A 36-year-old woman comes to the office due to recurrent dysuria. She also has had dull pain in her right flank and cloudy urine that contains blood. The patient has a history of recurrent urinary tract infections since becoming sexually active in high school. Over the last year, she has had 3 infections accompanied by fever. Her last urine culture grew Klebsiella pneumoniae. The patient is in a monogamous relationship. For contraception, she uses a diaphragm or her partner uses a condom, both with spermicidal coatings.
Temperature is 38.1 C (100.6 F), blood pressure is 114/70 mm Hg, and pulse is 95/min. The abdomen is soft and nontender. Mild right costovertebral angle tenderness is present on percussion.
Laboratory results are as follows:
Which of the following would most likely treat the underlying cause of this patient's recurrent condition?

Question

A 36-year-old woman comes to the office due to recurrent dysuria.  She also has had dull pain in her right flank and cloudy urine that contains blood.  The patient has a history of recurrent urinary tract infections since becoming sexually active in high school.  Over the last year, she has had 3 infections accompanied by fever.  Her last urine culture grew Klebsiella pneumoniae.  The patient is in a monogamous relationship.  For contraception, she uses a diaphragm or her partner uses a condom, both with spermicidal coatings.
Temperature is 38.1 C (100.6 F), blood pressure is 114/70 mm Hg, and pulse is 95/min.  The abdomen is soft and nontender.  Mild right costovertebral angle tenderness is present on percussion.
Laboratory results are as follows:
 Which of the following would most likely treat the underlying cause of this patient's recurrent condition?

Quizplus · Accepted Answer

This patient's presentation-with hematuria, right flank pain, dysuria, a history of recurrent urinary tract infections (UTIs), and laboratory tests indicating very alkaline urine (pH >8) and a decreased glomerular filtration rate-is strongly suggestive of struvite stones. Struvite stones are caused by urease-producing bacteria (eg, Proteus, Klebsiella). These bacteria convert urea to ammonia, which raises the urine pH and crystallizes with magnesium and trivalent phosphate to form struvite crystals. Once present, struvite stones may rapidly expand over weeks to months and develop into a staghorn calculus, filling the entire renal collecting system. If left untreated, the stones will continue to seed infections, and urinary tract obstruction can lead to loss of kidney function. Eradication of staghorn calculi is difficult. Antibiotics alone do not eliminate the source of the infection, because the bacteria grow within the stone matrix and are not eradicated until the entire stone and its fragments are removed. In addition to antibiotics for the UTI, percutaneous nephrolithotomy, often with lithotripsy, is the preferred first-line therapy. Open surgical stone removal is indicated for morbidly obese individuals (in whom fluoroscopy is difficult) and for patients with a large stone burden and a distorted collecting system anatomy. Nephrectomy is reserved for patients with a staghorn stone in a chronically infected kidney that is nonfunctioning or poorly functioning. (Choice A) Spermicides have been linked to an increased frequency of UTIs in women. However, stopping the use of spermicides alone will not eliminate this patient's UTI or treat her struvite stone. (Choice B) High-volume fluid intake and allopurinol are effective for treating and preventing uric acid, but not struvite, stones. (Choice C) Postcoital antibiotics can help patients whose UTIs are linked to sexual intercourse. However, they would not eliminate this patient's source of infection (bacteria growing within the stone matrix) unless the entire stone and its fragments were removed. (Choice E) Urinary alkalization can be useful in patients with recurrent uric acid stones or calcium oxalate stones associated with low urine citrate excretion, but it is not useful in the prevention of struvite stones. Urinary acidification is occasionally used for treatment and prevention of recurrent struvite stones, but medical therapy alone is rarely successful and not considered first-line therapy. Educational objective: Recurrent urinary tract infections in patients with alkaline urine should raise the possibility of a struvite stone. Antibiotics alone do not remove the source of the infection; elimination of the stone is required. __________ References: Reduced glomerular filtration rate and hypercalciuria in primary struvite nephrolithiasis. (http://www.ncbi.nlm.nih.gov/pubmed/3430961) Long-term results of percutaneous nephrolithotomy for treatment of staghorn stones. (http://www.ncbi.nlm.nih.gov/pubmed/21166763)

A 36-Year-Old Woman Comes to the Office Due to Recurrent