A 52-year-old woman from Mumbai presents with a 3-month history of progressive right upper quadrant pain, weight loss of 4 kg, and low-grade fever. On examination, she is icteric with a palpable gallbladder. Laboratory investigations show total bilirubin 4.2 mg/dL, direct bilirubin 3.8 mg/dL, and alkaline phosphatase 320 IU/L. Transabdominal ultrasound reveals a thick-walled gallbladder with a large stone impacted at the neck, dilated intrahepatic bile ducts, and a hypoechoic mass in the gallbladder fundus that does not move with position change. What is the most likely diagnosis?

Explanation

## Clinical Presentation and Imaging Correlation **Key Point:** The combination of a fixed, non-mobile hypoechoic mass within the gallbladder fundus on USG, chronic obstructive jaundice, and constitutional symptoms (weight loss, fever, pain) is highly suggestive of gallbladder carcinoma. ### Diagnostic Features of Gallbladder Carcinoma | Feature | Finding in This Case | Significance | |---------|----------------------|---------------| | **Gallbladder wall thickness** | Diffusely thick (>3 mm) | Infiltrative carcinoma | | **Intraluminal mass** | Hypoechoic, fixed, non-mobile | Malignant tumor, not stone | | **Bile duct dilatation** | Intrahepatic ducts dilated | Obstruction from tumor at hilum | | **Associated stone** | Large impacted stone at neck | Risk factor; Mirizzi-like appearance but mass is pathognomonic | | **Jaundice pattern** | Obstructive (direct hyperbilirubinemia) | Tumor compressing CBD or at hepatic confluence | ### Why This Is Gallbladder Carcinoma, Not Mirizzi Syndrome **High-Yield:** Mirizzi syndrome presents with external compression of the CBD by an impacted stone at the gallbladder neck—there is NO intraluminal mass. The presence of a fixed, non-mobile hypoechoic lesion within the gallbladder lumen is the distinguishing feature of malignancy. **Clinical Pearl:** Gallbladder carcinoma is often diagnosed late because early symptoms mimic benign biliary disease. Risk factors include chronic cholecystitis, gallstones (present in 80% of cases), and porcelain gallbladder. The prognosis is poor; median survival is 4–6 months without resection. ### Imaging Characteristics on CT/USG 1. **Thickened gallbladder wall** (>4 mm) — diffuse or focal 2. **Intraluminal mass** — hypoechoic on USG, enhancing on CT 3. **Loss of fat planes** — invasion of liver bed or adjacent organs 4. **Dilated intrahepatic bile ducts** — from obstruction at hepatic confluence or porta hepatis 5. **Metastatic disease** — hepatic metastases, ascites, regional lymphadenopathy **Mnemonic: GALLBLADDER CARCINOMA IMAGING — "THICK MASS"** - **T**hick gallbladder wall (>4 mm) - **H**ilar/hepatic duct obstruction - **I**ntraluminal mass (fixed, non-mobile) - **C**holedocholithiasis (often coexistent) - **K**eep high suspicion with jaundice + weight loss - **M**etastases (liver, peritoneal) - **A**ssociated stones (risk factor) - **S**onographic/CT enhancement of mass - **S**ystemic symptoms (fever, weight loss) [cite:Robbins 10e Ch 18] ## Why Acute Cholecystitis Is Incorrect Acute cholecystitis presents with acute onset pain, fever, and Murphy's sign—not chronic progressive jaundice and weight loss. The hypoechoic mass is not consistent with acute inflammation alone.