A 35-year-old woman presents with acute right upper quadrant pain, fever, and elevated transaminases. Ultrasound shows a dilated common bile duct and echogenic material within the gallbladder. Regarding imaging for suspected acute cholecystitis and choledocholithiasis, all of the following are appropriate EXCEPT:

Explanation

## Imaging in Acute Cholecystitis and Choledocholithiasis ### Clinical Context The patient has clinical and biochemical evidence of biliary obstruction with concern for both acute cholecystitis and choledocholithiasis. The imaging strategy must confirm diagnosis and guide intervention. ### Appropriate Modalities (Options A, B, C) | Modality | Role | Sensitivity/Specificity | | --- | --- | --- | | **HIDA scan** | Confirms cystic duct patency; diagnoses acute cholecystitis if no gallbladder filling | 90–95% sensitivity for acute cholecystitis | | **MRCP** | Non-invasive visualization of entire biliary tree; detects ductal stones | 90–100% sensitivity for choledocholithiasis | | **Endoscopic ultrasound (EUS)** | High-resolution imaging of distal CBD; detects small stones with high accuracy; can be immediately followed by ERCP with sphincterotomy for stone extraction in the same session | 95–100% sensitivity for small stones | **Note on EUS:** While EUS itself is primarily a diagnostic modality, it is routinely performed in conjunction with ERCP for therapeutic stone removal in the same endoscopic session. This combined approach is well-established in clinical practice and guidelines (Harrison's 21e, Ch. 310), making EUS an appropriate part of the management algorithm for choledocholithiasis. ### Why Abdominal Radiography Is the EXCEPT Answer (Option D) **High-Yield:** Plain abdominal X-ray has **no meaningful role in the diagnosis of acute cholecystitis or choledocholithiasis** in this clinical scenario. **Clinical Pearl:** Abdominal radiography can occasionally detect: - **Pneumobilia** (air in the biliary tree — suggests bilioenteric fistula or prior sphincterotomy; an acute but rare finding) - **Porcelain gallbladder** (calcified gallbladder wall — a chronic, incidental finding unrelated to acute cholecystitis) However, these are incidental or rare findings. Plain films have **near-zero sensitivity** for detecting gallstones or ductal stones — gallstones are radio-opaque in only ~15% of cases. Plain radiography **cannot confirm acute cholecystitis, cannot identify choledocholithiasis, and cannot guide management** in this setting. **Key Point:** This patient requires ultrasound (already performed), MRCP for ductal detail, or EUS ± ERCP for therapeutic intervention — not plain abdominal radiography. Abdominal X-ray is therefore the EXCEPT answer: it is NOT an appropriate imaging modality for this clinical scenario [Harrison's Principles of Internal Medicine, 21e, Ch. 310; Schwartz's Principles of Surgery, 11e]. ### Diagnostic Algorithm ``` Acute RUQ pain + fever + elevated LFTs ↓ Ultrasound (first-line) ↓ Dilated CBD + echogenic material? ↓ ↓ MRCP (non-invasive EUS ± ERCP-ES ductal detail) (therapeutic) ↓ HIDA scan (if acute cholecystitis diagnosis remains unclear) ❌ Abdominal X-ray — NOT indicated (no sensitivity for stones; cannot guide management) ``` **Mnemonic — HUME for biliary imaging:** - **H**IDA — gallbladder function / cystic duct patency - **U**ltrasound — first-line screening - **M**RCP — non-invasive ductal detail - **E**US — high-resolution + therapeutic (via ERCP) Plain **X-ray** is not part of the biliary imaging algorithm.