Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Acute pelvic pain differential diagnosis
Obstetrics and gynaecology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Resuscitate before refining the diagnosis
Shock, syncope, peritonism, shoulder-tip pain, heavy bleeding, sepsis, or sudden severe pain with vomiting can indicate ruptured ectopic pregnancy, adnexal torsion, internal haemorrhage or another surgical emergency.
Action: Use an ABCDE approach, obtain intravenous access, send urgent bloods and crossmatch when bleeding is possible, give appropriate analgesia, test for pregnancy without delaying resuscitation, and call senior gynaecology, surgical and anaesthetic support according to the likely source.
Overview
Triage sudden pelvic pain safely, exclude pregnancy-related and time-critical surgical causes, and use focused examination, testing and imaging to reach a defensible working diagnosis.
Acute pelvic pain is pain below the umbilicus of sudden or recent onset. The first task is not to name every possible condition but to identify instability and preserve time-sensitive organs and life. Haemoperitoneum from ectopic pregnancy or a ruptured cyst, ovarian or adnexal torsion, severe pelvic infection, appendicitis, ureteric obstruction and bowel pathology can present with similar pain, nausea and tenderness. The diagnostic frame must therefore include reproductive, urinary, gastrointestinal, vascular and musculoskeletal systems from the start.
Establish pregnancy potential without assumptions about age, identity, contraception, fertility history or reported menstrual timing. Ask about the last normal period, bleeding, previous ectopic pregnancy, tubal surgery, pelvic infection, assisted conception and pregnancy symptoms. NICE advises thinking about a pregnancy test for reproductive-age patients even when symptoms are non-specific and notes that about one third of ectopic pregnancies have no recognised risk factor. A negative urine test is reassuring only when its timing and sensitivity fit the possible conception date; use serum hCG when clinical suspicion remains important.
Practice
Two practice questions
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Question 1 of 2
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Obstetrics and gynaecologyOriginal SBA
Immediate branch in pelvic pain
A 27-year-old with a levonorgestrel intrauterine system presents with unilateral pelvic pain, light vaginal bleeding and cervical-motion tenderness. Observations are stable. What is the most important immediate investigation?
Sources and review status8 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem ·
Build a high-resolution pain history: exact onset, maximum intensity, side, radiation, movement or intercourse trigger, relation to menstruation and ovulation, and progression. Record vomiting, syncope, shoulder-tip pain, bleeding, discharge, fever, urinary symptoms, bowel disturbance and recent procedures. Ask about known cysts, endometriosis, fibroids, pelvic inflammatory disease, operations and fertility treatment. Recent ovarian stimulation adds ovarian hyperstimulation, enlarged-ovary torsion and thromboembolism to the differential.
Examination begins with observations and perfusion, followed by abdominal inspection, palpation and assessment for guarding, rebound, masses and renal-angle tenderness. Pelvic examination is targeted, consented and chaperoned according to preference. Speculum examination can identify bleeding source, discharge, tissue, trauma or a foreign body; bimanual examination may show cervical-motion, uterine or adnexal tenderness. None of these findings is specific enough to rule a dangerous diagnosis in or out alone, and examination should not delay urgent imaging or theatre in a deteriorating patient.
Select tests to answer immediate questions. Urine or serum hCG determines the pregnancy pathway. Full blood count measures anaemia and inflammatory response but can be initially normal after acute bleeding. Urinalysis may support infection or calculus but contamination is common. Vaginal and cervical nucleic-acid testing supports infection assessment, yet negative lower-tract tests do not exclude pelvic inflammatory disease. Ultrasound assesses pregnancy location, free fluid, ovaries, adnexal masses and uterine pathology; CT is reserved for important non-gynaecological diagnoses or when ultrasound cannot answer an urgent broader abdominal question, with radiation and pregnancy considered.
Management runs in parallel. Treat pain and nausea, correct fluid loss, involve the correct surgical team early and use local major-haemorrhage or sepsis pathways when indicated. Start empirical broad-spectrum antibiotics when pelvic inflammatory disease is clinically likely rather than waiting for every microbiology result. Suspected torsion needs urgent gynaecological assessment because definitive diagnosis is surgical and ovarian salvage declines with delay. Stable patients can leave only with a plausible plan, explicit return symptoms, results ownership and timed follow-up.
Key points
Start with physiology and pregnancy status: instability overrides the diagnostic sequence, while every person with pregnancy potential should be offered prompt urine or serum hCG even when contraception was used or the history seems atypical.
Separate pregnancy-related causes, gynaecological causes and non-gynaecological causes, then prioritise by harm: ectopic pregnancy, torsion, haemorrhagic cyst, pelvic infection, appendicitis, urinary obstruction and bowel disease can overlap clinically.
