Diarrhoea Tutor Handbook PDF 2017/2018

TUTOR'S HANDBOOK INTEGRATED LEARNING ACTIVITY (ILA) FOUNDATION OF MEDICAL SCIENCES 1 MODULE CASE SCENARIO: DIARRHOEA UNIVERSITI KUALA LUMPUR –ROYAL COLLEGE OF MEDICINE PERAK YEAR 1 MBBS PROGRAMME SESSION 2017/2018 ...

TUTOR'S HANDBOOK INTEGRATED LEARNING ACTIVITY (ILA) FOUNDATION OF MEDICAL SCIENCES 1 MODULE CASE SCENARIO: DIARRHOEA UNIVERSITI KUALA LUMPUR –ROYAL COLLEGE OF MEDICINE PERAK YEAR 1 MBBS PROGRAMME SESSION 2017/2018  CASE SCENARIO: DIARRHOEA A 23-year-old female presented to the Accident and Emergency Department with history of frequent loose stools with few episodes of vomiting. She said she felt very thirsty and was passing less urine than usual. The symptoms started a day after consumption of food from a night market stall. On physical examination, she was found to be dehydrated. She was admitted with the clinical diagnosis of acute gastroenteritis with severe dehydration. She was given intravenous fluids and oral rehydration solution. LEARNING OBJECTIVES: By the end of the ILA sessions, the students should be able to: 1. Define diarrhoea (normal frequency of defecation), and state the different types of diarrhoea. 2. Describe the mechanism of defecation 3. Describe the different parts of the gastrointestinal tract 4. Describe the type and functions of the mucosal lining of each part of the gastrointestinal tract. 5. Describe body fluid compartments and its constituents. 6. Describe the transport of molecules across membranes. 7. Describe the etiological agents of infective diarrhoea. 8. Discuss the clinical and laboratory diagnosis of infective diarrhoea. 9. State the composition and function of intravenous and oral rehydration solutions and indication of their uses. 10. Discuss the prevention, control and epidemiology of diarrhoea. Diarrhoeal disease Key facts  Diarrhoeal disease is the second leading cause of death in children under five years old. It is both preventable and treatable.  Each year diarrhoea kills around 760 000 children under five.  A significant proportion of diarrhoeal disease can be prevented through safe drinking-water and adequate sanitation and hygiene.  Globally, there are nearly 1.7 billion cases of diarrhoeal disease every year.  Diarrhoea is a leading cause of malnutrition in children under five years old. Diarrhoeal disease is the second leading cause of death in children under five years old, and is responsible for killing around 760 000 children every year. Diarrhoea can last several days, and can leave the body without the water and salts that are necessary for survival. Most people who die from diarrhoea actually die from severe dehydration and fluid loss. Children who are malnourished or have impaired immunity as well as people living with HIV are most at risk of life-threatening diarrhoea. Diarrhoea is defined as the passage of three or more loose or liquid stools per day (or more frequent passage than is normal for the individual). Frequent passing of formed stools is not diarrhoea, nor is the passing of loose, "pasty" stools by breastfed babies. Diarrhoea is usually a symptom of an infection in the intestinal tract, which can be caused by a variety of bacterial, viral and parasitic organisms. Infection is spread through contaminated food or drinking-water, or from person-to-person as a result of poor hygiene. Interventions to prevent diarrhoea, including safe drinking-water, use of improved sanitation and hand washing with soap can reduce disease risk. Diarrhoea can be treated with a solution of clean water, sugar and salt, and with zinc tablets. There are three clinical types of diarrhoea:  acute watery diarrhoea – lasts several hours or days, and includes cholera;  acute bloody diarrhoea – also called dysentery; and  persistent diarrhoea – lasts 14 days or longer. Scope of diarrhoeal disease Diarrhoeal disease is a leading cause of child mortality and morbidity in the world, and mostly results from contaminated food and water sources. Worldwide, 780 million individuals lack access to improved drinking-water and 2.5 billion lack improved sanitation. Diarrhoea due to infection is widespread throughout developing countries. In developing countries, children under three years old experience on average three episodes of diarrhoea every year. Each episode deprives the child of the nutrition necessary for growth. As a result, diarrhoea is a major cause of malnutrition, and malnourished children are more likely to fall ill from diarrhoea. Dehydration The most severe threat posed by diarrhoea is dehydration. During a diarrhoeal episode, water and electrolytes (sodium, chloride, potassium and bicarbonate) are lost through liquid stools, vomit, sweat, urine and breathing. Dehydration occurs when these losses are not replaced. The degree of dehydration is rated on a scale of three.  Early dehydration – no signs or symptoms.  