What compensatory change may occur in the contralateral kidney in unilateral renal artery disease?

What compensatory change may occur in the contralateral kidney in unilateral renal artery disease?

• A. Kidney size <9 cm
• B. Absence of visible main renal artery
• C. Compensatory hypertrophy of contralateral kidney
• D. Damped infrarenal flow signs

Answer: (C)

When one kidney loses function from unilateral renal artery disease, the other (contralateral) kidney often takes on more work to keep overall renal function adequate. That increased workload prompts hypertrophy of the healthy kidney, so it enlarges as an adaptive response. On ultrasound this appears as a larger contralateral kidney compared with the affected side, reflecting compensatory hypertrophy. The other options describe findings not related to this adaptive change: a kidney smaller than typical suggests atrophy or chronic disease of the kidney itself; absence of a main renal artery implies a vascular anomaly or occlusion rather than a compensatory process; and damped infrarenal flow signs point to downstream vascular flow issues, not a kidney's adaptive enlargement.

When one kidney loses function from unilateral renal artery disease, the other (contralateral) kidney often takes on more work to keep overall renal function adequate. That increased workload prompts hypertrophy of the healthy kidney, so it enlarges as an adaptive response. On ultrasound this appears as a larger contralateral kidney compared with the affected side, reflecting compensatory hypertrophy.

The other options describe findings not related to this adaptive change: a kidney smaller than typical suggests atrophy or chronic disease of the kidney itself; absence of a main renal artery implies a vascular anomaly or occlusion rather than a compensatory process; and damped infrarenal flow signs point to downstream vascular flow issues, not a kidney's adaptive enlargement.