Updated October 2025
Imaging First Decisions
Acute Abdomen: Diagnostic Approach and Imaging Choices
In acute, non‑traumatic abdominal pain, prioritize timely risk stratification, bedside ultrasound, and targeted cross‑sectional imaging to narrow differentials and guide urgent management. Contrast‑enhanced MDCT is generally preferred for severe or generalized pain; ultrasound remains first‑line for RUQ, gynecologic, and biliary etiologies; noncontrast CT is preferred for suspected renal colic; MRI is a radiation‑free alternative in selected populations. Integrate clinical context, hemodynamic status, and radiation/contrast risks to choose the right test the first time.
Clinical question
What is an evidence-based, clinically pragmatic diagnostic pathway for the acute abdomen, and how should imaging be selected by presentation and risk?
Emergency MedicineRadiologyGeneral SurgeryPoint-of-Care UltrasoundInternal Medicine
Key points
Stabilize and risk-stratify before imaging
Hemodynamic instability, peritonitis, or septic shock mandate immediate surgical/critical care involvement and do not delay life-saving interventions for imaging.
Choose the right test the first time
Severe or nonlocalized pain: use contrast-enhanced MDCT. RUQ/biliary or gynecologic etiologies: prioritize ultrasound. Suspected stones: noncontrast CT.
POCUS accelerates triage
Bedside ultrasound rapidly answers focused questions (free fluid, AAA, gallbladder, hydronephrosis) and guides whether CT is immediately needed.
Minimize harm
Avoid unnecessary radiation and iodinated contrast in vulnerable patients; consider MRI when available, especially in pregnancy or contrast contraindication.
Synthesize imaging with clinical data
Combine exam, labs, and imaging to refine differentials; imaging results should change management—if not, reassess the diagnostic question.
Evidence highlights
Contrast-enhanced MDCT
Preferred initial test in severe generalized pain
Ultrasound
RUQ pain first-line
Noncontrast CT
Suspected renal colic
Clinically Oriented Diagnostic Pathway
A stepwise approach that prioritizes stabilization, pretest probabilities, and imaging tailored to presentation.
1
Stabilize and identify red flags
Assess ABCs, vitals, and provide analgesia. Look for peritonitis, GI bleed, shock, or ruptured AAA features. If unstable with suspected surgical catastrophe, call surgery/IR and proceed to operative or damage-control pathways; imaging should not delay resuscitation [1], [2].
2
Define pain pattern and risk
Localize pain (RUQ, RLQ, LLQ, flank, diffuse), characterize onset, and integrate age, pregnancy, immunosuppression, and prior surgery. Labs: CBC, BMP, LFTs, lipase, urinalysis ± pregnancy test; use them to set pretest probabilities that guide the imaging question [1], [3].
3
Use POCUS to accelerate decisions
Focused questions: free fluid, biliary dilation/cholecystitis, hydronephrosis, AAA, bowel dilatation, or appendiceal and gynecologic clues. POCUS can shorten time-to-diagnosis and determine immediate need for CT [4], [5], [6].
4
Select the first-line imaging by presentation
• Severe/nonlocalized pain: contrast-enhanced MDCT is preferred for broad differential and detection of life-threatening conditions [7], [8], [2]. • RUQ/biliary: ultrasound first; CT if nondiagnostic or complications suspected [9], [6]. • Renal colic: noncontrast CT is gold standard; US can be initial in young/pregnant to limit radiation [4]. • RLQ suspected appendicitis: CT with IV contrast in adults; US first in young/pregnant, then CT/MRI if equivocal [9], [2]. • Gynecologic etiologies: transabdominal/transvaginal ultrasound first [9]. • Suspected high-grade SBO/ischemia: contrast-enhanced CT for transition point and ischemia signs [7], [8], [2].
5
Escalate or de-escalate
If initial imaging is nondiagnostic but suspicion remains high, proceed to problem-focused CT or MRI. Conversely, if imaging confirms a benign, self-limited condition, avoid repeat imaging; provide return precautions and follow-up [7], [3], [2].
Imaging Choices by Clinical Scenario
Align modality with the dominant differential, balancing accuracy, speed, radiation, and contrast safety.
Severe or generalized pain
Preferred: contrast-enhanced MDCT for broad differential, obstruction, ischemia, perforation [7], [8].
Strength: High diagnostic yield; rapid; detects extra-abdominal mimics [7], [3].
Caution: Contrast nephropathy risk is low but consider AKI; hydrate and weigh risks/benefits [8].
Right upper quadrant (biliary)
First-line: ultrasound for gallstones, wall thickening, sonographic Murphy sign [9], [6].
CT if equivocal/complications (emphysematous cholecystitis, perforation) [9].
POCUS useful to triage and expedite surgery/ERCP when positive [4], [5].
Renal/ureteric colic
First-line: noncontrast CT for stones and alternative diagnoses [4].
Ultrasound to reduce radiation in pregnancy/young; look for hydronephrosis and twinkle artifact [4], [9].
Right lower quadrant (appendicitis)
Adults: CT with IV contrast is highly accurate and reduces negative appendectomy [9].
Children/pregnancy: ultrasound first, then MRI or CT if equivocal [9], [2].
Gynecologic etiologies
First-line: transvaginal + transabdominal ultrasound for torsion, ectopic pregnancy, PID, hemorrhagic cyst [9].
MRI if equivocal or to avoid radiation/contrast [2].
Suspected SBO/ischemia/perforation
Contrast-enhanced CT to identify transition point, closed-loop, pneumatosis, free air/fluid [7], [8], [2].
Oral contrast usually unnecessary in high-grade obstruction; use IV contrast unless contraindicated [8].
Special populations and safety
Pregnancy: Ultrasound first, MRI without gadolinium when needed; avoid ionizing radiation when possible [2].
Renal impairment/iodine allergy: prefer US or MRI; consider noncontrast CT if appropriate [2].
Repeated ED visits: minimize cumulative radiation; leverage prior imaging and US [3].
References
Source material
Primary literature that informs this article.
The acute abdomen: A surgeon's approach to diagnosis ...
www.sciencedirect.com
Imaging patients with acute abdominal pain
pubmed.ncbi.nlm.nih.gov
Diagnostic imaging for acute abdominal pain in an ...
pubmed.ncbi.nlm.nih.gov
Point-of-care ultrasound for the acute abdomen in the...
journals.lww.com
diagnostic ultrasonography for the acute abdomen
www.uptodate.com
The role of US examination in the management of acute ...
link.springer.com
acute and generalized non-traumatic abdominal pain | British ...
academic.oup.com
Acute Nonlocalized Abdominal Pain
www.uptodate.com
Diagnostic imaging of acute abdominal pain in adults
pubmed.ncbi.nlm.nih.gov
Diagnostic Imaging of the Acute Abdomen
link.springer.com
POCUS for acute abdominal pain: practical scan protocols ...
link.springer.com
acute abdominal pain: diagnostic strategies
pubmed.ncbi.nlm.nih.gov