The spleen was regarded by Galen as “an organ of mystery,” by Aristotle as unnecessary, and by Pliny as an organ that might hinder the speed of runners.¹ In many societies, the spleen was also thought to be affiliated with mood. The word spleen comes from a Greek word that has idiomatic equivalent of the heart in English, that is, to be good-spleened means to be good-hearted or compassionate. In contrast, the spleen has also been associated with melancholy, and in 19th-century England, women in bad humor were said to be afflicted by the spleen or the vapors of the spleen.

Until relatively recently, the spleen was considered expendable. The gradual realization of the valuable role of the spleen in host defense, beginning with reports of fulminant sepsis in children after splenectomy for hematologic disease, has increased interest in splenic conservation techniques.^2,3 The indications for splenectomy in both the emergency and elective settings continue to evolve. The introduction of laparoscopic approaches has decreased the morbidity of surgery, but a balance between the indications for splenectomy and the long-term consequences of splenectomy, particularly sepsis, must always be considered.

In this chapter, we review the anatomy, physiology, and pathology of splenic diseases, before addressing operative techniques and strategies, focusing on the laparoscopic approach.

Gross Anatomy

The spleen arises by mesenchymal differentiation along the left side of the dorsal mesogastrium in juxtaposition to the anlage of the left gonad in the 8-mm embryo. The organ ultimately migrates to the left upper quadrant.

In the healthy adult, the spleen weighs 150 g (range, 75-250 g), although there are variations based on sex, age, and racial background.⁴ Although the ultrasonographic upper limit of normal for spleen size is 12 cm, it is larger in men and taller or heavier people, and sex- and size-corrected normal values are available.⁵ The spleen is not normally palpable in adults. When the spleen tip can be felt below the left costal margin, splenomegaly should be assumed and further investigated.

The spleen resides in the posterior portion of the left upper quadrant lying deep to the 9th, 10th, and 11th ribs, with its long axis corresponding to that of the 10th rib. Its convex superior and lateral surfaces are immediately adjacent to the undersurface of the left leaf of the diaphragm. The configuration of the concave medial surface of the spleen is a consequence of impressions made by the stomach, pancreas, kidneys, and splenic flexure of the colon (Fig. 77-1).

The position of the spleen is maintained by several suspensory ligaments, which need to be divided during a splenectomy to allow full mobilization of the organ. These are the gastrosplenic, splenophrenic, splenocolic, and splenorenal ligaments (Figs. 77-2 and 77-3). The gastrosplenic ligament contains the short gastric vessels that course to the splenic hilum from the greater curvature, whereas the splenorenal ligament contains the pancreas and the splenic vessels. The remaining ligaments are generally avascular, except in patients with portal hypertension or myeloproliferative disorders. The tail of the pancreas is in direct contact with the spleen in 30% of cases and within 1 cm of the spleen in three-quarters of patients.⁶

Accessory spleens, which are distinct and separate masses of splenic tissue, have been reported in 14% to 30% of patients undergoing splenectomy, with a higher incidence in patients with hematologic disorders and a lower incidence at autopsy in people without hematologic or splenic disease (7%).⁷ They are present in decreasing order of frequency in the hilum of the spleen, tail of the pancreas, greater omentum, gastrosplenic ligament, and splenocolic ligament (Fig. 77-4A). Accessory spleens may also occur in the pelvis, either in the presacral region or adjacent to the left ovary in the female, and in the scrotum in juxtaposition to the left testicle in the male (Fig. 77-4B). The accessory spleens can vary in size and may be small lesions that can be easily missed unless a careful examination is performed (Fig. 77-5). The accuracy for intraoperative localization of accessory spleens seems higher than computed tomography (CT) scan, and so routine preoperative imaging for the purpose of diagnosis of accessory spleens prior to splenectomy is not routinely recommended.⁸

Splenoptosis (wandering spleen) refers to a rare condition in which the spleen hangs by a long pedicle from the mesentery and may present itself as an asymptomatic mass or with symptoms of intermittent or acute abdominal pain due to torsion. Treatment involves splenectomy in cases of ischemia, but splenopexy should be considered in other cases.⁹

Splenic Blood Supply

The spleen is supplied by the splenic artery, the short gastric vessels, and the left gastroepiploic artery. The splenic artery commonly arises from the celiac axis and is the longest of its 3 branches. Most of the splenic arterial supply is derived through this vessel. The 3 to 5 short gastric vessels lie in the gastrosplenic ligament, and there is often a connection between some of the short gastrics and the superior polar branch of the splenic artery. Similarly, there is often a connection between the left gastroepiploic and the inferior polar branch of the splenic artery. The splenic artery has a very tortuous course and has a highly variable pattern of distribution. In 1942, Michels divided the splenic arterial supply into 2 types: distributed and magistral.¹⁰

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  Distributed type: The most common variation seen in 70% of cases. Here the main splenic artery is short, dividing into many long branches (6-12) that originate between 3 and 13 cm from the hilum and enter the spleen on the medial aspect, involving 75% of the medial surface (Fig. 77-6A).

  
  
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  Magistral or bundled type: The less common variation seen in 30% of cases. Here a long main trunk divides near the hilum into 3 to 4 large branches that enter the spleen medially but only involve 30% of the spleen’s medial surface (Fig. 77-6B).

The common splenic artery divides into 2 lobar arteries (superior and inferior) in 86% of cases and 3 lobar arteries in 12% of cases (superior, inferior, and accessory). Each lobar artery divides into segmental arteries with a total of 3 to 5 segmental arteries in 94% of cases. These segmental arteries supply blood to a corresponding wedge-shaped splenic segment. There is a relatively avascular plane between the lobes and segments, so resection of the segmentally devascularized spleen can be performed without significant blood loss. Understanding these relationships is important in performing partial splenectomy.¹⁰

The splenic artery also has a pancreatic branch (pancreatica magna) that is worthy of note. Occlusion of this branch, most often seen after proximal splenic artery embolization, can lead to pancreatitis.

The major venous drainage flows through the splenic vein, which usually receives the inferior mesenteric vein centrally and then joins the superior mesenteric vein to form the portal vein. The veins generally lie behind the arteries except in the hilum where the anatomy is variable.