Pain character helps but does not decide the diagnosis: abrupt maximal pain supports torsion, rupture or colic; progressive bilateral pain with discharge supports infection; cyclical pain suggests endometriosis but an acute complication can coexist.
Use consented abdominal examination and, when it will change care, speculum and bimanual examination; severe pain, trauma history or inability to tolerate examination should lead to modification or deferral, not coercion.
Transvaginal ultrasound is usually the most informative pelvic imaging test when acceptable, but early ectopic pregnancy, torsion and superficial endometriosis may remain occult; interpret imaging alongside trajectory and examination.
Do not postpone empirical treatment of clinically suspected pelvic inflammatory disease while awaiting swabs, because delayed treatment increases risks of chronic pain, ectopic pregnancy and infertility.
Aetiology
01
Pregnancy-related
Tubal implantation, early pregnancy loss, corpus-luteum haemorrhage and, after assisted conception, heterotopic pregnancy can cause pain and internal or vaginal bleeding.
02
Adnexal and uterine
Torsion, ovarian cyst rupture or haemorrhage, degeneration of a fibroid, endometriosis and obstructed menstrual outflow produce pain through ischaemia, bleeding, inflammation or distension.
03
Infective and extra-gynaecological
Ascending genital infection, appendicitis, urinary infection or calculus, bowel inflammation or obstruction and abdominal-wall or pelvic-floor injury may all localise to the pelvis.
Pathophysiology
1
Haemorrhage and peritoneal irritation
Blood from a ruptured ectopic pregnancy or cyst irritates the peritoneum, producing guarding, referred shoulder pain and progressive hypovolaemia before haemoglobin necessarily falls.
2
Adnexal ischaemia
Rotation of the infundibulopelvic and utero-ovarian pedicles obstructs venous and lymphatic return first, causing oedema, then arterial compromise and tissue necrosis.
3
Ascending inflammation
Microorganisms ascend from the lower genital tract, causing endometritis and salpingitis; delayed control can progress to abscess, peritonitis, tubal scarring and chronic pain.
Clinical features and red flags
Ectopic pattern
Positive pregnancy testing with unilateral pain, vaginal bleeding, shoulder-tip pain, syncope or pelvic tenderness is ectopic pregnancy until location and clinical course make another diagnosis secure.
Torsion pattern
Abrupt severe unilateral pain, often with vomiting and an adnexal mass, supports torsion; episodes may fluctuate when the adnexa twists and untwists.
Infection pattern
Bilateral lower pain, abnormal discharge or bleeding, fever and cervical-motion or adnexal tenderness support pelvic inflammatory disease, though mild disease can lack fever.
Cyst complication
Sudden pain during activity or intercourse with free fluid may reflect cyst rupture or haemorrhage; haemodynamic change and serial haemoglobin determine urgency.
Non-gynaecological pattern
Migration to the right iliac fossa, bowel obstruction features, colicky loin-to-groin pain or urinary sepsis should redirect testing and specialist involvement.
Red flags requiring action
Hypotension, tachycardia, pallor, collapse, guarding or rebound tenderness indicates haemorrhage, sepsis or visceral perforation until proved otherwise and requires immediate senior review.
A positive pregnancy test with abdominal, pelvic or cervical-motion tenderness needs immediate early-pregnancy or out-of-hours gynaecology assessment because ectopic pregnancy remains possible at any hCG concentration.
Investigations
01Pregnancy test and quantitative serum hCGFirst step
Why
Identify pregnancy-related risk and establish a baseline when pregnancy location is uncertain.
Interpretation and limitations
A positive result with tenderness requires urgent early-pregnancy assessment. A single hCG value neither locates a pregnancy nor excludes rupture. For pregnancy of unknown location, use 2 measurements as near as possible to 48 hours apart but not earlier to assess trophoblastic proliferation and guide subsequent management; clinical symptoms take precedence over the result.
A definite intrauterine pregnancy substantially changes ectopic probability but does not exclude heterotopic pregnancy after assisted conception. Normal flow does not rule out torsion, and an empty uterus with positive hCG is a pregnancy of unknown location.
03Full blood count, inflammatory markers and metabolic profile
Why
Measure anaemia, infection response, renal impairment and electrolyte effects of vomiting or sepsis.
Interpretation and limitations
Normal early haemoglobin cannot exclude acute blood loss and inflammatory markers are non-specific. Use serial results and physiology rather than isolated thresholds.
