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  Analgesic administration should not be delayed while obtaining laboratory and radiology studies.

  
  
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  Abdominal aortic aneurysm should be considered in the differential of elderly patients being evaluated for kidney stones.

  
  
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  Noncontrast computed tomography of the abdomen and pelvis is the test of choice for diagnosing nephrolithiasis.

  
  
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  Urologic consultation is indicated in patients with coexisting infection or worsening renal insufficiency.

Kidney stones occur when urinary solutes precipitate out of the urine and form crystalline stones in the genitourinary (GU) tract. Nephrolithiasis is common in the United States, with an estimated prevalence of 7% in men and 3% in women. Kidney stones most often affect people in the third to fifth decades of life, but can occur at all ages. The recurrence rate is 30% within the first year and 50% at 5 years. Patients with a family history of kidney stones are more likely to develop stones, and Caucasians are affected twice as often as African Ameri-cans and Asians. Specific risk factors for kidney stones include dehydration, hypercalcemia, hyperuricemia (gout), certain urinary tract infections (Proteus, Klebsiella, Pseudomonas), and medications (protease inhibitors, diuretics, laxatives). The 4 main types of kidney stones are listed in Table 39-1

The GU tract has several anatomic areas of narrowing that may limit passage of a stone. The most common areas are the renal calyx, the ureteropelvic junction (UPJ), the pelvic brim (where the ureter passes over the pelvic bone and iliac vessels), and the ureterovesical junction (UVJ). Ureteral obstruction occurs when a stone blocks the passage of urine, resulting in hydroureter (dilated ureter) and hydronephrosis (dilated renal pelvis and calices).

Timely evaluation, a broad differential, and prompt administration of appropriate analgesia is paramount to proper emergency department (ED) management. Although disposition of these patients is often uncomplicated, certain factors may warrant more extensive workup, emergent urology consultation, and hospital admission.

History

Patients often present with rapid onset of severe sharp pain, which is usually episodic (“renal colic”) and lasts minutes to hours. Pain often originates in the flank and radiates to the abdomen and groin along the course of the ureter. Nausea, vomiting, and diaphoresis are common. Urinary symptoms, such as frequency and urgency, may vary, depending on where the stone is located, and often increase in severity when the stone nears the bladder.