Differentials
Miscarriage
SIGNS / SYMPTOMS
Includes anembryonic gestation, threatened abortion, incomplete abortion, complete abortion, missed abortion.
Often presents with vaginal bleeding in the first trimester, accompanied by abdominal discomfort secondary to uterine contractions.
History may yield disappearance of pregnancy symptoms such as breast tenderness and nausea.
INVESTIGATIONS
Ultrasound shows intrauterine pregnancy.
Pelvic examination may note dilation of the cervix, as well as presence of tissue at the cervical os.
Consecutive serum chorionic gonadotrophin levels often do not rise appropriately (53% in 48 hours), and progesterone levels often <15.9 nmol/L (<5 ng/mL).
Acute appendicitis
SIGNS / SYMPTOMS
Anorexia and periumbilical pain followed by nausea, right lower quadrant pain, and vomiting.
INVESTIGATIONS
Ultrasound sensitivity of 85% to 90% and specificity of 92% to 96%; may show appendix with outer diameter >6 mm, no compressibility, lack of peristalsis, or periappendiceal fluid.
WBC count >10,000 cells/mm³.
Ovarian torsion
SIGNS / SYMPTOMS
Sudden onset, severe, unilateral lower abdominal pain that worsens intermittently over many hours.
Peritoneal signs are often absent.
INVESTIGATIONS
Ovarian enlargement secondary to impaired venous and lymphatic drainage is the most common sonographical finding in ovarian torsion.
Absence of arterial blood flow may also be used for diagnostic purposes, but this is often absent in the early stages of torsion.
Pelvic inflammatory disease (PID) or tubo-ovarian abscess
SIGNS / SYMPTOMS
Lower abdominal tenderness on palpation, adnexal tenderness, and cervical motion tenderness.
May also have oral temperature >38.4°C (101°F) and abnormal cervical or vaginal discharge.
INVESTIGATIONS
Although rare in pregnancy, can occur in the first 12 weeks of gestation before the decidua seals off the uterus from ascending bacteria.
WBC count often >10,000 cells/mm³.
Ultrasound not used in uncomplicated PID, but is a valuable adjunct in diagnosis of tubo-ovarian abscess.
Ruptured corpus luteal cyst or follicle
SIGNS / SYMPTOMS
Non-specific nausea, vomiting, low grade fever, and pelvic pain, which is often sharp, intermittent, sudden in onset, and severe.
At times the ruptured cyst may lead to profuse bleeding and result in haemorrhagic shock.
INVESTIGATIONS
Doppler ultrasonography usually diagnostic, especially when transvaginal and transabdominal modalities are used together.
Nephrolithiasis
SIGNS / SYMPTOMS
Classically writhing in pain, pacing about, and unable to lie still, in contrast to a woman with peritoneal irritation, who remains motionless to minimise discomfort.
Often presents with unilateral or bilateral flank pain.
INVESTIGATIONS
Haematuria (presence of >1 RBC/hpf) and pyuria (>5 WBC/hpf on a centrifuged specimen) common.
Due to potential risks to the fetus, the only imaging modalities used in pregnant women are ultrasonography (direct visualisation of the stone, hydroureter >6 mm in diameter, and perirenal urinoma suggesting calyceal rupture) and MRI (if ultrasound is non-diagnostic).
Urinary tract infection (UTI)
SIGNS / SYMPTOMS
Dysuria with accompanying urinary urgency, frequency, and abdominal discomfort along the surface of the bladder.
INVESTIGATIONS
May have pyuria (>5 WBC/hpf on a centrifuged specimen).
Presence of nitrites is highly specific for a UTI, but its absence should not exclude the diagnosis.
In all pregnant women with suspected UTI, urine culture must be obtained because the infection increases risk of pre-term labour and pregnancy loss.
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