What is the appropriate workup for a patient with nephrolithiasis (kidney stones)?

From the Guidelines

A kidney stone workup should begin with a comprehensive medical history, physical examination, and urinalysis to confirm the presence of blood or crystals, followed by initial imaging with a non-contrast CT scan, which is the gold standard for detecting stones with 95-97% sensitivity, as recommended by the American College of Radiology 1. The initial evaluation should also include laboratory tests such as complete blood count, comprehensive metabolic panel (particularly calcium, phosphorus, and uric acid levels), and urinalysis with culture. For patients with recurrent stones, a 24-hour urine collection is recommended to assess metabolic abnormalities like hypercalciuria, hyperoxaluria, or hypocitraturia, as suggested by the American College of Physicians 1. Stone analysis, when possible, provides valuable information about composition (calcium oxalate, calcium phosphate, uric acid, struvite, or cystine) to guide prevention strategies. Treatment depends on stone size, location, and symptoms, ranging from conservative management with pain control and hydration for small stones (<5mm) to surgical interventions like ureteroscopy, extracorporeal shock wave lithotripsy, or percutaneous nephrolithotomy for larger stones, as outlined in the American Urological Association guideline 1. Preventive measures include increased fluid intake (2-3 liters daily), dietary modifications based on stone composition, and medications such as thiazide diuretics for calcium stones, allopurinol for uric acid stones, or potassium citrate to increase urine pH. Key considerations in the workup and management of kidney stones include:

• Patient history and physical examination to identify risk factors and symptoms
• Imaging studies, such as non-contrast CT scan or ultrasound, to confirm the presence and location of stones
• Laboratory tests, including urinalysis and blood chemistry, to assess for underlying metabolic abnormalities
• Stone analysis to guide prevention strategies
• Treatment options, ranging from conservative management to surgical interventions, based on stone size, location, and symptoms
• Preventive measures, including increased fluid intake, dietary modifications, and medications, to reduce the risk of recurrent stone formation.

From the Research

Kidney Stone Workup

• The initial evaluation of kidney stones involves excluding concomitant infection, imaging with a non-contrast computed tomography scan, and consideration of medical expulsive therapy or surgical intervention depending on stone size and location 2.
• The use of non-contrast computed tomography (CT) scans is recommended for the diagnosis of kidney stones due to its high sensitivity and specificity 3.
• Stone size and location are significant factors in determining treatment outcomes, with larger stones and those in certain locations being more likely to require further treatment 4.
• Metabolic evaluation is also an important part of the workup, with increasing fluid intake recommended to reduce the risk of recurrence 2.
• The mean attenuation value (MAV) of the stone, as measured by CT scan, may be a useful predictor of treatment success, with higher values indicating a lower likelihood of successful treatment 4.

Imaging and Diagnosis

• Non-contrast helical CT is a valuable tool in the diagnosis of kidney stones, allowing for rapid and accurate diagnosis without the need for contrast media 3.
• The use of non-contrast-enhanced CT scans may not provide significant advantages over kidney-ureter-bladder (KUB) films in all cases, but can be useful in certain scenarios 4.
• Imaging studies should be used to guide treatment decisions, taking into account factors such as stone size, location, and density 4.

Treatment and Management

• Medical expulsive therapy or surgical intervention may be considered depending on stone size and location 2.
• Extracorporeal shock wave lithotripsy (ESWL) is a safe and efficient treatment option for urinary stone disease, with an overall stone-free rate of 85% in one study 4.
• The outcome of ESWL can be influenced by factors such as stone size, location, and density, as well as the skin-to-stone distance (SSD) and mean attenuation value (MAV) of the stone 4.

Note: The study 5 is not relevant to the topic of kidney stone workup.