BASIC SCIENCE QUESTIONS
1. More than 80% of accessory spleens are found in the splenic hilum. What is the second most common location for an accessory spleen?
A. The greater omentum
B. The gastrocolic ligament
C. The tail of the pancreas
D. The splenocolic ligament
The most common anomaly of splenic embryology is the accessory spleen. Present in up to 20% of the population, one or more accessory spleens may also occur in up to 30% of patients with hematologic disease. Over 80% of accessory spleens are found in the region of the splenic hilum and vascular pedicle. Other locations for accessory spleens in descending order of frequency are the gastrocolic ligament, the pancreas tail, the greater omentum, the stomach’s greater curve, the splenocolic ligament, the small and large bowel mesentery, the left broad ligament in women, and the left spermatic cord in men. (See Schwartz 9th ed., p 1246.)
2. Which of the following is the primary function of the spleen in humans?
A. Production of red cells
B. Production of white cells
C. Storage of blood
D. Host defense
Many mammals have splenic capsules and trabeculae with abundant smooth muscle cells, which upon autonomic stimulation contract to expel large volumes of stored blood into the general circulation. Such spleens are descriptively characterized as storage spleens. The human splenic capsule and trabeculae, by contrast, contain few or no smooth muscle cells, and their function is largely related to immunologic protection. Thus the term defense spleencharacterizes the human organ. Historically the four splenic functions have been accurately noted as (a) filtration, (b) host defense, (c) storage, and (d) cytopoiesis. For the adult human, the most important, dominant functions are filtration and host defense. (See Schwartz 9th ed., p 1248.)
3. Approximately what volume of aged red blood cells are removed by the spleen every day?
A. 2 mL
B. 20 mL
C. 100 mL
D. 250 mL
The spleen acts as the major site for clearance from the blood of damaged or aged red blood cells and in addition has a part in the removal of abnormal white blood cells and platelets. A minimum of 2 days of the erythrocyte’s 120-day life cycle is spent sequestered in the spleen. Daily, approximately 20 mL of aged red blood cells are removed. (See Schwartz 9th ed., p 1248.)
4. In a normal patient what percentage of platelets are sequestered in the spleen?
The life cycles of cellular elements vary widely in human blood. A neutrophil in circulation has a normal half-life of approximately 6 hours. The spleen’s role in the normal clearance of neutrophils is not well established. It is clear that hypersplenism may result in neutropenia through sequestration of normal white blood cells or the removal of abnormal ones. Platelets, on the other hand, generally survive in the circulation for 10 days. Under normal circumstances a third of the total platelet pool is sequestered in the spleen. Thrombocytopenia may result from excessive sequestration of platelets as well as accelerated platelet destruction in the spleen. Splenomegaly may result in sequestration of up to 80% of the platelet pool. (See Schwartz 9th ed., p 1248.)
5. Which of the following proteins is abnormal in patients with hereditary spherocytosis?
Hereditary spherocytosis (HS) results from an inherited dysfunction or deficiency in one of the erythrocyte membrane proteins (spectrin, ankyrin, band 3 protein, or protein 4.2). The resulting destabilization of the membrane lipid bilayer allows a pathologic release of membrane lipids. The red blood cell assumes a more spherical, less deformable shape, and the spherocytic erythrocytes are sequestered and destroyed in the spleen. Hemolytic anemia ensues; in fact, HS is the most common hemolytic anemia for which splenectomy is indicated. The spleen produces opsonins, tuftsin, and properdin, which are all part of the humoral host defense and area not related to red blood cell membrane deformation. (See Schwartz 9th ed., p 1250.)
6. Transposition between the bcr gene on chromosome 9 and the abl gene on chromosome 22 is the hallmark of which of the following conditions?
A. Chronic myeloid leukemia
B. Chronic myelomonocytic leukemia
C. Acute myeloid leukemia
D. Polycythemia vera
Chronic myeloid leukemia (CML) is a disorder of the primitive pluripotent stem cell in the bone marrow that results in a significant increase in erythroid, megakaryotic, and pluripotent progenitors in the peripheral blood smear. The genetic hallmark is a transposition between the bcr gene on chromosome 9 and the abl gene on chromosome 22. CML accounts for 7 to 15% of all leukemias, with an incidence of 1.5 in 100,000 in the United States. It is often asymptomatic, but CML can cause fatigue, anorexia, sweating, and left upper quadrant pain and early satiety secondary to splenomegaly. Enlargement of the spleen is found in roughly one half of patients with CML. Splenectomy is indicated to ease pain and early satiety. (See Schwartz 9th ed., p 1254.)
