Expected genitourinary changes during pregnancy
Renal function
- GFR increases 40-65% due to increased blood flow
- Hyponatremia: mild (4-5mmol/L below baseline) secondary to lower threshold for ADH secretion
- Kidneys enlarge ~1cm
- Pelvicalyceal dilation: seen in ~90%, 15mm on R side and 5mm on L
- Ureteral dilation due to smooth muscle relaxation and uterine compression (starts during 2nd month, worse on R side)
- Hydronephrosis: usually physiologic, attempt conservative therapy (analgesia, positioning, IV fluids) if symptomatic
Urinalysis findings
- Glucosuria: intermittent normal, but persistent is concerning for diabetes
- Proteinuria expected up to 300mg (albuminuria up to 30mg)
- Calciuria: doubles during pregnancy but serum ionized levels are unchanged
- Hematuria: seen in up to 20%, usually benign due to increased vascularity, but consider other causes if persistent, unclear if associated with preeclampsia
Imaging and Operative Planning
Imaging considerations
- Exposure: should not exceed 50mGy or 10 rads fetal exposure
- Timing: most concerning during first trimester due to organogenesis and rapid cell division, decreased radiation sensitivity during 2nd/3rd trimesters but potential increased risk for childhood cancers
- Type: US and MR imaging have no associated risks, XR, CT, and NM studies should be offered with understanding of potential risk, but exposure is lower than harmful level
- Contrast: minimal overall proven risk, but only use if "benefits outweigh risks"
- Intraop use: use shielding and lower doses
- Fetal risks: mutagenesis (0.1-0.4% risk per rad of fetal exposure), developmental delay (0.4% risk per rad of fetal exposure), childhood cancer (~0.05% risk per rad of fetal exposure), teratogenetis (rare below 10rads), spontaneous abortion (potentially before implantation, otherwise rare below 10rads)
Operative considerations
- Anesthetic agents: not proven to have any teratogenic effects
- Considerations: indicated surgery must be recommmended regardless of pregnancy status, nonurgent surgery should be performed during 2nd trimester - preterm contractions and spontaneous abortion are least likely
- Intraop tips: OB provider with C-section capabilities should be available, fetal heart monitoring recommended, venous return may be decreased due to IVC compression, can perform open or laparoscopic surgery during pregnancy, insufflate to 10-15mmHg
- Preterm delivery: occurs 16% during 3rd trimester surgeries, including 10% ureteroscopy
- Hematologic changes: patients become anemic and at higher risk for coagulopathy (venous stasis in legs + increased clotting factors)
References
- AUA Core Curriculum
- Kaufman, M. "Urologic Considerations in Pregnancy." Campbell-Walsh-Wein Urology. 12th ed. Elsevier (2020): 1129-1201.
- Wieder JA: Pocket Guide to Urology. Sixth Edition. J.Wieder Medical: Oakland, CA, 2021.