Pathophysiology of Diseases of Colon, Rectum, Anal, and Perianal (PDF)

Pathophysiology of diseases of (Colon, Rectum, Anal, and Perianal) Prepared by Dr Ibrahim Mousa Maaroof Higher Diploma student M.B.Ch.B. Dr Sarmad Nadhem Ismael Higher Diploma student M.B.Ch.B. Supervised by Assist. Prof. Dr Baderkhan Saeed Ahmed Assist. Prof. Dr Azhy Muhammed Dewana 16 January 2024...

Pathophysiology of diseases of (Colon, Rectum, Anal, and Perianal) Prepared by Dr Ibrahim Mousa Maaroof Higher Diploma student M.B.Ch.B. Dr Sarmad Nadhem Ismael Higher Diploma student M.B.Ch.B. Supervised by Assist. Prof. Dr Baderkhan Saeed Ahmed Assist. Prof. Dr Azhy Muhammed Dewana 16 January 2024 1 Colorectal pathophysiology Lower Gastrointestinal Hemorrhage • Epidemiology: Lower gastrointestinal (GI) bleeding is a common clinical problem with an annual incidence of 20 to 27 cases per 100,000 population • Etiology Ischemic colitis , a mostly self-limiting disease, is characterized by the sudden onset of left-sided abdominal pain with bloody diarrhea. Other common etiologies • • • • • • • • • Diverticular disease Ischemia Anorectal disease (hemorrhoids, anal fissure, rectal ulcer) Neoplasm (polyp or cancer) Angiodysplasia Inflammatory bowel disease Radiation colitis Small bowel/upper Gl bleeding Post polypectomy hemorrhage 90% of patients with recurrent or profuse bleeding have either diverticular disease or colonic angio dysplasia Large Bowel Volvulus General principles • In volvulus, the bowel twists on its own mesenteric axis , leading to bowel obstruction. Venous congestion may lead to bowel infarction. • The most common site for volvulus in the large bowel is sigmoid colon (approximately 75 % of all cases of volvulus). followed by the cecum and (rarely) the transverse colon Large bowel volvulus Sigmoid volvulus Epidemiology and etiology • Sigmoid volvulus accounts for about 5% of all cases of large bowel obstruction in developed countries. The incidence is higher in the Third World, which has been attributed to fiber-rich diets. • The narrow mesenteric base of the sigmoid colon, along with an elongated floppy loop , makes it particularly susceptible to twisting on its axis . • This condition is seen mostly in elderly, institutionalized patients with chronic medical conditions. • It is postulated that psychotropic drugs affect colonic motility, thus predisposing to volvulus Cecal volvulus • Cecal volvulus is uncommon and presents with abdominal pain and distention. • A much more common condition is a cecal bascule, in which a mobile cecum folds cephalad on a fixed ascending colon. This results in intermittent bowel obstruction. Pseudo-obstruction • This condition is characterized by pronounced abdominal distention, suggestive of a mechanical large bowel obstruction, in the absence of an obstructing lesion. • Commonly seen in hospitalized patients with chronic medical conditions Pseudo-obstruction Diverticular Disease "pseudodiverticula" General principles • Colonic diverticula are mucosal outpouchings through the submucosa and the muscular layer of the colon. • They occur most commonly in the sigmoid colon, and in 10% of patients , they involve the entire colon. • They arise between antimesenteric taenia and the mesenteric taenia at the site of entry of the blood vessels. Diverticular Disease Epidemiology and etiology • Diverticular disease of the colon is an acquired condition. • This condition is a disorder of modern civilization and is associated with consumption of refined food products. It is rare in rural African and Asian populations where dietary fiber is high. • The appendix and rectum have a continuous longitudinal muscle layer, rather than taenia, and thus do not have diverticula. Diverticular Disease Ulcerative Colitis. • This diffuse inflammatory disease affects the mucosa of the colon and rectum. Epidemiology and etiology • New cases of ulcerative colitis are seen each year at the rate of 1 to 15 new cases per 100 ,000 population. • The disease has a bimodal distribution, with most cases occurring in the teen years followed by a second peak in the 40s. • Positive family history is seen in about 1 0% of patients. Ulcerative Colitis. • Etiology is uncertain. Changes in fecal flora, a history of nonsmoking, appendectomy, milk allergy, and certain genes have all been considered important in the etiology. Ulcerative Colitis. Pathology: The primary pathologic process remains unknown. • Macroscopic appearance a. The disease is limited to the mucosa and submucosa. b. The rectum is always involved. The proximal colon may be the site of variable disease . c. Th e mucosal surface is ulcerated with areas of heaped regenerating mucosa called pseudo polyps. • Microscopic appearance: Crypt abscesses form at the base of the mucosa. Ulcerative Colitis. Crohn Disease Epidemiology and etiology • Crohn disease is a transmural IBD that can affect any part of the GI tract from the mouth to the anus. • The incidence is about 3 new cases for every 100,000 people, with a prevalence of about 30 cases for every 100,000 people. Crohn Disease Both genetic and environmental factors are implicated. • About 