**3.2. Prevalence and epidemiology**

SAAs are the most common of the splanchnic artery aneurysms and account for as many as 60% of all reported splanchnic aneurysms. They are recognized for their significant potential

**Figure 4.** A Peripherally calcified, and thrombosed splenic artery aneurysm, (CT view)

to rupture. In spite of their relatively high prevalence in comparison to other splanchnic aneurysms, there are few large series in the literature. The prevalence of the lesion in the general population is low. A large general autopsy study estimated their all incidence to be 0.01 %( 12), whereas more specific examination of the splenic arteries in an autopsy study of patients older than 60 years revealed an incidence of 10 %( 13).

The prevalence of incidentally noted aneurysmal changes in the splenic artery on arteriographic studies was reported to be 0.78%, and such changes have been found incidentally in 0.1% to 10% of autopsies. (11).

In contrast to routine atherosclerotic or degenerative aneurismal diseases, SAAs are found much more commonly in women than in men with an approximate ratio of 4:1. (11), they are also noted to occur in younger patients at a mean age of 52 years. (14)

SAAs are usually saccular and less than 2 cm in diameter, with the majority being in the mid or distal portion of the splenic artery or at its bifurcation points. (14)

Giant SAAs with diameter larger than 10 cm have been reported, and in contrast to smaller SAAs, these lesions appear to be more common in men. (15)

#### **3.3. Pathogenesis and aetiology**

The most clinical risk factors are the following:

1. Female gender.

140 Aneurysm

**2.4. Storage of erythrocytes** 

**3.1. General considerations** 

absence of an aneurysm. [7]

arteries with their branches.

to be the following:

2. Hepatic artery, 20%

4. Celiac artery, 4%

3. Superior mesenteric artery, 6%

5. Gastric and gasrtoepiploic arteries, 4% 6. Jejunal, ileal, and colic arteries, 3%

8. Gastroduodenal artery, less than 1.5% 9. Inferior mesenteric artery, less than 1%. (11)

**3.2. Prevalence and epidemiology** 

7. Pancreaticoduodenal and pancreatic arteries, 2%

[11]

**3. Splenic Artery Aneurysms (SAAs)** 

recognized since more than 200 years. [8, 9]

elderly. They have a variable sizes, shapes, and locations.

The RBCs are stored in the spleen. Approximately 8% of the circulating RBCs are present

An arterial aneurysm is one of the most common vascular disorders causing morbidity and mortality in humans. It occurs in most arteries of the body and is especially common in the

An aneurysm is defined as a permanent localized dilatation of an artery having at least a 50% increase in diameter compared to the expected normal arterial diameter, so clinicians should know the normal arterial diameters throughout the body to decide the presence or

Splenic artery aneurysms are a type of splanchnic arteries aneurysm, although the later are rare but clinically very important vascular conditions. These interesting lesions have been

Splanchnic artery aneurysms represent intra-abdominal aneurysms that are not part of the aorto-iliac system and include aneurysms of the celiac, superior and inferior mesenteric

Of all intra-abdominal aneurysms, only approximately 5% affect the splanchnic arteries. (10) In general population, their prevalence has been estimated to be varying from 0.1% to 2 %.

The frequency of the anatomic distribution of the splanchnic arteries aneurysms is estimated

SAAs are the most common of the splanchnic artery aneurysms and account for as many as 60% of all reported splanchnic aneurysms. They are recognized for their significant potential

1. Splenic artery aneurysms (SAAs), 60% (see the image below).

within the spleen. However, this function is seen well in animals than humans.[6]

2. Multiple pregnancies.


In one reported series, it was noted that 80% of the patients with SAAs were females who had an average of 4.5 pregnancies and 50% of females with SAAs had more than 6 pregnancies. (17, 18).

Portal hypertension may be present in 25% of patients with SAAs, while about 10% are awaiting liver transplantation. (19).

Blunt splenic trauma and pancreatitis frequently noted in association with SAAs. Local hemodynamic aspects, hormonal factors, and medial degeneration have all been considered as causative factors in the development of SAAs. (20).