04Urinalysis, urine culture and STI testing
Differential diagnosis
01
Ectopic pregnancy
Consider with any credible pregnancy and pain, including atypical gastrointestinal or urinary symptoms; rupture can occur without a prior scan or recognised risk factor.
02
Adnexal torsion
Sudden unilateral pain and vomiting, particularly with ovarian enlargement, a mass, pregnancy or fertility treatment, warrants urgent surgical assessment.
03
Pelvic inflammatory disease
Bilateral pain, cervical-motion or adnexal tenderness, discharge and abnormal bleeding support infection, but presentations range from subtle to septic with abscess.
04
Cyst accident or endometriosis
Ovulatory or pathological cysts can rupture or bleed acutely; endometriosis more often causes cyclical pain but endometriomas may rupture or coexist with torsion.
05
Urinary or gastrointestinal disease
Appendicitis, diverticulitis, inflammatory bowel disease, obstruction, pyelonephritis and ureteric colic remain essential mimics whose treatment pathway is not gynaecological.
Management
01Unstable patientControl haemorrhage or sepsis nowFirst stepObservations, perfusion or examination suggests shock, major internal bleeding, peritonitis or severe sepsis.+
1Run ABCDE, summon senior gynaecology, anaesthesia and the relevant surgical team, obtain large-bore access and activate local emergency protocols.
2Send pregnancy testing, blood count, coagulation, renal profile, lactate and crossmatch while giving analgesia, warmed fluid or blood products according to physiology.
3Use focused bedside imaging only if it changes the immediate route; do not delay theatre or interventional treatment for comprehensive imaging in a deteriorating patient.
02Pregnancy possibleLocate the pregnancy and protect against rupturePregnancy testing is positive, equivocal or still credible despite an early negative urine result.+
1
Complications
01
Circulatory collapse
Unrecognised intra-abdominal bleeding or sepsis can progress rapidly to shock, coagulopathy, organ injury and death despite initially compensated observations.
02
Loss of reproductive tissue
Delayed treatment of torsion can cause ovarian necrosis, while ectopic pregnancy or severe infection may damage or require removal of a fallopian tube.
03
Chronic pelvic sequelae
Pelvic inflammatory disease, surgery and inflammatory injury can lead to adhesions, recurrent infection, persistent pelvic pain, subfertility and increased future ectopic risk.
Monitoring and follow-up
Repeat observations, pain score and abdominal findings after initial resuscitation and analgesia; symptom relief does not by itself exclude torsion or internal bleeding.
Trend haemoglobin, renal function, lactate or inflammatory markers only when they answer an active clinical question, and escalate deterioration before waiting for a repeat result.
For pregnancy of unknown location, document the exact next hCG or ultrasound time, the service reviewing it and the action threshold for new pain or bleeding.
Review outpatient pelvic inflammatory disease clinically at about 72 hours; absent improvement requires diagnostic reconsideration, admission assessment and evaluation for tubo-ovarian abscess.
Close the loop on microbiology, imaging and histology, communicate changed diagnoses, and give a route back for recurrent severe pain, fever, syncope, vomiting or heavy bleeding.
Special situations
Contraception does not close the pregnancy branch
No contraceptive method is infallible, and pregnancy with an intrauterine device in situ has a higher conditional probability of being ectopic than pregnancy without one.
Doppler supports rather than vetoes
The ovary has dual blood supply and torsion may be intermittent, so arterial or venous flow on ultrasound cannot overrule a strongly suggestive clinical presentation.
Negative swabs are not negative tubes
Lower-genital-tract nucleic-acid tests may be negative in upper-tract infection; pelvic tenderness and clinical context justify empirical PID treatment after dangerous mimics are considered.
Free fluid needs context
A small physiological volume may occur around ovulation, whereas echogenic or increasing fluid with pain, anaemia or instability supports haemoperitoneum and urgent review.
Analgesia improves assessment
Appropriate pain relief does not erase clinically important peritonism; it supports humane, repeatable examination and should not be withheld to preserve diagnostic signs.
Common pitfalls
01
Excluding ectopic pregnancy because contraception was used, bleeding resembles a period or no classic risk factor is present.
02
Allowing a normal haemoglobin, inflammatory marker or single ultrasound to overrule worsening physiology and serial examination.
03
Using preserved ovarian Doppler flow as a stand-alone exclusion test for torsion.
04
Waiting for STI results before treating a convincing pelvic inflammatory disease syndrome.
05
Attributing all lower abdominal pain to gynaecology and failing to examine for appendicitis, urinary obstruction, bowel disease or hernia.
06
Discharging a pregnancy of unknown location without written safety-netting, timed reassessment and clear ownership of results.
