Diagnostic Ultrasound - Abdomen and Pelvis

Approach to Urinary Tract Sonography
Diagnoses: Urinary Tract
Imaging Anatomy
Standard retroperitoneal ultrasound includes transabdominal
scanning of the kidneys and bladder. The adrenal glands and
ureters are usually not visible unless they are enlarged or
dilated, respectively. The prostate gland is sometimes well
seen through the sonographic window of the bladder, but
dedicated prostate sonography requires a transrectal
approach.
Kidneys
• Bean-shaped parenchymal organs oriented obliquely in
upper retroperitoneum
• Perinephric space is filled with fat, invested by Gerota
fascia
• Serosal surface of kidney is covered by capsule; not
sonographically visible unless thickened
• Renal cortex is outer rind of parenchyma; may be
lobulated in infancy and generally thins with advancing
age
• Medullary pyramids extend from cortex into central
kidney, usually less echogenic than cortex
• Renal calyces converge on renal pelvis
• Renal sinus fat surrounds pelvis
Ureters
• Muscular tubes draining urine from kidneys to bladder
• Peristalsis occurs at regular intervals, increasing with
greater urine volume
• Rarely seen unless dilated
Bladder
• Hollow organ in central pelvis with muscular wall
• Ureteral orifices are posterior, at approximately 5 and 7
o'clock positions in supine patient
• Trigone is specialized muscular segment posteriorly that
connects internal urethral orifice and ureteral orifices
Imaging Protocols
Abdominal sonography should be performed with the highest
frequency technique that the patient body habitus allows, to
maximize resolution. Typically, this is a curved 3-8 MHz
transducer. As with other abdominal organs, visualization of
the urinary tract structures is quite dependent upon patient
body habitus and clinical status, as well as sonographer
experience and tenacity.
Kidneys
• May be imaged using liver or spleen as sonographic
window respectively, or posteriorly
• Multiple transverse and longitudinal images should be
obtained
• Correct obliquity is needed for accurate measurement of
length
• Harmonics often useful for deeply positioned organs or
to "clear" cyst; commonly used for best imaging and to
reduce artifact, for example in evaluating renal cyst
content
• Color Doppler evaluation needed to assess vascularity of
any indeterminate lesions
• Most institutions proceed to spectral Doppler
assessment of renal arteries, veins, and arcuate artery
resistive indices when collecting system dilation is
present
• Spatial compounding improves image quality but can
obscure posterior acoustic effects like shadowing and
enhancement; consider turning off to preserve these
features when needed for diagnosis
• Color Doppler with high-PRF settings (machine
maximum) may be useful to demonstrate "twinkling"
artifact on surface of stones
Bladder
• Bladder distension allows more accurate assessment of
wall thickness
• Post void residual volume may be measured in 3
dimensions and calculated when clinically requested
• Mobility and vascularity of any masses should be
evaluated
• Color Doppler can be used to evaluate for ureteral jets if
obstruction suspected; can also be performed
transvaginally in women
Clinical Implications
Top 4 Urinary Tract Issues Resolved With Ultrasound
For renal failure, rule out hydronephrosis
• Assessment of renal pelvis and calyceal dilation
• Evaluate renal cortical thickness and echogenicity; renal
insufficiency is usually chronic and nonmechanical in
origin in hospitalized patients
• Evaluate intrarenal resistive indices: Symmetric?
• Check ureteral jets if asymmetric collecting system
dilation
For pain, rule out stones
• Tiny stones often occult by sonography
• Echogenic shadowing focus with twinkling artifact has
highest positive predictive value
• Presence or absence of hydronephrosis governs
management
For lesion, rule out mass
• Differentiate cysts from masses
• Use harmonics to "clear" cyst
• Document septations, nodules, calcifications or layering
density in lesion
• Color Doppler to demonstrate vascularity in solid lesion
For infection, rule out structural abnormality
• Evaluate collecting systems for dilation or duplication
• Urothelial thickening or abscess may be seen in acute
infection
• Bladder imaging for jets, ureteroceles, trabeculations,
diverticula, debris, or masses
Selected References
1. Rahbari-Oskoui F et al: Renal relevant radiology: radiologic imaging in
autosomal dominant polycystic kidney disease. Clin J Am Soc Nephrol.
9(2):406-15, 2014
2. Remer EM et al: ACR Appropriateness Criteria(®) on renal failure. Am J Med.
127(11):1041-8.e1, 2014
3. Wagstaff PG et al: The role of imaging in the active surveillance of small renal
masses. Curr Urol Rep. 15(3):386, 2014
4. Kang SK et al: Contemporary imaging of the renal mass. Urol Clin North Am.
39(2):161-70, vi, 2012
5. Dillman JR et al: Sonographic twinkling artifact for renal calculus detection:
correlation with CT. Radiology. 259(3):911-6, 2011
6. Kim HC et al: Color Doppler twinkling artifacts in various conditions during
abdominal and pelvic sonography. J Ultrasound Med. 29(4):621-32, 2010
7. Kamaya A et al: Twinkling artifact on color Doppler sonography: dependence
on machine parameters and underlying cause. AJR Am J Roentgenol.
180(1):215-22, 2003
8. Diagnostic Ultrasound, 4th Ed. Rumack CM, Wilson SR, Charboneau JW,
Levine D, eds. Elsevier Mosby 2011
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