A general dietary assessment may begin by asking the patient if he or she follows any special diet. The words patients use to describe their overall dietary patterns, whether accurate or not, can be useful in interpreting the data obtained. Patients may then be queried about their appetite and whether any changes have occurred recently and about their weight history. Other information obtained during a general dietary assessment may include the extent to which patients eat more or less the same things every day, eat at the same times of day, eat out or bring home take-out foods, use condiments, participate in food preparation, skip meals, snack between meals, use alcohol, and avoid certain foods (and if so, why). Information obtained during the course of the assessment includes: details about where foods are consumed (e.g., home, work, school), portion sizes, methods of preparation, grocery shopping habits, food likes and dislikes, swallowing and dentition issues, food insecurity, knowledge of nutrition, and use of nutritional supplements. If quantification of intake is desired, data may be entered later into a nutrient analysis software program. Alternatively, a RDN may quantify in the clinic the foods and nutrients of interest by estimation, using his/her knowledge of nutritional composition and food tables that provide nutrient content.

Assessment may be targeted to the condition under evaluation and is always aimed at identifying the specific dietary mechanism(s) contributing to disease etiology, exacerbation, or risk of recurrence. The following is an analogy of a targeted assessment using the physical therapist (PT) as an example. A patient referred for a specific physical or muscular derangement is not typically assessed by the PT for his/her entire body and musculature as he or she might be if undergoing a general physical assessment. Rather, in the interest of time and efficiency and to address an acute injury or chronic problem, the PT will focus on body areas near to and involved in the problem of interest. In the area of urolithiasis, a targeted dietary assessment by the RDN or other person conducting it may be similarly indicated and should focus around the most common dietary risk factors, driven or informed by the presence of biochemical aberrations (Table 6.1).

Depending on how comprehensive and if targeted to certain foods or not, dietary assessment is frequently not accomplished in a couple of minutes. Without ample time, it is therefore understandable that shortcuts are taken. However, some shortcuts can lead to inaccurate assessment. A common problem in assessing the diets of patients is to ask leading questions, such as, “You don’t eat a lot of salt, do you?” or “Tell me which of these foods (provider hands the patient a list) you eat.” The appearance of judgment or expectation on the assessor’s part could lead to withholding or otherwise inaccurate patient reporting [20]. Thus, open-ended questions about specific foods of interest are best. Another problem is the inaccurate assessment of portion sizes . A patient might say, “I eat a lot of peanuts,” but his/her interpretation of “a lot” – or the assessor’s – could differ vastly from another who uses the same verbiage. Strategies to elicit accurate portion size estimations are widely employed by dietitians and include pictures or photos; synthetic (“fake”) foods; household measuring utensils; plates, bowls, and cups; food packages; and/or follow-up questions that result in the reasonable assurance of correct sizing [24]. Information about frequency of intake is also important. The frequent vs. infrequent intake of “high-risk” foods should be discerned. The patient who “loves spinach” but who only eats it once a month or so is likely to benefit little – if at all – from a restriction of spinach to address her risk of calcium oxalate stones. Yet another mistake is to ask only about meals. Rather than asking what the patient typically eats for breakfast, lunch, and dinner, use open-ended questions, such as, “Tell me about the first time in your day that you eat or drink anything.” This avoids the potential to miss between- and/or after-meal food and beverage intake, which could be significant. Moreover, some patients may follow a “grazing” dietary pattern and not identify with discrete “meals” when queried about them.

Beyond usual servings per day of certain foods – such as fruits and vegetables, meats, breads and baked goods, calcium-rich foods, and beverages – it is usually also desirable to quantify the intakes of specific nutrients, such as sodium and calcium, in milligrams or grams consumed per day. This requires detailed knowledge of the sources of foods that express these nutrients as well as the amounts they contain. While some may wish to quantify the amount of oxalate consumed, this is problematic due to the extensive variability in the reported oxalate content of foods, to the variable bioavailability of food oxalate, and to variations in human gastrointestinal tract physiology leading to significant differences in oxalate absorption [25]. Although these same problems exist to some degree in quantifying sodium and calcium, food values for these minerals are quite stable across multiple data sets .