Genitourinary and Obstetric/Gynaecological Imaging
Genitourinary and obstetric/gynaecological imaging tests safe decision-making in pregnancy, characterisation of renal and adnexal masses, and recognition of obstetric emergencies.
Renal and urinary
- A solid enhancing renal mass is renal cell carcinoma until proven otherwise; clear cell tumours are hypervascular.
- Bosniak classification stratifies cystic renal masses by septa, nodularity and enhancement.
- Non-contrast CT KUB is first-line for suspected stone; stones typically exceed 200 Hounsfield units.
- Hydronephrosis is diagnosed by dilated calyces, not by kidney size alone.
Obstetric and gynaecological
- First-trimester ultrasound distinguishes intrauterine from ectopic pregnancy; an empty uterus with an adnexal mass and free fluid suggests ectopic.
- The discriminatory human chorionic gonadotropin level (around 3,500 mIU/mL) is a guide, not an absolute rule.
- Ovarian torsion shows an enlarged ovary with peripheral follicles and a twisted pedicle.
- Placenta praevia is placental cover of the internal os; accreta is suggested by loss of the normal interface.
Worked example
A 28-year-old with 7 weeks of amenorrhoea, pain and hCG 2,500 has an empty uterus and a 3-cm right adnexal mass with free fluid. Ectopic pregnancy is the working diagnosis even below the discriminatory zone; a corpus luteum cyst would be intra-ovarian with a ring-of-fire Doppler pattern.
Traps
- Treating every adnexal cyst as ectopic.
- Giving methotrexate before excluding a live intrauterine pregnancy.
- Ignoring ionizing radiation risk when ultrasound answers the question.