Gastrointestinal Module (Cellular and Systematic Pathology) PDF

🧪 Gastrointestinal Module Cellular and Systematic Pathology Date @October 17, 2024 Lecturer Dr Gillian Gibson Week Week 5-6 DISORDERS OF THE UPPER GI TRACT AND...

🧪 Gastrointestinal Module Cellular and Systematic Pathology Date @October 17, 2024 Lecturer Dr Gillian Gibson Week Week 5-6 DISORDERS OF THE UPPER GI TRACT AND HEPATIC & BILIARY PATHOLOGY Topics covered Oesophagus: Gastro-oesophageal reflux disease (GORD) Stomach: Gastritis and Helicobacter infection Liver (hepato): Jaundice, hepatitis, cirrhosis Gallbladder (Biliary): Gallstones Learning Outcomes You should be able to identify microscopic structures from images provided Relate pathological changes to tissue and cell damage Understand how the pathological changes affect “normal” structure and function Gastrointestinal 1  You should learn the correct terminology to describe pathological changes (Review the “normal” structure and function of the organs discussed as this will not be revised in great detail) Oesophageal disorders Definitions: epithelial erosions ulcerations hyperplasia H&E of normal oesphagus: Gastrointestinal 2  A normal oesophagus would be a uniform colour with no breaches in the tissue and nice continual mucosal folds reaching down towards the pyloric sphincter. Inflammation presents as it does anywhere in the body, the tissue will be red, probably swollen and irregular in shape and appearance; this is due to the influx of white blood cells and the inflammatory processes which are taking place as a result of tissue damage. The tissue has become damaged as a result of the reflux of acidic contents from the stomach (the oesophagus does not have the same protective barriers against the effects of acid as the stomach has). The inflammation may result in very superficial damage to the tissue and this may heal without the need for medical intervention – the clinician would then observe scar tissue. If the inflammation prolongs, the tissue itself may become ulcerated, which simply means that the damage, caused by the acid and the inflammatory response, have breached the mucosal layer of the tissue and is now affecting the underlying structures within the oesophageal wall. A narrowing of the sphincter muscles may also be observed (stricture), which could be due to hyperplasia of mucosal cells or an influx of white blood cells – the definitive nature of the hyperplasia would only be observed by taking a biopsy and staining the tissues. Gastro-oesphageal reflux disease (GORD) What causes GORD? Obesity Consumption of fatty food Smoking, alcohol, coffee, chocolate Pregnancy Hiatal hernia Non-steroidal anti-inflammatory drugs (NSAID’s) Gastrointestinal 3  Everyone gets heartburn from time to time and this is normally a short-lived sensation which can be helped by over the counter medication. However, if symptoms continue and worsen and endoscopic analysis shows some pathology, it may be that the patient is suffering from GORD (GERD) Again, there is no one single causative factor in this condition, a combination of those listed above is often seen. Many of the above are lifestyle choices and the effects of GORD can be minimised/reversed if the causative factor is removed. Obesity is prevalent in developed countries and the underlying cause of many conditions. If you are carrying too much fatty tissue, not only does this impede your physical movement but also has a negative impact on how the muscles contract within the body, i.e. sphincter muscles of the GI tract. Therefore if the sphincter cannot contract and relax as it should, this can mean that it is open for longer period times and combined with the overall posture of the obese patient, this can cause the reflux. Gastrointestinal 4  Ingestion of fatty foods, not only contributes to obesity but the stomach also takes longer to digest a fatty meal, meaning that the stomach is active for longer and producing more acid, which may leak back into the oesophagus. The chemicals in nicotine, alcohol, coffee and chocolate all weaken the sphincter muscle tone and this leads to reflux. The hormones produced during pregnancy are designed to relax the muscles in the body to allow the foetus to grow, this muscle relaxation is non-specific throughout the body, so not only will you find that pregnant women can be clumsy and have a tendency to fall, but also their stomach muscles will weaken, allowing reflux. There is no one definitive cause of hiatal hernia, it seems to be more prevalent in the over 50’s. A hiatal hernia is where part of the stomach moves up into the chest cavity (see the diagram above). This affects the normal physiology of the oesophagus and interferes with the activity and tone of the lower oesophageal sphincter. Where a hiatal hernia is the only cause of GORD, this can be fixed by a surgical procedure, but this is rare. Drugs such as ibuprofen and “high-dose” aspirin belong to a family of drugs known as NSAID’s. Whilst these are commonly used to relieve pain, reduce inflammation and fever, overuse of these can cause damage to the stomach wall, which impairs the normal function, can lead to excess acid production and hence reflux. These drugs are also a primary cause of ulceration in the stomach, which can lead to bleeding and anaemia. DIAGNOSIS Symptoms – if chest pain, rule out cardiac event Endoscopy – to look for pathological changes Hyperaemia - Granular mucosa Reactive thickening of squamous epithelium Irregular greyish/white patches Leukoplakia Mucosal damage Gastrointestinal 5  Erosions & ulcers - vertical linear streaks (eosinophilic oesophagitis – allergic condition) In GORD, there are very generic pathological changes noted when looking through an endoscope, however there may be specific patterns which would allow the clinician to give a more definitive diagnosis. Firstly, where chest pain is noted; rule out a cardiac event. Hyperaemia is a strong indicator of inflammation as blood vessels dilate and blood cells flow to the damaged area to attempt to repair the tissue damage. The effect of the white blood cells and cytokine release leads to the inflammation. There may also be granular mucosa observed and thickening of tissues, indicative of partial healing and formation of scar tissue – this is a good indicator of how long a patient may have been suffering with this condition. The