Which laboratory value increases when renal function decreases and urinary obstruction is present?

Which laboratory value increases when renal function decreases and urinary obstruction is present?

• A. Creatinine
• B. Uric Acid
• C. Aldosterone
• D. Lactate Dehydrogenase (LDH)

Answer: (A)

When kidney filtration declines, especially with urinary obstruction, serum creatinine rises. Creatinine is produced at a steady rate by muscle and is cleared by the kidneys through filtration; when the obstruction lowers the glomerular filtration rate, clearance drops and creatinine accumulates in the blood. This makes creatinine a reliable indicator of decreased renal function in obstructive uropathy. Uric acid can also increase with reduced renal clearance, but its levels are influenced by many factors beyond obstruction, so it’s less specific. Aldosterone reflects hormonal regulation of fluid and electrolyte balance rather than direct renal filtration status. LDH is a nonspecific marker of tissue injury and does not specifically track renal function or obstruction.

When kidney filtration declines, especially with urinary obstruction, serum creatinine rises. Creatinine is produced at a steady rate by muscle and is cleared by the kidneys through filtration; when the obstruction lowers the glomerular filtration rate, clearance drops and creatinine accumulates in the blood. This makes creatinine a reliable indicator of decreased renal function in obstructive uropathy.

Uric acid can also increase with reduced renal clearance, but its levels are influenced by many factors beyond obstruction, so it’s less specific. Aldosterone reflects hormonal regulation of fluid and electrolyte balance rather than direct renal filtration status. LDH is a nonspecific marker of tissue injury and does not specifically track renal function or obstruction.