PAE505 — Gastrointestinal and Genitourinary System: Lecture Note

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This is the complete lecture note for PAE505 Gastrointestinal and Genitourinary System. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.

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la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: PAE 505 Course title: Gastrointestinal and Genitourinary System Course credit load: 2 Units Series 1: Diarrhoeal Disease, Fluid Physiology, and Dehydration • Part 1.1: Diarrhoea in Children: Definition, Classification, and Aetiology o Sub Part 1.1.1: Definition and mechanisms of diarrhoea o Sub Part 1.1.2: Classification of diarrhoea o Sub Part 1.1.3: Epidemiology and aetiology of diarrhoea • Part 1.2: Assessment, Complications, and Management of Diarrhoea o Sub Part 1.2.1: Clinical assessment of a child with diarrhoea o Sub Part 1.2.2: Complications of diarrhoeal disease o Sub Part 1.2.3: General management and prevention of diarrhoea • Part 1.3: Vomiting and Fluid and Electrolyte Physiology in Children o Sub Part 1.3.1: Causes and evaluation of vomiting in children o Sub Part 1.3.2: Complications and management of vomiting o Sub Part 1.3.3: Physiology of fluid and electrolyte distribution in children • Part 1.4: Dehydration and Oral Rehydration Therapy o Sub Part 1.4.1: Types and severity of dehydration o Sub Part 1.4.2: Clinical assessment of hydration status o Sub Part 1.4.3: Oral rehydration therapy Introduction Picture an eighteen month old brought to a busy primary health centre by her mother, who reports three days of watery stool, poor feeding, and a child who now seems unusually quiet and less playful than usual. Findings such as these are among the most common reasons a child is brought to a clinician anywhere in the world, and diarrhoeal disease remains one of the leading causes of childhood illness and death globally, disproportionately affecting children in low resource settings such as much of Nigeria. This Series opens the PAE 505 course by building a

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS systematic understanding of diarrhoea, vomiting, and the fluid and electrolyte physiology that underlies the assessment and management of a dehydrated child. The aim of this Series is to equip you with the knowledge required to classify and assess a child with diarrhoea or vomiting, to understand the basic physiology of fluid and electrolyte distribution in children, and to assess and manage dehydration, including through oral rehydration therapy. This Series begins with the definition, classification, and aetiology of diarrhoea, before turning to its assessment, complications, and management. Next, we examine vomiting in children alongside the physiology of fluid and electrolyte distribution, before concluding with dehydration and oral rehydration therapy. Series Learning Outcomes At the end of this Series, you should be able to: • SLO 1.1: describe the epidemiology and aetiology of diarrhoea, • SLO 1.2: classify diarrhoea and explain the mechanisms underlying watery diarrhoea, • SLO 1.3: describe the assessment of a child with diarrhoea and list its complications, • SLO 1.4: discuss the association between diarrhoea and malnutrition, and strategies for prevention, • SLO 1.5: describe the causes and evaluation of a child with vomiting, • SLO 1.6: describe the physiology of fluid and electrolyte distribution in children, • SLO 1.7: describe the types and severity of dehydration and its clinical assessment, and • SLO 1.8: describe oral rehydration therapy, its mechanism of action, and the composition of oral rehydration solution. 1.1 Diarrhoea in Children: Definition, Classification, and Aetiology 1.1.1 definition and mechanisms of diarrhoea Two mechanisms produce the same watery symptom Diarrhoea is defined as the passage of three or more loose or watery stools in a 24 hour period, or a clear increase in stool frequency and looseness from what is normal for the individual child. Two broad mechanisms underlie watery diarrhoea: osmotic diarrhoea, in which poorly absorbed solutes remain within the bowel lumen and draw water into it, and secretory