Moderate dehydration: o thirst o restless or irritable behaviour o decreased skin elasticity o sunken eyes  Severe dehydration: o symptoms become more severe o shock, with diminished consciousness, lack of urine output, cool, moist extremities, a rapid and feeble pulse, low or undetectable blood pressure, and pale skin. Death can follow severe dehydration if body fluids and electrolytes are not replenished, either through the use of oral rehydration salts (ORS) solution, or through an intravenous drip. Describe the mechanism of defecation Description This section is from the book "A Manual Of Physiology", by Gerald F. Yeo. Also available from Amazon: Manual Of Physiology. Mechanism of Defecation This is a point of much importance, for the evacuation of the lower bowel is intimately connected with feelings of comfort and health, and in illness the insuring of its accomplishment forms an essential part of the physician's duty. The movements of the intestine cause the various excretions and indigestible parts of the food to pass toward the sigmoid flexure of the colon, where their onward motion is checked for a time by the strong circular muscle of the rectum (called the superior, or tertius sphincter by Hyrtl), which does not carry on the peristaltic wave. The materials here get packed into a more or less solid mass, which is gradually augmented after each meal. The lower outlet of the alimentary canal is closed by two distinct sphincter muscles. One thin external superficial muscle, made up of striated fibres, belongs to the perineal group, and has little influence on the closure of the anus. The deep or internal sphincter, which is much stronger, surrounds the gut for rather more than an inch (3 centimetres, Henle) in height, and is one-quarter inch thick. It is made of smooth muscle, and therefore capable of prolonged (tonic) contraction. It would appear, however, that- this strong sphincter is merely a supernumerary guard to the anal orifice, but rarely called into action, for during the interval of rest between the acts of defecation, the faeces do not come in contact with the portion of intestine surrounded by this muscle. The rectum for quite one inch above the sphincter is perfectly empty, being kept free from feculent particles partly by a fold of the intestinal wall and partly by the repeated action of the voluntary muscles in the neighborhood, which, by intensifying the angle that exists at this point and flattening this inch of rectum, can squeeze back the approaching matters. Anyone familiar with the digital examination of the unevacuated rectum, knows that no faeces are met with for about two inches. Considerable accumulation may take place in the sigmoid flexure without much discomfort ensuing, but when the rectum is distended, an urgent sensation of wanting to empty it is experienced, and the voluntary movements mentioned above are performed by the levator ani and the neighboring perineal muscles, with the object of preventing any substance reaching the part of the rectum immediately above the sphincter. If the rectum be distended with fluid, the occasional anal elevation does not suffice to keep it back, and a continuous and combined action of the sphincters and levator ani, etc., is necessary to ward off the expulsion of the contents. When the lower bowel is habitually emptied at the same hour daily - a habit which should be carefully exercised - the sensations of requirement to go to stool occur with great punctuality, or can be readily induced by the will, so that normal defecation is reputed to be, and practically is, a voluntary act. But not completely so, for, somewhat like swallowing, the later stages of defecation consist essentially of a series of involuntary reflex events which we can initiate by the will, but when it is once started, are powerless to modify until the reflex sequence is completed. Under ordinary circumstances, the evacuation of the faeces is commenced by the voluntary pressure exercised on the abdominal contents by the respiratory muscles. The diaphragm is depressed, the outlet of the air passages firmly closed, and the expiratory muscles thrown into action, while at the same moment the muscles which close the pelvic outlet relax, and allow the anus to descend, so that the inferior angle of the rectum is straightened, and a voluntary inhibition of the sphincter is brought about. This voluntary expiratory effort seldom requires to be continued for more than three or four seconds before some fecal matter reaches the part of the rectum just above the sphincter. When this has occurred, no further abdominal pressure is necessary (except when the masses of faeces are large and hard), for the local stimulus starts a series of reflex acts which carry on the operation. Fig. 56. Auerbach's plexus from between the muscle coats of the intestine, with low power. Fig. 57. A nodal point of Auerbach's plexus under high power, showing the nerve cells. These consist of an increased peristaltic contraction of the colon and sigmoid flexure, the waves of which pass along the rectum. These waves are accompanied by synchronous rhythmical relaxation of the sphincter, which replaces its normal condition of tonic contraction. The effect of the voluntary effort, and the amount of the abdominal pressure required, depend upon the consistence of the faeces. When quite fluid, they constantly tend to come in contact with the sensitive point of the rectum, and a voluntary effort is required to prevent the reflex series of events from taking place; a momentary relaxation of the sphincter with voluntary abdominal pressure is sufficient to eject the contents of the bowel. On the other hand, when the faeces are firm, time is required in order that the slowly acting smooth muscle may pass the mass onward. In common constipation, the difficulty is to get the solid mass down to the sensitive exciting point, in which case a few drachms of warm fluid, used as an enema, may awaken the necessary reflex movements. Read more:http://chestofbooks.com/health/physiology/Manual/Mechanism-Of- Defecation.html#ixzz4KxIcCWWK Describe the type and functions of the mucosal lining of each