Diseases of the Spleen

Diseases of the Spleen, Enlargement of the Spleen, Rupture of the spleen, hematologic disorders for which splenectomy is potentially therapeutic, heroditary spherocytosis, thalassemia, sickle cell anemia, idiopathic thrombocytopenic purpura, secondary hypersplenism, myeloid metaplasia, lymphoma, accessory spleen, splenic artery aneurysm, splenic cysts and tumors, splenic abscess



Splenic Abscess

Splenic abscesses may be due to trauma, thrombotic or embolic infarction, or the hematogenous spread of in¬fection. Multiple abscesses most frequently represent fungal infections in patients with immune deficiencies. Although most patients have fever, leukocytosis, and usually a mass or tenderness in the left upper quadrant, the clinical diagnosis of a splenic abscess may be very difficult, and a missed diagnosis can have fatal consequences.

The plain radiographic findings of splenic abscess are variable and nonspecific, and include elevation of the left hemidiaphragm with sympathetic changes at the base of the left lung, splenomegaly, and extraluminal gas collections in the left upper quadrant. Radionuclide scanning with 99mTc sulfur colloid shows a splenic abscess as a nonspecific focai defect. Scanning with 67Ga citrate may demonstrate an area of focal radionuclide accumulation, but this study may take up to 3 days of vital time to complete; in addition, some neoplasms (especially lymphoma) may also concentrate the gallium.

Ultrasound and CT are the imaging modalities of choice in the diagnosis of splenic abscesses. The typical sonographic appearance of an abscess is an irregular, poorly defined anechoic mass with varying internal echogenicity and decreased acoustic transmission. Increased echogenicity and distal acoustic shadowing indicate gas within the abscess. Computed tomography shows an abscess as a hypodense or cystic lesion that lacks a well-defined wall and does not enhance following the intravenous administration of contrast material. A central core of higher density within an abscess may produce a target appearance.

where is the spleen located · diseases of the spleen · roundedfoci with calcific rims splenic artery aneurysms ·

Splenic Cysts and Tumors

Splenic cysts may be congenital, parasitic (primarily echinococcal), or post-traumatic, reflecting the final stage in the evolution of a splenic hematoma. Splenic cysts are variable in size and, when large, can produce discrete soft tissue densities in the left upper quadrant and displace adjacent contrast-filled organs. Calcification most frequently occurs in echinococcal cysts, which are often multiple and tend to have thicker and coarser rims of peripheral calcification than congenital or post-traumatic cysts.

Because of its noninvasive nature, ultrasound is often the initial modality in evaluating a splenic cyst presenting as gross splenomegaly or a left upper quadrant mass. A splenic cyst appears as a sonolucent mass with a thin wall, good posterior enhancement, and no internal echoes. Computed tomography demonstrates splenic cysts as well-circumscribed, spherical lesions that are sharply demarcated from the adjacent splenic parenchyma and contain fluid of water density. Extensive calcification may be seen within the walls of echinococcal cysts. Radionuclide spleen scans demonstrate a splenic cyst as a cold area within the spleen, but this modality cannot differentiate between a cystic and a solid lesion.

The spleen is often affected in patients with lymphoma. In most cases, CT demonstrates splenomegaly with or without focal low-density nodules in the parenchyma (see Figure 29.2). If there is homogeneous lym-phomatous infiltration of the spleen without enlargement, the CT appearance can be normal. In some series, an even more common cause of focal low-density nodules in the spleen is metastatic disease in patients with carcinoma or sarcoma originating in other areas. Malignant melanoma is often the tumor of origin, but metastases can also arise from tumors of the lung, breast, and a variety of other organs. Typical CT findings consist of one or more low-density nodules; metastatic nodules with areas of necrosis and liquefaction can contain irregularly shaped regions that approach water density.

difference between cancer lump and cyst on spleen · difference between tumors and cysts on spleen · melanoma and low density splenic lesions ·

Splenic Artery Aneurysm

Calcification within the media of the splenic artery is extremely common and produces a characteristic tortuous, corkscrew appearance. When viewed end-on, splenic artery calcification appears as a thin-walled ring. A similar, though larger circular pattern or bizarre configuration of calcification in the left upper quadrant can be due to a saccular aneurysm of the splenic artery. A definitive diagnosis of splenic artery aneurysm can be made by arteriography.

