In a pregnant patient with suspected kidney stones, which imaging modality is preferred?

• A. CT abdomen/pelvis without contrast
• B. MRI
• C. X-ray
• D. Ultrasound

Answer: (D)

In pregnancy, the key idea is to diagnose suspected kidney stones without exposing the fetus to ionizing radiation. Renal ultrasound fits this goal because it has no radiation, is readily available, and can reveal signs of obstruction such as hydronephrosis, plus assess the kidneys and bladder to guide urgent management. Its main limitation is that it may miss small distal ureteral stones, and image quality can be affected by patient factors, but it remains the safest and most informative first test during pregnancy.

If ultrasound doesn’t explain the symptoms or obstruction is still suspected, noninvasive MRI without contrast can be used next to evaluate the kidneys and urinary tract without radiation. CT of the abdomen/pelvis without contrast provides excellent stone detection but involves ionizing radiation, which is undesirable in pregnancy unless absolutely necessary. Plain X-ray is less sensitive for most stones and also involves radiation, making it a poor initial choice in this setting.