7. Abnormal storage of sphingomyelin is found in
A. Gaucher’s disease
B. Niemann-Pick disease
D. Felty’s syndrome
Niemann-Pick disease is an inherited disorder of abnormal lysosomal storage of sphingomyelin and cholesterol in cells of the macrophage monocyte system. Four types of the disease (A, B, C, and D) exist, with unique clinical presentations. Types A and B result from a deficiency in lysosomal hydrolase and are the forms most likely to demonstrate splenomegaly with its concomitant symptoms.
Gaucher’s disease is an inherited lipid storage disorder characterized by the deposition of glucocerebroside in cells of the macrophagemonocyte system. The underlying abnormality is a deficiency in the activity of a lysosomal hydrolase. Abnormal glycolipid storage results in organomegaly, particularly hepatomegaly and splenomegaly.
Amyloidosis is a disorder of abnormal extracellular protein deposition. There are multiple forms of amyloidosis, each with its own individual clinical presentation, and the severity of disease may range from asymptomatic to multiorgan failure. Patients with primary amyloidosis, associated with plasma cell dyscrasia, have splenic involvement in approximately 5% of cases.
The triad of rheumatoid arthritis, splenomegaly, and neutropenia is called Felty’s syndrome. It exists in approximately 3% of all patients with rheumatoid arthritis, two thirds of whom are women. (See Schwartz 9th ed., p 1256.)
8. Which of the following is the most common cause of congenital hemolytic anemia?
A. Glucose-6-phosphate dehydrogenase deficiency
B. Pyruvate kinase deficiency
C. Hereditary spherocytosis
D. Hereditary elliptocytosis
The most common red blood cell enzyme deficiency to cause congenital chronic hemolytic anemia is pyruvate kinase (PK) deficiency. Its pathophysiology is unclear. PK deficiency affects people worldwide, with a slight preponderance among those of Northern European or Chinese descent. Clinical manifestations of the disease vary widely, from transfusion-dependent severe anemia in early childhood to well-compensated mild anemia in adolescents or adults. Diagnosis is made either by a screening test or by detection of specific mutations at the complementary DNA or genomic level. Splenomegaly is common, and in severe cases splenectomy can alleviate transfusion requirements.
Hereditary spherocytosis and elliptocytosis are disorders of the red blood cell membrane, and not enzymatic deficiencies. (See Schwartz 9th ed., p 1251.)
1. An 18-year-old otherwise healthy woman is incidentally found to have a 2-cm splenic aneurysm of the mid portion of the splenic artery. Which of the following is the treatment of choice for this patient?
A. Observation only
C. Ligation or resection of the aneurysm
Although splenic artery aneurysm is rare, it is the most common visceral artery aneurysm. Women are four times more likely to be affected than men. The aneurysm usually arises in the middle to distal portion of the splenic artery. In one series, mortality was significantly higher in patients with underlying portal hypertension (>50%) than in those without it (17%). Indications for treatment include presence of symptoms, pregnancy, intention to become pregnant, and presence of pseudoaneurysms associated with inflammatory processes. Aneurysm resection or ligation alone is acceptable for amenable lesions in the midsplenic artery, but distal lesions in close proximity to the splenic hilum should be treated with concomitant splenectomy. An excellent prognosis follows elective treatment. Splenic artery embolization has been used to treat splenic artery aneurysm, but painful splenic infarction and abscess may follow. (See Schwartz 9th ed., p 1256.)
2. A 48-year-old patient presents with isolated bleeding gastric varices, splenic vein thrombosis, and normal liver function. Which of the following is likely to be the treatment of choice?
A. Beta blockers and banding
B. Splenorenal bypass
C. Splenic vein ligation
Portal hypertension secondary to splenic vein thrombosis is potentially curable with splenectomy. Patients with bleeding from isolated gastric varices who have normal liver function test results, especially those with a history of pancreatic disease, should be examined for splenic vein thrombosis and treated with splenectomy if findings are positive. (See Schwartz 9th ed., p 1256.)
