Instrumental diagnostics of kidney and urinary tract diseases

Baseline instrumental diagnostics

Ultrasound examination (US) is always the first step in visualizing the urinary system. It is completely safe, carries no radiation exposure, and is recognized as a mandatory screening method for all children without exception.

During the ultrasound procedure, the diagnostic physician specifically evaluates the following set of parameters:

• Topography and exact dimensions of the kidneys.
• Presence of gross developmental anomalies (e.g., hypoplasia or duplication of the organ).
• Condition of the pelvicalyceal system (PCS) and distal ureters. In particular, their deformation or dilatation is detected.
• Presence of calculi (stones) within the lumen of the tracts.
• Characteristics of renal blood flow.

In addition, echography makes it possible to suspect an inflammatory process. Ultrasound signs of pyelonephritis depend on the stage: in an acute process, parenchymal edema (in one or both kidneys) is clearly visualized, whereas in chronic pyelonephritis, changes in the thickness of the renal parenchyma come to the forefront.

Comprehensive nephrourological examination

If screening results raise questions or the patient has a specific clinical history, a comprehensive examination is prescribed. Its main goal is precise topical diagnosis of inflammation, detection of structural anomalies, urodynamic disorders (in both upper and lower tracts), and assessment of the degree of renal tissue damage.

Strict rule: all studies from this package are allowed to be performed exclusively during the period of clinical and laboratory remission of the disease.

Indications for initiating a comprehensive diagnostic workup include:

1. Detection of any organic or functional pathology during screening ultrasound.
2. Even a single episode of symptomatic urinary tract infection (UTI) in boys.
3. Two episodes of symptomatic UTI in girls.

The diagnostic arsenal of the comprehensive exam includes X-ray, radionuclide, urodynamic (cystometry, uroflowmetry), endoscopic (cystoscopy) methods, as well as MRI urography.

Specific imaging methods

Each method has its own strict tasks and fields of application. The main methods are divided into radiological and radionuclide ones.

Radiological evaluation

• Voiding cystourethrography: recognized as the method of choice for assessing the condition of the lower urinary tract. It aims to detect vesicoureteral reflux (VUR), the presence of infravesical obstruction, as well as diverticula and calculi of the urinary bladder itself.
• Excretory urography: used to assess the anatomy and urodynamics of the upper urinary tract. The method allows for the most detailed visualization of the size, contours, mobility of the kidneys, as well as the structural features of the PCS and ureters. Urography data are used to calculate the renocortical index and compare the actual area of the kidneys with age norms.

Radionuclide diagnostics (nephroscintigraphy)

This method is essential for an in-depth assessment of the functional state and viability of the renal parenchyma.

• Static renal scintigraphy (using dimercaptosuccinic acid — DMSA): detects foci of decreased radiopharmaceutical uptake. This is the main marker of sclerosis, i.e., scarring of the renal tissue. It is important to remember that the scar formation process takes 1–2 years, and the risk of developing severe nephrosclerosis is directly proportional to the number of recurrent infection episodes.
• Dynamic renal scintigraphy: evaluates the stages of urine production (secretory and excretory functions) and urodynamics in real time. A major advantage is the ability to assess function both globally and separately for each kidney.

Instrumental diagnostics of the lower urinary tract

Specialized approaches are used for a targeted assessment of the functional and anatomical state of the lower urinary tract:

1. Functional methods: include uroflowmetry and cystometry. They are necessary for an accurate assessment of urodynamics at the level of the bladder and urethra.
2. Endoscopic methods: cystoscopy is the primary one. It provides a direct visual assessment of the condition of the bladder mucosa and allows for the study of the anatomical shape and spatial arrangement of the ureteral orifices.

Class and exam questions

What else to study on this topic

• Methodology and stages of voiding cystourethrography
• Formula and calculation rules for the renocortical index
• Interpretation of uroflowmetry and cystometry charts
• Indications for MRI urography in pediatrics

Other topics in "Chapter 8. Kidney and Urinary Tract Diseases"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.