granular tissue can lead to the formation of polyps which is essentially a “clump” of cellular tissue that grows out from the normal mucosal surface and can cause blockages and can be a pre- cancerous indicator. Leukoplakia is a white substance that covers the mucosa, is often seen in the mouth but can extend throughout the GI tract and is also indicative of increased cancer risk. With all of these pathologies, there is a negative effect on structure and function of the oesophagus and this can lead to superficial damage or ulceration and excess bleeding etc. Vertical linear streaks are seen in “eosinophilic oesophagitis” where the patient has an imbalance in their eosinophil cell number but this would also need to be examined using a biopsy to confirm this (this has the same symptoms as GORD). BIOPSY OF TISSUES Gastrointestinal 6  Having detected some irregularities using the endoscope, the clinician would next arrange for biopsies of the tissue to be taken. The above images are all H&E stains (the immune cells are magnified). Panel A shows the normal structure of the oesophagus where you can see the thick mucosa and the underlying lamina propria and muscles. Panel B indicates lengthening of the lamina propria tissues extending into the mucosa, this observation is a common find in GORD and is indicative of the tissue damage and contributes to the disruption to the function of the tissue. Panel C shows the basal cell hyperplasia, where cells (both immune and non-immune) have increased in number, probably as a protective mechanism in the first instance. This hyperplasia becomes problematic when the imbalance of cell types in the tissue leads to abnormal regulation of function. In panel C, it is clear that there is very little “normal” structure to be seen comparing with Panel A. If the hyperplastic cells comprise greater that 70% of the oesophageal tissue, this is indicative of chronic inflammation. The clinician would note these features and together with the patients symptoms and the endoscopy findings, would definitively diagnose GORD. The biopsy also rules out tumour, which presents very differently from this pathology (we will not discuss oesophageal cancer in these lectures). GORD SYMPTOMS Burning pain often after eating or when lying down Regurgitation Difficulty swallowing is known as Gastrointestinal 7  dysphagia Intolerance to certain foodstuffs Much of this is due to altered feedback mechanisms at the pyloric sphincter In the first instance, a patient might present at their GP with any or all of the above symptoms, to different degrees of severity. The patient might feel a slight burning in their chest area, particularly after eating a meal. The more common name for this is heartburn and this is a common condition amongst the population, often remedied by taking antacids such as “Tums”, “Rennies”, “Gaviscon” etc. This becomes more serious if the symptoms prolong and worsen and rather than this just being considered a mild case of heartburn, further investigation would be carried out to determine if there was something more serious. The burning pain can often be accompanied by increased salivation, as the stomach is not clearing material properly, this affects the feedback mechanisms therefore the stomach often anticipates that food is coming when in fact it is not. Gastrointestinal 8  Regurgitation can be an issue as the material passes from the stomach into the oesophagus, it is partially digested and can result in vomiting etc. The patient may feel a difficulty in swallowing, this is often caused by strictures in the sphincter muscles, this is where hyperplasia of cells has occurred and effectively narrows the sphincter opening making it difficult to swallow; sometimes a patient may also experience a choking sensation as a result of this (in very severe cases). Increased belching (burping) may also be a sign that there is something wrong, again this is due to the anticipation of food resulting in increased saliva production and swallowing and hence the taking in of more air. CLASSIFICATION OF GORD Los Angeles Grading - diagnosis generally looks at endoscopy Gastrointestinal 9  Pathological changes are often given some sort of “grading” criteria so the clinician can determine the extent of the condition and treat accordingly. Note here that the LA grading looks at “mucosal breaks” where the mucosal layer is ruptured/ulcerated and to which extent does this extend beyond mucosal folds (remember the normal structure of the oesophagus shows nice even folds as the organ extends down to the stomach). At a glance, however, you can see how distorted the tissue looks The Lyon Consensus this takes into consideration to acid reflux, acid exposure time (AET) and the oesophageal gastric junction (OG-J/EG-J) motor function this works alongside the LA grading system to give a better prognosis and outcome for the patient Typically the following will be noted: >6% AET would indicate GORD Between 40-80 reflux episodes in a 24h period would indicate GORD A manometry examination would measure contractions of the OG-J and hence muscle tone and function As with all conditions, there are always changes/amendments to criteria; the Lyon consensus not only considers the endoscopy diagnosis but now considers the motor function and measurement of acid reflux in a patient. Greater than 6% longer than “normal” acid exposure time would be considered pathogenic and 40-80 episodes of reflux in a day would also show pathology. Diagnosis of this can be carried out using manometry. MANOMETRY Gastrointestinal 10  The image is fairly self-explanatory. Just remember that the Lower oesophageal sphincter (LOS) is under neuronal control and should relax and contract in response to normal physiological processes, i.e when food is digesting in the stomach, it should be closed to prevent backflow. Therefore the manometer, can measure the muscle tone in the LOS and note if there are any abnormal Gastrointestinal 11  behaviours. The abnormal reading shows that the sphincter is relaxing when there is no swallow event, meaning that it is not functioning as it should. TREATMENT Drugs Neutralise acid – antacids, alginic acid (foam) (Gaviscon) Decrease acid production – H2 receptor blocking antagonists (Zantac), proton pump inhibitors (Omeprazole) Lifestyle changes Elevate head (stature) Improves acid