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS diarrhoea, in which the intestinal mucosa actively secretes excess fluid and electrolytes into the lumen, often in response to a bacterial toxin. A useful clinical distinction is that osmotic diarrhoea typically improves with fasting, since it depends on the ongoing presence of unabsorbed solute in the gut, while secretory diarrhoea continues even when the child is fasted, since the underlying secretory process is largely independent of oral intake, a distinction that can help narrow the differential diagnosis in a child with persistent diarrhoea. Fill in the blank: Osmotic diarrhoea typically improves with ________, unlike secretory diarrhoea. 1.1.2 classification of diarrhoea Diarrhoea is classified by duration into acute diarrhoea, lasting less than 14 days, the most common presentation and usually infectious in origin, persistent diarrhoea, lasting 14 days or more, and chronic diarrhoea, a term sometimes used for diarrhoea lasting beyond one month, often reflecting an underlying non-infectious cause such as malabsorption. Diarrhoea is also classified by character into watery diarrhoea, the most common type, and dysentery, diarrhoea containing visible blood, which suggests invasive bacterial infection such as Shigella and requires different management. This dual classification, by both duration and character, is clinically important because it directly influences the likely causative organism, the necessary investigations, and the appropriate treatment approach, meaning the classification should always be actively established early in the assessment of any child presenting with diarrhoea. Fill in the blank: Diarrhoea lasting 14 days or more is classified as ________ diarrhoea. 1.1.3 epidemiology and aetiology of diarrhoea Diarrhoeal disease remains one of the leading causes of morbidity and mortality in children under five years of age globally, particularly in low and middle income countries, where poor access to safe drinking water, inadequate sanitation, and limited hygiene practices all contribute substantially to transmission. The most common infectious causes of acute watery diarrhoea in children include rotavirus, the leading viral cause, particularly in unvaccinated infants, together with bacterial causes such as enterotoxigenic Escherichia coli and, in dysentery, Shigella and Campylobacter species. Non-infectious causes, while less common, include dietary factors, certain medications such as antibiotics disrupting normal gut flora, and, in persistent or chronic diarrhoea, underlying

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS conditions such as malabsorption syndromes, which should be considered when diarrhoea fails to resolve within the expected timeframe for an infectious cause. Fill in the blank: ________ is the leading viral cause of acute watery diarrhoea in unvaccinated infants. Table 1.1: Classification of diarrhoea by duration and character. Classification Definition Typical implication Acute diarrhoea Lasting less than 14 days Usually infectious, most commonly viral Persistent diarrhoea Lasting 14 days or more May reflect ongoing infection or early malabsorption Chronic diarrhoea Lasting beyond one month Often reflects a non-infectious underlying cause Dysentery Diarrhoea containing visible blood Suggests invasive bacterial infection Pilot questions 1.1 1. Define diarrhoea and distinguish osmotic from secretory diarrhoea. (Linked to SLO 1.1) 2. Explain why osmotic diarrhoea characteristically improves with fasting. (Linked to SLO 1.1) 3. Distinguish acute, persistent, and chronic diarrhoea by duration. (Linked to SLO 1.2) 4. What does the presence of visible blood in stool suggest, and what is this presentation called? (Linked to SLO 1.2) 5. Name the leading viral cause of acute watery diarrhoea in children. (Linked to SLO 1.1) 1.2 Assessment, Complications, and Management of Diarrhoea 1.2.1 clinical assessment of a child with diarrhoea What the history and examination must establish Assessment of a child with diarrhoea should establish the duration, frequency, and character of stools, including the presence of blood or mucus, together with associated symptoms such as fever, vomiting, and poor oral intake. A focused history should also explore potential sources of infection, including recent travel, contact with other unwell children, and the home water

la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS and sanitation situation, since this context both supports the likely diagnosis and informs subsequent prevention advice. Examination must always include a careful assessment of hydration status, discussed in detail later in this Series, together with assessment of the child's general condition, nutritional status, and abdominal examination to identify any signs of an acute abdomen or significant distension that might suggest an alternative or coexisting diagnosis requiring urgent attention. Fill in the blank: Assessment of a child with diarrhoea must always include a careful assessment of ________ status. 1.2.2 complications of diarrhoeal disease The most immediate and important complication of diarrhoea is dehydration, arising from ongoing fluid and electrolyte losses in the stool, and, if severe and untreated, progressing to hypovolaemic shock. Associated electrolyte disturbances, particularly hyponatraemia or hypernatraemia and hypokalaemia, may also develop, particularly with large volume losses or inappropriate fluid replacement, and require specific correction alongside general rehydration. Beyond the acute episode, persistent or recurrent diarrhoea can significantly impair a child's nutritional status, contributing to malnutrition through reduced nutrient absorption, reduced appetite, and increased metabolic demand, which in turn increases susceptibility to further infections, creating a harmful cycle that is particularly important to recognise and interrupt in resource limited settings. Fill in the blank: Severe, untreated dehydration from diarrhoea can progress to hypovolaemic ________. 1.2.3 general management and prevention of diarrhoea Management of diarrhoea centres on appropriate fluid replacement, most commonly through oral rehydration therapy,

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