Splenic artery aneurysms are rare entities and can be catastrophic causing fatal exsanguinating hemorrhage if they rupture. However, improved imaging techniques and minimally invasive treatment options have improved the prognosis of this condition.
The causative factors for an aneurysm of the splenic artery are not very well known and many different theories have been postulated. According to one author, degeneration of the media, weakening of the vessel wall due to atherosclerotic changes and high blood flow states such as pregnancy and chronic portal hypertension, which result in increased splenic blood flow volume, are all implicated in the pathogenesis of the aneurysm. Of all these factors, hypertensive states [both essential and portal hypertension] resulting in hyperkinetic flow states seems to be an established risk factor in developing splenic artery aneurysms. Pregnancy is associated with increased risk of rupture of the aneurysm. A pseudoaneurysm may be secondary to trauma, infection or pancreatitis.
Gray scale and color Doppler sonography play a key role in the diagnosis of splenic artery aneurysm, since many of these aneurysms are either detected as incidental findings or they present with rupture and as acute abdomen.
1. The aneurysm is seen as a rounded cystic appearing structure in very close proximity to the splenic artery.
2. It may be intra- or extra-splenic in location and can be single or multiple.
3. The wall of the aneurysm may show calcifications. If it is heavily calcified, the aneurysm may be obscured on gray scale ultrasound.
4. Color and power Doppler demonstrate the turbulent flow in the aneurysm, often appearing as the classic yin-yang pattern within the aneursymal cavity.
5. Spectral waveform analysis shows an arterial waveform with elevated flow velocities.
6. Amany of these patients have associated portal hypertension as the causative factor, splenomegaly and splenic hilar varices may also be seen. The splenic varices represent porto-systemic communications that occur as a compensatory mechanism secondary to elevated pressures in the portal venous system. These veins in the splenic hilar region represent collaterals between the splenic, coronary or short gastric veins and the left renal or adrenal vein.
A conservative approach in cases of small aneurysms, aneurysmectomy [open or laparoscopic], splenic artery ligation and coil embolization are some of the treatment options available. For the treatment of symptomatic varices, sclerotherapy or surgical ligation is the treatment.