Histology

The spleen is made up of a capsule that is normally 1 to 2 mm thick and trabeculae that surround and invaginate the pulp. Approximately 25% of the parenchyma (Fig. 77-7) is made up of “white pulp” that functions as an immunologic organ, with the remaining 75% made up of the “red pulp” that phagocytizes particulate matter from the blood. The 2 zones are separated by a narrow marginal zone.

The white pulp, which is central and surrounds a central artery, is made of lymphatic nodules with germinal centers and periarterial lymphatic sheaths that constitute a reticular network filled with lymphocytes and macrophages. Peripheral to the white pulp is the marginal zone that contains end arteries arising from the central artery and from peripheral penicilliary arteries. The marginal zone contains lymphocytes and macrophages and red blood cells (RBCs) that have exited from terminal arteries. The marginal zone also contains the marginal sinus, which filters material from the centrally located white pulp. Locally produced immunoglobulins enter the marginal zone, eventually coursing to the bloodstream.

Physiology

The spleen receives 250 to 300 mL of blood per minute, which corresponds to 5% of the cardiac output. At any given time, however, it contains only 30 to 40 mL of blood. Although the spleen is not necessary for human life, it performs important functions that are generally attributed to its unique blood flow pattern. As the blood enters the spleen, it can take 2 paths of flow: a fast (closed) circulation that takes the blood directly from the arterioles to the venules or a slower (open) circulation that takes the blood through the pulp. The majority (90%) of flow is of the slow (open) type, which exposes the circulating cells and erythrocytes to splenic macrophages in the red pulp (see Fig. 77-7).

Functions of the spleen can be divided into the following:

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  Erythrocyte quality control and removal of defective red cells: This is achieved through pitting and culling. Pitting refers to the removal of rigid structures such as Heinz bodies (denatured intracellular hemoglobulin), Howell-Jolly bodies, and hemosiderin granules from red cells. The process involves the removal of nondeformable intracellular substances from deformable cells. The rigid body is phagocytized, while the deformable cytoplasmic mass passes into the sinus and returns to the general circulation. The postsplenectomy blood smear is thus characterized by the presence of circulating erythrocytes with Howell-Jolly and Pappenheimer bodies (siderotic granules).

  
  
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  Culling is the term applied to the spleen’s ability to remove red cells that are aged or abnormal. During its 120-day life cycle, the red cell spends an estimated minimum of 2 days within the spleen. Normally, as the red cell ages after a life span of approximately 120 days, it loses osmotic balance and membrane integrity and therefore deformability. When these cells lose their deformability, they are phagocytized by native macrophages. The spleen does not represent the only site for red cell destruction, and there is no difference in red cell survival after splenectomy. About 20 mL of RBCs are removed daily from the blood.

  
  
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  Pooling: In health, the spleen does not serve as an important reservoir for blood cells but does so for platelets. Normally, about one-third of the platelet mass is pooled in the spleen, and this pool exchanges freely with the circulating platelets that have a life span of about 10 days. With splenomegaly, a large proportion of platelets are sequestered in the spleen (up to 80%), and this, coupled with accelerated platelet destruction in the spleen, accounts for thrombocytopenia. The role of the spleen in platelet storage also explains the elevation in platelet count that is seen after splenectomy.

  
  
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  The neutrophil has a half-life of about 6 hours; hence, 85% of neutrophils either migrate at random into tissues or are destroyed within 24 hours. Although the role of the spleen in the destruction of neutrophils under normal conditions is not well quantified, this role is amplified in some hypersplenic states, with resulting neutropenia. This augmented removal can occur because of splenic enlargement and accelerated sequestration of granulocytes or because of enhanced splenic removal of altered granulocytes, as seen in immune neutropenias.

  
  
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  Hematopoiesis: The spleen has an important hematopoietic function in fetal life that ceases by the seventh intrauterine month and does not occur in healthy adults with exception in certain pathologic conditions where bone marrow is unable to meet the needs (ie, extramedullary hematopoiesis).

  
  
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  Filtration: Macrophages residing in the splenic parenchyma capture cellular and noncellular material from blood, including encapsulated bacteria such as pneumococci, and destroy them. This function explains the increased risk of infections caused by encapsulated organisms that is seen after splenectomy.

  
  
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  Antibody synthesis in the white pulp: In addition to the phagocytosis of antibody-coated cells, the immunologic functions of the spleen include antibody synthesis (especially immunoglobulin M [IgM]); generation of lymphocytes; and production of tuftsin, opsonins, properdin, and interferon. Foreign antigens that are filtered in the white pulp are presented to lymphoid cells. Here the immunoglobulin response is mounted, leading to release of antibodies.

Etiology

Splenic rupture is defined as any disruption of the splenic parenchyma or capsule. It can be spontaneous, iatrogenic, or traumatic.

Spontaneous splenic rupture is a rare surgical emergency usually caused by splenic infiltration by hematologic, neoplastic, or infectious diseases. In a review of over 800 cases of spontaneous rupture, 6 major etiologic groups were defined: neoplastic (30.3%), infectious (27.3%), inflammatory (20.0%), drug and treatment related (9.2%), mechanical (6.8%), and normal spleen (6.4%). The majority of patients were treated with splenectomy with an overall mortality rate of 12%.¹¹

Iatrogenic splenic injuries during abdominal procedures, especially colectomy, are well documented (Fig. 77-8). In a 16-year review of nearly 14,000 colectomies performed at the Mayo Clinic, splenic injury requiring a splenectomy or repair occurred in 0.4%. Although repair was attempted in 50% of cases, the majority of these patients ultimately required splenectomy. Those with an incidental splenectomy had high 30-day morbidity (34%) and mortality (15%).¹² A review of the national inpatient sample database focusing on colorectal surgery between 2006 and 2008 reported a higher incidence of splenic injury of 1%, with 85% of patients treated with splenectomy.¹³ Patients who undergo an incidental splenectomy during colorectal surgery for cancer have a poorer prognosis compared to the nonsplenectomized group, suggesting a negative long-term impact of splenic injury in these patients.¹⁴

Colonoscopy has also been associated with splenic injury. Although the rate is extremely low at 0.001%,¹⁵ it is associated with significant morbidity, with more than 70% of patients requiring an operative intervention, and 5% mortality.¹⁶

The most common cause of splenic rupture is traumatic injury. Mechanism of injury can be blunt or penetrating. The trajectory of the penetrating wound may pass through the anterior abdominal wall, the posterior abdominal wall, the flank, or transthoracically, piercing the pleural space and diaphragm. It can be either isolated to the spleen or associated with injuries to surrounding structures including the stomach, left kidney, left adrenal gland, colon, pancreas, and root of the mesentery.