3. Splenectomy is indicated in a child with sickle cell following
A. 1 episode of sequestration
B. 2 episodes of sequestration
C. 3 episodes of sequestration
D. None of the above
Sequestration occurs in the spleen, with splenomegaly resulting early in the disease course. In most patients subsequent infarction of the spleen and autosplenectomy occur at some later time. The most frequent indications for splenectomy in sickle cell disease are recurrent acute sequestration crises, hypersplenism, and splenic abscess. The occurrence of one major acute sequestration crisis characterized by rapid painful enlargement of the spleen and circulatory collapse, generally is considered sufficient grounds for splenectomy. Preoperative preparation should include special attention to adequate hydration and avoidance of hypothermia. (See Schwartz 9th ed., p 1251.)
4. Which of the following is associated with an increased risk for pulmonary hypertension following splenectomy?
A. Sickle cell disease
B. Warm antibody auto-immune hemolytic anemia
D. Idiopathic thrombocytopenic purpura
Treatment for thalassemia involves red blood cell transfusions to maintain a hemoglobin level of >9 mg/dL, along with intensive parenteral chelation therapy with deferoxamine. Splenectomy is indicated for patients with excessive transfusion requirements (>200 mL/kg per year), discomfort due to splenomegaly, or painful splenic infarction. Careful assessment of the risk:benefit ratio is essential. Thalassemia patients are at high risk for pulmonary hypertension after splenectomy; the precise etiology of this sequela is under investigation. The increase in infectious complications is likely to be due to a coexisting immune deficiency, in large part brought about by iron overload, which may be associated both with the thalassemia itself and with transfusions. The disproportionately high rate of overwhelming postsplenectomy infection in thalassemia patients has led some investigators to consider partial splenectomy in children; some success in reducing mortality has been reported. However, splenectomy should be delayed until after the age of 4 years unless it is absolutely necessary. (See Schwartz 9th ed., p 1252.)
5. What percentage of patients referred for surgery for idiopathic thrombocytopenic purpura will have a permanent response (i.e., not need further steroids)?
The usual first line of therapy [for ITP] is oral prednisone at a dosage of 1.0 to 1.5 mg/kg per day. No consensus exists as to the optimal duration of steroid therapy, but most responses occur within the first 3 weeks. Response rates range from 50 to 75%, but relapses are common. IV immunoglobulin, given at 1.0 g/kg per day for 2 to 3 days, is indicated for internal bleeding when platelet counts remain 5000/mm3or when extensive purpura exists. IV immunoglobulin is thought to impair clearance of immunoglobulin G–coated platelets by competing for binding to tissue macrophage receptors. An immediate response is common but a sustained remission is not. Splenectomy is indicated for failure of medical therapy, for prolonged use of steroids with undesirable effects, or for most cases of first relapse.
Prolonged use of steroids can be defined in various ways, but a persistent need for more than 10 to 20 mg/d for 3 to 6 months to maintain a platelet count of >30,000/mm3 generally prompts referral for splenectomy. Splenectomy provides a permanent response without subsequent need for steroids in 75 to 85% of patients. (See Schwartz 9th ed., p 1253, and Table 34-1.)
TABLE 34-1 Platelet response after laparoscopic splenectomy for idiopathic thrombocytopenic purpura
6. A patient who presents with altered mental status, thrombocytopenia, and lower extremity petechia will most likely benefit from
C. Plasma exchange
TTP occurs in approximately 3.7 individuals per million, but this rare disorder’s dramatic clinical sequelae and favorable response to early therapy demand an understanding of its clinical presentation to ensure an early diagnosis. Clinical features of the disorder include petechiae, fever, neurologic symptoms, renal failure, and, infrequently, cardiac symptoms such as heart failure or arrhythmias. Petechial hemorrhages in the lower extremities are the most common presenting sign. Along with fever, patients may experience flulike symptoms, malaise, or fatigue. Neurologic changes range from generalized headaches to altered mental status, seizures, and even coma. Generally, however, the mere presence of petechiae and thrombocytopenia are sufficient to lead to the diagnosis of TTP and consideration of treatment. The diagnosis is confirmed by the peripheral blood smear, which shows schistocytes, nucleated red blood cells, and basophilic stippling. Although other conditions such as tight aortic stenosis or prosthetic valves may lead to the presence of schistocytes, these conditions generally are not accompanied by thrombocytopenia. (See Schwartz 9th ed., p 1253.)
