Diseases of the gastrointestinal system. H Awad Lecture 2: small intestine/ part 2 and appendix

Transcription

1 Diseases of the gastrointestinal system H Awad Lecture 2: small intestine/ part 2 and appendix

2 Malabsorption most important causes of malabsorption: Celiac disease tropical sprue Lactase deficiency Whipple disease Cystic fibrosis Infections

3 Tropical sprue = environmental enteropathy it is a malabsorption disease occurring in Africa, South America, Asia.. affects mainly children and presents with stunted growth and malabsorption. Can affect adults who visit tropical areas. it is thought to be due to infection, but no pathogen was linked to the disease histological features exactly similar to celiac disease.

4 Geographic distribution of tropical sprue

5 Lactase deficiency Lactase enzyme is a disaccharidease

6 Remember that disacchridases are present on the brush border Intraluminal Digestion Terminal digestion Transepithelial transport Lymphatic transport

7 Lactase deficiency there are two types of lactase deficiency 1. Congenital deficiency. 2. Acquired deficiency in both types biopsy will normal because the problem is a biochemical one ( lack of an enzyme) so there are no histopathological changes.

8 Congenital lactase deficiency autosomal recessive. very rare disease. caused by a mutation in the lactase gene. due to the deficiency,lactose cannot be digested.. this causes diarrhoea Symptoms start soon after birth because lactose is the main sugar in milk. Note that the word lactose comes from two words: lact meaning milk ( lactation) and ose meaning sugar. Symptoms improve after stoping milk and milk products.

9 Acquired lactase deficiency= lactose intolerance caused by acquired down regulation of lactase gene expression. this occurs after childhood. So patients could drink milk when they were children with no problems, but after childhood they might start having diarrhoea when drinking milk The exact cause of this down regulation is not certain. Sometimes this down regulation occurs after viral infection.

10 Whipple disease rare systematic infection caused bytropheryma whipplei It can affect GI tract, joints, heart, brain, skin GI infection causes malabsorption.

11 Biopsy shows the bacteria, which is highlighted by the PAS stain

12 cystic fibrosis Autosomal recessive disease. caused by defect in a gene called: cystic fibrosis transmembrane conductance regulator ( CFTR) this genetic defect causes abnormal function of epithelial chloride channel protein.

13 Epithelial chloride channel Regulates movement of Cl to outside of the cells. This channel is regulated by the CFTR

14 in the epithelium, there is a Cl channel and also a sodium channel ENaC

15 pathogenesis Normally CFTR allows chlorine to move out of the epithelial cells to the lumen, through the chlorine channel. there is also a sodium channel in the epithelium called epithelium sodium channel (ENaC) these channels regulate movement of CL and Na. in CF there is a defect in Cl channel, so chlorine stays inside the cell because chlorine is negative, to keep charges balanced more Na passes through the Na channel from the epithelium to the lumen. So we have more CL and Na in cells as compared to lumen. So water moves from outside the cell ( from the lumen) to the cells. So there is less water in the lumen mucus in the lumen is thickened because it is dehydrated.

16 Pathogenesis

17 Cystic fibrosis Cystic fibrosis causes defective epithelial transport affecting fluid secretion in exocrine glands and epithelial lining of the respiratory, GI and genitourinary tracts. this results in thick mucoid secretions. these secretions are responsible for the patients symptoms.

18 thick mucus, mainly in respiratory and GI tract

19 Thick mucus in pancreatic ducts make movement of digestive enzymes from pancreatic duct to intestine difficult.

20 cystic fibrosis: thick mucus within glands

21 Diseases of the appendix Acute appendicitis Tumours

22 acute appendicitis

23 Acute appendicitis Occurs mostly in adolescents and young adults. Males affected slightly more than females Clinically patients present with umbilical pain which then localises to the right lower quadrant. the pain is followed by fever, nausea and vomiting

24 Pathogenesis Acute appendicitis is thought to be due to increased intraluminal pressure which presses venous outflow. in many cases there association with luminal obstruction by small stone- like mass of stool called fecalith. the ischemia and stasis cause acute inflammatory reaction.

25 Tumours of the appendix The most common tumour of the appendix is carcinoid tumour. Mostly affects the tip of the appendix. Good prognosis, very rarely metastasise. Incidental finding

26 Carcinoid tumours arise from the neuroendocrine cells. Carcinoid tumours occur anywhere in the GI tract but also in other sites of the body including lungs. they might secrete hormones.

27 Carcinoid : yellow mass at the tip of the appendix

28 Carcinoid

29 THAN