| Clinical Question | Best Study | Notes |
|---|
| Chest pain -ACS ruled out, PE suspected | CTPA | Wells score first. If low probability โ D-dimer. If D-dimer positive or high probability โ CTPA. V/Q scan if contrast allergy or CKD. |
| Stroke symptoms (< 24h) | CT Head without contrast (rule out hemorrhage) โ CTA head/neck (LVO) โ MRI DWI (confirm ischemic) | CT to rule out bleed before tPA. CTA for large vessel occlusion (thrombectomy candidate). MRI DWI most sensitive for acute ischemia. |
| Abdominal pain | CT abdomen/pelvis with IV contrast | Most versatile. RLQ pain in young female โ consider US first (ovarian pathology, avoid radiation). RUQ pain โ RUQ US first (gallstones, cholecystitis). |
| GI bleed -upper vs lower | EGD first. CT angiography if massive/unstable. | CTA abdomen/pelvis if active bleeding (extravasation). Tagged RBC scan if slow intermittent bleed. Colonoscopy within 24h for lower GIB. |
| Renal colic / stones | CT abdomen/pelvis WITHOUT contrast | Non-contrast CT is gold standard for stones (contrast obscures them). US is first-line in pregnancy. |
| Biliary disease | RUQ ultrasound | First-line for gallstones, cholecystitis. MRCP for common bile duct stones if US equivocal. HIDA scan for acalculous cholecystitis (EF < 35%). |
| DVT suspected | Compression ultrasound | Sensitivity > 95% for proximal DVT. If negative but high clinical suspicion โ repeat in 5โ7 days or whole-leg US. |
| Aortic dissection | CTA chest/abdomen/pelvis | Gold standard. TEE is alternative (especially if too unstable for CT). D-dimer < 500 has high NPV for dissection. |
| Pleural effusion workup | CXR โ US-guided thoracentesis | Lateral decubitus CXR to confirm free-flowing. Bedside US for marking. CT chest with contrast if concern for malignancy, empyema, or loculated. |
| Pulmonary nodule found | Follow Fleischner criteria | Size, morphology (solid vs GGO vs part-solid), risk factors determine follow-up interval. Part-solid nodules have highest malignancy risk. PET-CT for solid nodules โฅ 8 mm. |
Contrast contraindications: eGFR < 30 (risk of CIN -but don't withhold if life-threatening indication like PE, dissection, stroke), contrast allergy (premedicate: prednisone 50 mg at 13h, 7h, 1h before + diphenhydramine 50 mg 1h before). Metformin: hold day of contrast, resume 48h later if Cr stable.