Diagnostic Studies

Signs associated with bleeding might be seen on investigation. A complete blood count might show a decrease in hemoglobin or hematocrit or an increase in white blood cell (WBC) count. A blood gas obtained in the trauma bay might show an increased lactate or abnormal base excess depending on how severe the bleeding is and how long the patient has been bleeding. Findings on routine abdominal films such as fractured ribs, elevated left hemidiaphragm, enlarged splenic shadow, medial gastric displacement, and widening of the space between the splenic flexure and the preperitoneal fat pad may be helpful. A focused assessment with sonography for trauma (FAST) examination may show evidence of intra-abdominal fluid accumulation. However, all these finding are not specific and can be found in trauma patients with no splenic injuries. Intravenous contrast-enhanced CT scan is the gold standard diagnostic study that will also provide detailed information regarding the American Association for the Surgery of Trauma (AAST) grading for severity of injury¹⁷ (Table 77-1).

Management

The first total splenectomy for trauma was performed by Nicolaus Matthias in 1678 in Cape Town, South Africa, on a patient whose spleen protruded through a flank wound. However, partial splenectomy for trauma antedated this procedure, with the first successful partial splenectomy for trauma reported by Franciscus Rosetti in 1590. Increasing understanding of the functions of the spleen and increased risk of infection in splenectomized patients have rejuvenated interest in splenic salvage in trauma. The first successful partial splenectomy for trauma in modern times was reported by Campos Christo in 1962.¹

The observation that splenic injury may heal itself has also supported nonoperative management (NOM) of splenic injuries. While this practice was largely accepted in the treatment of injured pediatric patients to salvage the spleen and its immunologic function, NOM is also the treatment of choice for hemodynamically stable adults with blunt splenic injuries, regardless of injury severity (Fig. 77-9). Penetrating injuries, hemodynamic instability, and associated peritonitis are all treated with laparotomy, as per the 2012 Eastern Association for the Surgery of Trauma (EAST) guidelines.¹⁸

NOM of blunt spleen injury requires a multidisciplinary strategy including careful clinical monitoring, repeated laboratory testing, and radiologic investigations. NOM should only be carried out in an institution that has a monitored intensive care unit, available surgical expertise, and easy access to the operating room. NOM procedures include supportive medical management and angioembolization. The success rate depends on severity of injury and is reported greater than 95% for grade I injuries, greater than 90% for grade II injuries, and greater than 80% for grade III injuries. Splenic salvage is much less likely with grade IV and V injuries. In a multicenter review of 338 patients with grade IV or V blunt splenic injuries, 40% of patients were operated on immediately, while the remainder had an attempt at NOM. The success rate for NOM in these selected patients was 66% for grade IV and 40% for grade V injuries. Thus, overall, nearly two-thirds of patients with grade IV or V injuries required surgery, and there was higher mortality in patients who failed NOM compared to those in whom it was successful.¹⁹ Prognostic factors that predict failure of NOM of blunt splenic trauma were evaluated in a systematic review.²⁰ The strongest predictors were age >40, Injury Severity Score >24, and grade III to V injury, with moderate evidence for presence of contrast extravasation or “blush” on CT scan.²⁰

Splenic artery embolization (SAE) is an important adjunct for NOM, but its precise role remains controversial.¹⁸ A meta-analysis to evaluate NOM of blunt splenic injury found that the overall failure rate was 8.4% (95% confidence interval [CI], 6.7%-10.2%) with failure rates increasing with more severe injuries, from about 5% in grade I to 83% in grade V.²¹ The addition of SAE was associated with higher splenic salvage rates for more severe injuries compared to observational management alone (56% vs 83% for grade IV and 17% vs 75% for grade V).²¹ Most studies have suggested that splenic function is preserved after SAE, but multiple different parameters were used. There are no reported cases of overwhelming postsplenectomy infections after SAE, and routine vaccination is not used.²² Splenic embolization, however, has its own risks and may be complicated by splenic abscess, infarction, pain, fever, coil migration, pleural effusion, contrast nephropathy, and bleeding.²³ Currently, angiography is recommended for hemodynamically stable patients with grade III to V injuries, contrast blush, moderate hemoperitoneum, or clinical evidence of ongoing bleeding.¹⁸

NOM of splenic injuries should not exceed 24 hours. Failure of NOM is defined as persistent bleeding evident by laboratory testing, hemodynamic changes, or persistent requirement of blood transfusion after 24 hours. Failure of NOM is treated by laparotomy and splenectomy or splenorrhaphy.

After discharge, there is a lack of consensus on restriction of activities, with most restricting activity for >2 months for high-grade injuries managed nonoperatively.²⁴ Patients should be aware of the risk of delayed splenic rupture, with the 180-day risk of readmission for splenectomy of 1.4% in one population-based study.²⁵

Splenic Artery Aneurysm

Splenic artery aneurysm was first described by Baussier in 1770, and St. Leger Brockman described one of the first surgical cases in 1930. Although mycotic aneurysm can be seen in the splenic artery, the majority are idiopathic. The splenic artery is the most common visceral artery aneurysm and the third most common site of intra-abdominal aneurysms, after aneurysms of the abdominal aorta and iliac arteries. The incidence in autopsy series ranges between 0.02% and 0.16%, with a female predominance (4:1). They are commonly associated with pregnancy and portal hypertension. The incidence of splenic aneurysm is much higher in patients with cirrhosis and portal hypertension. Splenic artery aneurysms have been reported in 14% of patients awaiting liver transplant, which can lead to major hemorrhage after transplant.²⁶ Splenic artery aneurysms are also seen at a higher incidence in patients with arteritis, arterial fibrodysplasia, collagen vascular disease, and α₁-antitrypsin deficiency.²⁷ Most are true aneurysms, but pseudoaneurysms may also develop as complications of pancreatitis and trauma.

