Adnexal mass in early pregnancy — structured SAQ (15 marks)

(a) Sonographic characterisation (3 marks)

One mark for naming the system; one for listing the B and M features; one for stating the application rule. [1]

• I would characterise the mass using the International Ovarian Tumour Analysis (IOTA) Simple Rules, escalating to the ADNEX model or expert subjective assessment if the Simple Rules were inconclusive.
• Five B features (predict benign): unilocular cyst; solid components under 7 mm in largest diameter; acoustic shadows; smooth multilocular tumour under 100 mm; no detectable blood flow. Five M features (predict malignant): irregular solid tumour; ascites; at least four papillary structures; irregular multilocular solid tumour 100 mm or more; very high colour content.
• Application rule: one or more M and no B classifies malignant; the reverse classifies benign; both or neither makes the rules inconclusive, and the next step is expert subjective assessment or ADNEX (10% malignancy threshold).[1][2]

(b) Tumour markers in pregnancy (2 marks)

One mark for the principle; one for the reason. [3]

• Tumour markers — CA-125, AFP, hCG, inhibin, LDH — are uninterpretable in pregnancy and should not be sent routinely on a sonographically characterised mass.
• CA-125 is expressed by peritoneum, decidua and amniotic fluid and rises physiologically, particularly in the first trimester; AFP, hCG and inhibin are produced by the pregnancy itself. Mid-range values are non-informative; only extreme values or a rising trend should influence the decision.[3]

(c) Most likely diagnosis and management (5 marks)

One mark for the diagnosis; two for the supporting evidence; two for the management. [3]

• Most likely diagnosis: a decidualised endometrioma — papillary projections with flow in a woman with known endometriosis, in pregnancy.
• Supporting evidence: in the Barcroft pregnancy-specific IOTA two-step pilot (291 pregnant women), presumed decidualisation occurred in 31.1% of endometriomas and had resolved in 89.5% by the first postnatal scan; the ADNEX model misclassified 34% of benign masses as malignant, over half of which were decidualised endometriomas. Decidualisation is progesterone-driven stromal change producing vascular papillary projections that mimic the M features of malignancy.[3]
• Management: resist surgery, use expert subjective assessment and serial imaging, and rescan postnatally. Counsel honestly that this is the great mimic, not a cancer. Avoid gadolinium if MRI is needed.[3]

(d) Sudden pain at 16 weeks (3 marks)

One mark for the diagnosis; two for the management. [4]

• Diagnosis: ovarian torsion until proven otherwise. Sudden severe unilateral lower abdominal pain with vomiting in a pregnant woman with a known adnexal mass is torsion — ovarian salvage is time-critical.
• Management: analgesia, intravenous access, bloods, nil by mouth, anaesthetic and theatre. Laparoscopic detorsion with ovarian conservation (even when the ovary looks dusky), with oophorectomy reserved for confirmed necrosis. Document the fetal heart before and after surgery. Obstetric outcomes are favourable — live birth around 92% and preterm delivery around 19% in the largest cohort.[4]

(e) Consent numbers for non-obstetric surgery (2 marks)

One mark for citing the cohort; one for the absolute numbers. [5]

• The numbers come from the Balinskaite cohort of 6.5 million pregnancies.
• Non-obstetric surgery during pregnancy was associated with one additional stillbirth per 287 operations, one additional preterm delivery per 31, one additional low-birthweight baby per 39, one additional caesarean per 25, and one additional long inpatient stay per 50. Attributable risk is low and surgery is generally safe, but these are the numbers to quote.[5]