clearance Avoid certain foods Fats, onions, chocolate. Decrease sphincter pressure Citrus juice, coffee etc. Irritate oesophagus No food before bedtime Smoking & alcohol. Decrease sphincter pressure and increase acid exposure Mild heartburn can be treated easily using over the counter drugs and occasionally something stronger on prescription, if necessary. The common drugs use a number of different mechanisms to alleviate symptoms. The drugs which neutralise acid, do just that. Most are sodium bicarbonate based and act by simply counteracting the effects of the excess acid. Alginic foam is alginic acid which works with the sodium bicarbonate in the saliva to form an alginic foam. This foam coats the mucosal surfaces and provides a pH neutral barrier against the acid. Drugs which decrease acid production, either work to block the H2 receptors or to actively inhibit proton pumps, thereby limiting the production of acid at source (remember the acid is produced by parietal cells in the stomach). Gastrointestinal 12  In the first instance, the patient would be advised to make lifestyle changes and avoid the foods that are the probable cause of their discomfort. Many of the long term symptoms are caused by the prolonged exposure to the acid and hence tissue damage and loss/change of function. In some cases these effects are non- reversible but would be managed using dietary/drug regimes. SURGERY AND OTHER PROCEDURES Laparoscopic Nissen fundoplication (NF) Endoscopic injection of bulking agents Edoluminal gastroplication Endoscopic augmentation with hydrogel implants Endoscopic radiofrequency ablation Laparoscopic insertion of a magnetic bean band (LINX Surgery is relatively rare for this condition and only offered as a last resort. The LNF procedure is essentially using the stomach to encapsulate the lower part of the oesophagus in order to make the sphincter narrower and prevent it from opening and allowing reflux of acidic material. The other procedures are fairly new and you will find more information on these here; COMPLICATIONS Haemorrhage Fibrosis & stricture Metaplasia of mucosa Barrett’s oesophagus Squamous epithelium replaced by columnar Reparative process stricture formation Short segments or entire lower oesophagus Gastrointestinal 13  With all pathological conditions, there is always the risk of complications and with GORD, this is no different. Excessive bleeding can be fatal if not detected as the blood can accumulate in the chest and abdominal cavities, where perforations have occurred due to acid erosion. Fibrosis and stricture can lead to blockages, occlusion of blood flow which again can be fatal if left untreated. In some cases, the cells can undergo metaplastic changes, where normal oesophageal mucosa (squamous) becomes more columnar in nature (see the diagram above). This occurs at the cardiac sphincter junction and is readily visible on biopsied tissues. This change is indicative of a condition known as Barrett’s oesophagus and is a pre-cancerous condition. Initially, the cells will change in order to replace damaged cells, but since these cells are different in structure and function, this alters the behaviour of the tissue, which can become thickened and fibrotic and lead to further blockage/damage. Gastrointestinal 14  💡 Review the pathology associated with GORD What pathological changes would be noted on an endoscope? What are the common symptoms and relate these to the pathology How is GORD diagnosed? What are the treatment options for GORD and how are they related to correcting the physiological changes noted in this condition? Describe the changes a clinician might see in a biopsy (remember to note the normal structure vs abnormal) Gastritis (Stomach) Inflammation of gastric mucosa No damage to submucosa or muscle layers Acute Gastritis (erosive) Endoscopic Gastritis – hyperaemia, ulcers Neutrophils present Chronic gastritis (non-erosive) Histological Gastritis Neutrophils absent Lymphocytes & Plasma cells (B-cells) present Gastritis is essentially inflammation of the stomach and relates closely to the pathology seen in the oesophagus. In fact, much of what is described has a similar pattern due to the fact that the 4 main base layers that line the intestine are conserved along its length. Note the subtle differences between the terminology. In gastritis, the mucosal layer of the stomach is affected, ulceration does occur Gastrointestinal 15  but is not always present. Gastritis is categorised into 2 different types; acute and chronic. Whilst these can be caused by the same pathogen/tissue damage (injury) etc., acute gastritis normally occurs suddenly and is debilitating over a shorter period of time, where chronic gastritis develops over a longer period and might not be associated with the intense pain and other symptoms seen in the acute type. You may also see these conditions termed as erosive and non-erosive, referring to their gross morphology. In acute gastritis, you would observe an influx of neutrophils, remember that these cells are part of the early innate immune response and can often control an infection without the need for the adaptive response to get involved. In the chronic version, the innate response has largely been and gone and on histological analysis, T & B cells may be more prevalent, indicative of a longer infection. ACUTE GASTRITIS Clinical signs Vague abdominal discomfort Epigastric tenderness Bleeding (sometimes v. serious) Usually heals spontaneously Helped by antacids and other drugs Endoscope Mucosa superficially damaged Mucosal hyperaemia/haemorrhage- haemorrhagic gastritis Widespread May extend deeper Erosion – break in mucosa Ulcers – large lesions with apparent depth Gastrointestinal 16  Accompanied by acute inflammatory response 💡 Regarding acute gastritis, what might the technician see down the scope? Include all these in the answer (stuff above) CHRONIC GATSRITIS Clinical signs Dyspepsia - predominant Nonspecific Some asymptomatic Can be mild to severe Chronic Inflammatory diseases of the stomach: - Type A Autoimmune atrophic gastritis - Type B *Helicobacter Pylori gastritis (Multifocal atrophic gastritis) - Type C caused by irritants such as alcohol or NSAID overuse Endoscopy shows heterogeneous disorders – diagnosis would depend on further tests/biopsy (H.pylori will be covered separately) The term “epigastric” relates to the area surrounding the stomach, the upper abdomen just below the rib cage. The clinician would first ascertain with the patient, a list of clinical symptoms, which can often be confused with GORD in the first instance. The presence of bleeding however, is strongly indicative that there is a powerful immune reaction and widespread ulceration, which would steer the diagnosis towards gastritis. Thereafter, an endoscope investigation would be carried out, this would probably show the oesophagus to be unaffected (ruling out GORD) and upon entering the stomach, the inflammation would be obvious, the presence of ulceration might also be clearly seen. Bleeding can occur and can be fatal in some cases. Gastrointestinal 17  The clinician would then need to determine the cause of the gastritis, whether bacterial, viral, caused by chronic drug/alcohol abuse etc. Look at the endoscopy and note the evidence of inflammation – redness, swelling, engorged vessels etc. you can hypothesise the inflammatory response from your previous knowledge. Review the normal structure of the stomach; there is a diagram in slide 26 for reference. The rugae folds allow the stomach to expand when full and as the stomach contractions are under neuronal control, the loss of rugae can affect how the stomach contracts and relaxes normally. Therefore, abnormal structure leads to abnormal function. Histology Gastrointestinal 18  These H&E stains show disordered mucosa – label the diagram as part of your revision. In the gastritis H&E slide, you see that there is little evidence of normal structure (this slide is a particularly severe case), how might the loss of structure affect the function? Think about the normal structure of thee stomach and which areas produce certain chemicals, enzymes and hormones etc. what would be the effect on the function if these areas could no longer function? The clinician might also observe damage extending into the lamina propria where fibrous tissue is present. Necrosis may also be evident. Although, the inflammation is normally mild, the tissue may heal leaving scarring behind and if the primary cause is not treated, the condition may become chronic. Autoimmune atrophic gastritis (type A) Autoimmune-mediated destruction of parietal cells (antibody mediated) Affects fundus & body (corpus) Decreased Acid & pepsin production Reduced production of intrinsic factor Malabsorption of Vit B12 leads to pernicious anaemia - common + 70% patients - Ab to intrinsic factor 50% Ab to intrinsic factor-Vit12 complex Elevated pH - increased risk of infection Reduced feedback to G-cells - Hyperplasia of G cells & hypergastrinemia Gastrointestinal 19  As the name suggests, this is an autoimmune condition and involves the production of antibodies against parietal cells (what do parietal cells do?). This type of gastritis is found in the fundus/body of the stomach and is categorised by a decrease in acid and pepsin production – think about what parietal cells do normally and hypothesise the effect of their destruction. As a consequence, there is also a reduction in the production of intrinsic factor, which is a vital glycoprotein needed for the absorption of vitamin b12. A loss of vitamin b12 in the body leads to a condition known as pernicious anaemia. In addition to the antibodies produced against the parietal cells themselves, approx.. 70% of patients have Ab’s against intrinsic factor itself and about 50% of patients have Ab’s against the intrinsic factor-vitb12 complex. Since the parietal cells are acid-producing cells, a decrease in acid production will cause the pH of the stomach to rise and this could lead to further infection; most pathogens are not able to withstand the acidity in the stomach but these can become opportunistic where that defence is reduced. The production of gastrin from G-cells is also dependant on regulation from acid secretion so therefore an imbalance here could lead to hyperplasia of G cells and a surge of gastrin; gastrin plays a role in the digestive processes and can be an antimicrobial agent- but in increased amounts, this can be problematic Gastrointestinal 20  and can be a pre-cancerous marker. The images above (a) shows a loss of the normal glands that you might expect to see in the stomach lining. These glands are the long tube-like, cell-lined structures indicated by the red arrow and are normally uniformly present in the mucosa. The H&E stain also shows a collection of smaller gland-like structures at the bottom of the image, red oval, which the clinician would observe as abnormal morphology and ask for further investigation. The clinician would ask for an immunohistochemical analysis of the cells present and, as one of the key indicative factors in this condition is endocrine cell hyperplasia, staining for an endocrine cell-marker, such as chromogranin-A would be a stronger diagnostic tool. Diagram for information Multifocal atrophic gastritis (associated with type B) Unknown cause but 75% of cases associated with H.pylori infection More common than autoimmune variety - x4 Gastrointestinal 21  Found in antrum & adjacent areas of stomach body Not autoimmune Often associated with decreased HCl - hypochlorhydria End stage of chronic gastritis Age & geographic distribution similar to gastric cancer suggesting is might be a precursor of gastric tumour – metaplasia can occur As previously stated, this is a coverall term for gastritis conditions that cannot be attributed to types A but may be associated with B, therefore this is categorised as the most common type of atrophic gastritis. The presentation of features does differ from the autoimmune type; pathology found in different anatomical areas, no evidence of antibody involvement. Like the autoimmune type, a loss of HCL is noted but where total loss would be seen in the autoimmune type, some HCL can still be detected in the multifocal gastritis. With this condition, it is often thought to be a precursor to developing gastric cancers as the age and geographical distribution are similar. We will not discuss gastric cancer in these lectures. Atrophy Gastrointestinal 22  Note the word “atrophic” in these conditions. The above shows a normal H&E on the left and a section showing ‘atrophied’ glands on the right (thin atrophic mucosa). NSAID gastritis (type C) - how do these drugs cause