Okay, let's tackle this question. The patient is a 4-year-old with leg and ankle swelling, pitting edema, 2+ proteinuria, and normal BUN/creatinine. After corticosteroids, she recovers. So, the main issue here is nephrotic syndrome, right? Because the key features are edema, proteinuria, and normal renal function.

Nephrotic syndrome in children is usually minimal change disease, which is the most common cause. Minimal change disease is known for its response to corticosteroids. Now, the question is about what urine findings would be expected before treatment. The options aren't given, but from the core concept, I need to think about the typical urinary findings in minimal change disease.

In minimal change disease, the urine would show heavy proteinuria (which is given here as 2+), but the sediment is usually bland—no red cells or inflammatory cells. The absence of RBCs and inflammatory cells in the sediment is a clue. So, the correct answer would be the option that mentions heavy proteinuria without red cells or casts.

The wrong options might include things like hematuria (which is present in nephritic syndrome), RBC casts (seen in glomerulonephritis), or maybe WBCs (indicating infection or inflammation). Also, if there were abnormal renal function, that would point to a different diagnosis.

Clinical pearl: Remember that minimal change disease is the most common cause of nephrotic syndrome in children and responds well to steroids. The urine sediment is typically negative for RBCs and inflammatory cells.

**Core Concept**
This case describes **nephrotic syndrome** in a child, characterized by heavy proteinuria, hypoalbuminemia, edema, and normal renal function. The key pathologic feature is **podocyte injury** leading to increased glomerular permeability. Minimal change disease (MCD) is the most common cause in pediatric cases and is steroid-responsive.

**Why the Correct Answer is Right**
In **minimal change disease**, the urine shows **proteinuria (typically >3.5 g/day)** with **no hematuria, red blood cell (RBC) casts, or inflammatory cells** in the sediment. The absence of RBCs and inflammatory cells differentiates it from nephritic syndromes (e.g., post-streptococcal glomerulonephritis) or interstitial nephritis. The bland urinary sediment is a hallmark of MCD, as the glomerular basement membrane remains intact, preventing RBC leakage.

**Why Each Wrong Option is Incorrect**
**Option A:** Hematuria suggests a nephritic process (e.g., IgA nephropathy), which is not consistent with MCD.
**Option B:** RBC casts indicate glomerulonephritis (e.g., post-streptococcal), but MCD lacks basement membrane damage.
**Option C:** WBCs or leukocyte casts imply pyelonephritis or interstitial nephritis, unrelated to steroid-responsive nephrotic syndrome.
**Option D:** Myoglobinuria (from rhabdomyolysis) causes dark urine and acute kidney injury, not isolated proteinuria.

**Clinical Pearl / High-Yield Fact**
**Minimal change disease** is the most common cause of nephrotic syndrome in children (<

✓ Correct Answer: C. Lipid droplets