In a contemporary review of 217 splenic aneurysms seen at the Mayo Clinic, the mean age at presentation was 62 years, with 79% of patients being female. Over 90% of the patients were asymptomatic, with a mean aneurysm size of 3.1 cm. Although more than 10% of men presented with a rupture, this rate was less than 3% in women, in large part due to larger aneurysm sizes in men. The mean size for nonruptured cases was 2.2 cm, and the smallest-diameter aneurysm to rupture was 2.2 cm.²⁸

Splenic artery aneurysms are often incidental findings in asymptomatic patients. Most are under 2 cm in size, but on occasion, they can be much larger. They are generally saccular and solitary, and occur at a bifurcation in the splenic hilum.²⁹ Peripheral calcification and mural thrombus are frequently noted (Fig. 77-10). Patients may present with symptoms of left upper quadrant or epigastric pain radiating to the shoulder. The overall risk of rupture is less than 2% but is higher for aneurysms larger than 2 cm, in liver transplant patients, and in pregnancy.²⁹ Such ruptures have been associated with maternal and fetal death rates of 22% and 15%, respectively.³⁰ Ruptures occur in the third trimester of pregnancy in 69% of cases.³¹

Rupture of the aneurysm is manifested by sudden abdominal pain. If the rupture is initially contained in the lesser sac, the patient may have upper abdominal pain but be hemodynamically stable. Once the rupture overflows into the peritoneal cavity, diffuse pain and hemorrhagic shock ensue. This sequence of events is termed the “double rupture phenomenon.” Mortality after emergency surgery is as high as 40%.³²

Surgical resection in all symptomatic aneurysms is recommended; however, criteria for elective repair of asymptomatic aneurysms are not firm. In general, the presence of an aneurysm larger than 2 cm is an indication for surgery if the patient is a reasonable operative risk.²⁹ Asymptomatic patients with aneurysms between 1 and 2 cm should be closely monitored with serial imaging done initially every 6 months.³³ Aneurysms of any size detected in pregnancy should be treated because many of the ruptured aneurysms during pregnancy are less than 2 cm in size.³⁰ This should be done before the third trimester, when the risk of rupture is at its peak. Liver transplant patients have a higher incidence of aneurysms and a higher risk of rupture, including in the posttransplant period, with a mortality over 50%. This has led to recommendations to treat splenic artery aneurysms over 1.5 cm in size with embolization prior to liver transplantation.³⁴

The traditional approach to repair for lesions in the proximal or middle of the artery includes resection and primary end-to-end anastomosis, or proximal and distal ligation with resection of the involved segment.³⁵ Proximal ligation is reasonable because the spleen will not become ischemic following central ligation of the main splenic artery. Distal lesions located close to the hilum generally require splenectomy with resection of the involved splenic artery, now generally done laparoscopically (Fig. 77-11). The overall mortality rate ranges from 1% to 3%, with a perioperative complication rate of 9% to 25% due to splenic or pancreatic injury.³³

Percutaneous transcatheter embolization techniques have been increasingly used and are preferred over surgery for most splenic artery aneurysms if the anatomy is suitable.³⁶ The endovascular therapeutic options include stenting, coil embolization, and the use of glue, N-butyl-2-cyanoacrylate; their uses vary based on aneurysm size and location, and there is not enough evidence to support the use of one over another. These techniques have been increasingly used since 2000, and a systematic review reports a technical success rate of over 95%.³⁷ Complications of endovascular repair include treatment failures, postprocedural pain, and abscess formation, as well as pancreatitis due to occlusion of the pancreatica magna vessel.³⁸ Major postoperative complications are higher in the open repair (1.1%) versus endovascular patients (0.8%). In the long term, however, there are more late complications in the endovascular group with a greater need for subsequent interventions compared to open repair (3.2% vs 0.5% per year).³⁷ Follow-up after endovascular repair is mandatory. Decision analysis modeling suggests that the endovascular approach is less costly and more effective than open surgery.³⁹ The endovascular approach has also been used in the emergency setting to treat ruptured aneurysms.

Cysts

Splenic cysts are classified as primary or secondary (pseudocysts). Some splenic tumors may also have a cystic component (Fig. 77-12). Primary cysts have an epithelial lining and can be nonparasitic or parasitic (echinococcal).

PARASITIC PRIMARY CYSTS

Worldwide, Echinococcus infection (hydatid disease) is the most common cause of a splenic cyst. The spleen is the third most common site of disease, after the liver and lung. Echinococcus granulosus, the most commonly implicated species, usually results in a unilocular cyst composed of an inner germinal layer (endocyst) and an outer laminated layer (ectocyst) surrounded by a fibrous capsule. Unlike the nonparasitic cysts, these are filled with fluid under positive pressure and also contain daughter cysts and infective scolices. Echinococcal cysts are usually asymptomatic unless they reach a size causing pressure symptoms or become secondarily infected or rupture. Overall, splenic involvement is rare, even in endemic areas, and comprises only 0.5% to 4% of all hydatid disease.⁴⁰ Once splenic disease is found, concomitant disease is usually found in other organs, with the liver and peritoneum the most common locations.

Splenic hydatid cysts grow slowly, approximately 0.3 to 2.0 cm per year,⁴¹ and most patients remain asymptomatic for a long time. Symptoms occur due to the mass effect on nearby organs, usually with nonspecific and/or left upper quadrant abdominal pain. Diagnosis is made using imaging tests including ultrasound, CT, and magnetic resonance imaging (MRI) studies that demonstrate a septated cystic mass that contains daughter cysts. For diagnostic purposes, the older Casoni skin test has been replaced with serologic testing. Multiple serologic tests are available and include immunophoresis, enzyme-linked immunosorbent assay (ELISA), and latex and indirect hemagglutination. Sensitivity rates of 85% to 90% are seen with both ELISA and indirect hemagglutination testing; overall, ELISA testing is thought to be optimal. These are used for screening and diagnosis and can also be used on follow-up to detect any recurrences.^40,41

