Fibrosis of the renal parenchyma
Chronic kidney disease of any nature - diabetic nephropathy, glomerulonephritis, hypertensive nephrosclerosis - ends with the same morphological result: replacement of functioning tissue with fibrous tissue. The extent of this fibrosis predicts prognosis better than a single creatinine level, but is traditionally assessed only by kidney biopsy, a procedure with a real risk of bleeding.
Elastography allows you to measure cortical stiffness non-invasively and repeat the measurement over time. This is of particular value in patients with a kidney transplant: the increase in graft stiffness can outpace the increase in creatinine and signal chronic dysfunction earlier.
Interpretation requires caution. The result is influenced by the depth of the kidney, the thickness of the subcutaneous tissue, the degree of hydration and intrarenal pressure - with urinary tract obstruction, stiffness increases regardless of fibrosis. Therefore, the measurement is always compared with conventional ultrasound, tests and clinical picture.
What does elastography show?
Elastography measures the stiffness (elasticity) of tissue - a parameter that a doctor could previously assess only with his hands during palpation. Healthy tissue is soft and easily deformed, while scar, fibrous and tumor tissue is dense and rigid. The method translates this feeling into objective numbers that can be compared between studies.
The main practical value is in the differential diagnosis of focal formations. Benign nodes usually retain the elasticity of the surrounding tissue, while malignant ones are noticeably stiffer. This helps decide which nodes need to be monitored and which ones require a biopsy.
Compression and shear wave techniques
Compression elastography is based on light pressure with a sensor: the device compares tissue deformation and builds a color map. The method is qualitative - it shows what is harder and what is softer, but does not give absolute values.
Shear wave elastography (shear wave, which also includes liver fibroscan) uses the acoustic pulse of the device itself and measures the speed of propagation of the shear wave. The result is quantitative - in kilopascals, which allows you to track the dynamics during treatment.
Limitations of the method
The result is influenced by severe obesity, edema and active inflammation in the area of interest, as well as the depth of the formation: the deeper it is, the less reliable the measurements. Large calcifications and cysts produce artifacts.
Elastography is not an independent diagnosis, but one of the parameters. The final conclusion about the nature of the formation is given by a morphological study, that is, a biopsy.