10 Large Intestine Anatomy and Histology
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Questions and Answers

What is a common symptom of transmural infarction in ischemic bowel disease?

  • Intense itching
  • Severe abdominal pain (correct)
  • Decreased appetite
  • Weight gain

    • Which condition is NOT a mechanism contributing to ischemic bowel disease?

  • Venous thrombosis
  • Non-occlusive ischemia
  • Arterial thrombosis
  • Bronchial embolism (correct)

    • Chronic ischemic colitis is often confused with which other condition?

  • Celiac disease
  • Irritable bowel syndrome
  • Diverticulitis
  • Inflammatory bowel disease (correct)

    • What percentage mortality rate is associated with transmural infarction in ischemic bowel disease?

    <p>90%</p> Signup and view all the answers

    Angiodysplasia is characterized by dilated blood vessels typically found in which part of the gastrointestinal tract?

    <p>Caecum and right colon</p> Signup and view all the answers

    What is the primary cause of Hirschsprung's disease?

    <p>Arrested migration of neural crest cells</p> Signup and view all the answers

    Which area is most commonly involved in Hirschsprung's disease?

    <p>Rectum and sigmoid</p> Signup and view all the answers

    What type of anemia is associated with ischemic bowel disease?

    <p>Chronic anemia</p> Signup and view all the answers

    Which vessel supplies the rectum?

    <p>Internal pudendal artery</p> Signup and view all the answers

    What is a common complication of Hirschsprung's disease?

    <p>Enterocolitis</p> Signup and view all the answers

    What histological feature is NOT found in the large intestine?

    <p>Villi</p> Signup and view all the answers

    Which type of infarction involves necrosis of all layers of the bowel wall?

    <p>Transmural infarction</p> Signup and view all the answers

    What is the male-to-female ratio for Hirschsprung's disease?

    <p>4:1</p> Signup and view all the answers

    What role do Paneth cells serve in the large intestine?

    <p>Antimicrobial properties and immune mediators</p> Signup and view all the answers

    What consequence does the absence of ganglion cells in the muscle wall cause in Hirschsprung's disease?

    <p>Functional obstruction</p> Signup and view all the answers

    What is a common systemic manifestation of ulcerative colitis?

    <p>Ankylosing spondylitis</p> Signup and view all the answers

    What is a primary contributing factor to the development of diverticular disease?

    <p>Low fiber diet</p> Signup and view all the answers

    Which of the following is a potential complication of diverticulosis?

    <p>Diverticulitis</p> Signup and view all the answers

    Where do diverticula commonly arise in the colon?

    <p>Sigmoid colon</p> Signup and view all the answers

    What is a primary treatment option for diverticular disease?

    <p>High fiber diet</p> Signup and view all the answers

    Which of the following best describes a diverticulum?

    <p>A herniation of the bowel wall</p> Signup and view all the answers

    What condition is caused by inflammation of the diverticulum?

    <p>Diverticulitis</p> Signup and view all the answers

    Which of the following is NOT considered a mechanical cause of intestinal obstruction?

    <p>Diarrhea</p> Signup and view all the answers

    Which factors contribute to the development of hemorrhoids?

    <p>Venous stasis of pregnancy</p> Signup and view all the answers

    What is the primary cause of antibiotic-associated colitis?

    <p>Infection by Clostridium difficile</p> Signup and view all the answers

    What characterizes Crohn's disease on gross examination?

    <p>Transmural involvement with skip lesions</p> Signup and view all the answers

    What are the common clinical features of ulcerative colitis?

    <p>Bloody mucoid diarrhea and anemia</p> Signup and view all the answers

    Which of the following is a common complication associated with Crohn's disease?

    <p>Fistula formation</p> Signup and view all the answers

    Which micronutrient deficiency is particularly associated with Crohn's disease?

    <p>Vitamin B12</p> Signup and view all the answers

    What feature distinguishes ulcerative colitis from Crohn's disease?

    <p>Continuous lesions limited to mucosa and submucosa</p> Signup and view all the answers

    What defines necrotizing enterocolitis primarily in neonates?

    <p>Acute necrotizing inflammation of bowel</p> Signup and view all the answers

    Which principle is critical in the pathogenesis of idiopathic inflammatory bowel disease?

    <p>Polymorphism in genetic loci</p> Signup and view all the answers

    Which medication is commonly used to treat antibiotic-associated colitis?

    <p>Metronidazole</p> Signup and view all the answers

    What typically triggers episodes of inflammatory bowel disease?

    <p>Emotional stress</p> Signup and view all the answers

    In ulcerative colitis, what does the incidence of colitis-associated neoplasia depend on?

    <p>Duration and extent of disease</p> Signup and view all the answers

    What is a common feature of the microscopic examination of ulcerative colitis?

    <p>Ulcero-inflammatory cryptitis</p> Signup and view all the answers

    Which demographic group shows the highest incidence of inflammatory bowel disease?

    <p>Caucasians and Ashkenazi Jews</p> Signup and view all the answers

    Which mechanism is NOT associated with ischemic bowel disease?

    <p>Lymphatic obstruction</p> Signup and view all the answers

    What is a common clinical feature seen in transmural infarction of the small intestine?

    <p>Severe abdominal pain</p> Signup and view all the answers

    Chronic ischemic colitis is often mistaken for which condition due to overlapping symptoms?

    <p>Inflammatory bowel disease</p> Signup and view all the answers

    Angiodysplasia is commonly associated with which of the following conditions?

    <p>Aortic stenosis</p> Signup and view all the answers

    In the context of ischemic bowel disease, which outcome has the highest mortality rate?

    <p>Transmural infarction</p> Signup and view all the answers

    What is the primary reason for the formation of diverticula in the colon?

    <p>Focal weaknesses where blood vessels penetrate</p> Signup and view all the answers

    Which systemic manifestation is associated with ulcerative colitis?

    <p>Erythema nodosum</p> Signup and view all the answers

    What complication may occur due to diverticulitis?

    <p>Fistula formation</p> Signup and view all the answers

    Diverticular disease increases the risk of which of the following events?

    <p>Hemorrhage</p> Signup and view all the answers

    What is the recommended dietary change to help manage diverticular disease?

    <p>High fiber diet</p> Signup and view all the answers

    Which of the following conditions is most commonly involved in inflammatory bowel disease complications?

    <p>Obstruction due to adhesions</p> Signup and view all the answers

    What contributes to the pathogenesis of diverticular disease in adults over 60?

    <p>Sedentary lifestyle</p> Signup and view all the answers

    Which inflammatory condition is often associated with ulcerative colitis?

    <p>Ankylosing spondylitis</p> Signup and view all the answers

    Which structures are primarily supplied by the inferior mesenteric artery?

    <p>Transverse colon to rectum</p> Signup and view all the answers

    What is the primary defect associated with Hirschsprung's disease?