part of the gastrointestinal tract. Parts of GIT Type of epithelium Function of epithelium Oral cavity Stratified squamous non keratinized Protection epithelium Oesophagus Stratified squamous non keratinized Protection epithelium Stomach Simple columnar Secretion Small intestine Simple columnar with brush border Secretion Absorption Large intestine Simple columnar with goblet cells Secretion Absorption Anal canal (lower Stratified squamous non keratinized Protection part) epithelium Describe body fluid compartments and its constituents. BODY FLUIDS, FLUID COMPARTMENTS AND ITS CONSTITUENTS The human body contains large quantities of water in different compartments. The maintenance of the correct amounts of fluid, of the correct composition in the different compartments is essential. Water is essential all chemical reactions in the body. Virtually all biochemistry happens in solution. Chemicals moving around and through the body either diffuse through water for short distances, or for longer distances in bulk flow in blood circulation. TOTAL BODY WATER (TBW) of a 70 kg man is about 60% of body weight (42 L). This percentage varies with age and weight (adiposity). Babies at birth are about 80% water, while an elderly person may only have about 50% water. As the amount of adipose tissue increases, the proportion of body water decreases. An average 70 kg man is about 20% fat and 60% water whereas a 100 kg person with 40% fat will only have 44% water. The TBW is divided into two main compartments, which have different ionic compositions. The intracellular fluid (ICF) found inside all cells, is about two-thirds of the TBW (or 40% of body weight = 28 L). The extracellular fluid (ECF) which surrounds all cells is about one third of the TBW (or about 20% of body weight = 14 L). The ECF is divided into two main compartments: the interstitial fluid (ISF, also referred as tissue fluid, intercellular fluid) – about three-quarters of ECF (or about 15% TBW = 10.5 L). The ISF surrounds the cells but is outside the blood vessels. It contains very little proteins few cells in suspension. The blood plasma (intravascular fluid) is one quarter of ECF (or about 5% TBW = 3.5 L). It is found inside blood vessels and carries the other components of blood (whole blood with red and white blood cells, plasma proteins, and platelets) in suspension around the body. The ECF also includes fluids in particular areas for examples the cerebrospinal fluid (CSF) bathing the brain, fluid inside the eye (aqueous and vitreous humours), fluid inside joints (synovial fluid), in the peritoneum, pericardium, and pleura. These fluids are also called transcellular fluids. There are fluids in the gastrointestinal and the urinary tracts. The total blood volume for a 70 kg man is about 5.5 L but only 3.5 L is blood plasma. The ratio (or percentage %) of volume of red blood cells to the volume of whole blood is the haematocrit. On average it is between 0.36 and 0.53 (men 0.42 – 0.53; women 0.36 – 0.45). The fluid compartments are separated by semi-permeable barriers with different characteristics. Cells are surrounded by cell or plasma membranes which let water in and out of cells but restrict the movement of major extracellular cation, sodium. The ISF is separated from blood plasma by the endothelial cells of the capillaries. Gaps between cells allow the movement of water and ions but under normal conditions restrict the blood cells and proteins to the vascular compartment. Water can move freely among compartments but sodium does not enter cells; proteins and blood cells remain in the blood vessels. The movement of water between compartments is determined by the differences in hydrostatic and osmotic pressures in the different compartments. Hydrostatic pressure is from the pumping of the heart and osmotic pressure from the concentration of solute particles. Water moves from dilute to concentrated solutions. The more solute particles there are in the solution, the greater the ‘pull’ on the water molecules. Osmolarity is determined by the number of osmotically active particles per litre and the normal osmolarity of body fluids is 290 mOsm/L. The tonicity is the actual effect of a solution on a living cell. A solution is isotonic when it does not cause cells to take up or lose water. A hypertonic solution causes cells to lose water and shrink. A hypotonic solution causes cells to take up water until they burst (lysis). The tonicity of a solution not only depends on the solute concentration but also the nature of the solute. A 290 mOsm/L NaCl solution is isotonic but 290 mOsm/L urea solution is hypotonic (cells lyse) because urea can permeate cells. SOLUTE CONTENTS The major extracellular ions are sodium (Na+) and chloride (Cl-). The major intracellular ions are potassium (K+) and large anions such as proteins and phosphates. The distribution of Na+ and K+ are determined by specific transporters, the Na+/K+-ATPases. The ISF is different from plasma in that blood contains proteins that cannot cross the endothelium of the capillary. The ionic content of ISF and plasma is the same but the proteins in plasma have an osmotic pull (colloid osmotic pressure = oncotic pressure) that opposes the hydrostatic pressure of blood. Ions in solution are electrolytes, capable of conducting electricity. Composition of intracellular and extracellular fluids ION EXTRACELLULAR (mmol/L) INTRACELLULAR (mmol/L) Na+ 145 12 K+ 4 155 Cl- 120 3.8 Bicarbonate (HCO3-) 27 8 Phosphates 2 13 Protein anions 0-9 155 Ca2+ 1.8