Enlargement of the spleen

The spleen is a meeting place of medicine and surgery. Table 53.1 summarises the many causes of enlargement of the organ. In connection with Table 53.1, the following points should be noted. In idiopathic thrombocytopenic purpura (ITP) the spleen, although somewhat enlarged, is seldom palpable. In psittacosis the enlarged spleen can be palpated regularly after the first few days of the illness; this enlargement is helpful to differentiate the condition from other varieties of pneu­monia. In portal hypertension the spleen is enlarged sec­ondary to hepatic cirrhosis or portal vein thrombosis (Chapter 52). As emphasised in Table 53.1, not all causes of splenomegaly will require splenectomy as part of their treatment. Elective splenectomy is required to treat haematological disease with medically uncontrolled hypersplenism, occasionally to stage and diagnose lymphoma, to treat splenic cysts, turnouts and abscesses, and for the relief of the discomfort associated with splenomegaly.

Idiopathic thrombocytopenic purpura

Purpura

Not all cases of purpura (purpura = porphyra (Greek) = purple) benefit from splenectomy. Purpura is defined as local haemorrhage into the skin. A history of purpura and evidence of it on examination should be sought before any surgical procedure is undertaken. Purpura may result from the following.

1. Increased capillary fragility, as in steroid-induced or Henoch—Schönlein purpura.

2. Defective platelets (thrombocytopathies), for example, after taking aspirin which inhibits thromboxane and prostaglandin, and reduces their property of making the platelet adhesive.

3. A reduced number of normal platelets (thrombocyto­penia). This can be a consequence of:

(a)  decreased platelet production by marrow megakaryocytes; for example, because of marrow suppression by cytotoxic chemotherapy or in aplastic anaemia;

(b)  increased platelet consumption, as seen in disseminated intravascular coagulation where the clotting cascade is triggered by septicaemia and platelets adhere to vascular endothelium, or in a large haemangioma in which platelets adhere to the abnormal endothelium;

(c)  increased platelet destruction by the spleen. This may be associated with autoimmune disease (e.g. systemic lupus erythematosus); with drug reactions, for example, to quinine; and with certain infections (e.g. mononucleosis). Alternatively, as in ITP, the platelet destruction may not be associated with any other condition;

(d)  increased splenic sequestration of platelets. This can be associated with any condition that produces gross splenic enlargement, e.g. portal hypertension.

Splenectomy may sometimes be helpful in purpura associated with splenic destruction or sequestration (points 3c and 3d, above). It is most reliably of use in the management of ITP

Aetiology of idiopathic thrombocytopenic purpura

In most cases the low platelet count in ITP is due to the development of antibodies which damage the patient’s own platelets (the normal blood platelet count is 250 x 109—400 x 109/litre). Transfused platelets have a short survival time after transfusion into patients with ITP, and the children born to mothers with ITP may have temporary maternal antibody-induced thrombocytopenia after birth.

Clinical features

Purpuric patches (ecchymoses) occur in the skin and mucous membranes which tend to be more prominent in dependent areas because of a higher, gravity aided, intravascular pres­sure. A tendency to spontaneous bleeding from mucous membranes (e.g. epistaxis), and in women to menorrhagia, and prolonged bleeding of minor wounds is common. Urinary and gastrointestinal haemorrhage and haemarthrosis are rare. Intracranial haemorrhage is also rare, but is the most frequent cause of death. Cutaneous ecchymoses may be found on examination and the tourniquet test is positive. The spleen is palpable in only 25 per cent of cases, and gross splenic enlargement suggests that the diagnosis is not ITP

Investigations

The bleeding time is increased, but the clotting and pro­thrombin times are normal. The platelet count in the peri­pheral blood film is reduced (usually less than 60 x 109/litre). Bone marrow biopsy reveals a plentiful supply of platelet-producing megakaryocytes (the giant cells of bone marrow give origin to blood platelets).

Treatment

The behaviour of the disease is different in children and adults. In children, the disease regresses spontaneously in 75 per cent of cases after one attack. Short courses of cortico­steroids or occasionally azothiaprine are usually followed by recovery. Splenectomy is reserved for severe cases which have relapsed or girls approaching menarche. In adults, the initial attack is less severe than in children, but the disease relapses and becomes more severe. Splenectomy is indicated where the ITP has persisted for more than 6—9 months.

Sixty per cent of patients can be regarded as cured, 20 per cent will be improved and 15 per cent or more will derive no benefit from the splenectomy. It is often, although not invariable, that a response to steroids predicts a good response to splenectomy. If severe bleeding has not been controlled by steroids, fresh blood transfusion or transfusion with platelet concentrates before operation is often necessary. Splenec­tomy is contraindicated during the acute phase of ITP; the disease should first be controlled by medical treatment. Occasionally, in resistant cases, the antiplatelet immune response can temporarily be blocked by IgG transfusion to saturate the splenic Fe binding sites and reduce platelet destruction to allow the platelet count to rise at the time of surgery.

Splenectomy for other causes of thrombocytopenic purpura

Occasionally, splenectomy is of benefit in thrombocytopenia due to systemic lupus erythematosus and in hypersplenism; also in purpura associated with points 3c and 3d above.