Recommended management of splenic hydatid cysts is based on size and concomitant disease; options include medical management, percutaneous techniques (puncture, aspiration, injection, reaspiration [PAIR]), and surgical intervention. Medical management with anthelmintics (eg, albendazole, mebendazole, praziquantel) as a sole treatment modality is controversial given low absorption of orally administered medication and subtherapeutic concentration in the cyst. Some still advocate for small cysts being treated with anthelmintic drugs alone.⁴¹ The PAIR technique is used in conjunction with anthelmintic therapy in patients with prohibitive surgical risks or who refuse surgery and is safe for cysts under 5 cm in diameter. Larger and/or symptomatic cysts are treated surgically due to the risk of rupture. Traditionally, a complete splenectomy is advocated to reduce the risk of recurrence and is the treatment of choice. This is especially true for multiple or centrally located cysts or in patients with concomitant abdominal disease elsewhere. Care should be taken to avoid spilling the contents of the cyst. Intraoperatively, the lesions can be sterilized by instilling a 3% sodium chloride solution into the cysts. If intraperitoneal spillage occurs during the dissection, anaphylactic hypotension may occur and require epinephrine. With newer techniques emerging and concern for postsplenectomy septic complications, splenic-preserving procedures are being considered for small or peripherally located cysts. These include partial splenectomy, cyst enucleation, deroofing with omentoplasty, and internal drainage with cystojejunal anastomosis. Small case series show no recurrence after spleen-preserving procedures for small peripheral cysts in young patients.⁴⁰ Other studies comparing outcomes after total splenectomy and spleen-preserving surgery have found no difference in recurrence; however, these are all retrospective and heterogeneous studies, and definitive recommendations cannot be made. Larger studies are yet to be done, and the role of splenic-preserving procedures for hydatid cysts is not well established. The use of laparoscopy has also not been widely accepted in treating hydatid cysts because of a fear of spillage and anaphylaxis.⁴²

NONPARASITIC PRIMARY CYSTS

Nonparasitic primary cysts are increasingly discovered incidentally on imaging done for a variety of reasons. According to Morgenstern’s classification, nonparasitic splenic cysts are classified based on pathogenesis as congenital, neoplastic, traumatic, or degenerative (Table 77-2).⁴³

Cysts with mesothelial, epidermoid, or transitional epithelial linings are probably congenital in origin, originating from an infolding of peritoneal mesothelioma during splenic development. The cellular lining can desquamate and be absent in places, but these cysts have a characteristic gross appearance, with a white, glistening interior containing coarse fibrous trabeculations.⁴³ The cyst fluid can be clear or cloudy and ranges in color from almost clear to yellow, green, or brown. The fluid may show elevated levels of carcinoembryonic antigen (CEA) and CA 19-9. A calcified portion of the cyst wall may also observed in a small proportion of these cysts.

Congenital cysts of the spleen occur in children and in young adults in 75% of cases. About two-thirds of the patients are female. The clinical manifestations are dependent on the size and can include left upper abdominal discomfort, pain, or fullness. True dermoid cysts of the spleen are exceedingly rare; less than 10 cases have met the pathologic criteria of a squamous epithelium with dermal appendages such as hair follicles and sweat glands.

It can be difficult to differentiate these cysts from one another based on imaging only, and usually the diagnosis is made when symptomatic cysts, usually greater than 5 cm, are excised and analyzed histologically.⁴⁴ Asymptomatic cysts, which are often smaller, are observed with no need for surgical resection. The recommendation for resection of splenic cysts over 5 cm originated in 1992 based on a report by Musy et al⁴⁵ and was reinforced in subsequent literature.⁴³ Some sources cite the 25% spontaneous rupture risk for cysts larger than 5 cm with an associated high mortality rate, but this was in the context of hemangiomas. More recent work by Kenney et al⁴⁶ reviewed 115 patients with splenic cysts, including 16 with cysts larger than 5 cm. There was only 1 patient with a large cyst who presented with rupture after a fall. The authors concluded that size should not be used to determine the need for intervention.⁴⁶ This applied to asymptomatic cysts with typical imaging findings, including smooth, regular wall contours and no solid component.

Aspiration of the cyst is not a definitive treatment because it is usually not successful. Only compete removal of the cyst avoids recurrence. Spleen-conserving approaches are feasible for most cysts, unless they are centrally located. One attractive approach with very low morbidity is near total resection of the cyst wall, leaving just the part of the wall of the cyst attached to the spleen in situ (“unroofing” or “decapsulation”). This is associated with low morbidity, but radiologic recurrence in children may be >65%^47,48; however, these recurrences are usually smaller than the original cyst, and many are asymptomatic and can be managed conservatively.⁴⁷ In adults, reported long-term recurrence rates range from 20% to 60%.^49-51 Although partial splenectomy has higher potential morbidity related to bleeding or ischemia of the remnant, it is becoming a more common option given that it allows resection of the cyst itself but leaves splenic tissue behind, maintaining immunologic function. Leaving at minimum 25% of splenic tissue is thought to confer adequate immunologic function.⁵² This can also be done safely via the laparoscopic approach, as discussed below.

Splenic Abscess

Splenic abscesses tend to be rare, due to the spleen’s ability at fighting infections and bacteria. They are more frequently seen in areas with a high incidence of sickle cell anemia, with associated thrombosis of parenchymal vessels and subsequent splenic infarction.

The major risk factors for such abscesses in the West are intravenous drug use, human immunodeficiency virus (HIV) infection, other hematogenous spread (endocarditis), splenic trauma, and contiguous spread. Endocarditis can be complicated with splenic abscesses in 5% of cases. These are often multiple abscesses similar to what is seen in other organs; the spleen is just a part of overwhelming sepsis.⁵³ Most infections are polymicrobial and include such organisms as Staphylococcus, Salmonella, Escherichia coli, Proteus mirabilis, Streptococcus group D, Klebsiella pneumoniae, Peptostreptococcus, Bacteroides, Fusobacterium, Clostridium, Candida albicans, and Mycobacterium.

