Which imaging modality is the safest option for evaluating hydronephrosis during pregnancy?

• A. Renal ultrasound
• B. CT urography
• C. MRI
• D. IVP

Answer: (A)

Renal ultrasound is the safest option because it uses no ionizing radiation, which is crucial during pregnancy. It reliably visualizes the kidneys, ureters, and bladder and can show hydronephrosis as dilation of the renal pelvis and calyces, helping distinguish physiologic changes from potential obstruction. It’s quick, widely available, and safe for both mother and fetus, making it the preferred first-line test.

CT urography and intravenous pyelography rely on X-rays and contrast, exposing the fetus to radiation and carrying potential contrast-related risks, so they’re avoided in pregnancy unless absolutely necessary. MRI avoids radiation and is safe, but it’s typically reserved for cases where ultrasound is inconclusive or more detail is needed, due to cost and accessibility.