1 0% of patients give positive family history of IBD . The IBD 1 locus on chromosome 16 is strongly associated with Crohn disease. • Infective agents implicated in the pathogenesis include the measles virus and Mycobacterium paratuberculosis. • The etiologic factor that could provide a preventative or curative strategy remains elusive. Crohn Disease IBD Ulcerative Colitis and Crohn Disease Ulcerative colitis Crohn disease • Location : colon • Lesions : continuous from rectum to more proximal colon • Inflammation : limited to mucosa/submucosa • Neoplasms : high risk for development • Fissures : none • Fistulae : none • Granulomas : none • Location: entire GI tract • Lesions: skip lesions • Inflammation: transmural • Neoplasms: lower risk • Fissures: through submucosa • Fistulae: frequent • Granulomas: non caseating Colorectal Polyps General principles • Polyp is a discrete growth that protrudes into the lumen of the colon or rectum. • Polyps may be found throughout the colon and rectum. Epidemiology and etiology • Most commonly arise from the mucosa but may be submucosal • Mucosal polyps are divided into neoplastic or non-neoplastic. • Prevalence parallels that of colorectal cancer, being more common in the developed Western countries. • Adenoma prevalence increases with age in all populations. • From 20% to 40% of asymptomatic patients older than 50 years may have adenomatous polyps identified by colonoscopy. • From 30% to 50% of patients with one adenoma have a synchronous adenoma elsewhere in the colon. • Adenomas precede carcinomas in a given population by 5 to 10 years. • Relatively few adenomas progress to carcinomas Submucosal polyps • Any submucosal growth can expand and push the mucosa into the bowel lumen and appear as a polypoid lesion. Lipomas • Benign fatty tumors mostly seen in the cecum near the ileocecal valve but can be found throughout the colon or rectum. Smooth, yellowish-appearing polyps Neoplastic mucosal polyps • These are more commonly called adenomatous polyps. • Most colorectal cancers arise in preexisting adenomatous polyps. • Cancer risk is proportional to the following factors: a. The number of adenomas present b. The degree of dysplasia or atypia. c. The size of the lesion: Polyps greater than 2 cm have a 30% to 40% risk of harboring a malignancy d. The degree of villous component in the polyp . Non-neoplastic mucosal polyps (90 %) • Hyperplastic polyps a. Small sessile lesions frequently are seen in the distal colon and rectum. b. Indistinguishable from small adenomas , they have no malignant potential. c. These are found in one-third of the population older than 50 years of age Non-neoplastic mucosal polyps (90 %) • Juvenile polyps a. These growths are also known as retention polyps. b. They can occur sporadically or as part of familial adenomatous polyposis. c. Approximately 75% of these polyps occur in children less than 10 years of age and are seen in about 2% of asymptomatic children. e. Individually, the polyps have no malignant potential. • Inflammatory polyps: seen as idiopathic or severe chronic inflammation of any kind Colorectal Cancer Epidemiology and etiology • Colorectal cancer is the second most common malignancy in the United States ,with more the 155,000 new cases diagnosed annually. Incidence is highest in industrialized countries and is age specific, increasing steadily from the second to the ninth decades . • It is the second leading cause of all cancer-related deaths. • Rates of colon and rectal cancer are the same in men and women. • Animal fats play an etiologic role, They cause an increase in total fecal bile acids that stimulate the generation of reactive oxygen metabolites that promote cellular proliferation. • Fiber (cereal products , vegetables, and fruits) plays a protective role. Its exact effect is not known, but binding to carcinogens and thus reducing their contact with colonic epithelium may be important. • Increased calcium intake inhibits colonic proliferation and is associated with decreased risk of colorectal cancer Risk factors Familial • FAP accounts for less than 1% of all colorectal cancers. • Hereditary nonpolyposis colorectal cancer (HNPCC) accounts for 5% to 10% of all cancers. • IBD : Risk with chronic ulcerative colitis increases after 10 years of active disease by 1% cumulative/year. It is less in Crohn colitis . • Adenomatous polyps General • Age greater than 40 years • Family history of colon cancer • Personal history of colon polyps or cancer (threefold increase) • Pelvic radiation for gynecologic cancer (two- to threefold increase) Anal Cancer • Anal cancer is uncommon and accounts for 2% of large bowel cancers. Carcinoma of the anal margin • Squamous cell carcinoma (SCC) oGrows slowly and has rolled edges with central ulceration. oIt is usually well differentiated, and diagnosis is delayed. oAll anal ulcers should be biopsied to disprove SCC. Basal cell carcinoma • This rare cancer occurs 3 times more frequently in men than women. • Lesions are centrally ulcerated and irregular with raised edges ANORECTAL DISORDERS Hemorrhoids • In the upper anal canal, there are three cushions