ROUTINE PHYSICAL AND BIOCHEMICAL URINE tests questions and answers with solutions 2025
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Course
Urine
Institution
Urine
Which statement regarding renal function is true?
A. Glomeruli are far more permeable to H2 O and salt than other capillaries
B. The collecting tubule reabsorbs sodium and secretes potassium in response to antidiuretic hormone (ADH)
C. The collecting tubule is permeable to H2 O only in the prese...
ROUTINE PHYSICAL AND BIOCHEMICAL
URINE tests questions and answers with
solutions 2025
Which statement regarding renal function is true?
A. Glomeruli are far more permeable to H2 O and salt than other capillaries
B. The collecting tubule reabsorbs sodium and secretes potassium in response to antidiuretic hormone
(ADH)
C. The collecting tubule is permeable to H2 O only in the presence of aldosterone
D. The thick ascending limb is highly permeable to H2 O and urea - ANSWER A
The formation of plasma ultrafiltrate depends upon high hydrostatic pressure and permeability of the
glomeruli. Aldosterone is released when afferent arterial pressure falls, and ADH is released when
plasma osmolality becomes too high. The collecting tubule reabsorbs sodium and secretes potassium in
response to aldosterone, and is permeable to H2 O only in the presence of ADH. The thick ascending
limb is permeable to salt, but not to H2 O or urea.
Harr, Robert R. Medical Laboratory Science Review (Page 329). F.A. Davis Company. Kindle Edition.
Which statement regarding normal salt and H2 O handling by the nephron is correct?
A. The ascending limb of the tubule is highly permeable to salt but not H2 O
B. The stimulus for ADH release is low arterial pressure in the afferent arteriole
C. The descending limb of the tubule is impermeable to urea but highly permeable to salt
D. Renin is released in response to high plasma osmolality - ANSWER A
The tubules are able to concentrate the filtrate because the descending limb is highly permeable to H2 O
and urea but not to salt, and the ascending limb is permeable to salt. Salt leaving the ascending limb
creates a hypertonic interstitium that forces H2 O from the descending limb. Renin is released in
response to low hydrostatic pressure in the afferent arteriole, which stimulates the juxtaglomerular cells.
ADH is released by the posterior pituitary in response to high plasma osmolality.
Harr, Robert R. Medical Laboratory Science Review (Page 329). F.A. Davis Company. Kindle Edition.
Which statement concerning renal tubular function is true?
A. In salt deprivation, the kidneys will conserve sodium at the expense of potassium
,B. Potassium is not excreted when serum concentration is below 3.5 mmol/L
C. No substance can be excreted into urine at a rate that exceeds the glomerular filtration rate
D. When tubular function is lost, the specific gravity of urine will be below 1.005 - ANSWER A
Sodium is a threshold substance, meaning that no sodium will be excreted in the urine until the renal
threshold (a plasma sodium concentration of approximately 120 mmol/L) is exceeded. Potassium is not a
threshold substance and will be secreted by the tubules even when plasma potassium levels are low.
Patients on diuretics or who have hypovolemia become hypokalemic for this reason. Some substances
(e.g., penicillin) can be excreted at a rate exceeding glomerular filtration because the tubules secrete
them. The tubules are responsible for concentrating the filtrate in conditions of water deprivation and
diluting it in conditions of water excess. When tubular function is lost, salt and water equilibrate by
passive diffusion and the specific gravity of the urine becomes the same as the plasma, approximately
1.010.
Harr, Robert R. Medical Laboratory Science Review (Page 329). F.A. Davis Company. Kindle Edition.
Which of the following is inappropriate when collecting urine for routine bacteriologic culture?
A. The container must be sterile
B. The midstream void technique must be used
C. The collected sample must be plated within 2 hours unless refrigerated
D. The sample may be held at 2°C-8°C for up to 48 hours prior to plating - ANSWER D
Urine specimens should be plated and incubated within 2 hours of collection (some labs use a 1-hour
time limit), and within 24 hours if the sample is refrigerated at 2°C-8°C immediately following collection.
No additives are permitted when urine is collected for culture.
Harr, Robert R. Medical Laboratory Science Review (Page 330). F.A. Davis Company. Kindle Edition.
Which statement about sample collection for routine urinalysis is true?
A. Preservative tablets should be used for collecting random urine specimens
B. Containers may be washed and reused if rinsed in deionized H2 O
C. Samples may be stored at room temperature for up to 2 hours
D. First morning voided samples are not acceptable when renal disease is suspected - ANSWER C
The first morning voided sample is the most sensitive for screening purposes because formed elements
are concentrated, but random samples are satisfactory because glomerular bleeding, albuminuria, and
, cast formation may occur at any time. Preservative tablets should be avoided because they may cause
chemical interference with some dry reagent strip and turbidimetric protein tests. Changes in glucose,
bilirubin, and urobilinogen can occur within 30 minutes of collection. Therefore, samples should be
refrigerated if not tested within 2 hours.
Harr, Robert R. Medical Laboratory Science Review (Page 330). F.A. Davis Company. Kindle Edition.
Which urine color is correlated correctly with the pigment-producing substance?
A. Smoky red urine with homogentisic acid
B. Dark amber urine with myoglobin
C. Deep yellow urine and yellow foam with bilirubin
D. Red-brown urine with biliverdin - ANSWER C
Homogentisic acid causes dark brown or black-colored urine. Myoglobin causes a red to red-brown color
in urine, and biliverdin causes a green or yellow-green color. In addition to metabolic diseases and renal
disease, abnormal color can be caused by drugs (e.g., Gantrisin), dyes excreted by the kidneys (e.g., PSP),
and natural or artificial food coloring (e.g., beets).
Harr, Robert R. Medical Laboratory Science Review (Page 330). F.A. Davis Company. Kindle Edition.
Which of the following substances will cause urine to produce red fluorescence when examined with an
ultraviolet lamp (360 nm)?
A. Myoglobin
B. Porphobilinogen (PBG)
C. Urobilin
D. Coproporphyrin - ANSWER D
Myoglobin causes a positive test for blood but does not cause urine to fluoresce. PBG causes urine to
become dark (orange to orange-brown) on standing but does not fluoresce. Uroporphyrin and
coproporphyrin produce red or orange-red fluorescence. Unlike hemoglobin, porphyrins lack peroxidase
activity. Urobilin is an oxidation product of urobilinogen. It turns the urine orange to orange-brown but
does not produce fluorescence.
Harr, Robert R. Medical Laboratory Science Review (Page 330). F.A. Davis Company. Kindle Edition.
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