Increased blood volume which results into increased cardiac output, and portal congestion are thought to be related to an increased splenic artery blood flow and SAAs formation. (21).

Impaired elastin formation and degeneration of the internal elastic lamina could be added as hormonal factors which contribute to SAAs formation during pregnancy; It seems that splenic artery is more susceptible to these changes than other vessels. (22).

Histological changes which are noted microscopically during SAAs formation include calcifications, intimal hyperplasia, arterial dysplasia, fibromuscular dysplasia, and medial degeneration. (23).

#### **3.4. Clinical and diagnostic aspects of splenic artery aneurysms**

Most SAAs are found incidentally at the time of first presentation during abdominal imaging examination for unrelated disorders. A classic calcified ring may be noted in the left upper abdominal quadrant on a plain x—ray film of the abdomen. (see the image below):

There may be an abdominal bruit, but the majority of cases are showing normal physical examinations especially with asymptomatic patients.

Symptoms are including the following:


#### **Figure 5.**

142 Aneurysm

3. Portal hypertension. 4. Systemic hypertension. 5. Arterial fibrodysplasia.

7. Arteriosclerosis.

degeneration. (23).

6. chronic inflammatory processes

splenic artery origin. (16).

awaiting liver transplantation. (19).

as causative factors in the development of SAAs. (20).

examinations especially with asymptomatic patients.

1. Vague abdominal pain, nausea and vomiting.(24). 2. Symptoms related to compression of adjacent organs.

Symptoms are including the following:

diagnosed.(25,26).

8. Less commonly, polyarteritis nodosa, systemic lupus erythematosus, and anomalous

In one reported series, it was noted that 80% of the patients with SAAs were females who had an average of 4.5 pregnancies and 50% of females with SAAs had more than 6 pregnancies. (17, 18). Portal hypertension may be present in 25% of patients with SAAs, while about 10% are

Blunt splenic trauma and pancreatitis frequently noted in association with SAAs. Local hemodynamic aspects, hormonal factors, and medial degeneration have all been considered

Increased blood volume which results into increased cardiac output, and portal congestion are thought to be related to an increased splenic artery blood flow and SAAs formation. (21). Impaired elastin formation and degeneration of the internal elastic lamina could be added as hormonal factors which contribute to SAAs formation during pregnancy; It seems that

Histological changes which are noted microscopically during SAAs formation include calcifications, intimal hyperplasia, arterial dysplasia, fibromuscular dysplasia, and medial

Most SAAs are found incidentally at the time of first presentation during abdominal imaging examination for unrelated disorders. A classic calcified ring may be noted in the left upper abdominal quadrant on a plain x—ray film of the abdomen. (see the image below):

There may be an abdominal bruit, but the majority of cases are showing normal physical

5. Double-rupture phenomenon which may occur in bout 20% to 30% of cases provides a proper diagnosis of rupture into the lesser sac, before free intraperitoneal rupture

splenic artery is more susceptible to these changes than other vessels. (22).

**3.4. Clinical and diagnostic aspects of splenic artery aneurysms** 

3. Sever left-sided pain due to rupture or acute aneurysm expansion. 4. Shock, abdominal distension, and death due to intraperitoneal rupture.

6. Gastrointestinal tract, pancreatic ducts, or splenic vein rupture.(27).

The overall mortality of ruptured SAAs is about 25%.(26). Pregnancy may be associated with a rate of 20% to 50% of all ruptures.(28).

The association of SAAs and pregnancy is very well documented, in addition to that rupture during pregnancy usually occurs at the third trimester which can lead to maternal and fetal death of 80% to 90%, respectively.(29). Actually this can lead to understand the misdiagnosis of the situation as an obstetric emergency.

Rupture due to portal hypertension is associated with a rate of about 20% .(30).