gastritis? Non-steroidal anti-inflammatory drugs are used to combat inflammatory responses, alleviate pain and modify vasoactivity. The arachidonic pathway is common to all tissues in the body and regulates inflammation and haemostasis. In the stomach, the AA pathway causes decreased acid secretion and increased mucus and bicarbonate production (black arrows), these are effectively protective Gastrointestinal 23  measures to ensure against excess acid production and hence, tissue damage. NSIAD’s such as aspirin, inhibit the COX enzyme and as a result elicit the opposite effect in terms of the acid, mucus and bicarbonate. Therefore overuse of these drugs can lead to excess avid production, prolonged acid exposure and hence tissue damage. The endoscopy image shows the classic effects on the stomach caused by overuse of NSAID’s. The black lesions on the surface of the tissue are “haematin”, which is a breakdown product from blood cells and this accumulates in these tissues. This can become a chronic condition if the causative factor is not removed. Gastrointestinal 24 Gastrointestinal 25  💡 Review the normal structure and function of the stomach – which cells produce acid? Which cells produce pepsin etc. Compare and contrast acute and chronic gastritis – remember to include pathological and histopathological changes in your answer What mechanism of action leads to NSAID gastritis? Outline the pathology seen in Autoimmune Atrophic gastritis – for additional info, you could include something of your knowledge of the immune system/inflammatory response Outline the pathology seen in Multifocal Atrophic gastritis Helicobacter pylori gastritis (antral type B) Inflammation in antrum (mucus and gastrin producing region) Infection with H. Pylori Gram -ve bacterium Found on epithelial surface Not all have gastritis symptoms or inflammation Evidence for H. Pylori? Bacterium + Ab’s invariably found in sufferers Infect humans → gastritis Eradication resolves gastritis Bacterium found in areas of chronic gastritis Absent from uninvolved areas Gastrointestinal 26  Type B gastritis is associated with a bacterial infection caused by the gram –ve bacteria, Helicobacter pylori. This bacteria colonises in the antrum of the stomach and not all those who have it display symptoms or inflammation; it is suggested that a large % of the population may play host to this bacteria without every developing symptoms. In patients who are symptomatic, blood tests will show antibodies present to the bacteria and histological analysis of tissue slides will show bacterial presence in the tissues. This is one of the primary causes of chronic gastritis, however it is treatable and once treated, re-infection will only occur if re-exposure to the bacteria occurs. On histological analysis, where the bacteria colonises, there is evidence of tissue destruction and inflammation, but in areas where the bacteria is absent, tissues appear normal. The bacteria colonise the lower part of the stomach (antrum) and initially cause an inflammatory response at the mucosa. The bacteria produce acid-neutralising chemicals in order to allow them to survive the harsh environment and can use their flagella, together with enzymes, to penetrate the mucous barrier. Immune cells and inflammatory mediators are transported to the site of infection and effectively cause the painful symptoms associated with this infection. Prolonged infection can lead to ulceration and when severe, these may bleed leading to severe haemorrhage. The key reaction which leads to bacterial survival is shown in panel 2. The bacteria produce the enzyme, urease, which converts urea found Gastrointestinal 27  in secretions into acid-neutralising ammonia. The bacteria effectively destroy the mucus layer, allowing acid etc. to come into contact with the epithelial cells and this causes an inflammatory response and hence tissue damage. PATHOGENESIS The above slide outlines the immune response and shows the effect elicited by the toxins produced. NF-κB and AP-1 are transcription factors produced in response to the bacterial infection and these induce a pro-inflammatory response. The bacteria also produce toxins, CagA and VacA, which contribute to the destruction of cells and induce chemotactic events. In terms of the immunology shown in the diagram, use your previous knowledge to explain the role of the cells and cytokines. Note the areas highlighted in the red ovals; the enzyme arginase and the VacA toxin interfere with the production of Nitric oxide from macrophages and IL-2 from T-cells. The bacteria are using these as virulence factors to promote their own survival. HISTOLOGY Presence of H. Pylori on surface mucus Gastrointestinal 28  Inflammation in lamina propria No damage to submucosa or muscles Can lead to atrophy & intestinal metaplasia Linked to cancer Tissue damage in H. Pylori infection is usually limited to the mucosal layer only. An H&E (not shown) may show the presence of bacteria but is not always the most definitive way to diagnose. The above image shows an immunohistochemistry slide, stained with a polyclonal Ab against H.pylori. The black arrows indicate positive staining (brown colour) and therefore the presence of the bacteria. Gastrointestinal 29  There is a link to cancer development with this bacteria, as described previously for gastritis, the stomach cells can undergo metaplastic changes, start to resemble intestinal tissues, become dysplastic and hence form tumours. SYMPTOMS + TREATMENT Symptoms Often do not correlate with severity of disease Anorexia Nausea & Vomiting Food intolerance Epigastric pain Gastric bleeding sometimes only clinical sign Treatment Drugs Diet Omit caffeine, spices, alcohol, & cigarettes The symptoms do not necessarily correlate with disease severity, i.e. Patients may feel little pain/discomfort despite carrying a heavy bacterial load and vice versa. Symptoms include, anorexia which in this context simply means loss of appetite, nausea and vomiting. Food intolerance is often associated with particular foods; spicy foods, fatty foods, high salt/sugar etc. Epigastric pain may also be experienced where pain is felt in the upper abdominal cavity and extending into the thoracic cavity. Blood may be noticed in the sputum or in the faeces and this may be the 1st indication that there are any problems. Symptoms may not have presented