7. Which of the following is a common indication for splenectomy in a patient with agnogenic myeloid metaplasia?
A. Early satiety
D. Splenic rupture
The myeloproliferative disorders are characterized by an abnormal growth of cell lines in the bone marrow. They include chronic myeloid leukemia, acute myeloid leukemia, chronic myelomonocytic leukemia, essential thrombocythemia, polycythemia vera, and myelofibrosis, also known as agnogenic myeloid metaplasia. The common underlying problem leading to splenectomy in these disorders is symptomatic splenomegaly. Symptoms due to splenomegaly consist of early satiety, poor gastric emptying, heaviness or pain in the left upper quadrant, and even diarrhea. Hypersplenism, when it occurs in these conditions, usually is associated with splenomegaly. Splenectomy performed in the setting of the myeloproliferative disorders is generally for treatment of the pain, early satiety, and other symptoms of splenomegaly.
The term myelofibrosis may be used to describe either the generic condition of fibrosis of the bone marrow (which may be associated with a number of benign and malignant disorders) or a specific, chronic, malignant hematologic disease associated with splenomegaly, the presence of red blood cell and white blood cell progenitors in the bloodstream, marrow fibrosis, and extramedullary hematopoiesis, otherwise known as agnogenic myeloid metaplasia (AMM). (See Schwartz 9th ed., p 1254.)
8. The treatment of choice in an otherwise healthy 22-year-old patient with a large, sepatated splenic abscess is
A. Antibiotic therapy only
B. Antibiotics + percutaneous drainage
C. Antibiotics + partial splenectomy
D. Antibiotics + splenectomy
Abscesses of the spleen are uncommon, with an incidence of 0.14 to 0.7% based on autopsy findings. They occur more frequently in tropical locations, where they are associated with thrombosed splenic vessels and infarction in patients with sickle cell anemia. Five distinct mechanisms of splenic abscess formation have been described: (a) hematogenous infection; (b) contiguous infection; (c) hemoglobinopathy; (d) immunosuppression, including HIV infection and chemotherapy; and (e) trauma. Presentation frequently is delayed, with most patients enduring symptoms for 16 to 22 days before diagnosis. Clinical manifestations include fever, left upper quadrant pain, leukocytosis, and splenomegaly in about one third of patients. The diagnosis is confirmed by ultrasound or CT scan, which has a 95% sensitivity and specificity. Upon discovery of a splenic abscess, broad-spectrum antibiotics should be started, with adjustment to more specific therapy based on culture results and continuation of treatment for 14 days. Splenectomy is the operation of choice, but percutaneous and open drainage are options for patients who cannot tolerate splenectomy. Percutaneous drainage is successful for patients with unilocular disease. (See Schwartz 9th ed., p 1255.)
9. Patients undergoing elective splenectomy should receive vaccinations against Streptococcus pneumoniae, H. influenzae type B, and meningococcus
A. 2-4 weeks before surgery
B. The day of surgery
C. 1 week after surgery
D. 1 month after surgery
Splenectomy imparts a small (1 to 5%) but definite lifetime risk of fulminant, potentially life-threatening infection. Therefore, when elective splenectomy is planned, vaccinations against encapsulated bacteria should be given at least 2 weeks before surgery to protect against such infection. The most common bacteria to cause serious infections in asplenic hosts are Streptococcus pneumoniae, H. influenzae type B, and meningococcus. Vaccinations against these bacteria are available and should be given. If the spleen is removed emergently (e.g., for trauma), vaccinations should be given as soon as possible after surgery, with at least 1 to 2 days allowed for recovery. After splenectomy, annual influenza immunization is advisable. Splenectomized patients should be well educated regarding the potential consequences of overwhelming postsplenectomy infection and should be encouraged to maintain documentation of their own immunization status. (See Schwartz 9th ed., p 1256.)
10. The most common early complication after open splenectomy is
C. Subphrenic abscess
D. Wound infection
Left lower lobe atelectasis is the most common complication after OS; pleural effusion and pneumonia also can occur. Hemorrhage can occur intraoperatively or postoperatively, presenting as subphrenic hematoma. Transfusions have become less common since the advent of LS, although the indication for operation influences the likelihood of transfusion as well. Subphrenic abscess and wound infection are among the perioperative infectious complications. (See Schwartz 9th ed., p 1260.)