splenic artery aneurysm · saccular aneurysm in spleen · splenic artery aneurysms ·

Accessory Spleen

Accessory spleens occur in 10 to 30 percent of the population as a result of the failure of fusion during embryonic life of some of the multiple buds of splenic tissue in the dorsal mesogastrium. Most accessory spleens are found in the hilar region, where they may be completely isolated from the spleen or connected to it by thin bands of tissue. These nodules of normal splenic tissue are often multiple and vary from a few millimeters to several centimeters in diameter. Most are small, are of no clinical significance, and are only detected on CT performed for an unrelated condition.

Occasionally, a large or atypically located accessory spleen may mimic a tumor on excretory urography or ultrasound. The CT finding of a round to oval mass, especially if near the splenic hilum, that has the same attenuation as a normal spleen both before and after the injection of intravenous contrast material is virtually pathognomonic of an accessory spleen. If the CT diagnosis is equivocal, a 99mTc sulfur colloid radionuclide scan can demonstrate isotope activity in the splenic tissue.

Following splenectomy, an accessory spleen may enlarge dramatically and present as a left upper quadrant mass. It may even cause a recurrence of clinical symptoms in a patient whose splenectomy was performed for a hematologic disorder that resulted in hyper-splenism.

accessory spleen complications ·

Lymphoma

Lymphoma arises in the lymph nodes or in the lymphoid tissue of parenchymal organs such as the gastrointestinal tract, spleen, lung, or skin. Ninety percent of cases of Hodgkin’s disease originate in the lymph nodes; 10 percent are of extranodal origin. In contrast parenchymal organs are more often involved in non-Hodgkin’s lymphomas; about 40 percent of these lymphomas are of extranodal origin.

The spleen is often affected in patients with lymphoma of both the Hodgkin’s and non-Hodgkin’s types. The best imaging modality is CT, which most commonly demonstrates splenomegaly with or without focal low-density nodules in the parenchyma. However, if there is homogeneous lymphomatous infiltration of the spleen without enlargement, the CT appearance may be normal.

The manifestations of lymphoma involving the gastrointestinal tract are discussed in Chapters 22, 23, and 24. Intrathoracic lymphoma is described in Chapter 10.

Once the diagnosis of lymphoma is made, it is essential to determine the status of the abdominal and pelvic lymph nodes. This is necessary for both the initial staging and treatment planning and for assessing the efficacy of treatment and detecting tumor recurrence.

There is controversy about the best radiographic approach for the staging of a patient with known lymphoma. Although lymphography has long been the most accurate examination for demonstrating lymphomatous involvement of abdominal and pelvic lymph nodes, non-invasive cross-sectional imaging techniques (CT and ultrasound) are now considered by many to be the diagnostic methods of choice. Unlike CT and ultrasound, which rely primarily on an increase in node size as a criterion for determining tumor involvement, lymphography can detect microscopic tumor foci and alterations in architecture within normal-sized nodes. It also can distinguish large nodes that contain tumor from similarly enlarged nodes that demonstrate only benign reactive changes. Following formal staging procedures, postlymphography abdominal radiographs can provide an inexpensive and accurate means of assessing therapeutic efficacy and detecting relapse. However, the lymph nodes in the upper para-aortic, retrocrural, renal hilum, splenic hilum, porta hepatis, and mesenteric areas cannot be adequately examined by lymphography and require CT or ultrasound. Computed tomography is also useful in delineating the exact extent of the tumor mass. It often shows that the abnormality demonstrated with lymphography is only the tip of the iceberg and that more extensive disease, possibly important in planning radiation treatment, is actually present. Computed tomography can also be used to follow the response to treatment, especially since there may be insufficient residual contrast on postlymphography abdominal films to make a diagnosis.
In practice, CT is generally the first procedure employed in staging patients with lymphoma, especially those with non-Hodgkin’s lymphoma that tends to produce bulky masses in the mesenteric and high retrocrural areas, where the contrast material used in lymphography does not reach. An abnormal CT scan eliminates the need for the more invasive lymphography; a normal CT scan obtained at 2-cm intervals can exclude retroperitoneal adenopathy with high confidence. Lymphography is of value primarily in Hodgkin’s disease, which infrequently involves the mesenteric nodes, often does not produce bulky masses, and may cause alterations of internal architecture only (which cannot be detected with CT) in normal-sized nodes. Lymphography is also indicated when CT is equivocal because of either a lack of fat or gross motion artifact.

