E1.v · Tubular Function & Countercurrent Mechanisms

This VIVA will examine renal physiology and pharmacology. How does the kidney concentrate urine? (Image removed from report.)

This VIVA will examine your potassium physiology and pharmacology. Beginning at the glomerulus, describe how potassium is handled along the nephron? (Image removed from report.)

This viva will examine renal acid base physiology and pharmacology. Describe what happens to bicarbonate once it reaches the kidney. (Image removed from report.)

This viva will explore your understanding of urea and renal tubular function. Why do we produce urea and how effective is it as an osmole?

This viva will assess your knowledge of renal water handling. Explain how the kidney concentrates urine.

This viva will explore your knowledge of renal physiology and diuretics. Describe how sodium is handled in the nephron.

This viva will test your knowledge of respiratory physiology and the renal handling of sodium. Describe the oxygen cascade – from the atmosphere to the tissues (in a normal healthy adult) using appropriate PO2 values.

This viva tested knowledge of the renal handling of water and pharmacology of antihypertensive drug, in particular those the interact with the renin/ angiotensin system.

This viva tested knowledge of buffer systems in the body and the renal handling of acid. It went on to discuss drug ionization, pKa and dissociation and then the pharmacology of local anaesthetic agents

This Viva tested knowledge of renal physiology and related pharmacology. It explored understanding about acid base balance, renal handling of bicarbonate and moved on to the pharmacology of diuretics.

This Viva tested knowledge of renal physiology and diuretic pharmacology. It explored nephron structure and function, sodium handling and diruretic pharmacology.

This Viva tested knowledge of renal physiology and pharmacology. It began by asking what the normal Glomerular Filtration Rate (GFR) is and what the determinants of GFR are. It also explored knowledge of glomerular-tubular feedback, the counter current system and diuretics. Although most candidates had a good knowledge of GFR and its determinants, fewer were as confident to recall the actual values or to apply that physiology to scenarios like hypovolaemia. Some candidates struggled to explain the counter current mechanism, in particular the “multiplier” effect. Mechanism of action of diuretics was well answered.

The initial information given to the candidates was – This question is about the anatomy of the nephron and its blood supply. Please draw a picture of a nephron and label it. This viva explored a candidates understanding of anatomy of the nephron, unique details of renal blood flow, macula densa, glomerular filtration rate and its determinants, generation of a concentrated urine.

In order to pass this viva, candidates were expected to know the distribution of water in different body compartments, the difference in electrolytes composition in different compartments (E1), definition of osmosis and diffusion, and where osmosis and diffusion occurs in the body (B1f and D1), measurement and calculation of osmolality (E1), and how different intravenous fluids will be distributed in different body compartments (E2a). The common deficiency in the candidates’ answers included the difference in electrolytes composition between interstitial fluid and plasma and the reason behind it (F2a), how osmolality can be measured, the presence of an osmotic process in the medulla of the kidney where re-absorption of water occurs through the collecting tubules in the presence of anti- diuretic hormone (D1), and how the fluids will be distributed in the body when different intravenous fluids are administered. Syllabus : E1 2 References : Chapter 1 of Review of Medical Physiology by Ganong Vander’s Renal Physiology for details on this topic.

a period of prolonged vomiting. An arterial blood gas analysis was performed on room air, revealing the following findings. pH 7.59 (7.35 – 7.45) PaCO2 58 mmHg (35 – 45) PaO2 72 mmHg (90 – 110) HCO3- 59 mmol/L (22 – 32) Interpret the findings. This viva tested the candidate’s knowledge of renal physiology related to the control of urinary pH, effects of acetazolamide and frusemide upon metabolic acid base state and respiratory response to metabolic acid base changes. The main points expected for a pass were knowledge of : • Respiratory response to changes in metabolic acid base. Use of correctly labelled graph or common formulae • Renal handling of H+ at the proximal and distal tubules. • Mechanism of HCO3- reabsorption and regeneration • Urinary buffers such as phosphate, ammonia and glutamine • Mechanism of frusemide associated metabolic alkalosis • Affect of acetazolamide on HCO3- The use of illustrations greatly assisted candidates to answer questions within this viva Syllabus : D1-2e, D2a and B1c-2a & b Reference : Textbook of Medical Physiology by A. C Guyton & J. E Hall.