A 53-year-old woman comes to the emergency department with left-sided flank pain and dark urine. The patient's symptoms began this morning and are associated with dysuria and urinary urgency. Medical history includes type 2 diabetes mellitus and hypertension. Medications include lisinopril, amlodipine, atorvastatin, glargine insulin, and metformin. She does not use tobacco, alcohol, or illicit drugs.
Vital signs are normal, and physical examination is notable only for left upper abdominal tenderness.
Complete blood count is normal. Additional laboratory results are as follows:
A noncontrast abdominal CT scan reveals a dense, 4-mm stone in the distal left ureter without hydronephrosis. The patient is treated with intravenous hydration and analgesics, which relieve her symptoms. The stone is passed without further intervention and sent for analysis.
Which of the following is the best next step in evaluation of this patient's condition?

Question

A 53-year-old woman comes to the emergency department with left-sided flank pain and dark urine.  The patient's symptoms began this morning and are associated with dysuria and urinary urgency.  Medical history includes type 2 diabetes mellitus and hypertension.  Medications include lisinopril, amlodipine, atorvastatin, glargine insulin, and metformin.  She does not use tobacco, alcohol, or illicit drugs.
Vital signs are normal, and physical examination is notable only for left upper abdominal tenderness.
Complete blood count is normal.  Additional laboratory results are as follows:
 A noncontrast abdominal CT scan reveals a dense, 4-mm stone in the distal left ureter without hydronephrosis.  The patient is treated with intravenous hydration and analgesics, which relieve her symptoms.  The stone is passed without further intervention and sent for analysis.
Which of the following is the best next step in evaluation of this patient's condition?

Quizplus · Accepted Answer

This patient with nephrolithiasis has hypercalcemia, raising suspicion for symptomatic hyperparathyroidism leading to calcium stone formation. In patients with renal calculi, even high normal serum calcium levels should prompt evaluation for hyperparathyroidism. The diagnosis can be generally confirmed by persistent hypercalcemia with an elevated parathyroid hormone level. Patients with primary hyperparathyroidism who have nephrolithiasis or other complications (eg, osteoporosis, chronic kidney disease, symptomatic hypercalcemia) should be considered for parathyroidectomy. (Choice A) 24-hour urine collections can be used to evaluate for supersaturation of common stone metabolites (eg, calcium, oxalate, uric acid) but are not always required to diagnose hyperparathyroidism. A collection could be considered if parathyroid hormone level is normal or minimally elevated, as it could help distinguish between primary hyperparathyroidism (elevated urinary calcium excretion) and familial hypocalciuric hypercalcemia (low urinary calcium excretion). (Choice B) Cystoscopy is commonly performed to rule out malignancy in patients with hematuria. However, this patient is at low risk for bladder cancer (ie, female, age <65, nonsmoker) and has a compelling explanation for her hematuria (ie, nephrolithiasis). Cystoscopy could be reconsidered if hematuria persists after resolution of the kidney stones. (Choice C) Deferring further diagnostic studies until recurrence of nephrolithiasis may be appropriate for patients without risk factors (eg, obesity, diabetes, history of bariatric surgery) or abnormalities on initial workup. However, given this patient's hypercalcemia, hyperparathyroidism must be ruled out. (Choice E) Uric acid stones are relatively uncommon (5%-10% of stones), primarily occur in patients with persistently acidic urine (pH< 5.5), and have a low radiodensity. This patient's urine pH of 6.2, hypercalcemia, and presence of a dense stone on CT scan make calcium-based stones more likely. Educational objective: All patients who present with nephrolithiasis should undergo at least a basic workup, including imaging (eg, noncontrast CT scan), serum chemistry, urinalysis, and stone analysis. Hyperparathyroidism is the most common cause of hypercalcemia in patients with nephrolithiasis. __________ References: Primary hyperparathyroidism and nephrolithiasis. (http://www.ncbi.nlm.nih.gov/pubmed/25911000)

A 53-Year-Old Woman Comes to the Emergency Department with Left-Sided