Figure 35.1
Laboratory testing is achieved by a combination of outpatient laboratory serum and urine studies. Comprehensive metabolic analysis requires at-home urine collections
High quality imaging capabilities with available radiologic interpretation
Laboratory testing must be easy for patients to ensure proper follow-through. Initial metabolic evaluations and serum and point-of-care urinalysis can be performed in the clinic or in a neighboring laboratory. Complex metabolic evaluations, which include two 24 h urine studies on non-consecutive days, must be completed at home. At home urine collections can be arranged through one of several companies (in the USA, LithoLink is preferred by the authors), and the studies must be completed by the patient at least 2 weeks ahead of their appointment to insure that the results are available to the practitioner. These reference laboratories may be able to export results into the practitioner’s medical record system or provide an internet portal to view the results at the time of follow-up. For some practitioners, the 24 h urine studies can be evaluated by the hospital laboratory.
Initial kidney stone diagnosis will most often involve a low-dose CT of the Abdomen and Pelvis, however follow-up requires use of renal/bladder ultrasound, plain KUB or digital tomography of the abdomen. Follow-up imaging is used to determine whether a stone patient is metabolically active (enlarging known stones or forming new stones), and requires a change in treatment regimen [2]. Imaging systems within the clinic can provide additional ease for the patient, who can have follow-up imaging completed in the same setting, immediately prior to their routine visit.
Team-Based Approach
Management of complex stone disease is best accomplished with a collaborative team involving Urology and Nephrology and supported by dieticians and mid-level practitioners (Fig. 35.2). In the office setting, the Urologist is suited to manage basic metabolic issues derived from the metabolic evaluation and determine the need for surgery. The Urologist is often the point person in the stone center. A Nephrologist can offer management strategies for more complex metabolic derangements and management of other comorbid conditions (chronic kidney disease, hypertension, etc.). Involving a dietician in the care team can be of great utility by providing strategies to maintain major dietary changes; dietary recommendations can be time consuming and challenging for the physician. Mid-level practitioners can play an important role in diagnosis and management of a wide range of patients depending on their experience.
Figure 35.2
Members of the stone center
How to Structure Initial and Follow-Up Visits
The initial visit to a Stone Center is used to take a complete history and physical exam and review imaging (Fig. 35.3). The history focuses first on the aggressiveness of the stone disease, querying how many stones total, stone formation rate per year, duration of the disease and stone-related symptoms. Comorbid conditions such as recurrent UTIs, bowel disease or disorders of calcium hemostasis must be identified. Asking about environmental factors such as heat exposure and work environment can be important. A thorough dietary history should be taken, including consumption of fluids overall, protein, coffee, tea, and foods high in citrate, calcium, and oxalate. Look for family history of stone formation or genetic disorders such as primary hyperoxaluria, cystinuria or distal RTA. Medication and supplementation use can provide clues to stone formation as well.