Myeloid Metaplasia

Myeloid metaplasia (myelofibrosis) is a hematologic disorder in which gradual replacement of the marrow by fibrosis produces a varying degree of anemia, and a leu-k’emoid blood picture. Exframedullary hematopoiesis causes massive splenomegaly and often hepatomegaly and may form tumorlike posterior mediastinal masses that can be seen on plain chest radiographs. Although the disease is most commonly idiopathic, a large percentage of patients have antecedent polycythemia vera. Myelofibrosis has also been reported in association with metastatic carcinoma, chemical poisoning, chronic infection, leukemia, and histiocytosis X.


About halfjhe patients with myelofibrosis have radiographic evidence of osteosclerosis. This primarily affects the/spine, ribs, and pelvis but also can involve the long bones and skull. The typical radiographic pattern is a widespread, diffuse increase in bone density (ground-glass appearance). In the ribs, uniform obliteration of fine trabecular margins results in striking sclerosis that simulates jail bars crossing the thorax. Patchy osteosclerosis in long bones may produce a mottled moth-eaten appearance with the uninvolved bone appearing relatively osteolytic, a pattern that can suggest a destructive malignant process. In the vertebrae and long bones, endosteal cortical thickening can encroach on the medullary cavities and eventually obliterate them. In the skull, myelofibrosis may present as a generalized increase in bone density, as scattered small, rounded, lucent lesions throughout the calvarium, or as a mixed pattern of lu-cency and sclerosis.

Although splenectomy does not alter the general course of myelofibrosis, the procedure is indicated for control of anemia and thrombocytopenia and for symptoms attributable to splenomegaly. In patients with esophagogastric varices, splenectomy alone will usually produce significant reduction in portal venous pressure and obviate the need for a concomitant splenorenal or portacaval shunt.

Idiopathic Thrombocytopenic Purpura Idiopathic Thrombocytopenic Purpura

Acute idiopathic thrombocytopenic purpura typically presents with the sudden onset of severe purpura 1 to 2 weeks after a sore throat or upper respiratory infection in an otherwise healthy child. In most patients, the disorder is self-limited and clears spontaneously within a few weeks. Unlike the acute form, chronic idiopathic thrombocytopenic purpura occurs primarily in young women and has an insidious onset with a relatively long history of easy bruising and menorrhagia. Because most patients with this condition have a circulating platelet autoantibody that develops without underlying disease or significant exposure to drugs, chronic idiopathic thrombocytopenic purpura is generally considered to be an autoimmune disorder.

The radiographic changes caused by either acute or chronic idiopathic thrombocytopenic purpura primarily involve the gastrointestinal tract. Hemorrhage into the small bowel produces characteristic uniform, regular thickening of mucosal folds in the affected intestinal segment. Splenomegaly is commonly present; splenectomy is often required to remove this important site of platelet destruction and major source of synthesis of platelet antibodies.

Sickle Cell Anemia

n sickle cell anemia, secondary bone marrow hyperplasia is accompanied by focal ischemia and infarction in multiple tissues due to sludging of the abnormally shaped red blood cells. The findings are similar to those in thalassemia, though in sickle cell disease the radio-graphic changes are less frequent and tend to be less severe.

In the spine, expansile pressure of the adjacent in-tervertebral disk produces characteristic biconcave indentations on both the superior and the inferior margins of the osteoporotic vertebral bodies (“fish” vertebrae). Another typical appearance is the development of localized steplike central depressions of multiple vertebral end plates. This is probably caused by circulatory stasis and ischemia, which retard growth in the central portion of the vertebral cartilaginous growth plate while the periphery of the growth plate, which has a different blood supply, continues to grow at a more normal rate.

