Renal stone formation is a multistep process that includes supersaturation of the urine, lack of inhibitory substances, and urinary stasis. Which type of renal calculi is associated with Proteus infection?
**Core Concept**
Renal stone formation involves a complex interplay of factors, including supersaturation of the urine, lack of inhibitory substances, and urinary stasis. Infection stones, also known as struvite stones, are a specific type of renal calculus that forms in the setting of urinary tract infections (UTIs).
**Why the Correct Answer is Right**
Struvite stones are primarily composed of magnesium ammonium phosphate and are associated with alkaline urine pH. The presence of urease-producing bacteria, such as Proteus, leads to an increase in urinary pH, which promotes the formation of struvite stones. This is because urease breaks down urea into ammonia and carbon dioxide, raising the pH of the urine. The alkaline environment favors the precipitation of magnesium ammonium phosphate, resulting in the formation of struvite stones.
**Why Each Wrong Option is Incorrect**
**Option A:** Uric acid stones are associated with acidic urine pH, not alkaline urine pH, making them less likely to be associated with Proteus infection.
**Option B:** Calcium oxalate stones are the most common type of renal calculus, but they are not specifically associated with Proteus infection.
**Option C:** Cystine stones are rare and occur in patients with cystinuria, a genetic disorder that affects the reabsorption of cystine in the kidneys.
**Clinical Pearl / High-Yield Fact**
Remember that urease-producing bacteria, such as Proteus, can lead to the formation of struvite stones by raising the pH of the urine. This is a key clinical correlation to remember when evaluating patients with renal calculi.
**Correct Answer: C. Cystine stones are rare and occur in patients with cystinuria, a genetic disorder that affects the reabsorption of cystine in the kidneys.