A 35-year-old woman presents with severe back pain and a history of Klebsiella pneumoniae infection. What type of kidney stone is most likely to form in her case?

The formation of kidney stones can be influenced by various factors, including underlying medical conditions and specific urinary tract infections. In this case, the patient has a history of Klebsiella pneumoniae infection, which is significant in determining the type of kidney stone most likely to form.

Klebsiella pneumoniae is a urease-producing bacterium. Urease breaks down urea into ammonia and carbon dioxide, which leads to an increase in urinary pH (making the urine more alkaline). In an alkaline environment, certain types of crystals are more likely to precipitate and form stones. Specifically, struvite stones, also known as infection stones, are predominantly composed of magnesium ammonium phosphate and often develop in the context of urinary tract infections caused by urease-producing bacteria like Klebsiella.

Struvite stones can grow quite large and can form quickly in response to infection, often leading to complications such as obstruction or even renal failure. The patient's severe back pain could indicate complications related to the presence of these stones.

In considering the other stone types:

• Calcium oxalate stones form in acidic urine and are not specifically associated with urinary tract infections caused by urease-producing microbes.

• Cystine stones are the result of a genetic disorder