Diagnostic Ultrasound - Abdomen and Pelvis

Renal Angiomyolipoma
Diagnoses: Urinary Tract
Wilms Tumor
• Pediatric renal tumor that rarely contains fat
Renal Oncocytoma
• Solid renal tumor that rarely contains fat
• Well-defined, homogeneous, hypoechoic to isoechoic
masses
• Central scar cannot be confidently identified on ultrasound
Deep Cortical Scar
• Echogenic cortical defect ± underlying dilated calyx
Cortical Milk of Calcium Cyst (MCC)
• Round, echogenic, avascular lesion with ring-down artifact,
debris level, or acoustic enhancement
PATHOLOGY
General Features
• Etiology
○ Family of perivascular epithelioid cell tumors (PEComa)
• Genetics
○ Associated with tuberous sclerosis complex (TSC)
Gross Pathologic & Surgical Features
• Round, lobulated, yellow-to-gray color secondary to fat
content
Microscopic Features
• Classic triphasic AML: Varying proportions of angioid,
myoid, and lipoid components
• Fat-poor AML: May be composed almost entirely of smooth
muscle
• Epithelioid angiomyolipoma: Composed of numerous
atypical epithelioid muscle cells and few or no fat cells
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Majority detected as incidental finding on imagingor
during screening of tuberous sclerosis
○ May present with acute abdomen, flank pain, or flank
mass from spontaneous bleeding
○ Hematuria
• Other signs/symptoms
○ Hypertension & chronic renal failure
Demographics
• Age
○ Mean: 5th decade
• Gender
○ Sporadic form more common in females than males (F:M
= 3:1)
○ In TSC, M:F = 1:1
• Epidemiology
○ Most common benign solid renal neoplasm
○ 80% sporadic, prevalence 0.2%, 4th-6th decades; usually
unilateral and solitary
○ 20% associated with TSC; mean age younger; 55-75% of
patients with TSC will have AML by 3rd decade; any
subtype of AML, multiple and bilateral, also associated
with lymphangioleiomyomatosis
Natural History & Prognosis
• Slow-growing tumors
• Tend to grow faster when > 4 cm
○ Rapid tumor growth associated with increased
angiogenesis leading to vessel dilation, formation, and
aneurysms
○ Size > 4 cm or aneurysm > 5 mm found to predict
bleeding
• AML associated with TSC more likely to need some form of
treatment
○ Tend to grow more rapidly (1.25 cm/yr) compared to
sporadic AML (0.19 cm/yr)
○ Recurrent bleed more likely with TSC 43%, whereas
sporadic AMLs typically do not rebleed
• Complications: Hemorrhage and rupture
• Prognosis
○ Usually good after partial or complete nephrectomy
○ Poor with hemorrhage, rupture, no treatment
Treatment
• If asymptomatic, conservative treatment unless there are
complications
○ No consensus on which asymptomatic AML need followup
○ Follow-up not needed in tumors < 2 cm, except in young
patients with TSC
• Tumor size > 4 cm or symptomatic: Selective arterial
embolization or partial nephrectomy
• Spontaneous bleeding treated with transarterial
embolization
DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
• Well-circumscribed, discrete fatty renal mass
• Current practice is to confirm presence of fat with CT or
MR, as RCC can also be echogenic on US
• Presence of posterior shadowing from renal lesion on US is
more suggestive of AML than RCC
• Intratumoral hemorrhage may mask small amount of fat
leading to misdiagnosis of RCC
SELECTED REFERENCES
1. Fittschen A et al: Prevalence of sporadic renal angiomyolipoma: a
retrospective analysis of 61,389 in- and out-patients. Abdom Imaging.
39(5):1009-13, 2014
2. Hocquelet A et al: Long-term results of preventive embolization of renal
angiomyolipomas: evaluation of predictive factors of volume decrease. Eur
Radiol. 24(8):1785-93, 2014
3. Jinzaki M et al: Renal angiomyolipoma: a radiological classification and
update on recent developments in diagnosis and management. Abdom
Imaging. 39(3):588-604, 2014
4. Kaler KS et al: Angiomyolipoma with caval extension and regional nodal
involvement: Aggressive behaviour or just rare natural history? Case report
and review of literature. Can Urol Assoc J. 8(3-4):E276-8, 2014
5. Maclean DF et al: Is the follow-up of small renal angiomyolipomas a
necessary precaution? Clin Radiol. 69(8):822-6, 2014
6. Ouzaid I et al: Active surveillance for renal angiomyolipoma: outcomes and
factors predictive of delayed intervention. BJU Int. 114(3):412-7, 2014
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