids were more frequent than for colon cancer, diverticular disease, irritable bowel syndrome, or inflammatory bowel disease. Abbreviations used in this paper: HCUP, Healthcare Cost and Utilization Project; IRC, infrared coagulation; OR, odds ratio; PRO, patient-reported outcome. Most current article © 2019 by the AGA Institute 1542-3565/$36.00 https://doi.org/10.1016/j.cgh.2018.03.020 Clinical Gastroenterology and Hepatology 2019;17:8–15