Role of radiography in the diagnostic complex
A wide range of instrumental methods is used in clinical practice to visualize the urinary system. The baseline radiological examinations are plain abdominal radiography (standard radiography of the urinary system) and intravenous (excretory) urography. In addition to these, the diagnostic arsenal includes high-tech methods: computed tomography (CT) and magnetic resonance imaging (MRI) of the kidneys and adrenal glands.
Plain radiography traditionally occupies an important place in diagnostics, but its independent value is limited. The main drawback of the method is its extremely low diagnostic value when attempting to detect structural changes in the renal tissue (parenchyma) itself. That is why the baseline instrumental complex is not limited to a single X-ray: along with excretory urography, it necessarily includes an ultrasound examination (ultrasound) and cystoscopy.
Capabilities of excretory urography
To overcome the limitations of a standard image, excretory urography with intravenous administration of a radiocontrast agent is used.
What the contrast study allows to assess:
- Functional status: the rate and symmetry of contrast excretion by the left and right kidneys.
- Anatomy: deformation of the pelvicalyceal system (PCS).
- Structural defects: the presence of parenchymal scar changes characteristic of chronic processes (e.g., chronic pyelonephritis), as well as urinary tract developmental anomalies.
- Obstructive factors: calculi and strictures that disrupt urine passage and sustain prolonged inflammation.
- Specific lesions: in differential diagnosis (e.g., in renal tuberculosis), urograms may reveal petrificates (calcification areas) in the parenchyma outside the PCS. This is a sign of an advanced, late-diagnosed process.
Important rule: The use of contrast is associated with risks. Any contrast studies are performed strictly after a preliminary assessment of renal function. This is necessary to accurately calculate the risk of potential complications and timely prescribe preventive therapy.
Ultrasound as a baseline alternative
Despite the significance of radiography, the primary baseline method of instrumental diagnostics is ultrasound. It is a strictly mandatory screening examination for all children.
During echography, the physician assesses kidney topography and dimensions, congenital anomalies (hypoplasia, duplication), the state of the distal ureters and PCS (dilatation, deformation), as well as the presence of calculi and renal blood flow parameters.
In diagnosing pyelonephritis, ultrasound has high specificity:
- In an acute process, edema of the parenchyma of one or both kidneys is visualized.
- In a chronic process, changes in the thickness of the renal parenchyma are recorded.
Ultrasound is of particular importance in situations where ionizing radiation is undesirable (e.g., in pregnant women). In these cases, the method aims to exclude upper urinary tract obstruction, detect parenchymal destructive changes, and find an echo-negative trail from a calculus in the projection of the upper third of the ureter and below.
Evolution of approaches and related methods
Currently, classical excretory urography is increasingly yielding its position to ultrasound and CT. These modern methods are considered more informative and, in the case of ultrasound, free of radiation exposure. Nevertheless, intravenous urography retains its position and is included in the examination plan under strict indications, particularly for recurrent hematuria or a well-founded suspicion of urinary tract developmental anomalies.
For a comprehensive assessment of the urinary system, the algorithm is supplemented with endoscopic and functional methods, such as chromocystoscopy. Conventional cystoscopy is recognized as the most informative method for visualizing the urinary bladder mucosa. It is indispensable for assessing the state of the lower urinary tract, especially in recurrent infections associated with pyelonephritis.
Class and exam questions
Why is a plain kidney image rarely used as a standalone study?
Plain urography has extremely low diagnostic value for assessing the state of the renal parenchyma. Without the use of a contrast agent, the method does not allow for a detailed study of tissue structure.
What must be done before prescribing excretory urography?
Before administering a contrast agent, it is necessary to assess the excretory function of the kidneys. This allows for calculating the risk of complications and timely performing drug prophylaxis.
What signs of chronic inflammation can be seen on ultrasound and urogram?
On ultrasound in a chronic process (e.g., pyelonephritis), changes in parenchymal thickness are detected. On the excretory urogram, parenchymal scar changes and deformation of the pelvicalyceal system are visualized.
Does computed tomography replace classical radiography?
In modern practice, classical urography indeed increasingly yields to CT and ultrasound as more informative methods. However, radiography is still used for specific indications (suspected developmental anomalies, recurrent hematuria).
What else to study on this topic
- Detailed indications and methodology for CT of the kidneys and adrenal glands.
- Procedure features and diagnostic capabilities of MRI of the urinary system.
- Radioisotope imaging methods (nephroscintigraphy) in kidney diseases.
- Chromocystoscopy: execution technique and interpretation of results in urological practice.
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