History review The patient, male, 56 years old, was admitted to the hospital with seven days of gradually increasing abdominal pain with nausea and belching. He had a history of splenectomy after spleen injury, hyperlipidemia, obesity, and facial nerve palsy. an abdominal CT in 2007 had shown a small nodule resembling a parasplenium in the patient’s abdomen, with no remaining positive findings. Recently, the patient was taking orlistat for weight loss and had been taking the drug for 10 days before the onset of symptoms. Physical examination: stable respiration, normal temperature, abdominal tenderness, epigastric and left iliac fossa area tenderness, negative rectal finger examination. Laboratory tests: neutrophils and CRP were high, liver and kidney function, amylase and lipase were normal. The patient’s inflammatory markers continued to rise while awaiting gastrointestinal endoscopy, and the abdominal pain did not resolve despite the administration of reasonable antispasmodic drugs and proton pump inhibitors. The patient subsequently underwent CT enhancement and reconstruction of the abdomen. Diagnosis CT images showed non-occlusive acute portal and mesenteric vein thrombosis (white arrow shown below the thrombus). The patient’s diagnosis of acute portal and superior mesenteric vein thrombosis is to be considered in the clinical setting of unexplained abdominal pain lasting more than 24 hours. Portal vein thrombosis is similar to other causes of abdominal pain and its presentation is not characteristic. It is often clinically divided into acute portal thrombosis and chronic portal thrombosis, which is highly underdiagnosed. The disease is relatively rare, but there are no data on its incidence in the general population, which may be related to its atypical presentation and diagnostic difficulties. A multicenter study in Sweden showed an incidence of approximately 3.7/100,000. Acute portal thrombosis usually presents with sudden or progressive abdominal pain, which may be complicated by fever, nausea, vomiting, or diarrhea. Physical examination may reveal an abdominal bulge if subacute intestinal obstruction is present, but no other features of intestinal obstruction are present. There is usually no myalgias unless there is an inflammatory lesion or mesenteric infarction. Symptoms may be atypical in non-occlusive portal thrombosis, almost asymptomatic in chronic portal thrombosis, or biliary symptoms due to portal-associated biliary disease (see Complications section). The diagnosis should be highly suspected when a patient presents with these symptoms and risk factors for portal thrombosis are present. Local risk factors are cirrhosis, primary or secondary hepatocellular carcinoma, inflammatory diseases of the abdominal cavity including pancreatitis and factors of medical origin (fine needle aspiration biopsy of abdominal masses). The incidence of portal vein thrombosis is highest in patients with cirrhosis or hepatocellular carcinoma. Post splenectomy is another important risk factor. Portal thrombosis is a potential and often underestimated hazard after splenectomy, with a prevalence of about 3.3%, with some studies even reporting up to 55%. It often occurs within two weeks after surgery and is presumed to be related to the residual splenic veins that remain attached to the portal vein after surgery. Systemic risk factors include tumors, myeloproliferative disorders, obesity, pregnancy, and other causes of hypercoagulable states. The presence of all these factors should sound the alarm for persistent, non-characteristic abdominal pain. The systemic inflammatory response is more pronounced in acute portal thrombosis, manifested by fever and elevated protein in the acute phase. The patient’s liver function is usually normal unless liver disease is also present. Coagulation factor levels may be decreased and D-D dimer levels are usually elevated, although there is wide individual variation. Examination Examination measures should focus on clarifying the timing and triggers of thrombus formation and the presence of local triggers such as cirrhosis, tumors, and acute inflammation. As mentioned above, abdominal pain, fever, and gastrointestinal symptoms may suggest acute portal vein embolism, yet chronic individuals may be asymptomatic or present with biliary tract disease. When patients with acute portal vein thrombosis present with high fever and chills, complications of infectious thrombophlebitis should be considered and prompt blood cultures are required. There is an association between portal thrombosis and sepsis, especially in children, and abdominal sepsis is considered a risk factor for portal thrombosis. In conclusion, a careful history and detailed examination of the patient is needed to identify the cause of thrombosis. Abdominal imaging, such as enhanced CT, can help to clarify the diagnosis, distinguish acute from chronic, and identify potential local causes and complications. Dynamic imaging such as Doppler ultrasound and magnetic resonance angiography can also help in the diagnosis. The manifestations that support chronic portal thrombosis are well-developed cavernous angiomas or the formation of portal-portal and portal-body vein collateral circulation. Once acute mesenteric infarction due to