Clinical overview
Acute pelvic pain is one of the most common reasons women present to emergency departments and to gynaecology assessment units. The clinical task — distinguishing a life-threatening surgical emergency from a benign, self-limiting process — depends entirely on understanding why the pain exists. Pain mechanism dictates pain quality, distribution, time course, and the constellation of associated signs. A registrar who can map the symptom onto the underlying pathophysiology can triage confidently with a hand on the abdomen and a focused history, before any investigation returns.
The genital tract shares its visceral innervation, peritoneal coverage, and pelvic location with the urinary tract and lower bowel. This anatomical promiscuity is why "pelvic pain" is rarely purely gynaecological at the bedside — appendicitis, ureteric colic, diverticulitis, and irritable bowel can all masquerade as gynaecological pain, and vice versa. The chapter focuses on gynaecological mechanisms, but you must always hold the non-gynaecological differential in mind.
There are four dominant pathophysiological mechanisms producing acute gynaecological pelvic pain: (1) acute distension or rupture of a hollow viscus or capsule (ovarian cyst rupture, ectopic, ovarian torsion, haemoperitoneum); (2) acute inflammation with peritoneal involvement (PID, tubo-ovarian abscess, endometriosis flare); (3) ischaemia (torsion, infarcted fibroid, ovarian vein thrombosis); and (4) myometrial or cervical activity (miscarriage, labour pain in early gestations, dysmenorrhoea). Each of these has a characteristic pain footprint that you should learn to recognise.
Core knowledge
Pelvic visceral innervation — why the pain feels the way it does
The pelvic organs receive autonomic supply from the inferior hypogastric (pelvic) plexus, with parasympathetic input from S2–S4 (nervi erigentes) and sympathetic input from T10–L2 via the hypogastric nerves. Visceral afferents travel with the sympathetic fibres, so pain from the uterus and adnexa is referred to T10–L1 dermatomes — the suprapubic region, lower abdomen, and inner thigh. The ovary in particular, because of its midline embryological origin and ovarian vessel supply, refers pain to the periumbilical region (T10), which is one reason ovarian torsion is so often mistaken for early appendicitis.
The cervix is an exception: its pain is parasympathetically mediated and refers to the sacral dermatomes, producing the characteristic deep, dragging, low-back-radiating pain of cervical motion tenderness in PID or of an incomplete miscarriage with cervical dilatation.
Once the inflammatory process touches the parietal peritoneum, somatic innervation takes over: pain becomes sharp, well localised, and exacerbated by movement, cough, and palpation. This is the transition that turns a vague visceral pain into a "surgical abdomen" and is the single most important physical-sign transition to recognise.
Acute capsular distension and rupture
Rupture spills blood into the pouch of Douglas and irritates peritoneum, with diaphragmatic irritation causing shoulder-tip pain.
The ovarian cortex has a tough fibrous capsule under tension as a follicle or cyst enlarges. Visceral afferents in the capsule fire in response to stretch. The pain of a slowly enlarging functional cyst is dull and chronic; the pain of rupture is sudden, sharp, and often referred to one iliac fossa, coinciding precisely with the moment of capsule disruption. Free fluid then irritates the peritoneum (somatic pain), producing rebound and guarding. If the cyst is haemorrhagic, ongoing bleeding into the peritoneal cavity produces shoulder-tip pain via diaphragmatic (C3–C5, phrenic) irritation — a clue you should specifically ask about.
The classic ruptures: corpus luteum cyst at mid-luteal phase (often with ectopic-pregnancy-management as differential because of the timing in early pregnancy), endometrioma (chronic dull pain becoming acute and severe with often dramatic peritoneal signs because endometriotic fluid is intensely irritating), and follicular cyst (mid-cycle pain — Mittelschmerz — which is physiological release of follicular fluid).
Ischaemia: torsion and infarction
Ovarian (adnexal) torsion is rotation of the ovary on its pedicle, occluding venous return first, then lymphatic, then arterial. The pain is therefore initially of venous and lymphatic congestion (deep, severe, often associated with profound nausea and vomiting because of vagal stimulation by the swollen organ), then becomes infarction pain. Because venous flow is occluded first, the ovary becomes oedematous and grossly enlarged before it becomes non-viable — this is the surgical window during which detorsion preserves the ovary.
Three features of torsion are clinically critical and follow from the mechanics:
- Pain is often intermittent in the early phase as the ovary partially detorts spontaneously. A patient with "three episodes of severe pain over a week" who is well between episodes is not safe — she is at risk of imminent complete torsion.
- Doppler can show preserved arterial flow even in clear torsion because venous occlusion precedes arterial — so a "normal" Doppler does NOT exclude torsion.
- Vomiting out of proportion to abdominal signs is characteristic; this distinguishes torsion clinically from many other causes.
Risk increases with ovarian enlargement (cyst >5 cm, dermoid, ovarian hyperstimulation syndrome) and in pregnancy (laxity, hormonal effect on ligaments). The right ovary torts more than the left because the sigmoid colon restrains the left.
