Lecture 6 - The Kidney and Renal Function Tests Flashcards
What are the three main functions of the kidney?
The three main functions of the kidney are the excretion of waste products, regulation of acid-base balance and electrolytes, and endocrine functions, including the synthesis of vitamin D, erythropoietin, and renin.
What is the structure of a nephron and what are the main functions of its components?
A nephron consists of several components, including the glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. The glomerulus is responsible for ultrafiltration, the proximal tubule for selective reabsorption, the loop of Henle for osmoregulation, the distal tubule for selective reabsorption and secretion, and the collecting duct for variable reabsorption of water and ions.
What is the role of peritubular capillaries in nephron function?
Peritubular capillaries run parallel to nephron components and play a role in the reabsorption and secretion of substances between the tubules and the bloodstream.
How can glomerular function be assessed using laboratory tests?
Glomerular function can be assessed through tests such as serum creatinine, creatinine clearance, estimated GFR, and the measurement of glomerular proteinuria.
Explain the concept of glomerular filtration rate (GFR) and how it is related to creatinine levels.
GFR is the volume of plasma cleared of a substance by glomerular filtration per unit time. A decrease in GFR leads to increased serum creatinine levels, but this change is noticeable only after GFR has significantly decreased.
What is the significance of serum creatinine levels in assessing kidney function, and what are the limitations of this test?
Serum creatinine levels rise as GFR decreases. However, this test has limitations as significant kidney dysfunction must occur before a noticeable increase in serum creatinine is observed.
Describe the water deprivation test and its purpose.
The water deprivation test restricts fluid intake to assess the urine’s ability to become more concentrated. If the urine remains dilute, a desmopressin test (DDAVP) is performed to distinguish between central diabetes insipidus and nephrogenic diabetes insipidus.
What is the purpose of the acid load test, and how does it help diagnose renal tubular acidosis (RTA)?
The acid load test evaluates the kidney’s ability to excrete protons. If the urine pH remains higher than 5.3 during this test, it indicates renal tubular acidosis (RTA) where the kidney struggles to acidify urine.
Define osmolality and provide the formula to calculate it.
Osmolality is the concentration of molecules exerting osmotic pressure. The formula to calculate osmolality is: Osmolality = 2[Na+ + K+] + [glucose] + [urea].
Differentiate between acute renal failure and chronic renal failure in terms of onset, reversibility, and effects on electrolytes and hormone levels.
Acute renal failure has a fast onset and is reversible. It can lead to anuric or oliguric states, elevated electrolytes, and increased ADH and aldosterone. In contrast, chronic renal failure has a slow onset and is irreversible, causing polyuria, nocturia, elevated electrolytes, low vitamin D, anaemia, and increased urea and creatinine levels.
