Angiomyolipoma (AML)—a frequently seen solid renal tumor—is the most common benign
tumor of the kidney. It was considered to be hamartomatous in origin and is now considered
to be a member of the family of perivascular epithelioid cell (PEComa).[1 ] Classically thought to be associated with tuberous sclerosis that is an autosomal
dominant disease with TSC1 or TSC2 gene mutation, around 80% AMLs may present sporadically.[1 ] They are also seen in patients with lymphangiomyomatosis and included in its diagnostic
criteria.[2 ] Clinically, the tumor has myriad of presentations ranging from being completely
asymptomatic at the time of diagnosis to abdominal pain, hematuria, recurrent urinary
tract infection, and intratumoral bleed that can be occasionally massive requiring
urgent embolization or nephrectomy.[3 ] On ultrasound AMLs appear as markedly hyperechoic to hypoechoic depending on the
fat content. Though they are more frequently echogenic compared with renal cell carcinoma,
overlap in imaging features can occur.[4 ] On color Doppler, pseudoaneurysms are seen as anechoic structure showing internal
turbulent to-and-fro motion.[5 ] On computed tomographic (CT) scan, the diagnosis of renal AML depends on the detection
of intralesional fat.[6 ]
Case Presentation
A 24-year-old woman was referred to our interventional radiology unit from another
hospital for possible embolization of a large left renal pseudoaneurysm that was considered
as high risk for surgery. The patient had history of diffuse abdominal pain with enlarging
abdominal girth. On general examination, she was of thin built and emaciated with
significant pallor. On examining, there were no characteristic skin lesions. She was
having tachycardia, and a lump was palpable, which extended from left hypochondrium
to left lumbar region approximately 10 cm in length craniocaudally and 9 cm across
extending up to the umbilicus. She had low hemoglobin at 6.4 g/dL and a slightly raised
total leucocyte count of 12,000/mL. Abdominal ultrasonography using Logiq P5 ultrasound
system (General Electric Healthcare) with 3.5 to 5 MHz showed bilateral enlarged kidneys.
Right kidney shows well-defined three hyperechoic lesions of varying sizes suggestive
of fat as main content and left kidney shows well-defined heteroechoic lesion with
large pseudoaneurysm occupying upper two-thirds of parenchyma ([Fig. 1A, B ]). Digital subtraction angiography (DSA) using BV Endura C-arm X-ray machine (Philips)
confirmed the large left renal pseudoaneurysm ([Fig. 2C, E ]) along with significant tumor vascularity. Selective embolization of the tumor mass
with polyvinyl alcohol (PVA) particles (PVA 300, Cook Medical) was done. Following
this closure of the artery feeding, the pseudoaneurysm was attempted using 4-mm, 5
cm-fibered stainless steel coils (Cook) and 50% N -butyl cyanoacrylate (Endocryl, Samarth Pharmaceutical): Lipiodol (Gurbet Laboratories)
mixture Endocryl glue. Attempts to occlude the feeding artery failed due to high flow,
and the coils were dislodged into the pseudoaneurysm ([Fig. 2F ]). Next day ultrasound and contrast-enhanced CT (CECT) (128 multislice SOMATOM Definition
AS; Siemens AG) showed the formation of a large intracavitory thrombus ([Fig. 3A, D ]). The patient also developed post embolization fever and pain that was managed with
antibiotics and nonsteroidal anti-inflammatory drugs (NSAIDs). The patient was planned
for repeat embolization of the pseudoaneurysm along with either a vascular plug or
using a balloon percutaneous transluminal angioplasty (PTA) catheter-assisted flow
arrest during embolization coil deployment. However, before we could proceed, the
patient started complaining worsening of the pain on the day 5, followed by cardiac
arrest possibly from sudden severe internal hemorrhage due to rupture of the pseudoaneurysm.
Fig. 1 Ultrasound of a 24-year-old woman with bilateral renal angiomyolipoma and large left
renal pseudoaneurysm. (A) Enlarged right kidney with well-defined three hyperechoic lesions of varying sizes.
(B) Enlarged left kidney with well-defined round heterochoic lesion with posterior acoustic
enhancement occupying upper two-thirds of parenchyma indicative of pseudoaneurysm.
Fig. 2 Digital subtraction angiography (DSA) of a 24-year-old woman with bilateral renal
angiomyolipoma and large left renal pseudoaneurysm. (A, B) DSA of right kidney shows supernumerary renal arteries supplying right kidney without
evidence of any aneurysm. (C–E) DSA of left kidney shows multiple large and small intralesional pseudoaneurysms.
(F) Dislodged coils post attempted coiling due to large aneurysmal neck.
Fig. 3 Abdominal imaging of a 24-year-old woman with bilateral renal angiomyolipoma and
large left renal pseudoaneurysm 1 day after attempted coiling. (A, B) Ultrasound shows an eccentric heterochoic content in pseudoaneurysm without vascularity
suggestive of thrombus. (C, D) Contrast-enhanced CT scan in coronal and axial view shows the large left intrarenal
pseudoaneurysm; note that the clot cannot be readily appreciated.
Discussion
Angiomyolipoma is known to be more prevalent in females. Some studies have suggested
that AML can present in a wide age range from 19 to 93 years with overall prevalence
being to as high as 0.44%.[7 ] The tumor consists of smooth muscles, adipose tissue, and malformed blood vessels
as main components making it a triphasic tumor as described pathologically.[1 ] Up to 80% of AMLs occur sporadically, and whereas most of them present as classic
AML with abundant detectable fat on imaging, the rest few may show very small amount
of fat.[1 ] AML is commonly associated with aneurysm formation, seen in as many as 76% of the
patients.[8 ]
The predictors of rupture include tumor and aneurysm sizes. When tumors sized 4 cm
or larger and 6 cm or larger were used as predictors of rupture, sensitivity and specificity,
were 100% and 38%, respectively, for the former criterion and 100% and 67% for the
latter criterion. Mean aneurysm size was significantly larger in the group with ruptured
tumor (13.3 ± 6.2 mm; range: 5–22 mm) than in the group with unruptured tumor (2.4
± 2.9 mm; range: 2–11 mm). In their study of the eight ruptured aneurysms, all were
at least 5 mm in sizes, and if aneurysms sized 5 mm or larger were used as criteria,
rupture can be predicted with a sensitivity and specificity of 100% and 86%, respectively.[8 ] Our case records an aneurysmal size of 10.1 cm × 10.8 cm, which to our knowledge
is one of the largest aneurysms seen in a renal AML. Though the cause of possible
aneurysmal rupture in our case is not determined, we hypothesized that the intra-aneurysmal
thrombosis post attempted coiling might have led to a pathophysiologic cascade leading
to rupture of the aneurysm.
Conclusion
Angiomyolipoma is a common tumor involving the kidneys and presents with varied clinical
symptoms that may be associated with pseudoaneurysms. As discussed before, size of
the pseudoaneurysm determines the probability of rupturing. As happened in this case
in which the patient suddenly went into hypovolemic shock due to rupture of aneurysm,
these cases need immediate intervention for decreasing the mortality.
Grant
No grant taken for the said study.
