Choice of research methods in nephrology

Each of the radiation diagnostic methods has its own strengths and weaknesses. The choice of a method in a specific clinical situation is determined by its diagnostic capabilities (sensitivity, specificity, accuracy), safety for the patient, cost, and availability. At the same time, the task of the most accurate diagnostics often conflicts with the principle of the greatest safety, and methods with a more powerful diagnostic potential (CT, MRI, positron emission tomography) are the most expensive and less accessible.

Ultrasound differs from other methods by a combination of a wide range of diagnostic capabilities, high safety, relatively low cost and wide availability, so today it forms the basis of radiation diagnostics in nephrology. As a rule, examination of a nephrological patient begins with this visualization method, and in many situations it provides comprehensive information. USDG significantly expands the capabilities of ultrasound, allowing to detect changes in the renal vessels, urodynamic disorders and parenchyma structure. Therefore, it is desirable that the ultrasound diagnostic room where nephrological patients are examined be equipped with equipment that allows performing USDG, and the specialists working there have the appropriate skills.

In complex diagnostic cases, the task is to rationally combine diagnostic methods in accordance with their technical capabilities and advantages in different clinical situations, which is impossible without taking into account the patient’s medical history and clinical and laboratory data.

There are two tactics of radiation diagnostics:

• from simple to complex;
• the shortest path to the most complete information.

The first approach consists of the sequential use of several methods of radiation diagnostics, starting with the safest and most accessible and ending with the most expensive and associated with a high risk of complications. The second approach suggests starting with the most informative method.

When planning an examination, the physician should be guided by the following principles:

• the diagnostic power of the method must be adequate to the clinical task at hand;
• More expensive research methods that involve the risk of serious complications should be used only in cases where simpler and safer methods cannot provide complete information;
• use expensive methods and those associated with the risk of serious complications only in cases where their results can change the treatment and affect the prognosis;
• stage-by-stage diagnostics: use screening methods (more accessible and safer methods) in advance, and only for patients classified as at-risk based on their results, conduct clarifying studies using more expensive and dangerous methods;
• the frequency of repeated studies to assess the dynamics of the pathological process and the effectiveness of treatment should be rationally justified;
• avoid unnecessary duplication of methods that are similar in their capabilities in order to reduce the costs of examination and the workload of diagnostic departments;
• avoid, if possible, combinations of methods, each of which is associated with the use of high doses of radiation and/or toxic contrast agents.

According to the tactics of application, the methods are divided into two levels. The methods of the 1st level are used at the first stage of diagnostic search: the main studies allow to identify the key signs of the main disease; additional ones are used in special clinical situations for conducting extended differential diagnostics, clarifying concomitant conditions, functional indicators of the kidneys, etc. The second level of diagnostics is carried out only after the methods of the 1st level, taking into account their results in the case when they make it possible to suspect the disease or when their results seem controversial and doubtful. The second level of studies include methods that are associated with an increased risk of complications or are the most expensive, available only in large diagnostic centers.

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