Fibroid degeneration — particularly red degeneration in pregnancy — is ischaemic. Rapid growth in early pregnancy outstrips the vascular supply; the fibroid undergoes haemorrhagic infarction. The pain is localised over the fibroid, with low-grade fever, mild leukocytosis, raised CRP, and sometimes vomiting. It is self-limiting, managed with analgesia and reassurance. See fibroids for management detail.
Ovarian vein thrombosis is a rare cause, usually postpartum or post-pelvic surgery, often on the right (longer ovarian vein course, dextrorotation of the gravid uterus compressing it). Pain is unilateral flank/iliac fossa with low-grade fever; the diagnosis is by CT venogram and treatment is anticoagulation.
Acute inflammation
Pelvic inflammatory disease (PID) is the ascent of pathogens (predominantly Chlamydia trachomatis, Neisseria gonorrhoeae, and mixed anaerobes; Mycoplasma genitalium increasingly recognised) from the lower to the upper genital tract. The initial endometritis is often clinically silent. As the infection ascends into the fallopian tubes (salpingitis), the inflamed mucosa loses cilia, the lumen fills with purulent material, and pain becomes bilateral lower-abdominal, often with deep dyspareunia. Once the inflamed fimbriae and surrounding peritoneum are involved, pain becomes peritonitic — and the patient develops cervical motion tenderness because moving the cervix tugs on the inflamed broad ligament. Tubo-ovarian abscess is the end-stage where the tube and ovary form a single inflammatory mass; pain becomes constant, severe, with marked systemic features. See acute-pelvic-infection for full clinical pathway and tubal-infection-pathology for the pathology.
Endometritis — postpartum, post-instrumentation, or post-Mirena insertion — produces uterine tenderness without adnexal involvement, often with foul-smelling discharge.
Endometriosis flare: cyclical exacerbation of pain due to the inflammatory response to ectopic endometrial bleeding. Acute presentations include endometrioma rupture (sudden severe pain, peritonism), torsion of an endometrioma-laden ovary, or simply a severe episode of dysmenorrhoea with bowel/bladder involvement. The pathophysiology is detailed in endometriosis-pathophysiology.
Pelvic congestion / ovarian vein incompetence: chronic, but acute exacerbations occur — diagnosis often delayed because mechanism is poorly taught.
Early pregnancy mechanisms
Ectopic pregnancy. Implantation in the fallopian tube (95% of ectopics) produces pain by two mechanisms: trophoblastic invasion stretches the tubal wall (visceral, dull, unilateral pain), and then tubal rupture produces sudden severe pain plus intraperitoneal bleeding. The classic triad — pain, bleeding, amenorrhoea — is present in only ~50%. The pathophysiology and assessment of the ectopic are central; see ectopic-pathophysiology and ectopic-pregnancy-management.
Spontaneous miscarriage. Uterine contractions to expel the conceptus produce crampy, central, suprapubic pain, often with bleeding. Cervical dilatation refers pain to the sacrum (parasympathetic afferents). An incarcerated retroverted gravid uterus at 12–14 weeks can produce severe pain plus urinary retention. See spontaneous-miscarriage.
Heterotopic pregnancy — coexisting intra- and extra-uterine pregnancies — is rare in spontaneous conception (~1:30,000) but rises sharply to ~1:100 with assisted reproduction. Visualisation of an intrauterine pregnancy on ultrasound does NOT exclude an ectopic in an ART patient.
Dysmenorrhoea (primary)
Severe enough on its own to present as acute pelvic pain. Pathophysiology is prostaglandin-mediated myometrial hypoxia: endometrial PGF2α drives myometrial contraction so vigorous that intramuscular vessels are compressed, producing transient ischaemia, lactate accumulation, and nociceptor activation. Secondary dysmenorrhoea (endometriosis, adenomyosis, fibroids, IUD complications) has additional structural mechanisms — see endometriosis-pathophysiology.
Assessment
A pathophysiology-driven approach to history and examination:
Onset and time course. Sudden severe peak in seconds — think rupture (cyst, ectopic, viscus) or torsion. Build-up over hours — think inflammation. Cyclical and crescendo — think endometriosis or fibroid degeneration. Intermittent severe episodes with well periods — think intermittent torsion (do not be reassured).
Character. Dull, deep, poorly localised → visceral / capsular. Sharp, well-localised → somatic / peritoneal — implies the process has reached the parietal peritoneum and the threshold for surgical concern is now lower.
Radiation. Shoulder tip → haemoperitoneum (diaphragmatic irritation). Sacral / low back → cervical / lower uterine origin. Inner thigh → obturator irritation (think pelvic abscess, deep PID). Loin to groin → ureteric.
Associated symptoms. Vomiting out of proportion to pain → torsion or peritonism. Bleeding + amenorrhoea + pain → ectopic until proven otherwise. Discharge + fever + bilateral pain → PID. Dysuria + frequency → consider UTI but does not exclude PID. Bowel habit change → consider appendicitis, diverticulitis, IBS.
