Abdominal Pain

Most is benign: acute gastroenteritis and nonspecific abdominal pain are the two single most common diagnoses, followed by cholelithiasis, urolithiasis, diverticulitis, and appendicitis.

Extra-abdominal causes are common too — around 10% of patients over 65 have a respiratory cause.

Examination

Analgesia should be given before a diagnosis is reached. This includes opioid analgesics as they do not increase the risk of diagnostic errors.

Likelihood ratios:

• Murphy sign (cholecystitis): LR+ 15.6. Sonographic Murphy’s sign plus a visible gallstone has 92% positive and 95% negative predictive value.
• Appendicitis: RLQ pain LR+ 7.3–8.5; migratory pain LR+ 3.2; Rovsing sign LR+ 2.5; rebound tenderness LR+ 2 — but over a third of patients with appendicitis have no rebound tenderness, so its absence doesn’t exclude it.
• Diverticulitis: clinical impression, in a patient without complicated-disease risk factors, LR+ 32 — a clinical diagnosis is reasonable without imaging in this group.
• Carnett sign (tenderness increases when a supine patient tenses the abdominal wall by raising legs/shoulders): LR+ 6.5 for abdominal wall pain, LR+ 28 when combined with fixed, localised, superficial tenderness. Useful for chronic abdominal wall pain, but not accurate enough alone to exclude acute intra-abdominal pathology.
• AAA: the classic triad (abdominal/flank pain, hypotension, pulsatile mass) is often incomplete — up to 60% of AAA cases are initially misdiagnosed. Palpation is 68% sensitive/75% specific overall, rising to 100% for aneurysms ≥5cm in a patient with girth <100cm — not useful in a larger patient or smaller aneurysm.
• Testicular torsion: up to 20% of patients have abdominal or flank pain alone — always palpate the testes in male patients with lower abdominal pain.

Investigations

A pregnancy test should be performed in all women of reproductive age with acute abdominal pain, including those using reliable contraception. If positive, pelvic ultrasound follows to locate the pregnancy; keep ectopic pregnancy, adnexal torsion, and PID under consideration.

• CT with IV contrast: first-line for generalised, left-upper-quadrant, or lower abdominal pain when the diagnosis is unclear.
• Ultrasound: first-line for right-upper-quadrant pain (cholecystitis/ cholelithiasis). Point-of-care ultrasound can help with appendicitis, urolithiasis, and AAA at the bedside.
• Pregnancy: ultrasound first-line; MRI preferred over CT if ultrasound is inconclusive.

CT is disproportionately useful in older patients — one large retrospective analysis found it changed the treatment plan more than 65% of the time.

Mesenteric ischaemia (more common in older patients, ~50% embolic, often from atrial fibrillation) needs CT angiography even with renal impairment — a missed or delayed diagnosis is worse than the contrast risk.

Red flags for acute abdominal pain

History	Signs
Collapse at toilet	Pallor and sweating
Lightheadedness	Hypotension
Ischaemic heart disease	Atrial fibrillation or tachycardia
Progressive vomiting, pain, distension	Fever
Menstrual abnormalities	Prostration
Malignancy	Rebound tenderness and guarding
Lack of flatus	Decreased urine output

Gynaecological causes of acute lower abdominal pain in women

Consider ectopic pregnancy in all women with new onset low abdominal pain and a positive pregnancy test result.

History: pain characteristics and relation to the menstrual cycle, systemic symptoms, dyspareunia, vaginal bleeding/discharge, contraception, and risk factors for both ovarian torsion and PID.

Examine with speculum and bimanual palpation — cervical motion, uterine, and adnexal tenderness support PID.

Ovarian torsion — a gynaecological emergency:

• Complete or partial rotation of the ovary on its ligamentous supports, obstructing blood supply; prompt diagnosis is needed to preserve ovarian/tubal function.
• Risk factors: reproductive age, a mobile ovarian mass (especially >5cm), prior torsion — though it can occur with normal ovaries too.
• Presentation is often non-specific: sudden-onset pelvic pain, nausea/vomiting, low-grade fever, an adnexal or palpable pelvic mass (not always present); abdominal or pelvic tenderness is present in around two-thirds of patients.
• Pelvic (preferably transvaginal) ultrasound if suspected. Definitive diagnosis requires direct visualisation at surgery.

PID risk factors:

• Age <25
• Recent change of sexual partner
• Current or previous STI, especially repeat infections
• Inconsistent barrier contraception use
• Recent gynaecological procedure (D&C, IVF, IUD insertion, termination)
• Bacterial vaginosis

Clinically unstable (shock/collapse, BP <100/60, pulse >100/min): immediate ambulance transfer. While waiting — large-bore IV access, IV fluids, resuscitate as needed, analgesia.

Clinically stable: refer to the emergency department for suspected appendicitis, peritonism, acute surgical abdomen, ovarian torsion, or ectopic pregnancy with moderate-to-severe symptoms (call the gynaecology registrar first for the last one).

Urgent care and rural/peripheral practice

Elderly patients with abdominal, loin, or flank pain have a 14% mortality rate — symptoms can be vague with low tolerance for shock, so a systolic BP of 90mmHg may already be critical if the patient was previously hypertensive.

In anyone over 50 with abdominal, flank, or back pain: check BP in both arms — a difference of more than 20mmHg is abnormal and can indicate dissection.

A ruptured AAA can mimic renal colic, diverticulitis, or GI haemorrhage.

Complete a testicular examination if the cause of pain is unclear or there’s scrotal pain/swelling; suspected torsion needs urgent escalation, since delayed surgical management risks testicular loss.

Don’t withhold analgesia pending a diagnosis:

• Paracetamol for mild pain
• An opioid for moderate–severe pain
• An antiemetic if nausea/vomiting is present

Send basic pathology to guide the differential:

• FBC/UEC and urinalysis — most presentations
• Urine (and if positive, quantitative serum) βHCG — any woman of childbearing age
• LFTs/lipase — right-upper-quadrant or epigastric pain, or a history of alcohol use
• Troponin — where a cardiac cause is being considered
• INR — if the patient is on warfarin
• Blood cultures — if febrile

Escalate for medical/surgical review per local protocol if pain doesn’t settle with analgesia, or sooner for any red flag above.

Acute abdominal pain in children

Key points: repeated examination is useful to identify persistence or evolution of signs and response to treatment.

Most children need no investigations at all — target them to whatever’s clinically likely.

Appendicitis in young children (under 5) may not present with classic symptoms, and can present as sepsis or perforation, often diagnosed late.

Examination: serial examination of the abdomen is required.

• Peritonism in a child is often positional rather than a fixed sign — the child won’t want to move in bed and can’t walk or hop comfortably; internal rotation of the right hip can irritate an inflamed appendix.
• Genitalia should be examined (e.g. for testicular torsion); a rectal or vaginal exam is rarely indicated in a child and, if needed, should be discussed with a senior clinician and performed only once.

Management: Appropriate analgesia should be used and will not mask potentially serious causes of pain.

Consider consultation with the local paediatric team for:

• A suspected surgical cause
• Severe pain or peritonism
• Bilious vomiting
• Scrotal pain, redness, or swelling
• A child requiring admission

Consider transfer when the required care is beyond the local hospital’s comfort level — ensure adequate analgesia, venous access, and IV fluids first.

Safe for discharge when there are no concerning features, the presentation is consistent with non-specific abdominal pain, a clear follow-up plan is arranged (e.g. with the local GP), and parents have been given advice on when to seek further care.