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Normal renal Doppler ultrasound

Case contributed by Dennis Odhiambo Agolah
Diagnosis certain

Presentation

Systemic hypertension with thyroid nodule, to rule out secondary cause of hypertension and to exclude any adrenal mass.

Patient Data

Age: 20 years
Gender: Male
ultrasound

The kidneys are orthotopic and maintain their sizes, outline and parenchyma morphology.  The right kidney measures 123 ml while the left kidney measures 174 ml in volume. No renal focal lesions, calculi or features of ureterohydronephrosis bilaterally. 

Anterior and frank approaches used to indirectly evaluate the intra-renal (segmental arcuate and interlobar; upper poles, mid poles and lower poles) arterial spectral Doppler waveforms.  The renal arteries show normal wall outline/ caliber and also demonstrate low resistance profiles with continuous forward flow throughout the cardiac cycle.  The intra-renal arterial waveforms show normal acceleration times and early systolic peak with no pulsus Tardus or pulsus Parvus waveforms. 

The renal artery peak systolic velocity is within normal limits bilaterally.  The bilateral intra-renal arcuate and interlobar arterial resistive indices of 0.55, 0.56, 0.61, 0.58, ,0.54, and 0.55 for the right kidney and; 0.57, 0.64, 0.65, 0.46, 0.51 and 0.54 for the left kidney noted are within normal limits.

The urinary bladder is unremarkable as well with a pre-void volume of 254 ml and empties completely on voiding with no residue on immediate post voiding examination assessment.

                                         

ultrasound

                                                         

 

                                                              Peak systolic                           End diastolic

Prox. Aorta                                          161 cm/s                              33.0 cm/s

Right main renal artery                      112 cm/s                               38.6 cm/s

Left main renal artery                       91.3 cm/s                              35.9 cm/s

 

The renal/ aorta ratio (RAR) is within normal limits bilaterally; Right RAR = 0.70 while the Left RAR = 0.57. NB: each is <3.5 (normal).

 

Case Discussion

The indirect (distal) technique used sonographically to assess the intra-renal segmental areas including the right and left bipolar and middle pole regions bilaterally for the arcuates and the interlobar arteries. The resistive indices are normal and less than 0.70 bilaterally. Mean normal ranges in adults is <0.70 while in children at 4 years and below, >0.70 is considered normal1.

Any presence of renal artery stenosis have been excluded directly as well (proximal approach) where the systolic velocities of the bilateral main renal arteries have been divided (as a ratio) with the systolic velocity of the proximal abdominal aorta in each side, to arrive at the renal aortic ratios (RARs) values bilaterally with the right being 0.70 while the left being 0.57. Normal range value is <3.52.

Occasionally in practice, overtly gaseous abdomen may result in poor visualization of the main renal arteries proximally at their osteal ends. In such situations, Systolic velocity values of the main renal arteries may still be sampled distally (preosteal ends) just before their entry into the renal parenchymas. In this case however, the velocities have been sampled at their osteal ends. The abdominal aorta systolic velocity may be sampled a few centimeters proximal to the superior mesenteric bifercation. Also to document are:

  •  bilateral renal sizes.
  • gross bilateral renal morphology (cortical- medullary differentiation and cortical thickness).
  • bilateral renal color/power Doppler perfusion.
  • exclusion of nephropathies such as; hydronephrosis, features of acute infective process, masses, calculi or chronic atrophy changes/disease.

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