Investigation of choice in cholelithiasis is –
**Core Concept**
Cholelithiasis refers to the formation of gallstones in the gallbladder, which can cause biliary colic, cholecystitis, or pancreatitis. The investigation of choice is crucial for diagnosing the condition and planning the appropriate management.
**Why the Correct Answer is Right**
The investigation of choice in cholelithiasis is ultrasonography (USG). This is because USG is non-invasive, readily available, and highly sensitive for detecting gallstones, gallbladder inflammation, and bile duct dilation. It can also identify other complications such as gallbladder cancer or Mirizzi's syndrome. USG works by emitting high-frequency sound waves that bounce off the gallstones, gallbladder, and surrounding tissues, producing images that help diagnose the condition.
**Why Each Wrong Option is Incorrect**
**Option A:** X-ray is not the investigation of choice in cholelithiasis because it is less sensitive and may not detect small gallstones. X-rays can also show calcified gallstones, but not radiolucent ones.
**Option B:** CT scan is not the initial investigation of choice due to its higher cost, radiation exposure, and lower sensitivity compared to USG. However, CT scan may be used in complex cases or when the diagnosis is unclear.
**Option C:** MRI is not the first-line investigation in cholelithiasis due to its higher cost, limited availability, and lower sensitivity compared to USG. MRI may be used in cases where there is suspicion of gallbladder cancer or when the diagnosis is unclear.
**Clinical Pearl / High-Yield Fact**
The Alvarado score is a clinical scoring system used to diagnose acute cholecystitis. It includes factors such as right upper quadrant abdominal pain, fever, leukocytosis, and tenderness in the right upper quadrant. A score of 6 or more suggests acute cholecystitis.
**Correct Answer: A. Ultrasonography (USG)**