Nephrolithiasis Quiz: Ace Your Exams

A 57-year-old woman presents to the emergency department for evaluation of acute onset right flank pain for the past 6 hours and 3 days of dysuria and urinary frequency. The patient has a past medical history of recurrent urinary tract infections, hypertension, and diabetes. Temperature is 38°C (100.4°F), blood pressure is 176/65 mm Hg, heart rate is 101/min, respiratory rate is 17/min, and oxygen saturation is 98% on room air. The patient appears uncomfortable and is vomiting into an emesis basin. She is started on IV normal saline, IV ketorolac, and ondansetron. A CBC and basic metabolic panel are pending. Urinalysis findings are shown below. Non-contrast helical CT scan of the abdomen and pelvis shows an obstructing stone in the right ureter. What type of crystals are most likely to be identified on urine microscopy?  

Laboratory value	Result	Reference
Urinalysis
Color	Clear	Clear
pH	8.1	4.5-8.0
Specific gravity	1.013	1.002-1.028
Glucose	Negative	Negative
Blood	Large	Negative
Leukocyte esterase	Large	Negative
Nitrites	Present	Absent
Leukocytes	50-100/hpf	<5hpf
Erythrocytes	25-50/hpf	<5hpf
Dysmorphic RBCs	Absent	Absent
Casts	None	None
Gram stain	Gram-negative rods	No organisms