    <p>Absence of ganglion cells in the bowel wall</p> Signup and view all the answers

    What type of infarction in ischemic bowel disease involves necrosis of the mucosa only?

    <p>Mucosal infarction</p> Signup and view all the answers

    Which cellular type in the large intestine is primarily responsible for antimicrobial properties?

    <p>Paneth cells</p> Signup and view all the answers

    What percentage of sporadic cases of Hirschsprung's disease is associated with RET gene mutations?

    <p>15%</p> Signup and view all the answers

    Which class of bowel disease may present with both acute and chronic symptoms?

    <p>Ischaemic bowel disease</p> Signup and view all the answers

    In the normal histology of the large intestine, which layer contains the myenteric plexus?

    <p>Muscularis propria</p> Signup and view all the answers

    During the development of Hirschsprung's disease, which cells fail to migrate appropriately?

    <p>Neural crest cells</p> Signup and view all the answers

    What is a common complication following the massive dilation of the proximal colon in Hirschsprung's disease?

    <p>Perforation of the colon</p> Signup and view all the answers

    Which component of the large intestine's anatomy is responsible for the absorption of water and electrolytes?

    <p>Sigmoid colon</p> Signup and view all the answers

    What is the primary mechanism by which Crohn's disease leads to malabsorption?

    <p>Transmural inflammation impairing nutrient absorption</p> Signup and view all the answers

    Which symptom is most characteristic of ulcerative colitis compared to Crohn's disease?

    <p>Pseudopolyps on imaging</p> Signup and view all the answers

    What is the histological feature that is absent in ulcerative colitis?

    <p>Granulomas</p> Signup and view all the answers

    What complication is associated with the chronicity of ulcerative colitis?

    <p>Toxic megacolon</p> Signup and view all the answers

    What is a significant risk factor for the development of Crohn's disease?

    <p>Family history of autoimmune diseases</p> Signup and view all the answers

    What characterizes the distribution of lesions in Crohn's disease?

    <p>Segmental with skip lesions</p> Signup and view all the answers

    Which of the following is NOT a common extra-intestinal manifestation of Crohn's disease?

    <p>Hyperthyroidism</p> Signup and view all the answers

    During a flare of ulcerative colitis, which laboratory finding may commonly be observed?

    <p>Elevated inflammatory markers</p> Signup and view all the answers

    What is the primary pathology responsible for necrotizing enterocolitis in neonates?

    <p>Ischemia and gut immaturity</p> Signup and view all the answers

    What underlying condition is often associated with hemorrhoids?

    <p>Portal hypertension</p> Signup and view all the answers

    Which of the following factors significantly contributes to the risk of antibiotic-associated colitis?

    <p>Use of broad-spectrum antibiotics</p> Signup and view all the answers

    What clinical feature commonly distinguishes internal hemorrhoids from external hemorrhoids?

    <p>Rectal bleeding</p> Signup and view all the answers

    What unique microscopic feature can be observed in Crohn's disease?

    <p>Non-caseating granulomas</p> Signup and view all the answers

    What condition is related to significant malabsorption in Crohn's disease?

    <p>Short bowel syndrome</p> Signup and view all the answers

    What is a common feature of chronic ischemic colitis?

    <p>Intermittent bloody diarrhoea</p> Signup and view all the answers

    Which of the following is a mechanism of ischemic bowel disease?

    <p>Arterial embolism</p> Signup and view all the answers

    In which demographic is angiodysplasia most commonly found?

    <p>Elderly individuals</p> Signup and view all the answers

    What clinical feature may occur as a result of transmural infarction in ischemic bowel disease?

    <p>Peritonitis and sepsis</p> Signup and view all the answers

    What condition may cause ischemic bowel disease due to non-occlusive scenarios?

    <p>Heart failure</p> Signup and view all the answers

    What leads to the formation of diverticula in the colon?

    <p>Weakness where vessels penetrate the muscularis propria</p> Signup and view all the answers

    What type of complications may arise from diverticulitis?

    <p>Inflammatory mass formation</p> Signup and view all the answers

    Which systemic manifestation is commonly associated with ulcerative colitis?

    <p>Primary sclerosing cholangitis</p> Signup and view all the answers

    Which dietary change is recommended for managing diverticular disease?

    <p>High fiber diet</p> Signup and view all the answers

    Which statement about Hirschsprung's disease is correct?

    <p>It is more common in males than females.</p> Signup and view all the answers

    Where in the colon are diverticula most commonly found?

    <p>Sigmoid colon</p> Signup and view all the answers

    What is the main pathological feature of ischemic bowel disease?

    <p>Sudden occlusion of a major vessel leading to blood supply loss.</p> Signup and view all the answers

    What is a common symptom indicating diverticulitis?

    <p>Fever and chills</p> Signup and view all the answers

    Which type of infarction involves necrosis of the mucosa only?

    <p>Mucosal infarction</p> Signup and view all the answers

    Which region of the large intestine is primarily supplied by the inferior mesenteric artery?

    <p>Sigmoid colon and rectum</p> Signup and view all the answers

    What is typically the initial cause of diverticular disease development?

    <p>Low fiber diet</p> Signup and view all the answers

    Which of the following is a mechanical cause of intestinal obstruction?

    <p>Volvulus</p> Signup and view all the answers

    What describes the clinical presentation of Hirschsprung's disease?

    <p>Failure to pass meconium and abdominal distension.</p> Signup and view all the answers

    In normal histology of the large intestine, which cell type is NOT present?

    <p>Paneth cells</p> Signup and view all the answers

    Which complication is associated with untreated Hirschsprung's disease?

    <p>Megacolon leading to perforation</p> Signup and view all the answers

    Which vessel primarily supplies the proximal colon until the splenic flexure?

    <p>Superior mesenteric artery</p> Signup and view all the answers

    What is a characteristic feature of Paneth cells?

    <p>Their granules contain antimicrobial properties.</p> Signup and view all the answers

    In which part of the bowel does the arrested migration of neural crest cells occur in Hirschsprung's disease?

    <p>Muscle wall and submucosa of the rectum</p> Signup and view all the answers

    What is a primary characteristic of hereditary hemorrhagic telangiectasia?

    <p>It is marked by thin-walled blood vessels.</p> Signup and view all the answers

    Which factor is NOT considered a predisposing factor for hemorrhoids?

    <p>Excessive physical activity</p> Signup and view all the answers

    Necrotising enterocolitis is most commonly seen in which population?

    <p>Premature infants</p> Signup and view all the answers

    The presence of Clostridium difficile in antibiotic-associated colitis is primarily related to what?

    <p>Altered gut flora due to antibiotic use</p> Signup and view all the answers

    Which of the following diseases is classified as idiopathic inflammatory bowel disease?

    <p>Crohn's disease</p> Signup and view all the answers

    What type of ulcer is commonly seen in Crohn's disease?

    <p>Serpentine ulcers</p> Signup and view all the answers

    What histological feature is NOT associated with ulcerative colitis?

