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U N I T 7
Kidney and Urinary Tract Function
R E V I EW E X E R C I S E S
1.
A 32-year-old woman with diabetes is found to
have a positive result on a urine dipstick test for
microalbuminuria. A subsequent 24-hour urine
specimen reveals an albumin excretion of 50 mg
(an albumin excretion >30 mg/day is abnormal).
A.
Use the structures of the glomerulus in Figure
24-5 to provide a possible explanation for this
finding. Why specifically test for the albumin
rather than the globulins or other plasma
proteins?
B.
Strict control of blood sugars and treatment of
hypertension have been shown to decrease the
progression of kidney disease in persons with
diabetes. Explain the physiologic rationale for
these two types of treatments.
2.
A 10-year-old boy with enuresis (bed-wetting) was
placed on an ADH nasal spray at bedtime as a
means of treating the disorder.
A.
Explain the rationale for using ADH to treat
bed-wetting.
3.
A 54-year-old man, seen by his physician for an
elevated blood pressure, was found to have a serum
creatinine of 2.5 mg/dL. He complains that he has
been urinating more frequently than usual. His first
morning urine specimen reveals a dilute urine with
a specific gravity of 1.010.
A.
Explain the elevation of serum creatinine in
terms of a decrease in renal function.
B.
Explain the inability of persons with early
renal failure to produce a concentrated urine as
evidenced by the frequency of urination and the
low specific gravity of his first morning urine
specimen.
B I B L I O G R A P H Y
Hall JE.
Guyton & Hall Textbook of Medical Physiology
. 12th ed.
Philadelphia, PA: Elsevier Saunders; 2011:303–378.
Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular
filtration rate from serum creatinine and cystatin C.
N Engl J
Med.
2012;367(1):20–29.
National Kidney Foundation. Cystatin C: What’s is its role in
estimating GFR. 2008.
/
cystatinC.pdf. Accessed May 20013.
Nielson S, Kwon TH, Fenton RA, et al. Anatomy of the kidney.
In: Taal MW, Chertow GM, Marsden PA, et al.
Brenner and
Rector’s The Kidney
. 9th ed. Philadelphia, PA: Elsevier Saunders;
2012:31–92.
Ross GI, Pawlina W.
Histology: A Text and Atlas
. 6th ed.
Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams &
Wilkins; 2011:698–723.
Sherwood L.
Human Physiology: From Cells to Systems
. 8th ed.
Belmont, CA: Brooks/Cole; 2013:505–547.
Simon J, Amode M, Poggio EG. Interpreting the estimated
glomerular filtration rate in primary care: benefits and pitfalls.
Clev Clinic J Med.
2011;78(3):189–195.
Smith H.
From Fish to Philosopher
. Boston, MA: Little, Brown;
1953:4.
Stanton BA, Koepen BM. Elements of renal function and solute
and water transport along the nephron: Tubular function. In:
Koeppen BM, Stanton BA, eds.
Berne & Levy Physiology
. 6th ed.
Philadelphia, PA: Mosby Elsevier; 2010:557–618.
Stevens LA, Levey AS. Measurement of kidney function.
Med Clin
North Am.
2005;89:457–473.
Tanner GA. Kidney function. In: Rhoades RA, Bell DR, eds.
Medical
Physiology
. 2nd ed. Philadelphia, PA: Wolters Kluwer Health/
Lippincott Williams & Wilkins; 2013:399–406.
Porth Essentials Resources
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NCLEX-Style Questions and Other Resources
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Study Guide for Essentials of Pathophysiology
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Concepts in Action Animations
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SUMMARY CONCEPTS
■■
The composition of urine and blood samples
provides valuable information about kidney
function.
■■
Blood tests that measure serum levels of pH,
electrolytes, and by-products of metabolism
provide information about renal function.
Creatinine, a product of creatine metabolism in
muscles, is freely filtered in the glomeruli and
neither reabsorbed nor secreted into the tubules;
therefore, serum creatinine levels are commonly
used to estimate the GFR. Urea is formed in the
liver as a by-product of protein metabolism and is
eliminated entirely by the kidneys; thus, blood urea
nitrogen (BUN) is related to the GFR but, unlike
creatinine, is also influenced by protein intake,
gastrointestinal bleeding, and hydration status.
■■
Urinalysis and urine specific gravity is used to
assess the kidneys’ ability to concentrate urine.
Dipstick and 24-hour urine tests for proteinuria
and microalbuminuria are used to detect
abnormal filtering of albumin in the glomeruli.
