**Core Concept**
Gallstones are formed due to imbalances in bile composition, particularly cholesterol and bilirubin. Diabetes mellitus is associated with increased gallstone formation due to hyperglycemia-induced changes in bile acid metabolism and increased cholesterol saturation in bile.

**Why the Correct Answer is Right**
Diabetic patients have a significantly higher risk of developing gallstones, with studies showing up to 3–5 times higher incidence compared to non-diabetics. This is due to hyperglycemia-induced increased cholesterol synthesis, reduced gallbladder emptying, and altered bile acid metabolism. Diabetics also have higher levels of serum lipids and increased bile cholesterol saturation, promoting stone formation. This association is especially strong in type 2 diabetes and is a well-established clinical risk factor.

**Why Each Wrong Option is Incorrect**
Option A: Gallstones are actually more common in women than men, especially after age 40, with a ratio of about 3:1 in favor of women.
Option C: Only about 10–20% of gallstones are radio-opaque; most are composed of cholesterol and are not visible on plain X-rays.
Option D: Gallstones are typically less than 5 mm in size; stones larger than 50 mm are extremely rare and not clinically relevant.

**Clinical Pearl / High-Yield Fact**
Diabetes increases gallstone risk—patients with diabetes should be screened for gallstones, especially if presenting with abdominal pain or jaundice. A history of diabetes is a key risk factor in surgical evaluation of biliary disease.

✓ Correct Answer: B. There is an increased incidence of stones in diabetics.