    <p>Granulomas</p> Signup and view all the answers

    What is a common complication of Crohn's disease?

    <p>Fistula formation</p> Signup and view all the answers

    What is the typical clinical feature that distinguishes ulcerative colitis from Crohn's disease?

    <p>Continuous mucosal involvement</p> Signup and view all the answers

    Which demographic exhibits the highest incidence of ulcerative colitis?

    <p>Caucasians</p> Signup and view all the answers

    What characterizes the gross pathology of ulcerative colitis?

    <p>Continuous areas of ulceration</p> Signup and view all the answers

    Which complication is associated with long-standing ulcerative colitis?

    <p>Colitis-associated neoplasia</p> Signup and view all the answers

    What is a common systemic manifestation in patients with Crohn's disease?

    <p>Ankylosing spondylitis</p> Signup and view all the answers

    What is a clinical feature often seen in ulcerative colitis?

    <p>Bloody mucoid diarrhea</p> Signup and view all the answers

    Study Notes

    Large Intestine - Normal Anatomy

    • The Large Intestine measures 1-1.5m in length.
    • Key regions include: caecum, ascending colon, transverse colon, descending colon, sigmoid and rectum.
    • The Superior mesenteric artery supplies blood to: caecum to splenic flexure.
    • The Inferior mesenteric artery supplies blood to: remainder of colon to rectum.
    • The Haemorrhoidal branches of the internal iliac or internal pudendal artery supply: lower portion of the rectum.

    Normal Histology

    • The mucosa contains: crypts and surface epithelium.
    • The surface epithelium contains: columnar absorptive cells.
    • The crypts contain: goblet cells, Paneth cells and endocrine cells.
    • Paneth cells are found in the caecum and ascending colon and have antimicrobial properties and immune mediators.
    • The submucosa is made up of loose connective tissue with the plexus of Meissner.
    • The muscularis propria is made up of: an inner circular layer, an outer longitudinal layer and the myenteric plexus of Auerbach.
    • The outermost layer is: the serosa, which is made up of mesothelial cells and fibrous tissue.

    Developmental Anomalies - Hirschsprung's Disease

    • Hirschsprung's Disease is also known as Congenital Megacolon.
    • This is a rare disease with an incidence of 1 in 5000-8000 live births.
    • Males are more likely to be affected, with a male to female ratio of 4:1.
    • The most common area affected is: the rectum and sigmoid colon.

    Pathogenesis of Hirschsprung's Disease

    • This disease is caused by arrested migration of neural crest cells into the bowel wall.
    • The absence of ganglion cells in the muscle wall (Auerbach's plexus) and submucosa (Meissner's plexus) causes an aganglionic (aperistaltic) narrow segment in the rectum.
    • This leads to functional obstruction and dilatation of the unaffected proximal colon.
    • 50% of familial cases and 15% of sporadic cases have mutations in the RET gene.

    Clinical Features of Hirschsprung's Disease

    • Symptoms may include: Failure to pass meconium, constipation, abdominal distension and vomiting.
    • Complications: Proximal innervated colon may become massively dilated and may perforate.
    • Prognosis: Mortality rate is 5%.
    • Treatment: Resection of the involved bowel.

    Vascular Disorders

    • These include: Ischaemic bowel disease, Angiodysplasia, Hereditary haemorrhagic telangiectasia and Haemorrhoids.

    Ischaemic Bowel Disease

    • This condition can affect small, large or both intestines.
    • Can be acute or chronic.
    • Severity of injury depends on the vessels involved.

    Ischaemic Bowel Disease - Types of Infarction

    • Transmural infarction: Infarction of all layers of wall due to sudden occlusion of a major vessel (thrombosis/embolism).
    • Mural infarction: Necrosis of mucosa and submucosa.
    • Mucosal infarction: Necrosis of mucosa only.
    • Mural/Mucosal infarction: Hypoperfusion (esp in watershed areas).
    • Chronic ischemic bowel disease: Inflammation, ulceration, mucosal atrophy and fibrosis  strictures in some cases.

    Pathogenesis of Ischaemic Bowel Disease

    • Multiple mechanisms can cause this disease - Arterial occlusion, venous thrombosis and non-occlusive ischaemia.
    • Arterial thrombosis: Atherosclerosis and vasculitis.
    • Venous thrombosis: Hypercoagulable states and drugs.
    • Non-occlusive ischaemia: Heart failure, shock, and drugs.
    • Other causes: Radiation, volvulus, strangulation.

    Clinical Features of Ischaemic Bowel Disease

    • Transmural infarction: Older individuals, severe abdominal pain, bloody diarrhoea,  peristaltic sounds and rigidity.
    • Transmural infarction: May perforate  peritonitis & sepsis.
    • Transmural infarction: 90% mortality rate.
    • Mucosal and mural infarction: Non-specific abdominal complaints, intermittent bloody diarrhoea and may heal if lesion corrected.
    • Chronic Ischemic Colitis: Intermittent bloody diarrhoea and often confused with inflammatory bowel disease.
    • It's important to consider ischaemic bowel disease in patients with unexplained abdominal pain and/or GI bleeding.

    Angiodysplasia

    • This is a condition characterized by: Tortuous dilatations of blood vessels, usually in caecum and right colon (acquired malformed vessels in the mucosa and submucosa).
    • It is usually seen in: Elderly individuals.
    • Likely cause: Years of mechanical trauma.
    • Can cause: Chronic and acute lower GI blood loss if the blood vessels rupture.
    • Associations: Aortic stenosis, scleroderma, end stage renal disease, von Willebrand disease.

    Hereditary Haemorrhagic Telangiectasia

    • This is an autosomal dominant disorder.
    • This condition leads to: Thin walled blood vessels rupture in the mouth and the GI tract, causing bleeding.

    Haemorrhoids

    • This is a common condition characterized by: Variceal dilatation of submucosal venous plexi around anus and lower rectum.
    • Predisposing factors: Constipation, venous stasis of pregnancy and portal hypertension.
    • There are two types: internal hemorrhoids and external hemorrhoids.
    • Symptoms: Bright red stool, painful swelling around the anus with external hemorrhoids.

    Necrotising Enterocolitis

    • This condition affects: Neonates.
    • It is caused by: Acute necrotising inflammation of small and large bowel.
    • Most common in: Premature infants or low birth weight infants.
    • Can occur anytime in the first 3 months, but commonly on day 2-4.
    • Cause: Combination of ischaemia, colonisation by pathogenic organisms, excess protein in lumen and functional immaturity of the gut.

    Antibiotic- Associated Colitis (Pseudomembranous Colitis)

    • This type of colitis is characterized by: An adherent inflammatory exudate (pseudomembrane) composed of mucus, fibrin and inflammatory debris.
    • The cause is: Following a course of broad-spectrum antibiotics.
    • The infection is caused by: Clostridium difficile, which produces cytotoxins.
    • The clinical presentation is: Diarrhoea.
    • Diagnosis: Detection of cytotoxin in stool.
    • Treatment: Metronidazole and Vancomycin.

