Diagnostic Ultrasound - Abdomen and Pelvis

Kidneys
– Normal peak systolic velocity (PSV) 75-125 cm/s, not
more than 180 cm/s
□ > 200 cm/s is abnormal
– Resistive index (RI) is (peak systolic velocity - end
diastolic velocity)/peak systolic velocity; normal < 0.7
– Pulsatility index (PI) is (peak systolic velocity - end
diastole velocity)/mean velocity, normal < 1.8
• Renal veins
○ Normal caliber 4-9 mm
○ Formed from tributaries that coalesce at renal hilum
○ Right renal vein is relatively short and drains directly into
IVC
○ Left renal vein receives left adrenal vein from above and
left gonadal vein from below
○ Left renal vein crosses midline between aorta and
superior mesenteric artery
○ Spectral Doppler
– Normal PSV 18-33 cm/s
– Spectral Doppler in right renal vein mirrors pulsatility
in IVC
– Spectral Doppler in left renal vein may show only
slight variability of velocities consequent upon cardiac
and respiratory activity
Size
• Bipolar length is found by rotating transducer around its
vertical axis such that the longest craniocaudal length can
be identified
• Normal size between 10-15 cm
• Volume measurements
○ May be more accurate, but is time consuming
○ 3D ellipsoidal formula can be used for volume estimation
– Length x AP diameter x transverse diameter x 0.5
○ Consistency and changes in volume over time more
important
ANATOMY IMAGING ISSUES
Imaging Recommendations
• Right kidney
○ Liver used as acoustic window
○ Transducer placed in subcostal or intercostal position
○ Varying degree of respiration is useful
○ Raising patient's right side and scanning
laterally/posterolaterally may be useful
• Left kidney
○ More difficult to visualize due to bowel gas from small
bowel and splenic flexure
○ Usually easier to search for left kidney using
posterolateral approach with left side raised
○ Full right lateral decubitus with pillow under right flank
and left arm extended above head may be useful in
difficult cases
– Spleen can be used as acoustic window for imaging
upper pole of left kidney
○ Posterior approach
– Useful for intervention procedures (renal biopsy,
nephrostomy)
– Image quality may be impaired by thick paraspinal
muscles and ribs shadowing
• Renal arteries
○ Origins best seen from midline anterior approach
○ Right renal artery can usually be followed from origin to
kidney
○ Left renal artery often requires posterolateral coronal
transducer scanning position for visualization
• Renal veins
○ Best seen on transverse scan from anterior approach
○ May also be seen on coronal scan from posterolateral
coronal
Key Concepts
• Accessory renal vessels
○ Must be accounted for in planning surgery (e.g.,
resection, transplantation)
○ Often are best seen using multidetector row CT,
magnetic resonance angiogram, or digital subtraction
angiography rather than ultrasound
EMBRYOLOGY
Embryologic Events
• Congenital anomalies of renal number, position, structure,
and form are very common
○ Often accompanied by anomalies of other systems
○ VATER acronym: Vertebral, anorectal,
tracheoesophageal, radial ray, renal
○ Congenital absence of kidney
○ Anomalies of position (ectopia) are common
○ Anomalies of structure
– Congenitally large septum of Bertin (lobar
dysmorphism); asymptomatic
– Fetal lobulations (lobation), single or multiple
indentations of lateral renal contours
– Partial duplication: Commonly results in enlarged
kidney with 2 separate hila, 2 ureters (may join
downstream or join bladder separately); duplex kidney
= bifid renal pelvis, single ureter
Anatomy: Abdomen
45