A 32-year-old woman presents with acute right upper quadrant pain and fever. Ultrasound shows gallstones with a thickened gallbladder wall. All of the following are appropriate next imaging modalities EXCEPT:

## Investigation of Choice in Acute Cholecystitis ### Clinical Context The patient has imaging-confirmed acute cholecystitis (gallstones + thickened wall + fever + RUQ pain). The question asks which imaging modality is NOT appropriate for further evaluation. ### Appropriate Imaging Modalities **Key Point:** The standard diagnostic algorithm for acute cholecystitis involves ultrasound (already done), followed by functional or cross-sectional imaging to assess complications and ductal involvement. | Modality | Role in Acute Cholecystitis | Indication | |----------|----------------------------|------------| | **HIDA scan** | Gold standard for cystic duct obstruction | Confirms acute cholecystitis; shows non-filling of gallbladder = positive test | | **CT abdomen** | Excellent for complications | Evaluates for perforation, gangrene, pericholecystic collection, emphysematous cholecystitis | | **MRI/MRCP** | Best for biliary tree and ductal stones | Detects choledocholithiasis, cholangitis, intrahepatic duct dilation | | **Doppler ultrasound** | Assesses vascular flow | Used for hepatic artery/portal vein assessment — NOT part of cholecystitis workup | ### Why Doppler Ultrasound Is Wrong **High-Yield:** Doppler ultrasound evaluates **vascular perfusion** (hepatic artery, portal vein flow) and is used in cirrhosis, portal hypertension, and liver transplant assessment — NOT in acute cholecystitis. There is no role for assessing hepatic artery flow in the diagnostic or complication assessment of acute cholecystitis. **Clinical Pearl:** In acute cholecystitis, you need to know: 1. Is the cystic duct obstructed? → HIDA scan 2. Are there complications (perforation, gangrene)? → CT 3. Is there CBD stone or cholangitis? → MRCP You do NOT need hepatic artery Doppler unless evaluating liver synthetic function or vascular disease. ### Correct Imaging Sequence ```mermaid flowchart TD A[Acute RUQ pain + fever]:::outcome --> B[Ultrasound]:::action B --> C{Gallstones + thickened wall?}:::decision C -->|Yes| D[Acute cholecystitis confirmed]:::outcome D --> E{Assess cystic duct?}:::decision E -->|Yes| F[HIDA scan]:::action D --> G{Evaluate complications?}:::decision G -->|Yes| H[CT abdomen + IV contrast]:::action D --> I{Rule out CBD stone?}:::decision I -->|Yes| J[MRCP or MRI]:::action D --> K[Doppler ultrasound]:::urgent K --> L[NOT indicated]:::urgent ```