Essential thrombocythaemia: abdominal manifestations

Clinical History

A young female patient with unremarkable medical history sought attention at the emergency department due to severe malaise and bilateral lower extremity swelling for two weeks. Physical examination revealed enlarged painless spleen without palpable superficial lymphadenopathies.
Laboratory assays disclosed microcytic anaemia (haemoglobin 6.2 g/dL, mean corpuscular volume 65 fL) and increased platelet count (950.000/mmc).

Imaging Findings

Initially colour Doppler ultrasound (not shown) excluded venous thrombosis in the legs.
Requested to assess splenic enlargement, inferior vena cava, deep lymph nodes or masses, multidetector CT (Fig. 1) showed patent portal and superior mesenteric veins, homogeneous splenomegaly with a limited infarct, absent splenic vein, extensive perisplenic, perigastric and periduodenal venous collaterals, and gastric wall varices.
Bone marrow biopsy (megakaryocytic hyperplasia without blasts) diagnosed essential thrombocythaemia with positive Janus-Kinase2 gene mutation.
One year later, splenectomy was performed to relieve tender splenomegaly. Eighteen months after surgery, the patient complained of recurrent epigastric pain with persistently elevated (600.000/mmc) platelet count. Ultrasound (Fig. 2) and CT (Fig. 3) showed massive acute thrombosis of portomesenteric system and intrahepatic portal branches with transient geographic attenuation differences in the liver parenchyma, signs of cavernomatous portal transformation and minimal ascites.
After anticoagulation, repeated colour Doppler (Fig. 4) confirmed restored patency of the portal vein with normal hepatopetal flow, and the patient started alfa-interferon therapy.

Discussion

Uncommon in the general population, essential thrombocythemia (ET) is the commonest (0.77-2.53/100.000 estimated annual incidence) clonal myeloproliferative disorder, which occurs in adults (with a 2:1 female predominance) and is characterized by sustained platelet count elevation (over 600.000/mmc) and increased megakaryocytes at bone marrow biopsy. Janus-Kinase (JAK2) gene mutation is present in approximately half of patients [1-3]. Almost 30% of patients are asymptomatic, others suffer from vasomotor symptoms (headache, dizziness, visual changes, paresthesias, erythromelalgia). Present in 20-30% of cases, splenomegaly is an independent source of morbidity and detriment to quality of life causing bloating, early satiety, painful episodes of splenic infarction, or even portal hypertension. Required for refractory symptoms or splenic sequestration exacerbating cytopenias, splenectomy does not modify the life expectancy. Transformation into myelofibrosis, myelodysplasia or acute leukemia represents a rare, late event [1-5].
Despite a generally indolent course, ET may be complicated by acute vascular events which represent the leading causes of morbidity and mortality. The rare hemorrhages mostly affect patients with very high platelet counts. Conversely, thrombosis involving the cerebrovascular, coronary and peripheral circulation may manifest at diagnosis or in the preclinical phase (even at relatively low platelet counts) with an overall 6.6% patients/year risk. Particularly after splenectomy, spleno-portal-mesenteric system thrombosis (SPM-T) represents a well-recognized (4% prevalence) complication of ET. Manifesting with nonspecific abdominal pain, SPM-T has a non-negligible mortality and should be promptly recognized and treated with low-molecular-weight heparins followed by long-term anticoagulation. SPM-T may lead to portal hypertension, digestive bleeding or hypersplenism. Haematopoietic stem cell disorders represent the leading (30-40% of cases) cause of splanchnic vein thrombosis [4-6].
Colour Doppler ultrasound may recognize SPM-T with variable echogenicity and absent flow within the thrombosed segment. At CT, acute thrombus in the portal, superior mesenteric, or splenic vein appears as intraluminal hyperattenuation with possible venous enlargement on precontrast images, with corresponding filling defect partially or totally occluding the vessel lumen after intravenous contrast. Arterial-phase transient attenuating differences in the liver parenchyma are commonly noted as accessory signs. Features of portal hypertension including portosystemic collaterals may be present [7-9].
Patients with ET are stratified into high, intermediate and low risk according to age, more or less elevated platelet count, other cardiovascular risk factors or thrombophilia, and history of bleeding or thrombosis. According to risk class, treatment of ET may include antiaggregation (aspirin), platelet-lowering therapies (hydroxyurea, anagrelide and alfa-interferon) or cytoreductive drugs [1, 2].

Differential Diagnosis List

Final Diagnosis

Essential thrombocythaemia with portal hypertension. Portomesenteric venous thrombosis after splenectomy.

URL:	https://www.eurorad.org/case/12715
DOI:	10.1594/EURORAD/CASE.12715
ISSN:	1563-4086