#### **3.5. Treatment of splenic artery aneurysms**

Ruptured , symptomatic SAAs, and those in pregnant women require urgent treatment. Enlarging or those greater than 2 cm in diameter SAAs have less stringent indications, although these criteria are not absolute. Patients with portal hypertension or waiting for liver transplantation should be treated as well.(31). Patient's medical condition and age could play a role the treatment option. Most vascular surgeons would consider suitable elective intervention for asymptomatic patients with lesions those diameter is greater than 2 cm when the surgical risk is thought to be low. If one estimates the incidence of rupture to be 2% with a death rate of at least 25% when rupture has occurred, operative mortality rates should be less than 0.5% to justify elective surgical treatment, in one author's study.(31).

Traditional operative therapy of SAAs includes proximal and distal ligation or aneurysmectomy or both modalities for lesions in the proximal or middle part of the splenic artery.(see the images below).

**Figure 6.** Drawing illustrates how coils are placed distal and then proximal to the aneurysm, thereby trapping the aneurysm and isolating it from the circulation, with resultant thrombosis of the aneurysm.

Revascularization of the distal splenic artery in not generally warranted due to that collateral flow to the spleen in maintained by the short gastric arteries. For those lesions near to the splenic hilum, splenectomy is the most common procedure. Distal pancreatectomy may occasionally be needed for the treatment of these distal lesions as well. (24, 31, 32 and 33).

144 Aneurysm

**Figure 7.**

**Figure 6.** Drawing illustrates how coils are placed distal and then proximal to the aneurysm, thereby trapping the aneurysm and isolating it from the circulation, with resultant thrombosis of the aneurysm. Laparoscopic repair of SAAs by clipping or exclusion has been reported; intraoperative ultrasonography is believed to be an important adjunct to this procedure.(34). Laparoscopic occlusion combined with coil embolization has been proposed as a treatment for aberrant SAAs located in the retropancreatic position, for which traditional procedures would be exceptionally difficult.(24,35).

Endovascular exclusion of SAAs has been used more recently with good success. Treatment options include coil embolization of the splenic artery both proximal and distal to the aneurysm itself, thereby effectively trapping the lesion. Other options include embolization of the aneurysm sac with coils or cyanoacrylate glue or both modalities simultaneously or occlusion of the lesion with percutaneous or open thrombin injection.(24,36). In addition, stent-grafting has been performed, especially for saccular lesions of the mid splenic artery. There has been some concern regarding splenic infarction and pancreatitis when embolization of very distal splenic artery lesions has been performed. (24, 37 and 38).

The objective of splenic arterial embolization is to improve the results of nonsurgical management. Indications for splenic arterial embolization vary, depending on local management protocols. embolization is performed with microcoils as distally as possible, to preserve perfusion to the splenic parenchyma. Patients with a high risk for secondary rupture of the aneurysm should undergo embolization with coils in a more proximal segment of the splenic artery to reduce the pressure in the splenic parenchyma and help the reservation of the spleen. The placement of coils in a middle segment of the splenic artery allows reconstitution of the blood supply through collateral vessels, principally via the short gastric and gastroepiploic arteries, to the patent distal splenic, transgastric, and transpancreatic arteries. Proximal embolization performed exclusively with coils decreases the volume of splenic arterial blood flow and thereby produces relative hypotension in the splenic bed, which allows the spleen to repair itself without infarction (39)

In a review of 48 endovascular procedures for splanchnic artery pseudoaneurysms, 20 interventions on the splenic artery were performed. Six end-organ infarcts were noticed, all were within the splenic bed. Two additional patients developed splenic atrophy diagnosed on CT scanning after previous embolization of the splenic artery, without clear clinical evidence of initial splenic infarction. (40). In another study, one episode of splenic infarction associated with sever pancreatitis was noted after embolization of a distal splenic artery aneurysm. (37). (see the image below).

Post-embolization transverse contrast-enhanced CT scan obtained at follow-up shows a coil within the splenic artery (arrow), as well as complete infarction of the spleen, which is not contrast enhanced.

However, other authors have reported splenic infarction after embolization of even more proximal SAAs as well. (41).