The symptoms are usually nonspecific, such as malaise, weight loss, left upper quadrant pain, and fever. Most patients have a leukocytosis, and an ultrasound, CT, or MRI study establishes the diagnosis of a splenic abscess. Treatment consists of broad-spectrum antibiotics and percutaneous drainage, which, if it fails, will require laparoscopic or open splenectomy. Many patients have multiple other abscesses in other organs. Antibiotic treatment should continue until the drains or percutaneous catheters have been removed. If the spleen has multiple abscesses, splenectomy may be required.⁵⁴

Splenic Tumors

Splenic masses may be identified during workup of symptoms or incidentally during other imaging. Some of these masses have a large cystic component (see Fig. 77-12). Management of such lesions may result in difficult clinical decision making as imaging alone does not always result in a definitive diagnosis. Often, these lesions may need to be followed serially, or if concerning, splenectomy should be considered. The underlying pathology may depend on referral patterns. In a series of 44 such cases, half of whom were symptomatic and treated surgically, 75% of lesions were benign while the remainder were malignant.⁵⁵ In a similar study of 28 patients, the risk of a malignant diagnosis was significantly higher at 72%, although 25% of these patients had a previous history of lymphoproliferative disorder.⁵⁶ There are increasing data on the use of image-guided splenic fine-needle aspiration to differentiate such masses, with low complication rates.⁵⁷ Sensitivity and specificity of such aspiration have been reported as 94% and 79%, respectively,⁵⁸ with low risk of complications, even for core-needle biopsy.⁵⁹

BENIGN NEOPLASMS

Splenic neoplasms generally arise from the lymphoid or vascular elements of the spleen. They include a broad range of lesions, from benign (hemangioma, hamartoma, lymphangioma, and sclerosing angiomatoid nodular transformation) to intermediate (littoral cell angioma, hemangioendothelioma, and hemangiocytoma) to malignant (angiosarcoma). The more commonly found benign lesions are discussed here.

Hemangiomas are the most common benign neoplasms of the spleen with an incidence ranging from 0.02% to 16% and can be single or multiple.⁶⁰ Most are now diagnosed incidentally during imaging for other pathology. Hemangiomas vary from well-circumscribed to irregular vascular proliferations. They consist of a benign overgrowth of nonencapsulated proliferation of new blood vessels of variable size, from capillary to cavernous formations. They are thought to be congenital in origin, and most are cavernous in nature. On CT scan, hemangiomas appear as homogeneous, hypodense, or multicystic lesions with variable calcification and peripheral enhancement. On MRI, they have high signal intensity on T2-weighted images with peripheral enhancement on delayed images.⁶¹ The potential for malignant transformation to angiosarcoma is not known but appears to be low.

The majority of splenic hemangiomas do not require surgical intervention. Most are asymptomatic. Splenectomy is reserved for tumors that become symptomatic due to size or consumptive coagulopathy. Although there has traditionally been concern about risk of spontaneous rupture or rupture with blunt trauma, a contemporary series from the Mayo Clinic reported no spontaneous rupture among 32 patients with splenic hemangioma, 80% of whom were entirely asymptomatic.⁶⁰ Attempts at treatment using embolization of arterial branches or radiofrequency ablation have been reported, but more data are needed to understand their efficacy.

Sclerosing angiomatoid nodular transformation (SANT) is a benign vascular lesion first defined by Martel et al⁶² in 2004. SANT consists of altered red pulp trapped by nonneoplastic stromal proliferation.⁶³ There is often a central stellate scar. Patients are usually asymptomatic with a solitary splenic mass found incidentally on imaging. There is a 2:1 female predominance. Ultrasound shows a hypoechoic lesion. CT and MRI studies may show a central scar, enhancing capsule, and radiating bands corresponding to fibrosis.^61,64 The lesion may have ¹⁸F-fluorodeoxyglucose (FDG) avidity on positron emission tomography (PET) scan.⁶⁴ The average size in a case series of resected patients was 5.8 cm (range, 3.2-10.2 cm).⁶⁵ Although SANT often displays characteristic radiologic findings, differentiation from other benign and malignant lesions may be challenging, and splenectomy may be required (Fig. 77-13).

Littoral cell angioma (LCA) is a rare vascular tumor of the spleen. It is an endothelial cell neoplasm arising from the cells lining the sinus channels of the splenic red pulp. These rare lesions express vascular and histiocyte-associated antigens. The autopsy incidence ranges from 0.03% to 14%. They are seen at any age range, with no sex-based predilection. Two forms of LCA are seen: diffuse multiple nodular LCA and the more rare solitary form. Imaging features on ultrasound vary widely from heterogeneous echotexture with no specific nodules to hyperechogenic-, hypoechogenic-, or isoechogenic-appearing lesions. A comparison between sonographic and pathologic features has shown that lesions with minimal blood-filled spaces appear as hypoechoic spaces, whereas lesions with lots of blood-filled spaces appear as hyperechoic spaces. On an unenhanced CT imaging study, nodular LCA lesions are not visible unless they have a hemorrhagic component. On a contrast CT in the portal venous phase, LCAs appear as low-attenuation lesions; LCAs are iso-attenuating on delayed images.

Although classified as benign, recent literature classifies LCAs as having uncertain biologic behavior.⁶⁶ Malignant transformation to littoral cell angiosarcoma is very rare, but cases with dissemination to the liver and brain have been reported. An association with malignant lymphomas and other visceral organ cancers, including thyroid, colon, lung, pancreas, liver, brain, hematologic, ovarian, and testicular, has been reported.⁶⁷ This leads to reluctance in classifying it as a completely benign lesion. In addition, LCA is also associated with various congenital and immunologic conditions, including inflammatory bowel disease, Wiskott-Aldrich syndrome, Epstein syndrome, lymphocytic colitis, systemic lupus erythematosus, ankylosing spondylitis, psoriasis, Gaucher disease, myelodysplastic syndrome, chronic glomerulonephritis, and aplastic anemia.⁶⁸

The majority of patients are asymptomatic. Symptomatic patients present with abdominal pain, left upper quadrant fullness with satiety, splenomegaly, anemia, thrombocytopenia, or constitutional symptoms such as weight loss, anorexia, or fever of unknown origin.⁶⁹ A preoperative diagnosis of LCA can be made with an image-guided fine-need aspiration or needle biopsy. Some authors recommend close follow-up, but given its small malignant potential and possible concomitant malignancies, splenectomy may be recommended. The potential for familial predisposition has been raised, and screening for splenic lesions in family members is suggested.⁶⁶

Lymphangiomas are congenital malformations thought to be due to obstruction of the venolymphatic system (see Fig. 77-12B). Microscopically, these endothelium-lined spaces are filled with lymph and blood elements. The lesion may be focal or multiple, a small or large cystic mass, or may diffusely involve the spleen and account for splenomegaly. The diagnosis is made by ultrasound, CT scan, or MRI that reveals water-density cystic lesion(s) of the spleen. The lymphangioma may be isolated to the spleen or occur as a generalized lymphangiomatosis with multivisceral involvement and a poor prognosis. Symptoms, when present, are related to the size and mass effect of the lesion. Splenectomy is indicated for symptomatic lesions.

