Chapter 251. Kidney Stones

1. How do you diagnose nephrolithiasis?

2. How should kidney stones be managed in the inpatient setting?

3. What medical therapy facilitates stone passage?

4. When is urology or nephrology consultation indicated?

5. What follow-up and further testing is appropriate after discharge?

6. What drugs and dietary therapies are helpful in the secondary prevention of kidney stones?

Kidney stones are one of the most common and most painful disorders of the urinary tract. This chapter reviews the epidemiology of kidney stones, the pathophysiology and risk factors for their development, the typical clinical presentation, the initial diagnostic evaluation, the acute, often hospital-based symptomatic treatment, followed by the outpatient management focusing on secondary preventive measures.

Nephrolithiasis is a common disorder that inflicts recurrent pain and significant morbidity onto a substantial portion of the population, including many young and otherwise healthy individuals. In the United States, approximately 5% of women and 10% of men experience a symptomatic episode before the age of 70, and the cumulative 10-year recurrence rate is estimated at 40% for women and 60% for men.

Regional variations in the frequency and nature of kidney stone disease exist within the United States, with an increased prevalence in the southeastern region of the country. This variation may be related to differences in climate and sunlight exposure, as well as dietary habits and beverage consumption. Kidney stones develop more frequently among Caucasians than African Americans. Stones in the upper urinary tract are frequently seen in industrialized countries and are associated with a more affluent lifestyle, including high animal protein consumption, gout, and traits of the metabolic syndrome, including hypertension, impaired glucose tolerance, increased waist circumference, high triglycerides, and low-high-density lipoprotein (HDL) cholesterol. Bladder stones are more commonly seen in developing countries and more frequently affect individuals with a poor socioeconomic status.

Patients with kidney stones typically present with renal colic, characterized by severe pain and autonomic symptoms such as lightheadedness, diaphoresis, nausea, and vomiting. The severity of symptoms often results in a visit to a hospital emergency room, frequently requiring hospitalization and absenteeism from work. In the United States, kidney stones account for more than 2 million outpatient visits, over 600,000 emergency room visits, and approximately 0.4% of hospital admissions. Additional costs may arise from complications, such as ureteral obstruction, pyelonephritis, and the need for stone removal by instrumentation, surgery, or extracorporeal shock wave lithotripsy (ESWL). Patients with recurrent stone disease also have a heightened risk of chronic kidney disease. The annual cost of kidney disease in the United States, including hospitalizations, professional charges, and lost productivity, exceeds $2 billion.

Kidney stones can form from a variety of substances excreted in the urine and frequently consist of two or more different substances (Table 251-1). Calcareous (calcium oxalate or phosphate) stones are by far the most common, accounting for over 80% of kidney stones. Metabolic defects leading to stone formation include hypercalciuria in over 65% of cases, and less ...