    Idiopathic Inflammatory Bowel Disease

    • This includes: Crohn's Disease and Ulcerative Colitis.
    • Incidence of both Crohn's and ulcerative colitis is rising.
    • It is most common in: Teens and early 20s but can develop at any age.
    • This is more common: Caucasians and Ashkenazi Jews.

    Pathogenesis of Idiopathic Inflammatory Bowel Disease

    • There are several contributing factors including: Mucosal immunity, host-microbial interactions and genetic factors.
    • Treatment aims: Immune down-regulation.

    Crohn's Disease

    • This affects: 1-3/100,000 annually.
    • More common in: Western populations, females, whites and Jews.
    • Peak incidence: Teens and twenties with a minor peak in the fifties and sixties.

    Gross Features of Crohn's Disease

    • This condition can affect: Any area of the GIT (from mouth to anus).
    • The pattern is: Segmental involvement, "skip lesions" and transmural involvement of the bowel wall.
    • "Skip lesions" are areas of bowel wall that are separated by normal appearing bowel wall.
    • Gross features also include: Creeping fat, dull serosa and thickened wall (due to oedema, inflammation and fibrosis).
    • Other features: Strictures/narrow lumen, aphthous mucosal ulcers that coalesce into long, linear serpentine ulcers, fissures and fistulae or sinus tracts.

    Microscopic Features of Crohn's Disease

    • This condition is characterized by: Chronic mucosal damage, crypt architectural distortion, mucosal ulceration and fissuring.
    • There is: Transmural inflammation, cryptitis and crypt abscess.
    • Other microscopic features: Lymphoid aggregates and +/- non-caseating granulomas.
    • Dysplasia is possible: Late in the disease.

    Clinical Features of Crohn's Disease

    • The course of the disease is: Variable, relapsing and remitting.
    • Symptoms: Intermittent attacks of diarrhoea, abdominal pain and fever.
    • Precipitating factors: Emotional stress.
    • Other symptoms: Occult or overt faecal blood loss, anaemia, malabsorption, weight loss, hypoalbuminaemia, steatorrhoea, megaloblastic anaemia.

    Complications of Crohn's Disease

    • Obstruction (terminal ileum-secondary to transmural fibrosis/stricture).
    • Adhesions.
    • Fistula formation: involving adjacent small bowel, colon, urinary bladder, vagina and abdominal and perianal skin.
    • Malabsorption, with: Steatorrhoea (secondary to mucosal disease and surgical resection).
    • Increased risk of carcinoma (slight, especially when compared with UC).

    Systemic Manifestations of Crohn's Disease

    • Joints: Migratory polyarthritis, Sacroiliitis, ankylosing spondylitis.
    • Eyes: Uveitis.
    • Skin: Erythema nodosum.
    • Nails: Clubbing of finger tips.

    Ulcerative Colitis

    • This is: A chronic inflammatory disease of the colon, limited to mucosa & submucosa of large bowel.
    • Incidence: 4-12/100,000 annually.
    • Affects: Caucasians, equal sex predilection.
    • Affects: All ages; peak incidence between 20-25.
    • There can also be: Extra-intestinal manifestations as does Crohn’s.

    Gross Pathology of Ulcerative Colitis

    • The pattern is: Usually begins in rectum and extends proximally in a continuous fashion.
    • Possible areas affected: May involve the entire colon (pancolitis), without skip areas.
    • Gross features: Mucosa is red, large areas of ulceration confined to mucosa, often extensive and broad-based (not linear), isolated islands of regenerative mucosa, inflammatory pseudopolyps, wall is not thickened and normal serosa.

    Microscopic Features of Ulcerative Colitis

    • This condition is characterized by: Inflammation confined to the mucosa and submucosa, cryptitis and crypt abscesses, ulceration, architectural distortion of the crypts and epithelial dysplasia.
    • Granuloma is not present.

    Clinical Features of Ulcerative Colitis

    • The course of the disease is: Relapsing and remitting.
    • The disease can be precipitated by: Stress.
    • Symptoms: Intermittent attacks of bloody mucoid diarrhoea, abdominal pain, tenesmus, fever and weight loss.
    • Other symptoms: Anaemia (blood loss) and extra-intestinal manifestations are more common in UC than CD.
    • Diagnosis: Colonoscopy and colonic bx.

    Colitis-Associated Neoplasia

    • The risk is related to: Duration, extent of disease and inflammation.
    • Surveillance: Regular endoscopy with biopsy.

    Complications of Ulcerative Colitis

    • Toxic megacolon: Acute dilatation of the colon due to toxic damage to muscularis propria and neural plexus with shutdown of neuromuscular function.
    • Markedly increased cancer risk related to: Extent of colonic involvement and duration of the disease.
    • Preceded by: Dysplasia.

    Systemic Manifestations of Ulcerative Colitis

    • Joints: Migratory polyarthritis, Sacroiliitis, ankylosing spondylitis.
    • Skin: Erythema nodosum, Necrotising skin lesion- pyoderma gangrenosum, Clubbing.
    • Liver: Primary sclerosing cholangitis.
    • Eyes: Uveitis

    Diverticular Disease

    • This condition is characterized by: Blind pouch leading off the alimentary tract communicating with the lumen.
    • In the colon, these defects are commonly found: Where nerves and vessels penetrate the muscularis propria.
    • The prevalence is nearly 50% in adults over 60 in Western countries.

    Pathogenesis of Diverticular Disease

    • The cause is: Related to wall stress, associated with: Constipation, straining and low fibre diet.
    • Originate: Where the vasa recta traverse the muscularis propria (Focal weakness of the bowel wall).
    • Low fibre diet   stool bulk  peristaltic contractions   intraluminal pressure  herniation of the bowel wall through the anatomic points of weakness  diverticula.
    • Outpouching of the mucosa and submucosa (pseudo diverticulum).
    • Almost always in the: Sigmoid colon.

    Clinical Features of Diverticular Disease

    • Usually: Asymptomatic.
    • In 20% of cases: Patients have cramping or lower abdominal pain, constipation, sensation of never being able to empty the rectum completely.
    • Treatment: High fibre diet (may prevent progression), surgical intervention for: Obstructive or inflammatory complications.

    Complications of Diverticulosis

    • Inflammation (Diverticulitis): May be caused by: Obstruction of the narrow neck of the herniated diverticulum, impaction of faecal material, constriction of the blood supply and infection.
    • Other complications: Perforation, adhesions, fistula formation, pericolic abscess formation, inflammatory mass formation, haemorrhage, obstruction.

    Intestinal Obstruction

    • More common in the: Small bowel (small lumen).
    • There are two types: Mechanical and Functional.
    • Mechanical causes: Congenital (atresia, imperforate anus) and Acquired (volvulus, adhesions, hernia, intussusception, stenosis).

