**Core Concept**
Congenital pyloric stenosis is a condition characterized by the narrowing of the pyloric canal, leading to gastric outlet obstruction. Ultrasound (USG) is a reliable diagnostic tool for this condition, assessing parameters such as pyloric muscle thickness, canal length, and the presence of high gastric residuals.

**Why the Correct Answer is Right**
High gastric residues are not a reliable indicator of congenital pyloric stenosis. This is because high gastric residuals can be present in various conditions, including gastroesophageal reflux disease, gastric outlet obstruction due to other causes, and even normal physiological states. In contrast, specific ultrasound parameters such as muscle thickness and canal length are more reliable for diagnosing congenital pyloric stenosis.

**Why Each Wrong Option is Incorrect**
**Option A:** The accuracy of USG findings for congenital pyloric stenosis is indeed high, often reported as >95%. This makes option A incorrect because it does not explain why high gastric residues are an exception to USG findings.
**Option B:** A pyloric canal length of >16mm is a characteristic feature of congenital pyloric stenosis. This is because the normal length of the pyloric canal is typically 4mm is another characteristic feature of congenital pyloric stenosis. This is because the normal thickness of the pyloric muscle is typically <3mm. Therefore, option C is incorrect because it is a valid USG finding for the condition.

**Clinical Pearl / High-Yield Fact**
When diagnosing congenital pyloric stenosis using ultrasound, it is essential to assess both the pyloric muscle thickness and the canal length. A normal thickness of <3mm and a length of <10mm are generally considered within the normal range. Remember the mnemonic "4-3-10" to help you recall these parameters: 4mm for muscle thickness, 3mm for normal thickness, and 10mm for normal canal length.

**✓ Correct Answer: D. High gastric residues**