**Core Concept**
The child's chronic symptoms, including abdominal pain, bloody diarrhea, and renal colic, suggest a systemic condition with gastrointestinal and urinary manifestations. The presence of urinary gravel and a negative stool culture for known enteropathogens point towards a metabolic disorder.

**Why the Correct Answer is Right**
The clinical presentation, including the child's failure to thrive (short stature and low weight), suggests a disorder of calcium metabolism. The presence of urinary gravel indicates the presence of calcium oxalate stones, which are often seen in primary hyperoxaluria. The normal sigmoidoscopy and negative stool culture for known enteropathogens make an infectious cause unlikely. The Mantoux test is negative, making tuberculosis a less likely cause of the child's symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
Primary hyperoxaluria is a rare genetic disorder characterized by excessive production of oxalate, leading to its accumulation in the body and formation of calcium oxalate stones. Early diagnosis and treatment are crucial to prevent long-term complications such as end-stage renal disease.

**Correct Answer:** D. Primary Hyperoxaluria.