Kidney Functions in Medicine and Surgery
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Questions and Answers

What percentage of nephrons must stop functioning before the concentration of certain substances begins to increase in the blood?

  • 70%–80%
  • 90%–100%
  • 20%–30% (correct)
  • 50%–60%

    • What is the term for the rate at which a substance is removed or cleared from the blood into the urine?

  • Reabsorption
  • Filtration
  • Clearance (correct)
  • Secretion

    • Why is creatinine a nearly ideal substance for measuring clearance?

  • It is cleared by both glomerular filtration and secretion
  • It is reabsorbed by the kidneys
  • It is synthesized at a variable rate
  • It is synthesized at a constant rate (correct)

    • What is the purpose of measuring creatinine clearance?

    <p>To estimate the rate of glomerular filtration</p> Signup and view all the answers

    How is creatinine clearance calculated?

    <p>By relating the serum creatinine concentration to the urine creatinine concentration</p> Signup and view all the answers

    What is required for the measurement of creatinine clearance?

    <p>A 24-hour urine specimen and a serum creatinine value</p> Signup and view all the answers

    Why must the urine container be kept refrigerated?

    <p>To prevent contamination or degradation of the urine specimen</p> Signup and view all the answers

    What is measured in both serum and urine when calculating creatinine clearance?

    <p>Creatinine concentration</p> Signup and view all the answers

    What is the primary method by which the body rids itself of excess substances?

    <p>Urine formation</p> Signup and view all the answers

    Which hormone is involved in red blood cell production?

    <p>Erythropoietin</p> Signup and view all the answers

    What is the primary function of the kidneys in maintaining acid-base balance?

    <p>Secreting hydrogen ions to increase pH</p> Signup and view all the answers

    What is the majority of the nonprotein nitrogen waste excreted daily?

    <p>Urea</p> Signup and view all the answers

    What is the role of the kidneys in regulating blood pressure?

    <p>Secreting renin</p> Signup and view all the answers

    What is the byproduct of the degradative metabolism of nucleic acids, amino acids, and proteins?

    <p>Nonprotein nitrogen compounds</p> Signup and view all the answers

    What is the function of the kidneys in maintaining normal blood volume and composition?

    <p>Reabsorbing needed nutrients and excreting wastes</p> Signup and view all the answers

    Where does urea synthesis occur?

    <p>Liver</p> Signup and view all the answers

    What is the unit of measurement for creatinine clearance?

    <p>mL/min per 1.73 m2</p> Signup and view all the answers

    What is the purpose of the normalization factor (1.73/A) in the creatinine clearance formula?

    <p>To adjust for body surface area</p> Signup and view all the answers

    What is the range of creatinine clearance for males?

    <p>97-137 mL/min per 1.73 m2</p> Signup and view all the answers

    What is the advantage of using estimated GFR (eGFR) over traditional creatinine clearance?

    <p>It does not require a timed urine collection</p> Signup and view all the answers

    What is the formula used to calculate creatinine clearance?

    <p>UCr x VUr / PCr x 1440 / 1.73</p> Signup and view all the answers

    What is the recommended frequency for calculating estimated GFR (eGFR)?

    <p>Each time a serum creatinine level is reported</p> Signup and view all the answers

    What is the benefit of using estimated GFR (eGFR) over traditional creatinine clearance?

    <p>It results in earlier detection of chronic kidney disease</p> Signup and view all the answers

    What is the range of creatinine clearance for females?

    <p>88-128 mL/min per 1.73 m2</p> Signup and view all the answers

    What is the prevalence of Phenylketonuria (PKU)?

    <p>1:15000</p> Signup and view all the answers

    What is the primary cause of Phenylketonuria (PKU)?

    <p>Deficiency of phenylalanine hydroxylase (PAH)</p> Signup and view all the answers

    What is the role of biopterin-H4 in phenylalanine metabolism?

    <p>It is a coenzyme for phenylalanine hydroxylase</p> Signup and view all the answers

    What is the effect of phenylalanine hydroxylase deficiency?

    <p>Accumulation of phenylalanine</p> Signup and view all the answers

    What is the function of hydroxylases?

    <p>To introduce an oxygen molecule into the compound</p> Signup and view all the answers

    What is the role of vitamin C in phenylalanine metabolism?

