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Introduction

Renal angiomyolipoma (AML) is the most common solid renal lesion, accounting for 0.3-3% of all renal tumors and arising from the mesenchymal elements of the kidney^(1,2). The tumor is typically a solid lesion composed of varying amounts of three elements: dysmorphic blood vessels (angiocomponent), smooth muscle components (myocomponent), and mature adipose tissue (lipocomponent). While 80% of angiomyolipomas are sporadic, approximately 20% are associated with tuberous sclerosis complex (TSC), lymphangioleiomyomatosis, von Hippel-Lindau syndrome (vHL) and neurofibromatosis type 1 (NF1). The mean age of presentation in sporadic cases is 43 years old, with a female predilection (F:M 4:1). The complications encountered in AML include acute renal hemorrhage, one of the most common clinical urological emergencies^(1,4). Transarterial embolization of renal bleedings differentiates as a safe, minimally invasive and effective treatment method⁽¹⁾.

Case presentation

A 64-year-old female patient with solitary left congenital kidney and renal angiomyolipoma (no prior imaging studies in our hospital) presented with a history of nonspecific general symptoms such as malaise, fatigue and gingival bleeding during a dental procedure, which started one month prior to hospital admission. On admission to the hospital, the patient was referred to the hematology department. The clinical examination revealed multiple ecchymoses and general paleness, with normal heart rate (78 b/min) and blood pressure (120/80 mmHg). The complete blood count demonstrated moderately normocytic anemia (8.7 g/dl), thrombocytopenia (75x10³/ul), mild inflammatory syndrome, hypofibrinogenemia (78 mg/dl), elevated D-dimers (30xNSV) and mildly impaired renal function (Cr=1.01, eRFG=54.7 ml/min). Consumption coagulopathy was suspected and the patient was referred to our department for further imaging evaluation.

Imaging findings

Contrast-enhanced computed tomography (CECT) demonstrated the presence of a large subcapsular left renal hematoma, measuring 171/147/95 mm (craniocaudal/anteroposterior/transverse diameters) with active bleeding from an arterial feeding vessel (segmental branch of the left renal artery) – Figure 1 and Figure 2.
 

Lipid density tumoral fragments can be observed, located at the upper aspect of the hematoma, compatible with ruptured renal angiomyolipoma (Figure 3).
 

Renal angiography via right femoral approach with digital subtraction acquisitions (DSA) demonstrated active bleeding within the lesion (Figure 4). The embolization of the feeding vessel with multiple tornado-type metallic coils was performed, with the subsequent reduction of bleeding flow (Figure 4).
 

Discussion

Angiomyolipoma is a solid tumor encountered commonly in the kidney parenchyma. The image-based detection of intratumoral fat often begins with CT^(1,2). On unenhanced CT, the presence of regions of interest (ROI)-containing attenuations values less than -10 HU allows the confident identification of fat^(1-3). The CT appearance of a classic AML varies due to variable amounts of fat, blood vessels and smooth muscle components of the renal mass. When evaluating AML, a small amount of fat using CT acquisition with thin (1.5-3 mm) sections allows to detect fat that otherwise would not be possible because of partial volume-averaging. Intratumoral hemorrhage may occur, particularly in larger than 4 cm AML⁽⁴⁾. In this case, high attenuation blood may mask the fat, particularly if there is a small amount, and leads to misdiagnosing a classic angiomyolipoma as a renal cancer. A fat containing mass that originates in the kidney is likely an AML rather than liposarcoma⁽⁵⁾. The identification of enlarged or bridging vessels, aneurysms and perinephric hematomas are additional imaging features of AML that are rarely seen with liposarcoma⁽⁵⁾. Wilms tumors and renal cell carcinoma (RCC) may contain fat. Wilms tumors are uncommon in adults⁽⁶⁾. Since AML rarely contains calcifications, the presence of calcification and fat should raise the possibility of RCC. The classification of AML larger than 4 cm includes three groups based on their vascularity at angiography⁽⁷⁾. AML larger than 4 cm with minimal vascularity are significantly less likely to require intervention due to bleeding than those with marked vascularity⁽¹⁾. Renal arterial embolization and partial nephrectomy are typically used to treat renal AML⁽⁸⁾.

Conclusions

CECT imaging studies are essential for the proper management of complicated renal angiomyolipomas. Endovascular therapy is a viable, minimally invasive alternative to classical nephrectomy for the control of renal bleeding.  

Conflict of interests: The authors declare no con­flict of interests.