A 58-year-old man presents with painless jaundice, pale stools, and dark urine for 3 weeks. Abdominal examination reveals a palpable gallbladder. Laboratory investigations show elevated conjugated bilirubin and alkaline phosphatase. Regarding the diagnostic workup for obstructive jaundice in this patient, all of the following are appropriate initial investigations EXCEPT:

Explanation

## Diagnostic Approach to Obstructive Jaundice ### Initial Investigations — Rationale **Key Point:** The initial workup of obstructive jaundice relies on **non-invasive imaging** to identify the level and cause of obstruction before considering invasive procedures. ### Appropriate First-Line Investigations | Investigation | Role | Sensitivity | | --- | --- | --- | | **Ultrasonography** | Detects dilated intrahepatic/extrahepatic ducts; identifies stones, masses | 95% for ductal dilatation | | **Liver function tests** | Confirms cholestasis (↑ ALP, ↑ GGT, ↑ conjugated bilirubin) | Biochemical confirmation | | **Coagulation profile (PT/INR)** | Assesses synthetic function; guides correction before invasive procedures | Essential pre-procedure | | **CT abdomen/pelvis** | Characterizes lesions, assesses resectability, detects metastases | 90–95% for pancreatic cancer | ### Why Hepatobiliary Scintigraphy (HIDA Scan) Is NOT First-Line **High-Yield:** HIDA scan is a **functional imaging study** that measures hepatic uptake and excretion. It is: - **Not suitable** when there is complete biliary obstruction (tracer cannot reach the ducts) - **Useful only** for suspected biliary dyskinesia or partial obstruction (e.g., sphincter of Oddi dysfunction) - **Delays diagnosis** in obstructive jaundice — ultrasound and CT are faster and more informative - **Contraindicated** in complete ductal obstruction because the tracer will not visualize the biliary tree **Clinical Pearl:** HIDA scan is indicated for **functional assessment** (e.g., ejection fraction in suspected biliary colic), not for **anatomic obstruction**. In this patient with painless jaundice and palpable gallbladder (Courvoisier sign), the obstruction is **mechanical and complete** — HIDA will not help. ### Correct Diagnostic Sequence 1. **Liver function tests** → confirms cholestasis 2. **Ultrasonography** → detects ductal dilatation, stones, or mass 3. **CT abdomen/pelvis** → characterizes lesion, staging 4. **ERCP or MRCP** → therapeutic or further characterization (if needed) **Mnemonic:** **CULT** — **C**oagulation, **U**ltrasound, **L**FTs, **T**hen CT (for obstructive jaundice workup). [cite:Sabiston Textbook of Surgery Ch 54]