Acute Lower Abdominal Pain in a 25-Year-Old Female - Clinical Assessment

Step 1: Immediate Priority - Rule Out Life-Threatening Causes

1. Ectopic Pregnancy (MUST EXCLUDE FIRST)

"Because the history and physical examination of the patient with ectopic pregnancy are insensitive and nonspecific, pelvic ultrasonography and determination of serum hCG levels are essential to locate the pregnancy in any patient who has abdominal pain or vaginal bleeding and a positive pregnancy test result."

• Ectopic pregnancy accounts for ~1-2% of all pregnancies, but 10-16% of women presenting to ED with pain or bleeding in first trimester
• Classic triad: delayed/missed menses + lower abdominal pain + vaginal bleeding - but this triad is absent in many cases
• 15-20% of symptomatic ectopic patients have NOT missed a period
• Pain can radiate to the vagina/perineum from peritoneal irritation or blood pooling in the pouch of Douglas
• Risk factors include prior PID, tubal surgery, IUD use, smoking, prior ectopic
• Adnexal mass is palpable in only 10-20% of cases
• Do NOT exclude ectopic based on normal vitals - tachycardia and hypotension may be late signs

"The presence of peritoneal signs, cervical motion tenderness, or lateral or bilateral abdominal or pelvic tenderness indicates an increased likelihood of ectopic pregnancy." - Rosen's Emergency Medicine

Step 2: Differential Diagnosis

"Adnexal pathology can present acutely and may be due to rupture, bleeding, or torsion of ovarian cysts... Ovarian torsion typically presents as acute onset of unilateral, intermittent pain and is a diagnosis of exclusion unless absent blood flow to the ovary is demonstrated via Doppler ultrasound."

Step 3: History to Take Urgently

• LMP (last menstrual period) - is this overdue?
• Sexual activity and contraceptive use (IUD?)
• Character of pain: sudden vs. gradual, crampy vs. constant, radiation pattern
• Any vaginal bleeding or discharge?
• Dyspareunia (pain with intercourse)?
• Fever, nausea, vomiting?
• Prior history of STI, PID, ectopic, pelvic surgery?
• Urinary symptoms (to exclude UTI/renal colic)

Step 4: Examination

• Vitals: HR, BP, temperature, SpO2
• Abdomen: tenderness location, guarding, rigidity, rebound
• Pelvic exam:
  • Cervical motion tenderness (CMT) - suggests PID or ectopic
  • Adnexal tenderness and mass
  • Uterine size and tenderness
  • Vaginal discharge (mucopurulent = PID)
  • Cervical os - open/closed

Step 5: Investigations (in order of urgency)

1. Urine pregnancy test (UPT) - FIRST - If positive, treat as ectopic until proven otherwise
2. Serum beta-hCG - quantitative (levels >1500-2000 IU/L should show IUP on TV-US)
3. Transvaginal ultrasound - locate the pregnancy, assess adnexa, free fluid
4. CBC - leukocytosis (PID, appendicitis), anaemia (haemorrhage)
5. CRP / ESR - elevated in PID, appendicitis
6. Urine routine/microscopy - exclude UTI
7. Cervical swabs/NAATs for Chlamydia and Gonorrhoea (if PID suspected)
8. Colour Doppler ultrasound if ovarian torsion is suspected - look for absent/reversed flow

Step 6: Key Diagnoses Explained

Pelvic Inflammatory Disease (PID)

"Because PID causes significant morbidity, the CDC recommends a low threshold for the diagnosis and empirical treatment of PID." - Rosen's Emergency Medicine

Primary Dysmenorrhea

"The pain of primary dysmenorrhea usually begins a few hours before or just after the onset of a menstrual period... suprapubic cramping, and may be accompanied by lumbosacral backache, pain radiating down the anterior thigh, nausea, vomiting... The pain of dysmenorrhea is colicky in nature and, unlike abdominal pain caused by chemical or infectious peritonitis, is relieved by abdominal massage, counterpressure, or movement."

Ovarian Torsion (from Bailey & Love's Surgery)

• Sudden onset abdominal pain, nausea/vomiting
• Palpable adnexal mass, signs of peritonism
• Risk factors: enlarged ovary/cyst, para-ovarian cyst, hydrosalpinx
• Investigations: US shows unilateral ovarian enlargement, central adnexal mass, peripheral follicular displacement ("follicular ring sign"), absent Doppler flow
• Management: Surgical emergency - laparoscopic detorsion within 4-6 hours to preserve ovarian function

Step 7: Why the Pain Radiates to the Vagina

1. Shared innervation: The pelvic organs (uterus, ovaries, fallopian tubes) share thoracolumbar (T10-L1) and sacral (S2-S4) innervation. Blood or inflammatory fluid in the pouch of Douglas irritates sacral nerve roots causing vaginal/perineal pain.
2. Peritoneal irritation: Free blood from a ruptured ectopic or cyst, or purulent fluid from PID, pools in the pelvis and causes referred pain to the vagina/perineum.
3. Uterine cramping (dysmenorrhea) can radiate to the vagina via sacral nerves.

Step 8: Immediate Management

1. Establish IV access - assess haemodynamic stability
2. Urgent UPT - if positive → urgent US + beta-hCG → gynaecology consult
3. Do NOT give more NSAIDs without diagnosis - pain unresponsive to NSAIDs in a young female needs urgent work-up
4. Antispasmodic (e.g. Hyoscine butylbromide/Buscopan) may help if colic/spasm is a component
5. If PID is likely: Start empiric antibiotics per CDC regimen (Ceftriaxone + Doxycycline + Metronidazole)
6. If ectopic/torsion suspected: Surgical consultation, prepare for theatre
7. If haemodynamically unstable with positive hCG: Emergency laparoscopy/laparotomy

Red Flag Signs Requiring Immediate Action

• Positive pregnancy test + lower abdominal pain = ectopic until proven otherwise
• Haemodynamic instability (tachycardia, hypotension, pallor)
• Peritoneal signs (rigid abdomen, rebound tenderness)
• Fever >38.3°C + pelvic tenderness
• Pain unresponsive to analgesics (as in this case)
• Adnexal mass on exam