Answers

Short answers

1 Bilateral renal angiomyolipoma is the most likely cause of the masses seen in the figures. The computed tomography scans show that the renal parenchyma is abnormal, with enhancing vessels and low attenuation fat representing vascular and fatty components, respectively, within the angiomyolipoma.

2 The patient’s symptoms are caused by acute haemorrhage. Her physical condition and the imaging findings can be explained by haemorrhage from the vascular component of the angiomyolipoma.

3 Selective renal arterial embolisation is the treatment of choice. Embolisation not only stops further bleeding but is less invasive than surgery and spares functioning renal tissue. After our patient was scanned, she immediately went to angiography for embolisation.

Long answers
1 Bilateral renal angiomyolipomas
Angiomyolipomas are benign hamartomatous tumours composed of a variable mixture of smooth muscle, abnormal blood vessels, and fat. Although all three tissue elements should be seen to establish the diagnosis, angiomyolipomas usually have a prominent fatty component, which gives them a characteristic appearance on computed tomography. A diagnosis of angiomyolipoma can, therefore, be made on the basis of the computed tomography results.¹ The computed tomograms in this patient show that the renal parenchyma is abnormal, with enhancing vessels and low attenuation fat representing vascular and fatty components, respectively, within the angiomyolipoma (figs 3 and 4).

View larger version (395K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 3 Computed tomography of the mid-abdomen showing large bilateral heterogeneous angiomyolipomas, which have replaced the normal renal parenchyma. The extent of the right sided angiomyolipoma is delineated by the small white arrowheads. Areas of high attenuation within the angiomyolipoma are vessels or soft tissue (large white arrowhead), whereas areas of low attenuation are fat (white arrow)

 

View larger version (391K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 4 Computed tomography of the lower abdomen. Free fluid in the subhepatic region is seen as low attenuation (white arrowheads)

 
Around 80% of angiomyolipomas are found in adults between the ages of 30 and 50, and there is a strong female predominance. About 20% of these tumours occur in patients with tuberous sclerosis,² and they are the most common renal manifestation of the disease; other findings include cysts and rarely renal cell carcinomas. Angiomyolipomas associated with tuberous sclerosis are more likely to be multiple, bilateral, and symptomatic, and to occur at a younger age than those seen sporadically.

Tuberous sclerosis is an autosomal dominant neurocutaneous syndrome characterised by seizures, adenoma sebaceum, and hamartomatous lesions in multiple organ systems. The cutaneous and neurological features are well known to most clinicians, but the potential for life threatening haemorrhage from angiomyolipomas is less well recognised.

The abdominal images above show gross distortion and replacement of the renal parenchyma by multiple angiomyolipomas, which are seen as heterogeneous bilateral masses. Figure 1 shows the fatty components of the tumour as areas of low attenuation (dark areas) interspersed between regions of soft tissue attenuation (lighter areas).

Active haemorrhage is unusual in the context of bleeding from angiomyolipomas.³ It is identified by areas of contrast extravasation or intense homogeneous enhancement, which persist or even increase in later scans.

2 Acute haemorrhage
The patient presented with acute abdominal pain and was in shock, so triage using the ABCDE approach was indicated. The ABCDE survey is sometimes referred to as the "primary survey" (where A=airway, B=breathing, C=circulation, D=disability, and E=exposure). We suggest that C should encourage clinicians to include early computed tomography because this will identify the site and cause of the underlying problem.⁴

Although our patient’s presentation has many potential causes, including intra-abdominal sepsis and pancreatitis, the findings on computed tomography indicate acute haemorrhage. Specifically, fig 5 shows a large heterogeneous mass with an area of high attenuation within the right kidney, which is enhanced after contrast (fig 6), indicating intraparenchymal haemorrhage.

View larger version (382K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 5 Non-contrast scan at the level of the gallbladder showing an area of high attenuation representing renal parenchymal haemorrhage (white arrowheads)

 

View larger version (400K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 6 Post-contrast scan at the level of the gallbladder; the renal parenchymal haemorrhage is enhanced (white arrowheads)

 
Dysmorphic blood vessels within the angiomyolipoma can become dilated to form microaneurysms and macroaneurysms, which are prone to spontaneous rupture. It is generally accepted that treatment should be offered to patients with angiomyolipomas larger than 4 cm because 50-60% of angiomyolipomas of this size will bleed spontaneously. The risk of haemorrhage seems to be increased in multifocal angiomyolipomas and in people with a high degree of vascular abnormality.⁵ Angiomyolipomas associated with tuberous sclerosis evolve progressively and are more likely to need intervention. Such interventions are required if growth is rapid or the patient has symptoms caused by the haemorrhage or the large mass.⁵

The management options for angiomyolipomas larger than 4 cm are observation, surgery, and selective arterial embolisation. They have traditionally been treated with partial or radical nephrectomy, but nephron sparing techniques such as tumourectomy and renal arterial embolisation are becoming more common. Nephron sparing surgery may not always be possible, especially if the tumour is extensive and it is impossible to identify normal kidney.

3 Selective renal arterial embolisation
Selective embolisation via the renal artery can be performed under local anaesthesia, although a general anaesthetic may be required. Embolisation targets the area responsible for the current episode and preserves as much normal renal parenchyma as possible. It can also be used to prevent future haemorrhage, either by ablating solitary angiomyolipomas or targeting the largest aneurysms.⁶

Selective renal artery angiography was performed in our patient via the right common femoral artery. Small microcatheters were introduced into the principal feeding arteries, and angiography showed multiple tortuous irregular tumour vessels and a large saccular aneurysm (fig 7). The embolisation material (polyvinyl alcohol, particles measuring 350-500 nm) was injected with contrast into the feeders to verify vascular occlusion. Coils were also deployed to occlude the vessels that fed the aneurysm. Embolisation can be deemed successful if the tumour looks devascularised (fig 8).

View larger version (674K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 7 Selective renal angiography shows a false aneurysm (arrowhead) and bleeding vessel (arrow) within the right kidney

 

View larger version (658K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 8 Embolisaton coils (black arrow) and devascularised appearance of false aneurysm. Tortuous vessels are seen within the angiomyolipoma (white arrowheads)

 
Cite this as: BMJ 2009;338:b987