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1. Which substances are best suited to measure intracellular fluid volume? *

a. Inulin and 22Na
b. Heavy water and 125I-albumin
c. Inulin and heavy water
d. Inulin and 125I-albumin e. 51Cr red blood cells and 125I-albumin
2. Which diagram represents the changes (after osmotic equilibrium) in extracellular and
intracellular fluid volume and osmolarity after infusion of 2 liters of 3.0% dextrose? *
A) A
B) B
C) C
D) D
3. A male patient appears to be dehydrated, and after obtaining a plasma sample, you
find that he has hyponatremia, with a plasma sodium concentration of 130 mmol/L and a
plasma osmolarity of 270 mOsm/L. You decide to administer 2 L of 3% sodium chloride
(NaCl With M.W 58). His body weight was 70 kilograms before the fluid is administered.
What is his approximate plasma osmolarity after administration Of the NaCl solution and
after osmotic equilibrium? Assume the initial conditions previously described. *
a. 310 mOsm/L
b. 304 mOsm/L
c. 273 mOsm/L
d. 286 mOsm/L
Section 1 - (G)old: 12 questions

Section 2 - Guytons and Ganong's Reviews: 16 questions
Section 3 - Lippincotts & BRS Reviews and UWorld: 6 questions
Ayam Exams www.ayammed.com
4. A 36-year-old woman reports decreased in urination. Laboratory values reveal the

following information: Urine specific gravity = 1.09, Urine protein = negative, Plasma
sodium (Na+) = 165 mmol/L, Plasma potassium (K+) = 4.5 mmol/L, Plasma creatinine = .9
mg/dl, Blood pressure = 88/40 mm Hg, Heart rate = 115 beats/min. What is the most likely
cause of her elevated plasma Na+ concentration? *
a. Diabetes insipidus
b. Diabetes mellitus
c. Primary aldosteronism
d. Simple dehydration due to insufficient water intake and heavy exercise
e. Bartter’s syndrome
5. A person with normal body fluid volumes weighs 70 kg and has an extracellular fluid
volume of approximately 13.5 L, a blood volume of 5L, and a hematocrit of 0.45 ; 55% of
his body weight is water. What is the approximate interstitial fluid volume? *
a. 10.75 liters
b. 6.4 liters
c. 12.0 liters
d. 14 liter
e. 8.4 liters
6. Which of the following solutions, when infused intravenously, would result in an

increase in extracellular fluid volume, a decrease in intracellular fluid volume, and an
increase in total body water after osmotic equilibrium? *
a. 1 Liter of pure water
b. 1 Liter of 5% dextrose solution
c. 1 Liter of 0.9% sodium chloride (NaCl) solution
d. 1 Liter of 0.45% NaCl solution
e. 1 Liter of 3% NaCl solution
Feedback:
Guyton Review:
A 3% NaCl solution is hypertonic, and when infused intravenously, it
would increase extracellular fluid volume and osmolarity, thereby causing water to flow out of
the cell. This action would decrease intracellular fluid volume and further increase
extracellular fluid volume. The 0.9% NaCl solution and 5% dextrose solution are isotonic and
therefore would not reduce intracellular fluid volume. Pure water and the 0.45% NaCl solution
are hypotonic, and when infused, they would increase both intracellular and extracellular fluid
volumes.

7. A 35-year-old woman comes to the office due to frequent urination. She describes
drinking excessive amounts of water due to unquenchable thirst She does not take and
medications. Her blood glucose level is 86 mq/dL. A standard water deprivation test is
performed. The results of urine osmolality during 4 hours of dehydration are presented in
the table below. The patient's plasma osmolality after 3 hours of water deprivation was
found to be 200 mOsm/l, and vasopressin was then administered subcutaneously
(4hours) and the new osmolarity is 300 mosm/l.Which of the following is the most likely
diagnosis in this patient? *
a. Central diabetes insipidus

b. Complete nephrogenc diabetes insipidus
c. Partial nephrogenic diabetes insipidus
d. Post-obstructive polyuria
e. Primarv polydipsia
Feedback:
UWorld:
The collecting duct is impermeable to water in the absence of vasopressin (antidiuretic
hormone [ADH]). ADH activates G protein-coupled V2 receptors on the basolateral tubular
cell membrane, stimulating phosphorylation of intracellular proteins. This causes fusion of
vesicles containing aquaporin 2 to the luminal membrane, where aquaporin serves as a water
channel and allows water reabsorption in the collecting duct.
Diabetes insipidus (D1) is caused by either ADH deficiency (central DI) or complete/partial
unresponsiveness of the kidneys to ADH (nephrogenic DI). The end result is free water loss in
the urine with production of dilute unne (low specific gravity and urine osmolality) and
dehydration that causes excessive thirst. A water deprivation test with desmopressin (DDAVP)
administration can differentiate between central and nephrogenic In patients with central DI
and complete nephrogenic DI, the urine osmolality is persistently low despite an increase in
serum osmolality with
DI.
water deprivation. When desmopressin Is administered, patients with central D| show a rapid
increase in urine osmolality and reduction in urine volume, whereas those with complete
nephrogenic D! do not (Choice B).
(Choice C) Patients with partial nephrogenic DI! have a slow but steady rise in urine
osmolality with increasing serum osmolality after water deprivation. There ts no further
increase in urine osmolality with DDAVP., and the urine osmolality remains low (<500
mOsm/L).
(Choice D) Relief of urinary obstruction (eg, Foley catheterization in patients with benign
prostatic hyperplasia) may result in post-obstructive It is mostly seen in patients with a history
of reduced urine output from
diuresis as the kidneys act to normalize fluid volume and solute levels. chronic urinary
obstruction. Unne osmolality remains within normal limits.

