Clinical History
flank pain and hypotension
Imaging Findings
39 year-old female presented with
right flank pain and hypotension.
Following resuscitation she
underwent contrast enhanced CT of
the abdomen.Selected images Fig 1
and Fig 2 show a large right
retroperitoneal haematoma causing
anterior displacement of the kidney.
Within this haematoma there is a mass
arising from the lower pole of the
right kidney. The mass is of
heterogenous appearance but contains
some areas of fat attenuation. The
patient subsequently underwent
selective renal angiography Fig 3
which revealed abnormal vessels
feeding the mass. Some small saccular
aneurysms were identified. Selective
embolisation of the feeding vessels
was undertaken and the post-embolisation
angiogram is shown in Fig 4. Following
embolisation the patient made a good
recovery and later underwent elective
resection of the right renal mass.
Histology confirmed the diagnosis of
angiomyolipoma.
Discussion
Renal angiomyolipomas (AML) are benign hamartomas composed of varying amounts of fat, smooth muscle and blood vessels (1,2). AMLs are usually asymptomatic but larger AMLs may be complicated by spontaneous hemorrhage (2).
AML is the commonest benign renal tumor and many are detected as incidental findings in patients undergoing ultrasound (2,3). 80-90% of AMLs are sporadic, are most often single and occur in the 5th and 6th decades with a female prepoderance. AMLs also occur as secondary features of tuberous sclerosis (TS) and lymphangiomyomatosis (3,4). 50-80% of patients with TS (1,3) and 15% of patients with lymphangiomyomatosis have AMLs which tend to be multiple and bilateral (2).
Spontaneous hemorrhage is a recognised complication due to the vascularity of the lesion and the lack of a complete elastic layer in the vessel walls . AMLs of greater than 4-5 centimetres diameter are more likely to bleed (2,3). The commonest site for an AML is the renal parenchyma, however AMLs have been reported to arise from the renal capsule (1,4), renal sinus, retroperitoneum, liver, spleen, fallopian tube, mediastinum and lymph nodes (3-5).
Typical intrarenal AMLs may be diagnosed almost exclusively at imaging (1) by demonstrating the presence of fat within the lesion. There are, however, rare reports of intratumoral fat in renal cell carcinomas, oncocytomas and wilms tumor (1,3).
IMAGING FEATURES
AMLs are typically round, hyperechoic and well-circumscribed on ultrasound with 33% showing posterior acoustic shadowing. On CT the key diagnostic feature is the finding of areas of fat attenuation (less than –20 Hounsfield Units) within the tumor (1,3). Thin sections of less than 5mm may be required to demonstrate fat (1). AMLs show varying degrees of enhancement depending on the amount of soft tissue within them (1). AMLs exhibit high signal intensity on T1-weighted MR due to the presence of fat or of blood products (1,3). Use of fat-suppression techniques is helpful.
Most AMLs are hypervascular and often demonstrate a ‘whorled’ or ‘sunburst’ appearance at angiography. Saccular aneurysms may be present (1,3).
Differential Diagnosis List
Spontaneous haemorrhage in renal angiomyolipoma
Final Diagnosis
Spontaneous haemorrhage in renal angiomyolipoma