occlusive portal thrombosis is identified, urgent surgical exploration is required. Coagulation and other hematologic tests may also help to identify the cause of thrombosis. Hematologic disorders that form portal thrombosis include deficiencies of the coagulation factor inhibitors protein C and protein S, mutations in the coagulation factor gene, antithrombin deficiency, and the presence of antiphospholipid antibodies, including lupus anticoagulants. Screening for thrombotic tendencies is still controversial because of its high cost and its general lack of impact on the anticoagulation process. In addition, chronic liver disease may lead to decreased levels of protein C, protein S and antithrombin. As for the pathophysiological alterations resulting from functional defects are currently unknown. The overcompensation of the organism that occurs in paroxysmal sleep hemoglobinuria may produce systemic complications such as intravascular hemolysis and platelet activation, all of which may contribute to portal thrombosis and other thrombotic disorders. Another etiology of thrombophilia may be myeloproliferative disease and is sometimes the sole manifestation of the latter. JAK2 V617F has been reported to be positive in 5%-35% of patients with portal thrombosis, and functional mutations in the JAK2 gene have been associated with several myeloproliferative disorders. Thus, screening for JAK2 is recommended in patients with unexplained, extremely severe portal thrombosis. Some experts also recommend testing for this gene in all patients with portal thrombosis, but it is difficult to implement clinically. Treatment Anticoagulation is the main principle of treatment, although the optimal timing of treatment has not been determined. The American Association for the Study of Liver Diseases recommends that patients with acute portal thrombosis should be given anticoagulation for at least 3 months, or longer if the patient has other risk factors for thrombosis. Anticoagulation can be challenging for patients with cirrhosis because it increases their risk of gastrointestinal bleeding. It has been recommended that for such patients, the application of low molecular heparin may be more beneficial than vitamin K antagonists, especially if the patient already has coagulation abnormalities prior to treatment, but the evidence for this is insufficient. One thing is certain, patients with liver disease need to undergo gastroscopy to assess varices before receiving anticoagulation. If signs of infection are present, antibiotics should be given immediately, as portal phlebitis is potentially fatal. Broad-spectrum antibiotics covering gram-negative bacilli, anaerobes, and aerobes are recommended until blood cultures are available. Treatment of chronic portal thrombosis (i.e., portal vein cavernous hemangioma) includes prevention of recurrent thrombosis (consider long-term anticoagulant use), bleeding from ruptured varices, and treatment of portal-associated biliary tract disease. Screening and treatment of varicose veins in such patients is essential. Interventions such as portal shunts are necessary in patients with biliary disease who present with jaundice or recurrent biliary symptoms. In addition, therapeutic measures for primary conditions such as myeloproliferative disorders are necessary. Complications Portal thrombosis can be fatal in severe cases and may end in nonspecific abdominal discomfort or life-threatening ruptured variceal bleeding secondary to portal hypertension, or ultimately death from mesenteric ischemia or infarction. Except for very severe portal thrombosis, the patient’s liver function is usually at normal levels and may be associated with a compensatory increase in hepatic blood flow. However, in patients with cirrhosis, portal thrombosis may exacerbate the disease and make liver transplantation more difficult. Occult chronic portal thrombosis may contribute to conditions such as portal hypertension, which in developing countries is associated with portal thrombosis in about 40% of cases. Results Immediately after the CT findings were available, a hematology consultation was invited and the patient was treated with anticoagulation with low-dose small molecule heparin and warfarin according to the hematology opinion. The warfarin dose was adjusted according to the international normalized ratio (INR) to keep it between 2 and 3. The patient was discharged after gradual resolution of symptoms and was followed up regularly in the gastroenterology and hematology clinics. Later, the patient underwent a comprehensive screening for thrombotic predisposition and was negative for the JAK2 gene mutation, but had a factor V Leiden mutation. It is not known whether the patient’s current episode was related to orlistat or just a coincidence, and orlistat was discontinued as a safety precaution. After 3 months of anticoagulation, the patient had a repeat CT and the thrombus in the portal and superior mesenteric veins had dissolved. During the treatment period, the patient suffered non-vascular necrosis of the right ankle due to a traumatic injury, which limited his mobility, and coupled with his own obesity, after consideration, he was instructed to continue warfarin therapy and come back to the hospital for a review in 3 months.