(Choice E) Patients with primary polydipsia exhibit an increase in serum and urine osmolality
on water deprivation that is similar to partial nephrogenic DI. However, the correction in
primary polydipsia is more rapid, and the urine osmolality returns to a level closer to normal
(but still submaximal due to washout of the medullary osmotic gradient). A history of
psychiatric disorders or méedication-induced xerostomia is usually present.
his body weight is water. What is the approximate plasma volume? *
a. 2.3 liters
b. 2.75 liters
c. 2.0 liters
d. 3.3 liters e. 3.0 liters
e. 3.0 liters
his body weight is water. What is the approximate intracellular fluid volume? *
a. 25 liters
b. 21.4 liters
c. 19.6 liters
d. 17.1 liters
e. 28 liters
10. Using the indicator dilution method to assess body fluid volumes in a 40-year-old
man weighing 70 kg, the inulin space is calculated to be 16 liters and 125 -albumin space
is 4 liters. If 60% of his total body weight is water, what is his approximate interstitial fluid
volume? *
a. 4 L
b. 12 L
c. 16 L
d. 26 L
e. 38 L
f. 42 L
Feedback:
Guyton Review:
Interstitial fluid volume cannot be measured directly, but it can be calculated as the difference
between extracellular fluid volume (inulin space = 16 l) and plasma volume (125I-albumin
space = 4 l). Therefore, interstitial fluid volume is approximately 12 l.

11. A female patient has unexplained hypernatremia (plasma Na+ = 167 mmol/l) and
reports frequent urination and large urine volumes. A urine specimen reveals that the
Na+ concentration is 15 mmol/l (very low) and the osmolarity is 155 mOsm/l (very low).
Laboratory tests reveal the following data: plasma renin activity = 3 ng angiotensin I/ml/h
(normal = 1.0), plasma ADH = 30 pg/ml (normal = 3 pg/ml), and plasma aldosterone = 20
ng/dl (normal = 6 ng/dl). Which of the following is the most likely reason for her
hypernatremia? *
A) Simple dehydration caused by decreased water intake
B) Nephrogenic diabetes insipidus
C) Central diabetes insipidus
D) Syndrome of inappropriate ADH
E) Primary aldosteronism
F) Renin-secreting tumor
Feedback:
Guyton Review:
Hypernatremia can be caused by excessive sodium retention or water
loss. The fact that the patient has large volumes of dilute urine suggests excessive urinary
water excretion. Of the two possible disturbances listed that could cause excessive urinary
water excretion (nephrogenic diabetesinsipidus and central diabetes insipidus), nephrogenic
diabetes insipidus is the most likely cause. Central diabetes insipidus (decreased ADH
secretion) is not the correct answer because plasma ADH levels are markedly elevated.
Simple dehydration due to decreased water intake is unlikely because the patient is excreting
large volumes of dilute urine.
12. Which of the following has similar values for both intracellular and interstitial body
fluids? *
A) Potassium ion concentration
B) Colloid osmotic pressure
C) Sodium ion concentration
D) Chloride ion concentration
E) Total osmolarity
Feedback:
Guyton Review:
Intracellular and extracellular body fluids have the same total osmolarity under steady-state
conditions because the cell membrane is highly permeable to water. Therefore, water flows
rapidly across the cell membrane until osmotic equilibrium is achieved. The colloid osmotic
pressure is determined by the protein concentration, which is considerably higher inside the
cell. The cell membrane is also relatively impermeable to potassium, sodium, and chloride,
and active transport mechanisms maintain low intracellular concentrations of sodium and
chloride and a high intracellular concentration of potassium.



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Ayam Exams www.ayammed.

1. Which substances are best suited to measure intracellular fluid volume? *

Section 1 - (G)old: 12 questions

4. A 36-year-old woman reports decreased in urination. Laboratory values reveal the

6. Which of the following solutions, when infused intravenously, would result in an

Section 1 - (G)old: 12 questions

a. Central diabetes insipidus

Section 1 - (G)old: 12 questions

Section 1 - (G)old: 12 questions

Section 1 - (G)old: 12 questions

Section 1 - (G)old: 12 questions

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