as sufficiently severe as to take the patient to their GP and when bleeding starts, in advanced infection, the gastric ulcer is found. Treatment is successful with drugs which effectively rid the body of the bacteria although environmental, genetic and lifestyle factors may allow colonisation again. Patients will always be advised to omit the foods etc. from their diet which they know to be contributory factors to the discomfort. Gastrointestinal 30  DIAGNOSIS There are a few ways in which this bacteria is detected, without the need for an invasive biopsy. The urea breath test involves the patient ingesting a solution of radiolabelled urea, once inside the stomach the urea reacts with the urease produced by the bacteria to produce ammonia and carbon dioxide, the amount of exhaled CO2 is measured and if in excess of normal levels, it is most likely the patient has H.pylori. An ELISA sandwich assay can also be used with patient samples (blood or stool), to detect the presence of antigen. The rapid faecal test works in a similar way to a pregnancy test, the sample is applied to the test area and as this migrates through the cassette, if antigen is detected, a positive reaction will show in the test window. TREATMENT Neutralise acid antacids Prevent acid secretion Gastrointestinal 31  H2 receptor antagonists (cimetidine, ranitidine) Proton pump inhibitors (omeprazole) Promote healing (cytoprotectants) (sucralfate) Bismuth compounds increase mucus & prostaglandins can kill H.pylori There are a variety of treatments used to manage the symptoms experienced by H.pylori sufferers. Classically, if heartburn is present, ingestion of over-the- counter antacids can temporarily relive this. Similarly, drugs which prevent the release of HCL can offer relief (I’ve included some brand names if you want to look in the these further – self learning). Compound such as sucralfate mimic the protective barrier in the stomach, can be longer lasting and provide a +ve charge to neutralise acid – these also allow the underlying tissues some respite from the acid erosion and can promote healing. Bismuth compounds, such as “Pepto- bismol” neutralize acids but can also increase the production of mucus and prostaglandins and have been shown to have a depletory effect on the bacteria itself. TRIPLE-HERAPY REGIMEN Proton pump inhibitor + amoxicillin and either clarithromycin metronidazole OR taken for 7 days If symptoms still persist administer alternative either clarithromycin OR metronidazole (whichever wasn’t used before) taken for a further 7 days If symptoms still persist – review medication strategy THIS IS NORMALLY A CURATIVE APPROACH Gastrointestinal 32  💡 Outline the immune response to H.pylori infection What mechanisms do H.pylori use to infect and survive in stomach tissue? Describe the ways in which H.pylori is diagnosed Describe how H.pylori is treated Liver Review the normal structure and function of liver from previous lectures. The liver has a rich blood supply coming from the hepatic artery and from the GI tract via the hepatic portal vein. The blood from the intestines is nutrient-rich, as the liver is responsible for some metabolic pathways, however, given the nature of the intestinal flow, there may also be pathogens present which can infect the liver and lead to liver damage. If the liver is unable to carry out its normal functions, this can have catastrophic effects for the body. This liver is responsible for the production of bile and stores this in the gall bladder. The gall bladder releases bile into the duodenum which acts to neutralise acid coming in from the stomach and also plays a role in digestion. Gastrointestinal 33  The liver carries out a number of key functions in the body and is essential for your survival. It’s important to note the functions of the liver in terms of being able to describe what effects pathogenic changes would have on liver function. Since the liver derives a blood supply from the gut, it is under constant threat from micro-organisms and also potential overdose of medication. The liver itself has a large capacity for carrying out its functions, on average only about 10% of the liver capacity is used. The liver has excellent regeneration capacity and can overcome damage quite readily, where the damaging factor is removed. One of the key things that the liver does is metabolises bilirubin, a breakdown product from the metabolism of red blood cells. This pathway is one of the first things to be affected when the liver stops to function normally and is a key indicator of liver failure. The liver will fail where the regenerative capacity is overwhelmed and the ability to produce new hepatocytes declines. Unfortunately, the presentation of jaundice might be the first sign that the liver is non-functional and hence, damage may be too far advanced to repair. Bilirubin conjugation Gastrointestinal 34  In order to be excreted, bilirubin needs to be conjugated to make it more water soluble. When red blood cells expire, they are taken up by macrophages, phagocytosed and broken down into component parts for recycling or excretion. Bilirubin is a by-product from haem and in its unconjugated form, is insoluble. This makes it very difficult to get rid of through the normal excretory pathways (faeces & urine), therefore once the unconjugated bilirubin reaches the liver it is conjugated to glucuronic acid, which makes it more water soluble and transported through the bile and into the intestine. The conjugated bilirubin is then excreted in the faeces (90%) with a small proportion being recirculated, as urobilinogen and eventually excreted in the urine. This pathway is absolutely necessary to maintain good health and where the liver function is depleted, this pathway will not be carried out to full capacity and will result in jaundice. Jaundice is a very visible sign that something is wrong with the liver. Gastrointestinal 35  Jaundice / Icterus Normal bilirubin levels in blood - 5 – 12 µmol/l >40 µmol/l → hyperbilirubinemia yellow/brown skin and eye Almost always present in liver failure Often with pain - biliary colic Jaundice or Icterus (as it is medically termed) occurs when the levels of bilirubin in the blood exceed the normal reference range, excess bilirubin accumulation is called hyperbilirubinaemia. This condition becomes noticeable in patients as the skin