    <p>It is required for the oxidative decarboxylation of α-keto acid</p> Signup and view all the answers

    What is the percentage of PKU cases due to deficiency of BH4?

    <p>1-2%</p> Signup and view all the answers

    What is the relationship between phenylalanine and tyrosine?

    <p>Phenylalanine is an essential amino acid, while tyrosine is non-essential</p> Signup and view all the answers

    What is the effect of estrogens on bone metabolism?

    <p>They prevent osteoporosis in menopausal women</p> Signup and view all the answers

    What is the metabolic role of estrogens in protein metabolism?

    <p>They accelerate the incorporation of amino acids into proteins of the uterus</p> Signup and view all the answers

    What is the effect of estrogens on cholesterol levels?

    <p>They decrease the LDL to HDL ratio</p> Signup and view all the answers

    What is the metabolic role of progesterone in the female genital system?

    <p>It prepares the uterus for the embedding of the embryo</p> Signup and view all the answers

    What is the effect of progesterone on menstruation?

    <p>It inhibits menstruation</p> Signup and view all the answers

    What is the number of carbon atoms in progesterone?

    <p>21</p> Signup and view all the answers

    What is the site of progesterone synthesis in females?

    <p>Ovaries and placenta</p> Signup and view all the answers

    What is the fate of estradiol in the liver?

    <p>It is converted to estrone and estriol</p> Signup and view all the answers

    Study Notes

    Kidney Functions

    • The kidneys perform vital functions including urine formation, fluid and electrolyte balance, regulation of acid-base balance, and secretion of hormones such as renin, erythropoietin, and 1,25-dihydroxy vitamin D3.
    • They also eliminate nonprotein nitrogen compounds, including urea, creatinine, and uric acid.

    Kidney Function Tests

    • Clearance measurements are used to estimate the rate of glomerular filtration.
    • Creatinine clearance is a standard laboratory method to determine glomerular filtration rate (GFR).
    • Creatinine is an ideal substance for measurement of clearance because it is synthesized at a constant rate and cleared essentially only by glomerular filtration.
    • Calculation of creatinine clearance requires a 24-hour urine specimen and a serum creatinine value.
    • The formula for creatinine clearance (CCr) is: CCr = (UCr x VUr) / (PCr x 1440).

    Estimated Glomerular Filtration Rate

    • The National Kidney Foundation recommends that estimated GFR (eGFR) be calculated each time a serum creatinine level is reported.
    • The equation for eGFR includes serum creatinine, age, body size, gender, and race, and does not require a timed urine collection.

    Genetic Disorders of Amino Acids Metabolism

    • Phenylalanine is an essential amino acid, while tyrosine is nonessential.
    • Phenylalanine hydroxylase (PAH) is a group of enzymes that utilize oxygen molecules and introduce -OH into compounds.
    • Deficiency of PAH leads to phenylketonuria (PKU), an inborn error of amino acid metabolism.
    • PKU prevalence is 1:15000, and most cases are due to PAH deficiency, while 1-2% are due to deficiency of BH4, a coenzyme for PAH.

    Phenylketonuria (PKU)

    • PKU is characterized by the accumulation of phenylalanine due to PAH deficiency.
    • Deficiency of BH4, a coenzyme for PAH, can also lead to PKU.

    Steroid Hormones Biosynthesis

    • Estrogens, or female sex hormones, have metabolic roles in protein metabolism, lipid metabolism, and bone metabolism.
    • Estrogens accelerate the incorporation of amino acids into proteins, exert a lipotropic effect on the liver, and stimulate the closure of bone epiphysis.
    • Inactivation of estrogens occurs in the liver, where estradiol is converted to estrone and estriol, and excreted in the urine.
    • Progesterone is synthesized in the ovaries after ovulation and formation of the corpus luteum, and in the placenta during pregnancy.
    • Progesterone actions on the female genital system include preparing the uterus for embryonic implantation, maintaining pregnancy, and suppressing menstruation, ovulation, and LH hormone production.

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    Description

    This lecture covers the functions of the kidneys, including urine formation and excretion, and how to interpret kidney function tests. Students will learn to list the different functions of the kidney and enumerate kidney function tests.

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