of submucosal tissue composed of connective tissue containing venules and smooth muscle fibers. left lateral, right anterior, and right posterior. • Their function is to aid anal continence. During defecation, they become engorged with blood, cushion the anal canal, and support the lining of the canal. Hemorrhoid • Hemorrhoid is the term used to describe the downward displacement of the anal cushions, causing dilatation of the contained venules , and they develop when the supportive tissues of the anal cushions deteriorate. • External hemorrhoids are dilated venules of the inferior hemorrhoidal plexuses below the dentate line. Thrombosed external hemorrhoids are intra vascular clots in the venules. Classification Internal hemorrhoids are the anal cushions located above the dentate line that have become prolapsed. These are graded according to the degree of prolapse. oFirst degree: The anal cushions protrude into the anal canal but do not prolapse . oSecond degree: The anal cushions prolapse through the anus on straining but spontaneously reduce. oThird degree : The anal cushions prolapse through the anus on straining or exertion and require manual replacement into the anal canal. oFourth degree: The prolapse is not manually reducible. Hemorrhoids Classification Anal Fissure An anal fissure is an ulcer in the lower portion of the anal canal. • It may be acute or chronic. • The primary fissure occurs without association with other local or systemic diseases . • The secondary fissure occurs in association with Crohn disease, leukemia , or aplastic anemia. • Most tears of the anal canal can be traced to the passage of large, hard stool or explosive diarrhea, trauma to the anus, or a tear during vaginal delivery. • In men, almost all fissures are located in the posterior midline, whereas in women, 10% are in the anterior midline. Anal Fissure Anorectal Abscesses Etiology • In the wall of the anal canal, a variable number of anal glands ( 4 to 10) lined by stratified columnar epithelium have direct openings into the anal crypts at the dentate line. • Infection of the glands leads to perianal abscess. • Because the glands lie between the internal and external sphincter, an intersphincteric abscess is formed. Anorectal Abscesses • Infection then spreads to various spaces: perianal, ischiorectal, intersphincteric, and supralevator. • Supralevator abscesses, which are uncommon, can arise from upward extension of an intersphincteric abscess. Fistula-in-Ana • Etiology: In this chronic form of perianal abscess, the abscess cavity does not heal completely but becomes an inflammatory tract with the primary internal opening in the anal crypt at the dentate line and the secondary opening in the perianal skin. • Classification: The four main types are based on the relation of the fistula to the sphincter muscle: 1. Intersphincteric: Fistula tract traverses through the internal sphincter. 2. Transsphincteric: Fistula tract traverses through the external sphincter. 3. Suprasphincteric : Fistula starts in the intersphincteric plane and then passes upward to a point above the puborectalis muscle, and then laterally over this muscle and downward between the puborectal and levator muscles into the ischiorectal fossa. 4. Extrasphincteric: The fistula passes from the perineal skin through the ischiorectal fossa and levator ani muscle, and finally penetrates the rectal wall. This may arise from trauma, foreign body, pelvic abscess, or cryptoglandular abscess Pilonidal Sinus Epidemiology and etiology 1. Pilonidal sinus is more likely to occur in hirsute patients . 2. Incidence is highest in the second and third decades of life. 3 . The cause is an infected hair follicle in the sacrococcygeal area . Other associated factors are increased sweating, buttock friction, obesity, or poor hygiene. Typically, pilonidal disease does not occur after around 40yrs old Risk of recurrence remains high, with some studies reporting 50% recurrence at 3 years. Rectal Prolapse • Procidentia is an uncommon condition in which the full thickness of the rectal wall turns inside out into or through the anal canal. • The cause is poorly understood, and the disorder is a form of intussusception. • Most patients have a history of straining with intractable constipation or chronic diarrhea. • There is a high incidence in patients with mental retardation • Predominates in females with a female : male ratio of 5 : 1 to 6 : 1 Classification • Partial: prolapse of rectal mucosa only • Complete First degree with an occult prolapse: Several anatomic defects are demonstrated in patients with chronic rectal prolapse. • Complete second-degree; prolapse to , but not through, the anus • Complete third-degree; protrusion through the anus for a variable distance Rectal Prolapse REFERENCES • O'Connell, P.R., McCaskie, A.W., & Sayers, R.D. (Eds.). (2023). Bailey & Love's Short Practice of Surgery - 28th Edition • Brunicardi F, & Andersen D.K., & Billiar T.R., & Dunn D.L., & Kao L.S., & Hunter J.G., & Matthews J.B., & Pollock R.E.(Eds.), (2019). Schwartz's Principles of Surgery, 11e. 16 January 2024 54 Thank You 16 January 2024 55