Bone infarcts commonly occur in the long bones of patients with sickle cell anemia. In infants and children, these most frequently involve the small bones of the hands and feet, producing an irregular area of bone destruction with overlying periosteal calcification that may be indistinguishable from osteomyelitis. In older children and adults, a bone infarction may initially appear as an ill-defined lucent area that then becomes irregularly calcified. It may be associated with endosteal cortical thickening that encroaches on the marrow cavity and may even be separated from the original cortex by a thin lucent line to produce a bone-within-a-bone appearance. Ischemic necrosis of bone ends simulating Perthes’ disease is common and primarily involves the femoral or humeral heads. Bone infarctions affecting the epiphyseal cartilaginous plates often lead to growth disturbances of bone with shortening and epiphyseal deformity.

Acute osteomyelitis, often caused by Salmonella infection, is a common complication in sickle cell anemia. The resulting lytic destruction and periosteal reaction may be extensive, often involving the entire shaft and multiple bones. Radiographically, it may be impossible to distinguish between osteomyelitis and bone infarction without infection. Pathologic fractures are common.

The most common extraskeletal abnormality in sickle cell anemia is cardiomegaly due to the severe anemia and increased cardiac output. The heart has a globular “configuration reflecting enlargement of all thambers. Increased pulmonary blood flow produces engorgement of the pulmonary vessels, giving a plethoric appearance to the lungs. Pulmonary infarction, pulmonary edema and congestive failure, and pneumonia are frequent complications. In the kidney, a severe complication of sickle cell anemia is renal papillary necrosis, which is probably related to vessel obstruction within the papillae and may produce sinuses or cavity formation within one or more papillae.

Thalassemia

Thalassemia is a hereditary disorder of hemoglobin synthesis that causes a severe anemia and occurs predominantly in persons living about the Mediterranean, especially those of Italian or Greek descent. Thalassemia major (Cooley’s anemia) is a severe anemia of infants and children that produces more dramatic radiographic findings than any of the other childhood hemolytic anemias.

Extensive marrow hyperplasia, the result of ineffective erythropoiesis and rapid destruction of newly formed red blood cells, causes pronounced widening of the medullary spaces and thinning of the cortices. As the fine secondary trabeculae are resorbed, new bone is laid down on the surviving trabeculae, thickening them and producing a coarsened pattern. Normal modeling of long bones does not occur, because the expanding marrow flattens or eve. bulges the normally concave surfaces of the shaft. Focal collections of hyperplastic marrow cause localized radiolucencies that have the appearance of multiple osteolytic lesions.

In the skull, there is widening of the diploic space and thinning or complete obliteration of the outer table. When the hyperplastic marrow perforates or destroys the outer table, it proliferates under the invisible periosteum, and new bone spicules are laid down perpendicular to the inner table. This produces the characteristic hair-on-end appearance of vertical striations in a radial pattern. Marrow hyperplasia in the facial bones causes lack of pneumatization of the paranasal and mastoid sinuses that is usually not seen in any other anemia. Only the ethmoid sinuses are spared, because of the lack of marrow activity in the ethmoidal bone. Marrow overgrowth in the maxilla causes lateral displacement of the orbits and forward displacement of the upper central incisors, producing malocclusion and overbite and the “rodent fades” typical of thalassemia.

Extramedullary hematopoiesis is a compensatory mechanism of the reticuloendothelial system (liver, spleen, lymph nodes) in patients with prolonged erythrocyte deficiency due to the destruction of red blood cells or the inability of normal blood-forming organs to produce them. Paravertebral collections of hematopoietic tissue may appear on chest radiographs as single or multiple, smooth or tabulated, posterior mediastinal masses that are usually located at the lower thoracic levels.

thalassemia · hyperplastic bone marrow cooleys thalassemia · spinal radiolucencies associated anemia ·

Hereditary Spherocytosis

Hereditary spherocytosis is transmitted as an autosomal dominant trait and is the most common of the symptomatic familial hemolytic anemias. Because the anemia of hereditary spherocytosis is usually mild, bone changes are infrequent. With severe anemia, marrow hyperplasia can cause radiographic abnormalities that resemble those seen in thalassemia, except that they are of lesser degree and are usually limited to the skull (widening of the diploe, displacement and thinning of the outer table, hair-on-end appearance). Extramedullary erythropoiesis may produce paravertebral masses visible on chest radiographs. Excessive red blood cell destruction may lead to the formation of bilirubin stones that appear as lucent filling defects in the opacified gallbladder.

The sole therapy for hereditary spherocytosis is splenectomy, which usually has excellent results.

hereditary disease of the epleen ·