Urinary System and Fluid Balance Practice Questions

50 multiple-choice questions on Urinary system and fluid balance for paramedic and EMT students, from Chapter 8 (Anatomy and Physiology). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

50 practice questions

1. What is the functional unit of the kidney?

   1. A. Nephron
   2. B. Ureter
   3. C. Renal pelvis
   4. D. Glomerulus
   Show answer

   Answer: A. Nephron

   Each kidney has about 1 million nephrons.

2. Filtration of blood in the kidney begins at the:

   1. A. Loop of Henle
   2. B. Renal pelvis
   3. C. Collecting duct
   4. D. Glomerulus
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   Answer: D. Glomerulus

   The glomerulus filters plasma into Bowman's capsule.

3. The loop of Henle is mainly responsible for:

   1. A. Storing urine before voiding
   2. B. Filtering blood at the capillaries
   3. C. Releasing renin into the blood
   4. D. Concentrating urine
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   Answer: D. Concentrating urine

   Loop diuretics like furosemide act here to increase urine output. It reabsorbs water and sodium.

4. Urine travels from the kidneys to the bladder through the:

   1. A. Ureters
   2. B. Renal veins
   3. C. Urethra
   4. D. Nephrons
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   Answer: A. Ureters

   Ureters run from the kidneys to the bladder, and the urethra runs from the bladder out of the body.

5. The kidneys release renin in response to:

   1. A. High serum potassium
   2. B. Elevated blood pressure
   3. C. Low renal perfusion
   4. D. Increased urine output
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   Answer: C. Low renal perfusion

   Renin starts the renin-angiotensin-aldosterone system, which raises blood pressure.

6. The kidneys produce which hormone that stimulates red blood cell production?

   1. A. Renin only
   2. B. Erythropoietin
   3. C. Aldosterone
   4. D. Antidiuretic hormone
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   Answer: B. Erythropoietin

   This is why patients with chronic kidney disease are often anemic.

7. The kidneys help maintain acid-base balance by:

   1. A. Excreting acid, keeping bicarbonate
   2. B. Exhaling excess carbon dioxide
   3. C. Releasing antidiuretic hormone
   4. D. Secreting renin to adjust the blood pH
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   Answer: A. Excreting acid, keeping bicarbonate

   Renal compensation takes hours to days, while respiratory compensation takes minutes. Renin is released to raise blood pressure and volume; it does not regulate pH.

8. Normal adult urine output is approximately:

   1. A. 0.5-1 mL/kg/h
   2. B. 0.1 mL/kg/h
   3. C. 5 mL/kg/h
   4. D. 10 mL/kg/h
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   Answer: A. 0.5-1 mL/kg/h

   Output below 0.5 mL/kg/h suggests poor perfusion.

9. A dehydrated marathon runner has small amounts of dark, concentrated urine. Which hormone is mainly responsible?

   1. A. Aldosterone, causing sodium loss
   2. B. ADH, increasing water reabsorption
   3. C. Insulin, moving water into cells
   4. D. Calcitonin, lowering calcium
   Show answer

   Answer: B. ADH, increasing water reabsorption

   Dehydration raises plasma osmolarity, which triggers ADH release from the posterior pituitary. ADH makes the collecting ducts reabsorb water, producing concentrated urine. Aldosterone retains sodium rather than wasting it. Insulin and calcitonin do not control urine concentration.

10. The urinary system consists of the:

    1. A. Kidneys, liver, and bladder
    2. B. Kidneys, ureters, bladder, urethra
    3. C. Kidneys and adrenal glands
    4. D. Ureters, bladder, and adrenal glands
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    Answer: B. Kidneys, ureters, bladder, urethra

    The kidneys do the filtering; the rest transports and stores. The adrenal glands sit on the kidneys but are endocrine organs, not part of the urinary tract.

11. The kidneys are located:

    1. A. In the pelvis, behind the bladder
    2. B. In the anterior abdomen near the navel
    3. C. Retroperitoneally, beside the spine
    4. D. In the lower thorax, above the diaphragm
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    Answer: C. Retroperitoneally, beside the spine

    Flank pain often reflects kidney problems. They lie at about T12 to L3.

12. The kidneys receive approximately what portion of cardiac output?

    1. A. About 2 percent
    2. B. About 50 percent
    3. C. About 5 percent
    4. D. 20 to 25 percent
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    Answer: D. 20 to 25 percent

    This makes them sensitive to hypoperfusion.

13. Each kidney contains approximately:

    1. A. 10 million nephrons
    2. B. 1,000 nephrons
    3. C. 100 nephrons
    4. D. 1 million nephrons
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    Answer: D. 1 million nephrons

    Function is lost gradually as nephrons die.