A pregnancy of unknown location is a temporary classification and could still be ectopic: symptoms override hCG results, obtain 2 serum hCG measurements as near as possible to 48 hours apart but not earlier, then arrange the trajectory-specific clinical review, ultrasound or urine-test follow-up with written 24-hour safety-netting.
Reassess after analgesia and initial tests; worsening pain, new observations, falling haemoglobin or diagnostic discordance should trigger escalation and repeat senior examination rather than discharge by a normal single result.
Sudden unilateral pain with nausea or vomiting raises adnexal torsion; preserved Doppler flow or transient improvement does not safely exclude intermittent or partial torsion.
Fever, purulent discharge, marked pelvic tenderness or a suspected tubo-ovarian abscess suggests complicated pelvic inflammatory disease and may require admission, intravenous antibiotics and drainage.
Postmenopausal pain, a persistent or complex mass, unexplained weight loss, ascites or early satiety requires malignancy assessment rather than repeated symptomatic treatment.
Why
Look for urinary infection or haematuria and sample for chlamydia, gonorrhoea and other indicated infections.
Interpretation and limitations
Pyuria or blood can occur beside pelvic pathology, and negative genital swabs do not exclude upper-genital-tract infection; treat a convincing clinical PID syndrome empirically.
05CT abdomen and pelvis or MRI
Why
Evaluate appendicitis, bowel, urinary or complex pelvic disease when ultrasound and examination leave an important unresolved question.
Interpretation and limitations
Choose modality with radiology according to urgency and pregnancy status. Cross-sectional imaging must not delay operative care for shock, peritonism or strongly suspected torsion.
EscalationArrange prompt transvaginal ultrasound and quantitative serum hCG through an early-pregnancy or acute gynaecology service, escalating immediately for tenderness, significant pain or bleeding.
2Classify findings as a definite location or pregnancy of unknown location. Treat an unknown location as potentially ectopic, prioritise changing symptoms over hCG, take 2 serum hCG measurements as near as possible to 48 hours apart but not earlier, and use the trajectory to select clinical review, repeat ultrasound or urine-test follow-up rather than applying a single discriminatory value mechanically.
3Give written emergency symptoms, a 24-hour contact route and named result ownership. Under NICE guidance updated in June 2026, do not offer anti-D through 11+6 weeks; at 12+0 to 12+6 weeks offer at least 250 IU to an RhD-negative patient having medical management or a surgical procedure for ectopic pregnancy or miscarriage, and consider it for threatened miscarriage with heavy or recurrent bleeding. Use ultrasound dating when it conflicts with the last menstrual period, and explain that anti-D is a filtered protein obtained from blood plasma and contains no blood cells.
03Torsion or bleedingEscalate the adnexal emergencyEscalationPain is abrupt and unilateral, vomiting is prominent, a mass is known or free fluid and falling haemoglobin suggest bleeding.+
1Keep the patient nil by mouth when surgery is credible, establish venous access, treat pain and nausea and obtain urgent senior gynaecology assessment.
2Request expert pelvic ultrasound without treating preserved Doppler flow as exclusion of torsion; clinical concern can justify diagnostic laparoscopy despite equivocal imaging.
3Aim to conserve viable ovarian tissue when appropriate, manage haemorrhage according to stability and send suspicious or unexpected tissue for histopathology.
04Likely pelvic infectionSample, treat and review earlyPelvic tenderness accompanies abnormal discharge, bleeding, STI risk, fever or no stronger competing diagnosis.+
1Take pregnancy testing and genital samples, assess HIV and syphilis testing needs, and consider ultrasound for abscess without delaying empirical antibiotics.
2For uncomplicated non-pregnant outpatient PID, use the current BASHH regimen and address allergy, pregnancy, interactions and local antimicrobial policy before prescribing.
3Arrange review at about 72 hours, partner notification and sexual-health follow-up; admit for severe illness, pregnancy, abscess, inability to exclude surgery or failure of oral treatment.
Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
BASHH's recommended broad-spectrum outpatient regimen when clinical pelvic inflammatory disease is likely in a non-pregnant adult who can be followed safely.
Ceftriaxone plus doxycycline plus metronidazole for uncomplicated outpatient PID
Give ceftriaxone 1 g intramuscularly once, plus doxycycline 100 mg orally twice daily and metronidazole 400 mg orally twice daily, both for 14 days.
Check immediate beta-lactam allergy, pregnancy and breastfeeding, hepatic disease and interactions; avoid doxycycline in pregnancy, discuss alcohol-related adverse effects with metronidazole, and admit when severe disease, abscess or a surgical emergency is possible.