and eyeball become yellow due to the accumulation of bilirubin in tissues as the liver is unable to carry out the function of conjugation due to liver failure. There is often an associated pain with liver failure in the upper right portion of the abdomen, near the gall bladder – this is referred to as biliary colic. There are 3 stages of jaundice, pre-, intra-, and post- hepatic. TYPES OF JAUNDICE Gastrointestinal 36  The normal process of red blood cell removal is shown on the left of the table. In jaundice, this process can be affected in a number of ways and these are categorised into 3 specific types:- Prehepatic jaundice can occur where there has been over-activity of the immune response or the transfusion of the wrong blood type (although this is rare). Nominally any process that results in excessive heamolysis can lead to preheaptic jaundice. As a result of the increase in red blood cell waste, the liver can become overwhelmed and therefore fail to conjugate all the bilirubin. The bilirubin then accumulates in the blood, is transported to tissues and leads to the yellowing skin/eyes noted in sufferers. Prehepatic jaundice in newborns can lead to brain damage as the toxic bilirubin can cross the blood-brain-barrier, this is a condition known as kernicterus (this is very rare as newborn jaundice is relatively easy to manage). In intrahepatic jaundice, the haemolysis of RBC’s occurs at a normal rate, this form of jaundice is mainly caused by hepatocyte malfunction. This means that the liver is unable to conjugate the bilirubin and again this can accumulate. The liver cells can be damaged due to infection (viral hepaptitis), tumours, drug overuse, build Gastrointestinal 37  up of toxins etc. This is the most common form of jaundice and both conjugated and unconjugated bilirubin will be present in increased levels in the blood. Posthepatic jaundice again has normal levels of RBC recycled waste and the liver is generally able to process the bilirubin as normal. The problem comes after the liver has processed the bilirubin (hence “post” hepatic) and the conjugated bilirubin gets stopped along its path perhaps by a blockage, caused by obstruction of the bile duct, gallstones, blockage by tumour, damage caused by infection or toxin – there are any number of causes but this would occur after the liver has carried out its normal function. Note along the bottom of the table that these conditions can also be identified by stool colour, although this is not a definitive diagnosis. Hepatitis Inflammation in the liver Cause? autoimmune disorders viral infections toxic drug reactions infectious disorders Hepatitis is a coverall term which simply means “inflammation of the liver”, there are many things which can trigger this inflammation, as listed above. We will focus on viral hepatitis over the next couple of slides. VIRAL HEPATITIS Gastrointestinal 38  This table is just a brief overview of the different ‘types’ of hepatitis. The table compares and contrasts these types. Note that the condition can be chronic or acute and some will resolve without any medical intervention. The incubation period (IP) varies too. Note with HepD that this is only seen in patients who already have HepB infection and can convert the milder version of HepB into a more serious condition. Diagnosis is based on either detection on antibody in blood, detection of surface protein (tissue slide using immunohistochemistry) or detection of viral RNA using molecular assays. IMMUNOHISTOCHEMICAL DIAGNOSIS The above slide shows a liver sections stained for different hepatitis B viral markers (the markers are not important), by identifying specific proteins associated with each of the viruses, antibodies can be produced to detect these and hence provide a diagnosis. Note that these markers give a different distribution patter and may offer a differential diagnosis within a particular strain. The brown colour indicates a positive reaction. ACUTE HEPATITIS Gastrointestinal 39  The 3 phases of acute hepatitis are; (1) prodromal – can be similar to flu-like symptoms, therefore often misdiagnosed in the early stages. (2) the icterus phase is where the liver damage presents and jaundice can be visible. (3) convalescent period where symptoms begin to resolve. “Acute” is used to define infection that lasts from 0-6 months. Hepatitis A virus is the only one which causes a truly acute infection. CHRONIC HEPATITIS Inflammation > 6 months HBV, HCV, HDV, HEV Autoimmune Drug-induced Chronic Viral Hepatitis Main cause of chronic liver disease, cirrhosis, & hepatocellular cancer Chief reason for liver transplantation Symptoms variable Fatigue, malaise, occasional jaundice No simple effective treatment Interferons Gastrointestinal 40  Chronic hepatitis is an extended period of infection (6 months +) and inflammation which is associated with HepB, C, D & E infection. Chronic hepatitis can also be caused by specific autoimmune conditions or by the prolonged overuse of drugs or alcohol. Viral hepatitis is the most common cause of chronic liver disease and is a potential precursor to liver cancer. Anti-viral treatments have limited effectiveness, the treatment of choice would involve interferons such as IFN-α – use your knowledge of this to add more information in regards to how this might work. CIRRHOSIS Liver’s regenerative capacity overwhelmed Damaged tissue replaced by fibrous tissue Isolates “healthy” hepatocytes - nodules Nodules readily observable on surface Nodularity and fibrosis - cirrhosis Result of Hepatitis, Chronic alcohol abuse Toxic drug reaction Variable symptoms Jaundice, wasting, weakness, anorexia Often unnoticed until very advanced Cirrhosis can not be caused by a singular disease but rather is a manifestation of various conditions contributing to chronic liver disease, i.e. Chronic alcohol abuse, viral and non-viral hepatitis, toxic poisoning. The hepatic architecture is affected by a combined effect of fibrosis and appearance of nodules. Nodules arise where healthy liver cells are targeted within lobules and hence where fibrosis occurs, lobule-wide, nodules form. This is a very noticeable pathology and is shown on the next slide. Symptoms are described as above and it should be noted that Gastrointestinal 41  these symptoms can take time to appear as the liver’s regenerative capacity requires to be overwhelmed