14. The glomerulus is a:

    1. A. A muscular storage sac
    2. B. A tuft of filtering capillaries
    3. C. A coiled tubule that reabsorbs water
    4. D. A collecting tube for urine
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    Answer: B. A tuft of filtering capillaries

    It sits within Bowman capsule.

15. Bowman capsule functions to:

    1. A. Secrete renin into the blood
    2. B. Filter blood directly
    3. C. Collect glomerular filtrate
    4. D. Store urine before voiding
    Show answer

    Answer: C. Collect glomerular filtrate

    Filtrate then passes through the tubules.

16. Tubular reabsorption returns which substances to the blood?

    1. A. Large plasma proteins
    2. B. Urea, creatinine, and other wastes
    3. C. Water, glucose, and sodium
    4. D. Hydrogen ions and drugs
    Show answer

    Answer: C. Water, glucose, and sodium

    Most filtrate is reabsorbed. Other needed substances are also reclaimed.

17. Tubular secretion moves substances:

    1. A. Into the lymphatic vessels
    2. B. From the tubule into the blood
    3. C. From blood into the tubule
    4. D. Directly into the bladder
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    Answer: C. From blood into the tubule

    It helps eliminate drugs and hydrogen ions.

18. Approximately how much filtrate do the kidneys produce daily?

    1. A. About 10 L
    2. B. About 500 mL
    3. C. About 1 to 2 L
    4. D. About 180 L
    Show answer

    Answer: D. About 180 L

    Only about 1 to 2 L becomes urine. Most of it is reabsorbed.

19. Glomerular filtration depends primarily on:

    1. A. Daily urine volume
    2. B. Plasma potassium concentration
    3. C. Tubular reabsorption rate
    4. D. Renal blood flow
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    Answer: D. Renal blood flow

    Hypotension reduces filtration sharply. Renal perfusion pressure drives filtration. Potassium level does not set the filtration rate, and tubular reabsorption happens after filtration.

20. Antidiuretic hormone acts on the:

    1. A. Bladder, relaxing the detrusor
    2. B. Collecting ducts
    3. C. Ureters, increasing peristalsis
    4. D. Glomerulus, increasing filtration
    Show answer

    Answer: B. Collecting ducts

    It concentrates urine when fluid is scarce. It increases water reabsorption there.

21. A patient with Addison disease (adrenal insufficiency) typically has which electrolyte pattern?

    1. A. High sodium and low potassium
    2. B. Low sodium and high potassium
    3. C. High sodium and high calcium
    4. D. Low potassium and low calcium
    Show answer

    Answer: B. Low sodium and high potassium

    Aldosterone normally makes the kidneys retain sodium and excrete potassium. Without it, sodium is lost and potassium accumulates, which, along with low cortisol, can cause hypotension and dysrhythmias. High sodium with low potassium is the pattern of aldosterone excess. Calcium is not mainly controlled by aldosterone.

22. A patient bleeding internally has falling blood pressure. How do the kidneys respond?

    1. A. They release renin, producing angiotensin II and aldosterone
    2. B. They release erythropoietin to raise BP within minutes
    3. C. They increase urine output to restore volume
    4. D. They secrete ADH from the renal cortex
    Show answer

    Answer: A. They release renin, producing angiotensin II and aldosterone

    Reduced renal perfusion triggers renin release. Renin leads to angiotensin II, which causes vasoconstriction and aldosterone release, and aldosterone makes the kidneys retain sodium and water. Erythropoietin raises red cell production over days, not BP within minutes. The kidneys reduce urine output. ADH comes from the posterior pituitary.

23. A patient with end-stage kidney disease is chronically anemic. The main reason is:

    1. A. Increased red cell destruction by the spleen
    2. B. Iron lost in the urine
    3. C. Reduced erythropoietin production
    4. D. Excess erythropoietin suppressing the marrow
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    Answer: C. Reduced erythropoietin production

    The kidneys make erythropoietin, which stimulates red cell production in the marrow. Failing kidneys make less, which causes chronic anemia that is treated with erythropoiesis-stimulating agents. Splenic destruction and urinary iron loss are not the main mechanisms, and erythropoietin is reduced, not excessive.

24. The kidneys activate which vitamin?

    1. A. Vitamin K
    2. B. Vitamin D
    3. C. Vitamin A
    4. D. Vitamin C
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    Answer: B. Vitamin D

    This supports calcium absorption and bone health.

25. A COPD patient with a chronically high PaCO2 has a near-normal pH. Which compensation explains this?

    1. A. The lungs are blowing off extra CO2
    2. B. The kidneys excreted extra bicarbonate over days
    3. C. The kidneys retained bicarbonate over days
    4. D. Ventilation slowed to retain more CO2
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    Answer: C. The kidneys retained bicarbonate over days

    Chronic respiratory acidosis is offset by renal compensation: the kidneys excrete acid and retain bicarbonate over hours to days, bringing pH back toward normal. The lungs are the source of the problem, not the compensation. Excreting bicarbonate or retaining more CO2 would worsen the acidosis.