Inflammatory pseudotumor of the spleen is a reactive lesion characterized by a mixture of inflammatory cells and disorganized spindle cells.⁷⁰ It is infiltrative in nature and may mimic malignant lymphoproliferative disease. These are seen in middle-aged and older patients, with a higher incidence in women. This tumor is typically found incidentally and is generally asymptomatic but may present with systemic symptoms such as abdominal pain, splenomegaly, or symptoms suggestive of malignancy such as fever, malaise, and weight loss. Imaging studies are nonspecific. The differential diagnosis includes lymphatic neoplasms, inflammatory granulomatous processes, hamartomas, hemangiomas, hemangioendotheliomas, and angiosarcomas. Although inflammatory pseudotumors are benign, no method with adequate sensitivity or specificity is available to make a definitive diagnosis. The diagnosis can be made via percutaneous fine-needle aspiration cytology, but splenectomy may be required to rule out malignancy if a diagnosis cannot otherwise be made.

Other benign lesions of the spleen are uncommon. Splenic hamartomas are uncommon, with autopsy series noting an incidence of 0.024% to 0.13%. They are solid but may have a cystic or necrotic component.⁶¹ Peliosis is not a true neoplastic lesion but a blood-filled cystic lesion without an endothelial lining that may be associated with focal, patchy, or diffuse involvement of the spleen. This lesion is likely reactive as it has been associated with steroids, oral contraceptives, immunosuppression medications, tuberculosis, renal disease, and malignancy. Other benign splenic tumors, such as angiomyolipoma, lipoma, hemangiopericytoma, and fibroma, are rare.

PRIMARY MALIGNANT TUMORS

Primary, nonlymphoid, malignant tumors of the spleen are exceedingly rare. These include angiosarcomas, malignant fibrous histiocytomas, and plasmacytomas. Angiosarcoma is the most common nonlymphoid primary malignant neoplasm of the spleen. The clinical presentation may include abdominal pain, left upper quadrant abdominal mass, and constitutional symptoms. Metastasis is frequent and often involves the liver. Spontaneous rupture has been reported and is associated with a dismal outcome. Normocytic anemia is present in the majority of cases. Splenomegaly with hypersplenism is also seen. CT imaging often identifies a splenic lesion with central necrosis. The primary treatment is splenectomy. Cisplatin-based chemotherapy has also been used. However, even without rupture, splenic angiosarcoma holds a poor prognosis. Recent studies have reported 1-, 3-, and 5-year survival rates of 60%, 40%, and 40%, respectively.⁷¹

METASTATIC TUMORS

Splenic metastasis of nonhematologic malignancies is rarely seen clinically and usually represents widespread dissemination of disease. In a review of a German oncologic database, only 0.002% of patients with a malignancy developed reported splenic metastasis, with isolated splenic metastasis being extremely rare.⁷² Despite the rarity of clinically evident splenic metastasis, postmortem evidence is reported to be higher, although the exact prevalence of this is debated, with older literature reporting rates as high as 34%, while contemporary reports put this rate at approximately 3%.⁷³ The most frequent sites of primary tumors with splenic metastasis are lung, colorectal, ovary, melanoma, and breast.⁷⁴

The diagnosis of malignancy can be confirmed by PET scanning, although percutaneous biopsies for isolated lesions can also be performed (Fig. 77-14).⁷⁵ Splenectomy may be indicated to treat isolated metastatic disease, especially for patients with chemosensitive tumors or in whom cytoreductive surgery can improve outcomes.⁷⁴

In 1887, Sir Thomas Spencer Wells, the renowned gynecologist, performed a therapeutic splenectomy for what proved to be hereditary spherocytosis. The first splenectomy for autoimmune hemolytic anemia (AIHA) was performed in 1911 by Micheli. Six years later, Schloffer, at the suggestion of a medical student, Kaznelson, performed a splenectomy for idiopathic thrombocytopenic purpura.¹ The indications for splenectomy in hematologic disease are continuously evolving, but there are many conditions for which splenectomy plays an important role. The most common hematologic indications for splenectomy are immune thrombocytopenia purpura, hereditary spherocytosis, and AIHA.

Splenectomy is indicated for specific cases of anemia. The major categories of anemia that benefit from splenectomy are those caused by the following:

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  Membrane abnormalities: Hereditary spherocytosis and elliptocytosis

  
  
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  Enzyme defects: Pyruvate kinase deficiency

  
  
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  Hemoglobinopathy: Thalassemias and sickle cell

  
  
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  AIHA

Hereditary Spherocytosis

Hereditary spherocytosis (HS) is a hemolytic anemia that results from a genetic defect or deficiency in one of the components of the red cell cytoskeleton. It results in spherically shaped erythrocytes on blood smear, reticulocytosis, and splenomegaly. HS is transmitted as an autosomal dominant trait but occurs sporadically in rare instances. HS is the most common cause of familial chronic hemolytic anemia in North America and Northern Europe, with an incidence of 1 to 5 in 10,000 births, or even higher if mild cases of osmotic fragility are included.⁷⁶

Abnormalities of the proteins in the red cell membrane (spectrin, ankyrin, band 3, and/or protein 4.2) cause increased osmotic fragility and changes in morphology, resulting in the spherical shape and decreased deformability. The red cell membrane change results in splenic trapping of the abnormal cells in the microcirculation, followed by their destruction by phagocytosis.⁷⁷ Thus, the spleen plays a critical role in the pathophysiology of HS, as it is the main site of hemolysis. Cells that escape the spleen on first passage are more susceptible to trapping and destruction during each successive passage.

