Review literature: (Singer et al, 2006).
Sonography of the kidney is best done in supine position and with inspiration of the patient. In adverse conditions, an elevation of the examination side by 30 degrees is helpful.
Each kidney is scanned in longitudinal section and cross section. The upper pole is located more dorsally than the lower pole, the transducer must be tilted to the dorsum. Transducers use either sector or curved-array technology with 3.5 to 5 MHz.
The size of the parenchyma is measured from the convex outer edge to the tip of a papilla, the normal value is 13–18 mm. The kidney volume of 110–200 ml and can be calculated by using the following formula:
| kidney volume | = | length × width × depth × 0.5 |
The relationship between the dorsal parenchyma to pyelon to ventral parenchyma is normally 1:1:1. With increasing age, the kidney atrophy shifts the renal parenchyma pyelon index to 1:2:1.
The urogenital organs, especially the kidneys, have a broad range of anatomical variations, which cause confusion in ultrasound imaging. Tumor-like lesions have to be clarified with computed tomography (CT), often they are harmless [fig. renal pseudotumor].
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Ultrasound of a renal pseudotumor: CT-imaging revealed a buckling of the renal parenchyma. |
The resistive index (RI) is calculated with the peak systolic velocity (PSV or VPSV) and the end-diastolic velocity (EDV or VEDV) using following formula:
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Formula Resistive Index |
The location for the assessment of PSV and EDV are the arcuate arteries or interlobar arteries at the border between cortex and medulla. The standard value for the resistive index is 0.5 to 0.7. A RI of >0.7 or a side difference of more than 0.1 are seen in hydronephrosis, renal transplant graft rejection or intrinsic renal disease. An RI of less than 0.5 is a sign for a renal artery stenosis.
| 24-hour urine | Index | Examinations |
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Deutsche Version: Sonographie der Nieren
Last update:
Dr. med. Dirk Manski (E-Mail)