Acute Hypogastric (Lower Abdominal) Pain in a 21-Year-Old Woman — Approach & Management

Step 1: IMMEDIATE Assessment (First Minutes)

Vital Signs + Hemodynamic Status

• Blood pressure, pulse, SpO₂, temperature, respiratory rate
• Is she hemodynamically stable or unstable?
  • Unstable (hypotension, tachycardia) → surgical emergency — ectopic pregnancy/ruptured cyst until proven otherwise
  • Stable → proceed with structured workup

Step 2: MANDATORY First Test — Urine/Serum β-hCG

"A pregnancy test should always be obtained, because ectopic pregnancy and other pregnancy-related conditions may mimic PID." — Rosen's Emergency Medicine

Step 3: HISTORY — Key Questions

Classic "Three A's" of Ectopic Pregnancy:

• Amenorrhea
• Abdominal (pelvic) pain
• Abnormal vaginal bleeding (Present in 75–95% of ectopic pregnancies)

Step 4: PHYSICAL EXAMINATION

Abdominal exam:

• Suprapubic/lower quadrant tenderness, guarding, rigidity
• Rebound tenderness → peritoneal irritation (ruptured ectopic, appendicitis)

Pelvic/bimanual exam:

• Cervical motion tenderness (CMT) → PID (minimum criterion)
• Adnexal tenderness/mass → ectopic, ovarian torsion
• Uterine tenderness → PID, endometritis
• Mucopurulent discharge → PID

CDC criteria: Presumptive PID diagnosis in a sexually active woman at risk for STIs with lower abdominal pain if no alternative diagnosis and ≥1 of: CMT, uterine tenderness, or adnexal tenderness. — Rosen's Emergency Medicine

Step 5: INVESTIGATIONS

Transvaginal US + serum β-hCG combined: Empty uterus + positive β-hCG = strongly suggestive of ectopic pregnancy. Discriminatory zone: if β-hCG >1,200–1,500 mIU/mL with transvaginal probe and no intrauterine pregnancy seen = ectopic until proven otherwise. — Roberts & Hedges' Clinical Procedures in Emergency Medicine

Step 6: DIFFERENTIAL DIAGNOSIS

If β-hCG Positive:

If β-hCG Negative:

Step 7: TREATMENT

A. ECTOPIC PREGNANCY

• IM Methotrexate (folic acid antagonist, destroys trophoblastic tissue) — single-dose protocol
  • Success in 90% of cases; cumulative rate 95%
  • Monitor β-hCG: should fall ≥15% between days 4–7; if not → second dose or surgery
  • Conditions required: hemodynamically stable, no hemoperitoneum, normal CBC/LFT/renal function, patient able to follow up, mass < 3.5 cm, preferably < 8 weeks gestation
• Expectant management: only if β-hCG falling spontaneously and patient is reliable for follow-up

— Swanson's Family Medicine Review

B. PID (Pelvic Inflammatory Disease)

• Ceftriaxone 250 mg IM (single dose) +
• Doxycycline 100 mg PO BD × 14 days +
• Metronidazole 500 mg PO BD × 14 days (anaerobic coverage now routinely added)
• Follow-up at 72 hours to confirm response

• Tubo-ovarian abscess
• Cannot exclude surgical emergency (appendicitis)
• Pregnancy
• Severe illness, vomiting, high fever
• No response to oral therapy
• Unable to tolerate/comply with outpatient regimen

• Cefoxitin 2g IV q6h (or cefotetan) + Doxycycline 100 mg IV/PO q12h
• OR Clindamycin 900 mg IV q8h + Gentamicin (loading dose 2 mg/kg then 1.5 mg/kg q8h)
• Transition to oral after clinical improvement; total 14 days antibiotic therapy
• Sexual intercourse deferred until both patient and partner complete treatment

— Rosen's Emergency Medicine, Harrison's Principles of Internal Medicine 22e

C. OVARIAN TORSION

• Gynecologic consultation immediately — surgical emergency
• Laparoscopic detorsion (within hours to preserve ovarian function)
• Ovarian cystectomy if cyst/mass present
• Do not wait for negative Doppler if clinical suspicion is high

D. RUPTURED OVARIAN CYST

• Conservative management if hemodynamically stable: analgesia, observation, repeat ultrasound
• Surgery if hemodynamically unstable or hemorrhage uncontrolled

E. UTI / Cystitis

• Nitrofurantoin 100 mg BD × 5–7 days or Trimethoprim-sulfamethoxazole × 3–5 days or Fosfomycin single dose

Summary Algorithm

21F — Hypogastric pain (acute onset)
        ↓
   VITALS stable?
   NO → IV access, fluids, O₂, urgent surgical consult (ruptured ectopic?)
   YES ↓
   β-hCG (STAT)
   POSITIVE → Pelvic US (TVS) → ectopic vs. IUP → manage accordingly
   NEGATIVE → Pelvic exam → CMT/adnexal tenderness?
              YES → Presume PID → NAAT, CBC, CRP → empirical antibiotics
              NO → Consider torsion/cyst/appendicitis → US ± CT

Sources: Rosen's Emergency Medicine; Roberts & Hedges' Clinical Procedures in Emergency Medicine; Swanson's Family Medicine Review; Harrison's Principles of Internal Medicine 22e; Tintinalli's Emergency Medicine