**Question:** A young patient develops high grade fever with chills and rigors, mild jaundice and acute pain in the upper abdomen following cholecystectomy. On examination, she was jaundiced, toxic, haemodynamically stable and having vague fullness upper abdomen. What is the most probable diagnosis?

**Core Concept:**
The presented symptoms and examination findings can be related to postoperative complications following cholecystectomy, specifically bile leakage or bile duct injury. After a surgical procedure like cholecystectomy, bile leakage or bile duct injury may lead to post-operative complications like fever, chills, rigors, jaundice, and upper abdominal pain.

**Why the Correct Answer is Right:**
The correct answer is **D** - Cholangitis (Biliary Tract Infection) because:

1. Cholangitis is an infection of the biliary tract, which can occur post-operatively following cholecystectomy due to bile leakage or bile duct injury.
2. This can lead to high-grade fever, chills, rigors, and acute pain in the upper abdomen.
3. Mild jaundice is often seen due to raised bilirubin levels resulting from the infection and damage to the biliary tract.
4. The patient is toxic, which indicates severity of the infection and the body's response to it.
5. The patient is haemodynamically stable, suggesting that the patient's vital signs remain within normal limits despite the infection.
6. The vague fullness in the upper abdomen might be due to the infected gallbladder or liver.

**Why Each Wrong Option is Incorrect:**
A. Cholangitis (Biliary Tract Infection) should not be the primary focus of the question as it is a likely diagnosis, but the other options are less likely due to their specific characteristics:

1. **Option A (Post-operative wound infection):** This typically presents with more localised signs and symptoms, such as redness, swelling, and discharge at the surgical site. Additionally, it is less likely after cholecystectomy as the infection is more likely to spread systemically than locally.
2. **Option B (Post-operative wound abscess):** Similar to option A, wound abscess is less likely after cholecystectomy, as the infection is more likely to occur at the surgical site.
3. **Option C (Post-operative cardiac arrest):** This is an unlikely diagnosis as the patient's vital signs are stable, indicating that the patient is not critically ill.

**Why Option D is Right:**
**Option D (Cholangitis - Biliary Tract Infection):**

Cholangitis is the most probable diagnosis given the systemic symptoms and signs. Post-cholecystectomy, bile duct injury is common, leading to biliary tract infection.

**Clinical Pearl:**
In cases where a patient presents with fever and acute abdominal pain following cholecystectomy, it is crucial to consider cholangitis (biliary tract infection) as a primary differential diagnosis. This infection may occur due to bile duct injury during surgery,