Okay, let's tackle this question. The patient is a child with cola-colored urine, proteinuria 2+, and a history of a rash two weeks ago. Hmm. Cola-colored urine is a classic sign of hematuria, which can be due to red blood cells giving the urine a dark color. Proteinuria 2+ suggests some kidney involvement, like glomerulonephritis.

Now, the rash two weeks ago is a key clue. Post-infectious glomerulonephritis is a possibility here. Conditions like post-streptococcal glomerulonephritis often follow a streptococcal infection, which might present with a rash. But wait, the rash could also be part of an immune-mediated condition. Let me think—Henoch-Schönlein purpura (HSP) is a vasculitis that affects children and can cause purpuric rash, abdominal pain, joint pain, and renal involvement with hematuria and proteinuria. HSP typically presents with palpable purpura, which is a rash that doesn't blanch when pressed.

Another possibility is systemic lupus erythematosus (SLE), but the rash in SLE is often a malar rash or photosensitive, and the timeline of two weeks might be a bit short. Goodpasture's syndrome is another consideration, but it's more associated with pulmonary hemorrhage and anti-GBM antibodies, which isn't mentioned here.

Wait, the question mentions a rash two weeks ago. HSP is a common cause in children with these symptoms, especially with the triad of rash, arthritis, and renal involvement. The cola-colored urine points to hematuria, which is common in HSP. Post-strep glomerulonephritis usually follows a pharyngeal infection and might not present with a rash, unless there's a concurrent infection. But the rash here is two weeks prior, so maybe the infection was a trigger for HSP.

So, the probable diagnosis here is Henoch-Schönlein purpura. The key features are the rash (palpable purpura), abdominal pain, joint pain, and renal involvement. The presence of cola-colored urine (hematuria) and proteinuria fits with HSP. The other options like post-strep glomerulonephritis might not have the rash, and SLE is less likely with the acute presentation. Goodpasture's is a different entity with pulmonary symptoms. So, the answer should be Henoch-Schönlein purpura.

**Core Concept** The question tests recognition of Henoch-Schönlein purpura (HSP), a small-vessel vasculitis commonly seen in children, characterized by a classic quadruple (tetrad) of symptoms: palpable purpura, abdominal pain, arthritis, and renal involvement. Cola-colored urine indicates hematuria, a hallmark of HSP-related glomerulonephritis.

**Why the Correct Answer is Right** Henoch-Schönlein purpura is the most likely diagnosis here. The rash (palpable purpura) two weeks prior suggests an immune-mediated process. The cola-colored urine reflects hematuria, and proteinuria indicates glomerular injury. HSP is triggered by infections (e.g., viral or streptococcal), leading to IgA deposition

✓ Correct Answer: B. HSP