    Large Intestine - Normal Anatomy

    • The large intestine is approximately 1-1.5 meters long.
    • It consists of the following regions: caecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.
    • The superior mesenteric artery supplies blood to the caecum to the splenic flexure.
    • The inferior mesenteric artery supplies blood to the remainder of the colon to the rectum.
    • The haemorrhoidal branches of the internal iliac or internal pudendal artery supply the lower portion of the rectum.

    Normal Histology

    • Mucosa:
      • Contains crypts and surface epithelium.
      • No villi are present.
      • Lamina propria and muscularis mucosa are present.
    • Submucosa: Loose connective tissue containing Meissner's plexus.
    • Muscularis propria: Composed of an inner circular layer, outer longitudinal layer, and the myenteric plexus of Auerbach.
    • Serosa: Mesothelial cells and fibrous tissue, except for the rectum which has perimuscular tissue.

    Types of Mucosal Cells

    • The surface epithelium is covered by columnar absorptive cells.
    • Goblet cells are found in the crypts.
    • Paneth cells are found in the caecum and ascending colon. They contain granules with antimicrobial properties and immune mediators.
    • Endocrine cells produce products that modulate digestive functions.

    Developmental Anomalies

    • Hirschsprung’s Disease:
      • Congenital megacolon affecting 1 in 5000-8000 live births.
      • Male to female ratio is 4:1.
      • It is more common in patients with other anomalies, including 10% of individuals with Down's syndrome.
      • Most commonly involves the rectum and sigmoid colon.

    Pathogenesis of Hirschsprung’s Disease

    • Occurs due to arrested migration of neural crest cells into the bowel wall.
    • This results in an absence of ganglion cells in the muscle wall (Auerbach's plexus) and submucosa (Meissner's plexus).
    • The aganglionic (aperistaltic) narrow segment in the rectum causes functional obstruction and dilatation of the unaffected proximal colon (megacolon).
    • 50% of familial and 15% of sporadic cases have mutations in the RET gene.

    Clinical Features of Hirschsprung’s Disease

    • Failure to pass meconium, constipation, abdominal distension, and vomiting.
    • Complications:
      • Proximal innervated colon may become massively dilated and perforate
      • May lead to enterocolitis
      • 5% mortality rate.
    • Treatment involves resection of the involved bowel.

    Vascular Disorders

    • Ischaemic bowel disease: May affect the small and/or large intestine, and can be acute or chronic.
    • Angiodysplasia: Tortuous dilatations of blood vessels, usually in the caecum and right colon.
    • Hereditary haemorrhagic telangiectasia: Autosomal dominant disorder with thin-walled blood vessels in the mouth and GI tract.
    • Haemorrhoids: Variceal dilatation of submucosal venous plexi around the anus and lower rectum.

    Ischaemic Bowel Disease

    • May affect small, large, or both intestines.
    • Can present acutely or chronically.
    • Severity of injury depends on vessels involved.

    Types of Ischaemic Bowel Injury

    • Transmural infarction: Infarction of all layers of the wall due to sudden occlusion of a major vessel (thrombosis/embolism).
    • Mural infarction: Necrosis of the mucosa and submucosa.
    • Mucosal infarction: Necrosis of the mucosa only.
    • Mural/mucosal infarction: Hypoperfusion (especially in watershed areas).
    • Chronic ischemic bowel disease: Inflammation, ulceration, mucosal atrophy, and fibrosis leading to strictures in some cases.

    Pathogenesis of Ischaemic Bowel Disease

    • Arterial Occlusion:
      • Arterial thrombosis: Atherosclerosis, vasculitis
      • Arterial embolism: Clots, cholesterol, cardiac vegetation's
    • Venous thrombosis: Hypercoagulable states, drugs
    • Non-occlusive ischaemia: Heart failure, shock, drugs
    • Other causes: Radiation, volvulus, strangulation, etc.

    Clinical Features of Ischaemic Bowel Disease

    • Transmural infarction:
      • More common in older individuals.
      • Severe abdominal pain, bloody diarrhoea, decreased peristaltic sounds, rigidity.
      • May perforate leading to peritonitis and sepsis.
      • 90% mortality rate.
    • Mucosal and mural infarction:
      • Nonspecific abdominal complaints.
      • Intermittent bloody diarrhoea.
      • May heal if the lesion is corrected.

    Clinical Features of Ischaemic Bowel Disease (continued)

    • Chronic Ischemic Colitis:
      • Intermittent bloody diarrhoea.
      • Often confused with inflammatory bowel disease.
    • Always consider ischaemic bowel disease in patients with unexplained abdominal pain and/or GI bleeding.

    Angiodysplasia

    • Tortuous dilatations of blood vessels, usually in the caecum and right colon.
    • Often acquired malformed vessels in the mucosa and submucosa.
    • Occurs in elderly individuals.
    • Probably a result of years of mechanical trauma.
    • May cause chronic or acute lower bleeding if they rupture and bleed into the intestinal lumen.
    • Associated with aortic stenosis, scleroderma, end-stage renal disease, and von Willebrand disease.

    Hereditary Haemorrhagic Telangiectasia

    • Autosomal dominant disorder characterized by thin-walled blood vessels in the mouth and GI tract.
    • Can rupture and cause bleeding.

    Haemorrhoids

    • Variceal dilatation of submucosal venous plexi around the anus and lower rectum.
    • A common disorder with predisposing factors:
      • Constipation
      • Venous stasis of pregnancy
      • Portal hypertension
    • Divided into internal (inside the anus) or external (under the skin around the anus).
    • Clinical features:
      • Bright red stool.
      • Painful swelling around the anus with external haemorrhoids (thrombosis).

    Necrotising Enterocolitis

    • Affects neonates.
    • Acute necrotising inflammation of the small and large bowel.
    • Most common in premature infants or low birth weight infants.
    • Occurs anytime within the first three months, usually on days 2-4.
    • Caused by a combination of ischaemia, colonisation by pathogenic organisms, excess protein in the lumen, and functional immaturity of the gut.

    Antibiotic-Associated Colitis (Pseudomembranous Colitis)

    • Acute colitis characterised by an adherent inflammatory exudate (pseudomembrane) composed of mucus, fibrin, and inflammatory debris.
    • Occurs following a course of broad-spectrum antibiotics.
    • Caused by Clostridium difficile which secretes cytotoxins.
    • Clinical presentation is diarrhoea.
    • Diagnosis is made by detecting cytotoxin in the stool.
    • Treatment involves Metronidazole or Vancomycin.

    Idiopathic Inflammatory Bowel Disease

    • Chronic, relapsing inflammatory intestinal disorders of unknown cause.
    • Includes Crohn's disease and ulcerative colitis.
    • Incidence of both Crohn's and ulcerative colitis is rising.
    • Most frequently present in the teens and early 20s, but can develop at any age.
    • Most common among Caucasian and Ashkenazi Jews.