before the pathological processes can predominate. Note the “nodular” appearance on the cirrhotic liver HISTOLOGICAL ANALYSIS (H&E STAIN) The image on the left shows the normal liver histology showing the clear presence of a liver lobule and the blood vessels and ducts visible. On the right is an image showing a biopsy from a cirrhotic liver, with fibrotic tissue outlined in red. There is no clear definition of structures in this section although some of the vessels are still present (green arrow) Portal hypertension A consequence of liver failure / damage Increase BP in portal system Gastrointestinal 42  Result of decrease venous drainage regenerating tissue and nodule formation increased arterial loading flow through hepatic artery increased vascular congestion Blood by-passes congested liver decrease oxygen decrease conversion of NH3 Decrease Detoxification Collateral channels between portal & systemic veins Ascites Fluid in abdomen Late stage cirrhosis Splenomegaly Enlargement of the spleen Shunting of blood into splenic vein Portal hypertension is a consequence of liver failure. It is characterised by an increase in sustained portal vein pressure (above 12mmHg). In the normal circulation blood travelling from abdominal cavity to the heart accumulates in the portal vein and then travels through the liver before it arrives at the vena cava. Where portal hypertension occurs, there is an increase in blood pressure in the portal system as a result of decreased venous drainage, increased arterial loading and increased flow of blood through the hepatic artery. The blood vessels therefore become congested leading to this increase in blood pressure. As a consequence blood by-passes the liver as it appears congested and hence, there is a decrease of oxygen in the liver, decreased NH3 conversion and a reduction in detox functions, hence the liver can become damaged by toxins and tissue Gastrointestinal 43  necrotic as a result of low oxygen. Collateral channels may open up to allow blood to pass between the portal and systemic systems. Biliary system Bile is produced in liver and stored gall bladder 1L of bile/day (pH 7.6 - 8.6) Water Bile salts - fat emulsification Bile pigments - bilirubin As described in the liver slides, one of the key roles carried out by the liver is the production of bile, which is then stored in the gall bladder prior to release into the duodenum. The liver produces approx. 1L of bile per day. Bile is comprised mainly of water but does contain some other substances as listed above. Many of these are required to aid in the digestion process and in particular the digestion of fats. Bilirubin is also a component of the bile. Bile is released into the common bile duct and there is controlled release to the duodenum via the Sphincter of Oddi (red cross). Bile salts emulsify fats and are subsequently reabsorbed into the small intestine for recycling. Cholelithiasis Gallstone formation Idiopathic Gastrointestinal 44  Found in 15% of adults. Increasing occurrence with age Peak occurrence seen in obese females >40 yr Form when bile components precipitate Cholesterol: 80-90% Calcium bilirubinate Result of: Abnormalities in bile Stasis of bile Inflammation in gallbladder Gastrointestinal 45  Cholelithiasis is the medical term for gallstones. Gallstones form in the gall bladder and are often idiopathic, meaning that gallstones form spontaneously and the cause of their development is largely unknown. However, it is suggested that bile stasis, abnormalities of inflammation can lead to gallstone development. Gallstones may accumulate in the gall bladder and remain there, but they do have a tendency to move into the duct and cause blockages (see post-hepatic jaundice). Gallstones are relatively common, occurring in a bout 15% of the adult population and are found largely in obese females over 40. The bile components precipitate and calcify becoming hard lumps. Gastrointestinal 46  Gallstone formation can result in there being a very large amount of gallstones present and this would obviously result in some discomfort to the patient. The H&E slide shows the normal morphology of the gallbladder. Most asymptomatic When stone blocks bile duct - cholestasis Immediate pain - biliary colic Obstructive jaundice if obstruction remains Inflammation in gall bladder & ducts Necrosis & rupture Cholecystitis Inflammation often result of cholelithiasis Result of : Irritation by bile + mucosal swelling + ischaemia Pain - initiated by fatty meal May lead to perforation or gangrenous gallbladder Usual therapy is surgical removal Laporoscopic cholecystectomy Removal doesn’t interfere with digestion Gastrointestinal 47  Gall bladder stores & concentrates bile Most patients who suffer with gallstones do not display any symptoms. It is primarily when the gallstones cause a blockage that symptoms are experienced. When stones block the bile duct cholestasis forms where bile is unable to flow as it should. This causes pain, biliary colic, which is an intermittent pain normally experienced in the upper right of the abdominal cavity. Jaundice may appear and also inflammation. Prolonged blockage may lead to necrosis and rupture of the bile duct and hence passage of bile into the surrounding tissues. Cholecystitis often occurs as a result of gall stone formation, this is an inflammation of the gall bladder. Immune cells contribute to the pathology i.e. Mucosal swelling. Bile exacerbates the condition due to its abrasive nature and ischaemia can also result. As bile is required and hence produced in response to ingestion of food, pain is experienced after eating and is particularly bad after ingestion of high fat foods. Complications can include perforation or gangrene. The gallbladder can be removed using laparoscopic surgery and a patient who had their gallbladder removed can still digest foods, since the gallbladder is simply a storage vehicle and doesn’t affect the production of bile. 💡 Outline the normal functions of the liver Describe the bilirubin pathway and outline how liver failure can lead to jaundice What are the different types of jaundice? Compare and contrast the different types of viral hepatitis Describe the pathology seen in a cirrhotic liver What is portal hypertension and why might it occur? Define these terms: cholelithiasis, cholecystitis, cholestasis Gastrointestinal 48