26. The ureters transport urine by:

    1. A. Peristalsis
    2. B. Gravity alone
    3. C. Negative pressure from the bladder
    4. D. Ciliary beating
    Show answer

    Answer: A. Peristalsis

    A stone lodged in a ureter causes severe colicky pain.

27. Renal colic pain characteristically:

    1. A. Is localized to the lower chest
    2. B. Is wavelike and radiates to groin
    3. C. Is relieved by lying perfectly still
    4. D. Is constant, dull, and mild
    Show answer

    Answer: B. Is wavelike and radiates to groin

    Patients often cannot find a comfortable position. It typically starts in the flank.

28. The bladder's normal capacity is approximately:

    1. A. About 100 mL
    2. B. About 500 mL
    3. C. About 2 L
    4. D. About 50 mL
    Show answer

    Answer: B. About 500 mL

    It lies behind the pubic symphysis. The urge to void is usually felt around 300 mL.

29. The internal urethral sphincter is:

    1. A. A ring of elastic cartilage
    2. B. Involuntary smooth muscle
    3. C. Located at the urethral opening
    4. D. Voluntary skeletal muscle
    Show answer

    Answer: B. Involuntary smooth muscle

    The external sphincter is under voluntary control. It is muscle, not cartilage, and it sits at the bladder neck rather than at the outer urethral opening.

30. The female urethra is shorter than the male urethra, which:

    1. A. Raises the risk of kidney stones
    2. B. Increases UTI risk
    3. C. Reduces bladder capacity
    4. D. Increases urinary retention risk
    Show answer

    Answer: B. Increases UTI risk

    Bacteria have a shorter route to the bladder. Urethral length does not cause stones, and retention is more common in men, often from prostate enlargement.

31. A 70-kg trauma patient with a urinary catheter has produced 15 mL of urine in the past hour. This indicates:

    1. A. Normal output for an adult of this size
    2. B. Low output, suggesting poor perfusion
    3. C. Polyuria from the IV fluids given
    4. D. Fluid overload from the trauma itself
    Show answer

    Answer: B. Low output, suggesting poor perfusion

    Normal adult output is about 0.5 to 1 mL/kg/h, which is roughly 35 to 70 mL/h for 70 kg. Fifteen mL in an hour is oliguria and in trauma suggests hypoperfusion (shock). Polyuria is excessive output, and fluid overload does not reduce urine output in a healthy kidney.

32. Oliguria refers to:

    1. A. Painful or burning urination
    2. B. Abnormally low urine output
    3. C. Blood in the urine
    4. D. Excessive urination
    Show answer

    Answer: B. Abnormally low urine output

    Anuria means essentially no output.

33. Polyuria commonly results from:

    1. A. Urinary retention
    2. B. Excess ADH secretion
    3. C. Severe dehydration
    4. D. Hyperglycemia
    Show answer

    Answer: D. Hyperglycemia

    Osmotic diuresis is a common mechanism. Diuretics and diabetes insipidus are other causes.

34. Hematuria refers to:

    1. A. Painful urination
    2. B. Excess urination
    3. C. Protein in urine
    4. D. Blood in the urine
    Show answer

    Answer: D. Blood in the urine

    Trauma, stones, and infection are causes.

35. Dysuria refers to:

    1. A. Frequent urination at night
    2. B. Absence of urine output
    3. C. Painful urination
    4. D. Blood in the urine
    Show answer

    Answer: C. Painful urination

    It commonly accompanies infection. Urination may also be difficult.

36. Acute kidney injury may be caused by:

    1. A. Hypoperfusion, toxins, or obstruction
    2. B. Increased renal blood flow and filtration
    3. C. Overhydration and high urine flow
    4. D. Release of excess aldosterone
    Show answer

    Answer: A. Hypoperfusion, toxins, or obstruction

    Prerenal, intrarenal, and postrenal are the categories. More renal blood flow supports filtration rather than injuring the kidney, and aldosterone adjusts sodium and potassium handling without causing acute injury.

37. Chronic kidney disease produces:

    1. A. Raised erythropoietin and polycythemia
    2. B. Hypercalcemia and low phosphate
    3. C. Hypokalemia and metabolic alkalosis
    4. D. Hyperkalemia, acidosis, and anemia
    Show answer

    Answer: D. Hyperkalemia, acidosis, and anemia

    Dialysis replaces some of this function. Fluid overload is also common. Failing kidneys retain phosphate and activate less vitamin D, so phosphate usually rises and calcium falls.