    Pathogenesis of IBD

    • Involves mucosal immunity with polymorphisms in genetic loci that include both proinflammatory and anti-inflammatory genes (e.g., IL-10).
    • Host-microbial interactions play a role.
    • Final pathway is inflammation.
    • Therapy is directed towards immune down-regulation.

    Crohn's Disease (CD)

    • Affects 1-3/100,000 annually.
    • More common in Western populations.
    • More common in females, whites, and Jews.
    • Peak incidence is in the teens and twenties, with a minor peak in the fifties and sixties.

    Gross Features of CD

    • Can affect any portion of the gastrointestinal tract (from mouth to anus).
    • Segmental involvement with "skip lesions."
    • Transmural involvement of the bowel wall:
      • Creeping fat
      • Dull serosa
      • Thickened wall due to oedema, inflammation, and fibrosis
    • Other findings:
      • Strictures/narrow lumen
      • Aphthous mucosal ulcers that coalesce into long, linear serpentine ulcers along the bowel axis.
      • Linear ulcers with oedema of the intervening mucosa giving a "cobblestone" appearance.
      • Fissures.
      • Fistulae or sinus tracts.

    Microscopic Features of CD

    • Chronic mucosal damage with crypt architectural distortion.
    • Mucosal ulceration and fissuring.
    • Inflammation:
      • Transmural
      • Cryptitis: Neutrophils in the wall of the crypt
      • Crypt abscess: Collection of neutrophils within the lumen of the crypt
      • Lymphoid aggregates
      • +/- Non-caseating granulomas
    • Possible dysplasia late in the disease.

    Clinical Features of CD

    • Variable, relapsing and remitting course.
    • Intermittent attacks of diarrhoea, abdominal pain, and fever.
    • Attacks may be precipitated by emotional stress.
    • Occult or overt faecal blood loss leading to anaemia.
    • Malabsorption:
      • Weight loss
      • Hypoalbuminaemia
      • Steatorrhoea (Bile salts)
      • Megaloblastic anaemia (B12)
    • May have extra-intestinal manifestations.
    • Diagnosis is made via small bowel or colon biopsy.

    Complications of CD

    • Obstruction (terminal ileum - secondary to transmural fibrosis/stricture).
    • Adhesions.
    • Fistula formation involving adjacent small bowel, colon, urinary bladder, vagina, and abdominal and perianal skin.
    • Malabsorption with steatorrhoea (secondary to mucosal disease and surgical resection):
      • Generalised malabsorption (B12 and bile salts)
    • Increased risk of carcinoma (slight, especially when compared with UC):
      • Approximately 5-6-fold increase over controls.

    Systemic Manifestations of CD

    • Arthritis (migratory polyarthritis, sacroiliitis, ankylosing spondylitis).
    • Uveitis.
    • Erythema nodosum.
    • Clubbing of finger tips.

    Ulcerative Colitis (UC)

    • Chronic inflammatory disease of the colon, limited to the mucosa and submucosa of the large bowel.
    • Incidence: 4-12/100,000 annually.
    • Affects Caucasians, equal sex predilection.
    • Affects all ages, with peak incidence between 20-25 years old.
    • May also have extra-intestinal manifestations as does Crohn's disease.

    Gross Pathology of UC

    • Usually begins in the rectum and extends proximally in a continuous fashion.
    • May involve the entire colon (pancolitis), without skip areas.
    • Mucosa is red.
    • Large areas of ulceration, confined to mucosa, often extensive and broad-based (not linear).
    • Isolated islands of regenerative mucosa:
      • Inflammatory pseudopolyps.
    • Wall is not thickened.
    • Normal serosa.

    Microscopic Features of UC

    • Inflammation is confined to the mucosa and submucosa.
    • Cryptitis and crypt abscesses.
    • Ulceration.
    • Architectural distortion of the crypts.
    • May show epithelial dysplasia.
    • No granuloma present.

    Clinical Features of UC

    • Relapsing and remitting course.
    • Episodes may be precipitated by stress.
    • Intermittent attacks of bloody mucoid diarrhoea, abdominal pain, and tenesmus.
    • Fever and weight loss.
    • Anaemia (blood loss).
    • Extra-intestinal manifestations are more common in UC than CD.
    • Diagnosis is made via colonoscopy and colonic biopsy.

    Colitis-Associated Neoplasia

    • Risk is related to:
      • Duration: 10 years after onset (20x risk after 10 years).
      • Extent of the disease: Pancolitis > left-sided.
      • Inflammation: Frequency and severity of active inflammation.
    • Surveillance: Regular endoscopy with biopsy.

    Complications of UC

    • Toxic megacolon: Acute dilatation of the colon due to toxic damage to the muscularis propria and neural plexus with shutdown of neuromuscular function.
    • Markedly increased cancer risk related to the extent of colonic involvement and duration of the disease.
    • Preceded by dysplasia:
      • Especially if duration >10 years ( 20x risk after 10 years).
      • Regular endoscopy with biopsy.

    Systemic Manifestations of UC

    • Joint:
      • Migratory polyarthritis
      • Sacroiliitis
      • Ankylosing spondylitis
    • Skin:
      • Erythema nodosum
      • Necrotising skin lesion - pyoderma gangrenosum
      • Clubbing
    • Liver:
      • Primary sclerosing cholangitis
    • Uveitis.

    Diverticular Disease

    • Diverticulum: Blind pouch leading off the alimentary tract, communicating with the lumen.
    • Diverticula in the colon occur at defects in the muscle wall where nerves and vessels penetrate (where vasa recta traverse the muscularis propria).
    • Prevalence of diverticular disease approaches 50% in adults over 60 in Western countries.

    Pathogenesis of Diverticular Disease

    • Related to wall stress:
      • Associated with constipation, straining, and low-fibre diet.
      • Arise in areas where the vasa recta traverse the muscularis propria (focal weakness of the bowel wall).
    • Low-fibre diet leads to decreased stool bulk, increased peristaltic contractions, increased intraluminal pressure, herniation of the bowel wall through points of weakness (where vessels penetrate the muscularis propria), resulting in diverticula.
    • Outpouching of the mucosa and submucosa (pseudo diverticulum).
    • Almost always found in the sigmoid colon.

    Clinical Features of Diverticular Disease

    • Usually asymptomatic.
    • About 20% of cases have cramping or lower abdominal pain.
    • Constipation.
    • Sensation of never being able to empty the rectum completely.
    • Treatment:
      • High-fibre diet (may prevent progression).
      • Surgical intervention for obstructive or inflammatory complications.

