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Kidney Functions in Medicine and Surgery

Kidney Functions in Medicine and Surgery

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@UnrealRaleigh
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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?

20%–30%

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

Clearance

Why is creatinine a nearly ideal substance for measuring clearance?

It is synthesized at a constant rate

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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