Kala-Azar

Visceral Leishmaniasis (Kala-Azar). This is a chronic febrile disease caused by Leishmania donovani, transmitted by the bite of a sandfly (Phlebotomus). The visceral form results in emaciation, anemia, hepatomegaly and splenomegaly and is often fatal. It is prevalent among children and young adults in Mediterranean countries, eastern India and northern China. Leisliman-Donovan bodies, two to four microns in diameter, are found in macrophages in the liver and spleen. In the sandfly the flagellate organism (leptomonad form), which develops in the gut, migrates to the buccal cavity and is discharged through feeding. The sandfly becomes infected by ingesting the leish­manian forms described above.The incubation period of the disease is from six weeks to several months. A high fever for several weeks alternates with longer periods of remission. By the end of six months, the liver and spleen are markedly enlarged. The regional lymph nodes are appreciably enlarged, only if cutaneous leishmaniasis (so-called Oriental sore) de­velops. The bone marrow is hyperplastic. The intestinal villi may be enlarged by foci of the disease.

Infectious Splenomegaly

Hyperplasia of the spleen with infectious disease may be acute or chronic. Acute hyperplastic splenitis (acute splenic tumor) occurs with septicemia or in the presence of severe pyogenic infections. The spleen is enlarged and soft. The follicles may be enlarged and phagocytosis is active.
In protozoan and bacterial diseases that affect the reticuloendothelial system, such as visceral leishmaniasis, African trypanosomiasis, malaria, etc., the enlarged spleen acts as a clearing house for phagocytosis and is engorged with parasites and para­sitized macrophages.With chronic splenic hyperplasia found in advanced stages of syphilis, tuberculosis, brucellosis, malaria, leishmaniasis, trypanosomiasis, schistosomiasis and infectious ar­thritis (Felty's syndrome) there is increase of both the lymphoid and connective tissue elements. The capsule is often thick and opaque. There may be endothelial hyper­plasia and hyalin changes in the arterioles. The infectious diseases of the spleen and reticuloendothelial system are:

(1)Infectious mono nucleosis
(2)Brucellosis
(3)Sarcoidosis
(4)Visceral leish maniasis
(5)Malaria
(6)Bartonellosis
(7) Histoplasmosis
(8)Toxoplasmosis
(9)Schistosomiasis
(10) Trypanosomiasis(11)Relapsing fever
(12)Melioidosis and Glanders

Congestive Splenomegaly

Passive congestion of the spleen occurs with cardiac decompensation. The spleen is enlarged and firm because of the retention of blood in the pulp sinusoids.In Banti's syndrome more severe congestive splenomegaly occurs with portal hyper­tension. The retained blood dilates the sinusoids and thickens their walls. Increased blood destruction leads to anemia and leukopenia. The condition may result from hepatic cirrhosis or from pressure on or thrombosis in the portal or splenic veins. These are associated with gastric hemorrhages. In such cases anemia is relieved by splenectomy, but the gastrointestinal hem­orrhages may recur.