    Complications of Diverticulosis

    • Inflammation of the diverticulum (diverticulitis):
      • May be caused by obstruction of the narrow neck of the herniated diverticulum, impaction of faecal material, constriction of the blood supply, and infection.
    • Perforation.
    • Adhesions.
    • Fistula formation (e.g., bladder).
    • Pericolic abscess formation.
    • Inflammatory mass formation.
    • Haemorrhage (rectal bleeding).
    • Obstruction.

    Intestinal Obstruction

    • More common in the small bowel (small lumen).
    • Mechanical:
      • Congenital: Atresia, imperforate anus, etc.
      • Acquired:
        • Volvulus
        • Adhesions
        • Hernia
        • Intussusception
        • Stenosis (e.g., stricture)

    Large Intestine Normal Anatomy

    • The large intestine is approximately 1-1.5 meters in length
    • Divided into caecum, ascending colon, transverse colon, descending colon, sigmoid and rectum
    • Supplied by the superior mesenteric artery (caecum to splenic flexure) and inferior mesenteric artery (remainder of colon to rectum)
    • Haemorrhoidal branches of the internal iliac or internal pudendal artery supply the lower rectum

    Normal Histology

    • Mucosa includes crypts and surface epithelium, no villi
    • Submucosa is loose connective tissue with Meissner's plexus
    • Muscularis propria has an inner circular layer, outer longitudinal layer and myenteric plexus of Auerbach
    • Serosa is composed of mesothelial cells and fibrous tissue, perimuscular tissue in the rectum

    Types Of Mucosal Cells

    • Surface epithelium is covered by columnar absorptive cells
    • Goblet cells are found in crypts
    • Paneth cells are located in the caecum and ascending colon, granules contain antimicrobial properties and immune mediators
    • Endocrine cells produce products that modulate digestive functions

    Developmental Anomalies: Hirschsprung's Disease

    • Also known as congenital megacolon
    • Occurs in 1 in 5000-8000 live births
    • More common in males (M:F = 4:1)
    • More frequent in patients with other anomalies, 10% of patients with Down’s Syndrome have Hirschsprung’s Disease
    • Most commonly involves the rectum and sigmoid

    Pathogenesis of Hirschsprung's Disease

    • Arrest of neural crest cell migration into the bowel wall
    • Absence of ganglion cells in the muscle wall (Auerbach’s plexus) and submucosa (Meissner’s plexus)
    • Aganglionic (aperistaltic) narrow segment in the rectum causes functional obstruction, resulting in dilatation of the unaffected proximal colon (megacolon)
    • 50% of familial cases and 15% of sporadic cases have mutations in the RET gene

    Clinical Features of Hirschsprung's Disease

    • Failure to pass meconium, constipation, abdominal distension, vomiting
    • Possible complications:
      • Massively dilated proximal colon may perforate
      • Enterocolitis
    • 5% mortality rate
    • Treatment involves resection of the involved bowel

    Vascular Disorders

    • Ischaemic bowel disease
    • Angiodysplasia
    • Hereditary haemorrhagic telangiectasia
    • Haemorrhoids

    Ischaemic Bowel Disease

    • Can affect small, large or both intestines
    • Can be acute or chronic
    • Severity depends on the vessels involved
    • Types:
      • Transmural infarction: all layers of the wall due to sudden occlusion of a major vessel
      • Mural infarction: necrosis of the mucosa and submucosa
      • Mucosal infarction: necrosis of the mucosa only
      • Mural/mucosal infarction: hypoperfusion, especially in watershed areas
      • Chronic ischaemic bowel disease: inflammation, ulceration, mucosal atrophy, fibrosis resulting in strictures

    Pathogenesis of Ischaemic Bowel Disease

    • Arterial occlusion:
      • Arterial thrombosis: atherosclerosis, vasculitis
      • Arterial embolism: clots, cholesterol, cardiac vegetations
    • Venous thrombosis: hypercoagulable states, drugs
    • Non-occlusive ischaemia: heart failure, shock, drugs
    • Other causes: radiation, volvulus, strangulation

    Clinical Features of Ischaemic Bowel Disease

    • Transmural infarction:
      • Older individuals
      • Severe abdominal pain, bloody diarrhoea
      • Decreased peristaltic sounds, rigidity
      • May perforate leading to peritonitis and sepsis
      • 90% mortality rate
    • Mucosal and mural infarction:
      • Nonspecific abdominal complaints
      • Intermittent bloody diarrhoea
      • May heal if lesion corrected
    • Chronic ischaemic colitis:
      • Intermittent bloody diarrhoea
      • Often confused with inflammatory bowel disease

    Angiodysplasia

    • Tortuous dilatations of blood vessels, usually in the caecum and right colon
    • Acquired malformed vessels in the mucosa and submucosa
    • Usually in elderly individuals
    • Probably a result of years of mechanical trauma
    • May account for both chronic and acute lower GI blood loss if they rupture
    • Associated with aortic stenosis, scleroderma, end stage renal disease, von Willebrand disease

    Hereditary Haemorrhagic Telangiectasia

    • Autosomal dominant disorder
    • Thin walled blood vessels in the mouth and the GI tract may rupture and bleed

    Haemorrhoids

    • Variceal dilatation of submucosal venous plexi around the anus and lower rectum
    • Common disorder, predisposing factors:
      • Constipation
      • Venous stasis of pregnancy
      • Portal hypertension
    • Internal (inside the anus) or external (under the skin around the anus)
    • Clinical features:
      • Bright red stool
      • Painful swelling around the anus with external haemorrhoids (thrombosis)

    Necrotising Enterocolitis

    • Affects neonates, most common in premature infants or low birth weight infants
    • Acute necrotising inflammation of small and large bowel
    • Occurs any time in the first three months, usually day 2-4
    • Caused by a combination of ischaemia, colonisation by pathogenic organisms, excess protein in lumen and functional immaturity of the gut

    Antibiotic- Associated Colitis (Pseudomembranous Colitis)

    • Acute colitis characterised by an adherent inflammatory exudate (pseudomembrane)
    • Pseudomembrane is composed of mucus, fibrin and inflammatory debris
    • Occurs following a course of broad-spectrum antibiotics
    • Caused by Clostridium difficile which produces cytotoxins
    • Clinical presentation: diarrhoea
    • Diagnosis: detection of cytotoxin in stool
    • Treatment: Metronidazole, Vancomycin

    Idiopathic Inflammatory Bowel Disease

    • Chronic, relapsing inflammatory intestinal disorders of unknown cause
      • Crohn’s disease
      • Ulcerative colitis
    • Incidence of both Crohn’s and ulcerative colitis is rising
    • Most frequent onset in teens and early 20s but can develop at any age
    • Most common among Caucasian and Ashkenazi Jews

    Pathogenesis of Idiopathic Inflammatory Bowel Disease

    • Mucosal immunity: Polymorphism in genetic loci that include both proinflammatory and anti-inflammatory, e.g. IL-10
    • Host-Microbial interactions
    • Final pathway is inflammation
    • Therapy directed towards immune down-regulation