Examination findings and what they mean.
- Tachycardia + hypotension out of proportion to apparent illness → haemoperitoneum or septic shock. Get IV access; resuscitate while you investigate.
- Generalised peritonism → ruptured ectopic, ruptured TOA, perforated viscus, advanced PID.
- Cervical motion tenderness (CMT) → broad ligament inflammation — PID until proven otherwise.
- Adnexal mass plus tenderness → think torsion, TOA, ectopic with haematosalpinx, endometrioma.
- Closed cervix with passage of products (after the fact) — complete miscarriage.
- Open cervix with no products yet seen — incomplete miscarriage (urgent surgical / medical management).
Mandatory investigations on first presentation.
- Urine β-hCG — never omit. Negative reliably excludes ectopic and pregnancy-related pain.
- FBC, U&E, CRP, group-and-save (cross-match if any haemodynamic concern), lactate if septic.
- Pelvic ultrasound — transvaginal where possible, looking specifically for: free fluid, adnexal mass, intrauterine pregnancy / heterotopic, ovarian Doppler (recognising that normal Doppler does not exclude torsion).
- Endocervical swabs for chlamydia, gonorrhoea, M. genitalium if PID suspected.
- Urinalysis ± urine culture.
- HIV serology — South African practice requires routine offer in any acute presentation; HIV co-infection alters PID management. See hiv-counselling.
Management
Management of acute pelvic pain is covered in acute-pelvic-pain-management. From a pathophysiology lens, the management imperative depends on the mechanism:
- Suspected torsion — to theatre. Detorsion, not oophorectomy, is the default even if the ovary looks dusky; viability is hard to judge intraoperatively and recovery is excellent. Cystectomy of the underlying lesion at the same operation if feasible.
- Suspected ruptured ectopic with haemodynamic instability — IV access, blood products, theatre. See ectopic-pregnancy-management.
- Stable ectopic — methotrexate or laparoscopic salpingectomy/salpingostomy depending on β-hCG, size, fetal cardiac activity, contralateral tube status.
- PID — empiric IV antibiotics covering chlamydia, gonorrhoea, anaerobes (SA NDoH STG: ceftriaxone + metronidazole + doxycycline). TOA: percutaneous drainage if accessible, surgical drainage if not. Partner treatment + contact tracing.
- Cyst rupture without haemodynamic concern — analgesia, observation, NSAIDs.
- Fibroid red degeneration — analgesia (paracetamol + NSAIDs cautiously in pregnancy after 1st trimester; avoid third trimester), warm packs, time. Surgery rarely needed.
- Incomplete miscarriage — see spontaneous-miscarriage.
Red flags / pitfalls
- A "normal" Doppler does not exclude torsion. If clinical picture fits, take the patient to theatre.
- A positive β-hCG with no intrauterine pregnancy on transvaginal ultrasound is an ectopic until proven otherwise — not a "pregnancy of unknown location" you can ignore.
- An intrauterine pregnancy on ultrasound does NOT exclude an ectopic in an IVF patient — heterotopic is real.
- Cervical motion tenderness is a sign, not a diagnosis. Always exclude ectopic and torsion before settling on PID.
- A "cyst" on ultrasound in a postmenopausal woman with pain is not a "simple physiological cyst" — it is a mass and warrants malignancy workup.
- Right iliac fossa pain is appendicitis until proven otherwise — gynaecological causes do not exclude it; both can coexist.
- Shoulder-tip pain in a woman of reproductive age is a ruptured ectopic until you have proved otherwise.
- "Pelvic pain + IUD" — exclude ectopic (IUD use shifts ectopic risk up if pregnancy occurs despite it), exclude PID (highest in first 3 weeks post-insertion), exclude expulsion or malposition.
- Severe acute pain in early pregnancy with no IUP visible — do not be falsely reassured by a "normal" pelvic ultrasound. Serum β-hCG ≥1500 with no IUP on TVS is an ectopic until disproven.
- Pain in a woman with prior pelvic surgery — adhesional pain, small bowel obstruction, and gynaecological causes all coexist. Get a surgical opinion if the picture is mixed.
Evidence anchors
- RCOG Green-top Guideline No. 21 — Management of Tubal Pregnancy (mechanisms and management).
- RCOG Green-top Guideline No. 32 — Management of Acute Pelvic Inflammatory Disease.
- ESHRE Guideline — Management of Women with Endometriosis (2022 update).
- ACOG Practice Bulletin No. 174 — Evaluation and Management of Adnexal Masses.
- South African National Department of Health Standard Treatment Guidelines (latest edition): STI/PID management algorithms.
- BASHH 2018 UK National Guideline for the Management of PID.
- Hasson J, et al. Ovarian torsion: clinical features and management. (Doppler limitations literature.)
- South African STI Management Guidelines (NDoH, 2018, updated 2023 syndromic approach).