The salient clinical features include anemia, jaundice, and splenomegaly, with spherocytes on blood smear, increased osmotic fragility, and positive family history.⁷⁷ The severity of disease varies widely and is classified as mild, moderate, and severe based on hemoglobin, bilirubin, and reticulocyte count (Table 77-3).^78,79 Approximately 30% of cases are mild, maintaining near-normal hemoglobin and bilirubin levels and compensatory reticulocytosis. Patients with severe spherocytosis are transfusion dependent with baseline hemoglobulin level less than 6 g/dL.

The disease severity is related to the degree of red cell cytoskeleton protein deficiency, particularly spectrin shortage. The jaundice usually parallels the severity of anemia and generally is not intense. It is related to increased red cell destruction, resulting in abundant bile pigment that cannot be cleared by the liver. Most patients have mild to moderate spleen enlargement, but splenomegaly alone is not an indication for surgery. Increases in splenic size in patients with HS may be seen in the presence of acute infection. Periodic worsening of the associated anemia and jaundice may be seen, often following infection, emotional stress, fatigue, or prolonged exposure to cold. Gallstones are the most common complication of HS but are unusual in children younger than age 10 years. The gallstones are generally pigmented.

Splenectomy is effective in reducing the hemolysis associated with HS but at the price of a lifelong risk of severe sepsis from encapsulated organisms, and emerging evidence links splenectomy to late vascular complications such as pulmonary hypertension and atherosclerosis.⁷⁹ Splenectomy should not be recommended simply due to the diagnosis of HS but is based on the severity of anemia (see Table 77-3). Failures are uncommon and often reflect missed accessory spleens, which can be identified using radiocolloid liver-spleen scans.⁷⁷ The preferred approach is laparoscopic as it is associated with less postoperative morbidity and pain. Because of the increased risk of serious postsplenectomy sepsis among young children, with a subsequent mortality rate of 50% to 80%, splenectomy is reserved preferably for patients older than 6 years⁷⁹ and should not be done in children younger than age 3, even if chronic transfusions are needed.⁷⁸

Concern over postsplenectomy sepsis risks, especially in young children, has led to investigation of the effectiveness of partial splenectomy to control hemolysis while leaving some functional spleen behind for immunologic purposes.^80,81 Either the lower pole, based on the gastroepiploic, or the upper pole, based on the uppermost short gastrics, is preserved. This approach has somewhat less effective hemolytic control. A recent review of moderate-quality evidence reported that partial splenectomy resulted in increases of hemoglobin of 2.3 to 3.9 g/d, compared to 4 to 5 g/dL with total splenectomy, but both resulted in decreased reticulocyte counts, anemic crises, and transfusions. Most studies suggested that partial splenectomy maintained splenic immune function and phagocyte activity, but there was a lack of longer term studies comparing adverse events such as sepsis or vascular complications.⁸² A multi-institutional review of 62 children of all ages undergoing a partial splenectomy showed a good response with no postsplenectomy sepsis with up to 18 years of follow-up and only 4.8% of patients requiring completion splenectomy. They noted that splenic remnant regeneration correlated with the degree of recurrence of anemia and clinical symptoms,⁸³ but this is not a consistent finding.⁸⁴ The Splenectomy in Hemolytic Anemia (SICHA) Consortium Registry compared outcomes after total and partial splenectomy. Excellent hematologic response through 1 year was seen after both procedures, with a more robust response (ie, greater increase in hemoglobin) after total splenectomy.⁸⁵ Guidelines conclude that partial splenectomy may be beneficial, but further follow-up studies are required.⁷⁹

Concomitant cholecystectomy is performed if gallstones are present. Prophylactic cholecystectomy in the absence of stones is not required because patients no longer develop pigmented stones after splenectomy.⁷⁹ In a cohort of patients younger than 18 years, none developed cholelithiasis after splenectomy over a mean follow-up of 15 years.⁸⁶ The presence of Gilbert disease increases the risk of subsequent gallstones.⁸⁷ On the other hand, symptomatic gallstones have traditionally been an indication for concomitant splenectomy in children, due to the concern for the development of future biliary duct stones. This is now controversial in children with mild disease. In a series of 16 patients with mild HS having cholecystectomy without splenectomy, only 3 required subsequent splenectomy.⁸⁸

Hereditary Elliptocytosis

Hereditary elliptocytosis is a red cell hemolytic anemia affecting 3 to 5 of every 10,000 people with a heterogeneous array of genotypes and phenotypes. It is more common in people of African and Mediterranean origin, presumably because it results in some resistance to malaria.⁷⁷ It is a group of erythrocyte disorders that have in common the presence of elongated, oval, or elliptically shaped RBCs on the peripheral blood film. Most are transmitted as an autosomal dominant trait. Most patients are asymptomatic or have a mild form of the disease with compensated hemolytic anemia, as the defects often do not significantly shorten the red cell life span despite striking abnormalities seen on blood film. The presence of hemolysis often is a familial characteristic, and it has been suggested that excessive hemolysis occurs only when the gene for elliptocytosis is present in the homozygous form or is modified in some other way. The signs and symptoms are related directly to the severity of hemolysis resulting from the extent of decreased membrane stability and subsequent loss of membrane surface area. Occasionally an acute hemolytic episode may be precipitated by infection. The clinical syndrome is indistinguishable from that described for HS. Gallstones and chronic leg ulcers have been reported in symptomatic patients. The spleen is usually palpably enlarged in symptomatic cases. Diagnosis is established by the smear.

Therapy is rarely required. Indication for splenectomy is the same as for HS and is almost always followed by lasting effects. Decreased hemolysis and corrected anemia result from longer circulatory life span of the red cells, although the morphologic abnormality of the RBC remains unchanged. Associated cholelithiasis should be managed as in HS.

Pyruvate Kinase Deficiency

Pyruvate kinase deficiency is the most common RBC enzyme deficiency causing congenital nonspherocytotic hemolytic anemia. It is an autosomal recessive condition that has a much lower frequency than glucose-6-phosphatase deficiency (G6PD); however, it a more common cause of anemia because G6PD patients rarely suffer hemolysis.

Clinical manifestation varies from transfusion-dependent anemia to compensated chronic hemolysis. Splenomegaly is common. There is no curative therapy. Splenectomy has a role in transfusion-dependent individuals and can reduce or even abolish the need for transfusion.⁸⁹ As with other children being evaluated for splenectomy, the procedure should be delayed until after age 3 due to the immunosuppressive effect of the surgery.