    Crohn's Disease

    • Affects 1-3/100,000 annually
    • More common in western populations
    • More common in females, whites and Jews
    • Peak incidence in teens and twenties with a minor peak in the fifties and sixties

    Gross Features of Crohn's Disease

    • Can affect any portion of the GIT (from mouth to anus)
    • Segmental involvement “skip lesions”
    • Transmural involvement of the bowel wall:
      • Creeping fat
      • Dull serosa
      • Thickened wall due to oedema, inflammation and fibrosis
      • Strictures/narrow lumen
      • Aphthous mucosal ulcers coalescing into long, linear serpentine ulcers along bowel axis
    • Linear ulcers with oedema of the intervening mucosa  a “cobblestone” appearance
      • Fissures
      • Fistulae or sinus tracts

    Microscopic Features of Crohn's Disease

    • Chronic mucosal damage: crypt architectural distortion
    • Mucosal ulceration and fissuring
    • Inflammation:
      • Transmural
      • Cryptitis = neutrophils in the wall of the crypt
      • Crypt abscess = collection of neutrophils within the lumen of the crypt
      • Lymphoid aggregates
      • +/- non caseating granulomas
    • Possible dysplasia late in the disease

    Clinical Features of Crohn's Disease

    • Variable - relapsing and remitting course
    • Intermittent attacks of diarrhoea, abdominal pain and fever
    • Attacks precipitated by emotional stress
    • Occult or overt faecal blood loss anaemia
    • Malabsorption:
      • Weight loss
      • Hypoalbuminaemia
      • Steatorrhoea (Bile salts)
      • Megaloblastic anaemia (B12)
    • May have extra-intestinal manifestations
    • Diagnosis: small bowel or colon biopsy

    Complications of Crohn's Disease

    • Obstruction (terminal ileum-secondary to transmural fibrosis/stricture)
    • Adhesions
    • Fistula formation involving adjacent small bowel, colon, urinary bladder, vagina and abdominal and perianal skin
    • Malabsorption with steatorrhoea (secondary to mucosal disease and surgical resection):
      • Generalised malabsorption (B12 and bile salts)
    • Increased risk of carcinoma (slight, especially when compared with UC)
      • Approximately 5-6-fold increase over controls

    Systemic Manifestations of Crohn's Disease

    • Arthritis (migratory polyarthritis, sacroiliitis, ankylosing spondylitis)
    • Uveitis
    • Erythema nodosum
    • Clubbing of finger tips

    Ulcerative Colitis

    • Chronic inflammatory disease of the colon, limited to the mucosa and submucosa of the large bowel
    • Incidence: 4-12/100,000 annually
    • Affects Caucasians, equal sex predilection
    • Affects all ages; peak incidence between 20-25
    • May also have extra-intestinal manifestations as does Crohn’s

    Gross Pathology of UC

    • Usually begins in the rectum and extends proximally in a continuous fashion
    • May involve the entire colon (pancolitis), without skip areas
    • Mucosa is red
    • Large areas of ulceration, confined to mucosa, often extensive and broad-based (not linear)
    • Isolated islands of regenerative mucosa:
      • Inflammatory pseudopolyps
    • Wall is not thickened
    • Normal serosa

    Microscopic Features of UC

    • Inflammation confined to the mucosa and submucosa
      • Cryptitis and crypt abscesses
      • Ulceration
      • Architectural distortion of the crypts
      • May show epithelial dysplasia

    Clinical Features of UC

    • Relapsing and remitting
    • Episodes may be precipitated by stress
    • Intermittent attacks of bloody mucoid diarrhoea, abdominal pain, tenesmus
    • Fever and weight loss
    • Anaemia (blood loss)
    • Extra-intestinal manifestations are more common in UC than CD
    • Diagnosis: Colonoscopy and colonic bx

    Colitis-Associated Neoplasia

    • Risk is related to:
      • Duration: 10 years after onset (20X risk after 10 years)
      • Extent of the disease: Pan colitis > left-sided
      • Inflammation: Frequency and severity of active inflammation
    • Surveillance: regular endoscopy with biopsy

    Complications of UC

    • Toxic megacolon: acute dilatation of the colon due to toxic damage to muscularis propria and neural plexus with shutdown of neuromuscular function
    • Markedly increased cancer risk related to the extent of colonic involvement and duration of the disease
    • Preceded by dysplasia
      • esp.if duration >10 years (20X risk after 10 years)
      • Regular endoscopy with biopsy

    Systemic Manifestations of UC

    • Joint:
      • Migratory polyarthritis
      • Sacroiliitis
      • Ankylosing spondylitis
    • Skin:
      • Erythema nodosum
      • Necrotising skin lesion- pyoderma gangrenosum
      • Clubbing
    • Liver:
      • Primary sclerosing cholangitis
    • Uveitis

    Diverticular Disease

    • Diverticulum- blind pouch leading off the alimentary tract communicating with the lumen
    • In the colon, there are defects in the muscle wall where nerves and vessels penetrate (where vasa recta travers muscular is propria)
    • Prevalence approaches 50% in adults over 60, in western countries!

    Pathogenesis of Diverticular Disease

    • Related to wall stress:
      • Associated with constipation, straining and low fibre diet
      • Arise in where the vasa recta traverse the muscularis propria (Focal weakness of the bowel wall)
    • Low fibre diet   stool bulk  peristaltic contractions   intraluminal pressure  herniation of the bowel wall through the anatomic points of weakness (where vessels penetrate the muscularis propria)  diverticula
    • Outpouching of the mucosa and submucosa (pseudo diverticulum)
    • Almost always in the sigmoid colon

    Clinical Features of Diverticular Disease

    • Usually asymptomatic
    • In about 20% of cases, patients have cramping or lower abdominal pain
    • Constipation
    • Sensation of never being able to empty the rectum completely
    • Treatment:
      • High fibre diet (may prevent progression)
      • Surgical intervention for obstructive or inflammatory complications

    Complications of Diverticulosis

    • Inflammation of the diverticulum (diverticulitis):
      • May be caused by obstruction of the narrow neck of the herniated diverticulum, impaction of faecal material, constriction of the blood supply and infection
    • Perforation
    • Adhesions
    • Fistula formation (e.g.bladder)
    • Pericolic abscess formation
    • Inflammatory mass formation
    • Haemorrhage- rectal bleeding
    • Obstruction

    Intestinal Obstruction

    • More common in the small bowel (small lumen)
    • Mechanical:
      • Congenital: atresia, imperforate anus, etc.
      • Acquired:
        • Volvulus
        • Adhesions
        • Hernia
        • Intussusception
        • Stenosis: (e.g. strictures due to Crohn’s disease)

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    Explore the anatomy and histology of the large intestine in this comprehensive quiz. Discover key regions and blood supply, along with important histological features such as mucosa and submucosa. Test your knowledge on the structure and function of the large intestine's components.

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