38. A dialysis patient who misses treatments is at greatest immediate risk of:

    1. A. Hypokalemia and weakness
    2. B. Hypoglycemia and seizures
    3. C. Hyperkalemia and fluid overload
    4. D. Dehydration and hypovolemia
    Show answer

    Answer: C. Hyperkalemia and fluid overload

    Ask when they were last dialyzed. Hyperkalemia can cause dysrhythmias.

39. An arteriovenous fistula used for dialysis should:

    1. A. Be compressed to prevent bleeding
    2. B. Be covered with a tight dressing
    3. C. Be protected from BP cuffs and IVs
    4. D. Be used for routine IV access
    Show answer

    Answer: C. Be protected from BP cuffs and IVs

    A thrill should be palpable over it.

40. Urinary retention in an older man is commonly caused by:

    1. A. Excess fluid intake
    2. B. Simple dehydration
    3. C. Prostatic enlargement
    4. D. Acute kidney failure
    Show answer

    Answer: C. Prostatic enlargement

    It can cause significant pain and postrenal injury.

41. A urinary catheter draining cloudy, foul urine in an older adult suggests:

    1. A. Normal catheter findings
    2. B. A likely urinary infection
    3. C. Mild dehydration only
    4. D. An obstructing kidney stone
    Show answer

    Answer: B. A likely urinary infection

    Infection often presents atypically in the elderly. It may present as confusion.

42. Total body water is regulated primarily through:

    1. A. Kidneys under hormonal control
    2. B. Water lost in the stool
    3. C. Sweat losses through the skin
    4. D. Water lost in exhaled air
    Show answer

    Answer: A. Kidneys under hormonal control

    Thirst regulates intake. The kidneys adjust water excretion.

43. Which hormone is released when blood osmolarity rises?

    1. A. Antidiuretic hormone
    2. B. Aldosterone
    3. C. Atrial natriuretic peptide
    4. D. Parathyroid hormone
    Show answer

    Answer: A. Antidiuretic hormone

    Water is retained to dilute the blood.

44. Sodium's primary role in fluid balance is to:

    1. A. Buffer acids in the blood
    2. B. Set intracellular fluid volume
    3. C. Set extracellular fluid volume
    4. D. Generate plasma oncotic pressure
    Show answer

    Answer: C. Set extracellular fluid volume

    Sodium disorders are really water disorders. Water follows sodium. Potassium is the main intracellular cation, and plasma oncotic pressure comes mostly from albumin.

45. Hypernatremia usually reflects:

    1. A. Low plasma protein
    2. B. A water deficit
    3. C. Excess potassium
    4. D. Excess body water
    Show answer

    Answer: B. A water deficit

    It presents with thirst, weakness, and confusion. The deficit is relative to sodium.

46. Potassium abnormalities are dangerous mainly because they:

    1. A. Disturb cardiac conduction
    2. B. Alter blood pH directly
    3. C. Cause seizures from brain swelling
    4. D. Shift body fluid volume
    Show answer

    Answer: A. Disturb cardiac conduction

    Both high and low levels cause dysrhythmias. Seizures from brain swelling are a feature of sodium disorders such as severe hyponatremia.

47. Which organ system works with the kidney to regulate blood pressure?

    1. A. Digestive and hepatic
    2. B. Cardiovascular and endocrine
    3. C. Skeletal and muscular
    4. D. Integumentary and lymphatic
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    Answer: B. Cardiovascular and endocrine

    Volume and vascular tone are adjusted together. RAAS and ADH link these systems.

48. Why does a febrile, tachypneic child lose fluid faster than a calm, afebrile child?

    1. A. Fever and fast breathing raise insensible losses
    2. B. The kidneys stop concentrating urine during fever
    3. C. The child drinks more than usual when febrile
    4. D. Fever reduces sweating and traps fluid in tissue
    Show answer

    Answer: A. Fever and fast breathing raise insensible losses

    Insensible water loss through the skin and exhaled air rises with fever and fast breathing. Children have a large surface area and high metabolic rate, so they dehydrate quickly. The kidneys still concentrate urine. Drinking more would offset losses, and fever increases sweating rather than reducing it.

49. Which patient is at greatest risk of rapid dehydration?

    1. A. A healthy middle-aged adult
    2. B. A trained young athlete
    3. C. An adult with mild nausea
    4. D. An infant with vomiting
    Show answer

    Answer: D. An infant with vomiting

    Infants have high turnover and limited reserves. Diarrhea adds to the losses.

50. The urinary system contributes to blood pressure regulation by:

    1. A. Remodeling vessel walls
    2. B. Adjusting blood volume
    3. C. Changing the heart rate
    4. D. Producing catecholamines
    Show answer

    Answer: B. Adjusting blood volume

    This is a slower but sustained mechanism. It does this through sodium and water handling.