Acute occlusive aortic thrombosis is a rare condition that is lethal if not diagnosed. Nonocclusive aortic thrombosis is more common and occurs in the setting of aneurysmal disease, dissection, or severe atherosclerotic disease.^4–6 Other conditions associated with aortic thrombotic disease include diabetes, cardiomyopathy, blunt and penetrating abdominal trauma,^7–9 spinal surgery, polycythemia,⁴ thrombocytosis,⁴ nephrotic syndrome, exogenous estrogens, the classic hypercoagulable conditions (protein C and S deficiency, factor V Leiden deficiency, antithrombin III deficiency), malignancy,⁵ use of certain chemotherapeutic agents,¹⁰ antiphospholipid antibody syndrome,⁵ and previous aortic grafting.⁴ Because of the large diameter of the aorta, emboli (typically from the left ventricle) rarely lead to aortic occlusion. Patients with an acute thrombotic event typically present with symptoms of lower extremity ischemia: bilateral lower extremity pulselessness, pallor, pain, paresthesias, and possible paralysis.^4,11 Mesenteric ischemia may also be present. If the occlusion involves the artery of Adamkowicz, patients may also develop spinal cord infarction.¹² Signs of the anterior spinal artery syndrome include paralysis and loss of sensation to both light touch and pinprick, but preservation of vibratory sensation and proprioception.¹² In cases of chronic occlusion caused by atherosclerotic disease, there is time for the formation of collateral circulation to the distal structures.⁶ Leriche syndrome results from chronic obstruction of the distal aorta leading to chronic ischemia of the pelvis and lower extremities. Classically described in men, the triad of symptoms includes claudication, abnormal or absent lower extremity pulses, and erectile dysfunction.^13,14 Acute ischemia from aortic occlusive disease warrants emergent consultation with a vascular surgeon. Patients will likely need emergent laparotomy for thrombectomy or embolectomy, often with aortic bypass.⁴ The cause of the thrombus and other associated conditions (eg, aneurysm or dissection) determine the vascular surgery approach to treatment. In one series of 14 patients, mortality after surgery was 14%.⁴ Overall mortality in a retrospective case series of 48 patients by Babu and colleagues¹⁵ was 52%. Dossa and colleagues¹¹ reported a 40-year experience of 46 patients with an in-hospital mortality of 35%. The urgency of surgical consultation and intervention in patients with subacute or chronic occlusive disease is determined by the severity and progression of symptoms. Most patients will be admitted for observation, often with anticoagulant or antiplatelet agents.

Renal artery thrombosis is also a rare condition, most commonly seen in individuals aged 30 to 50 years.¹⁶ Similar to the other thromboses, the most common cause involves the development of a clot in situ on established atherosclerotic lesions. Thrombosis is also a known complication after renal transplantation because of both the surgical anastomoses, and immunosuppressive drugs being prothrombotic.¹⁷ Intra-aortic catheter or balloon pump placement,¹⁸ intravenous (IV) cocaine use,¹⁶ and renal angiography are also risk factors. The transplanted renal artery graft may also develop thrombosis secondary to surgical technique including torsion of the artery, kinking of the anastomosis, or dissection into the wall.¹⁹ Large case series have described rates of thrombosis after transplant between 0.5% and 3.5%.^19,20

Patients with acute renal artery occlusion typically present with flank pain, which may be associated with hypertension.^16,21 Accompanying symptoms may include nausea, vomiting, and upper abdominal pain on the affected side. Hematuria only occurs in between 30% and 50% of patients.¹⁶ An untreated occlusion of the renal artery leads to renal infarction. In the setting of renal infarct, the serum lactate dehydrogenase (LDH) is typically increased.²² Symptoms may be difficult to distinguish from renal colic. When renal colic is suspected, unenhanced computed tomography (CT) is the initial study. However, with severe symptoms and a CT without renal stones, the study can be repeated with intravenous contrast if renal artery thrombosis is a consideration. In the renal transplant recipient, duplex ultrasound is the preferred initial test.

Renal artery occlusion can also occur in the setting of trauma. Blunt trauma to the abdomen can lead to compression of the artery, as well as dissection and thrombosis.²³ Patients typically require surgical revascularization, and the timeliness of this intervention is linked with improved outcomes.^21,24,25

Nontraumatic thrombosis is treated with surgical revascularization or sometimes thrombolysis. Long-term sequelae of both traumatic and nontraumatic thromboses include renal artery stenosis, renal insufficiency or failure (more likely with bilateral disease), and hypertension.

Renal vein thrombosis may be either an acute or chronic process. Diagnosis depends on a high level of clinical suspicion, because the clinical findings mimic those of renal colic, renal artery occlusion, and pyelonephritis.²⁶ With acute thrombosis, patients experience flank pain often associated with nausea and vomiting. Hematuria and proteinuria may also be noted. In the setting of chronic thrombosis, the diagnosis may not be made until the development of complications such as impaired renal function or pulmonary embolism.²⁷ The left renal vein is affected more often than the right, but up to two-thirds of patients have bilateral thrombosis.²⁷

In contrast to occlusive arterial disease, renal vein thrombosis is also a disease of children and neonates. In the setting of severe volume depletion, dehydration, or sustained hypotension, blood flow is shunted from the renal vein, leading to sluggish flow that may eventually lead to the formation of a clot.^26–28 In children, a palpable mass in the flank may be present because of the enlargement of the kidney on the affected side.²⁸ The classic triad of symptoms in children includes a palpable mass, gross hematuria, and thrombocytopenia, although most patients do not have all three.²⁹

Thrombosis of the renal vein may occur as a result of the hypercoagulable, posttransplant, and postoperative states mentioned in previously. In addition, blunt trauma³⁰ and infection play roles in its development. The most common disease associated with the development of renal vein thrombosis is nephrotic syndrome.^27,28 Patients have direct loss of protein S and antithrombin III in their urine.²⁶ With excessive proteinuria, the liver is stimulated to produce new proteins, many of which are prothrombotic.²⁷

In patients receiving transplants, color Doppler sonography should be used to evaluate the flow in the graft. In all other patients, CT scan is the diagnostic study of choice. Intravenous contrast should be administered to visualize the vascular structures. In addition to visualizing the thrombus, the kidney on the affected side is typically engorged because of impaired venous drainage. Delayed images show a persistent enhancement from the contrast on CT scan because of the limited venous outflow.

Treatment of renal vein thrombosis is generally medical with systemic anticoagulation. Patients with, or at risk for, severe disease (eg, extensive clot progressing to the IVC, renal failure, bilateral disease, renal transplant) may be candidates for systemic or catheter-directed thrombolytic therapy.²⁷

The estimated lifetime risk of developing portal vein thrombosis in the general population is 1%.³¹ Up to 15% of cirrhotics develop this condition. It is rarely seen in patients without known liver disease or other risk factors that include adjacent inflammatory conditions (eg, pancreatitis, cholecystitis, diverticulitis, inflammatory bowel disease, appendicitis), malignancies (local or systemic), or hypercoagulable conditions (especially sepsis).^32,33 Mortality caused by portal vein thrombosis itself is low; however, these patients frequently have other significant comorbidities that combine to give them poor outcomes with this condition.

The mechanism by which cirrhosis leads to portal vein thrombosis is not clear. It is believed that decreased portal blood flow, periportal inflammation and fibrosis, and impaired production of anticoagulation factors lead to thrombosis.³⁴ Fifty percent of portal vein thrombosis in children and neonates is associated with an intra-abdominal infection, including umbilical infections in the very young.³⁴

With clot in the portal vein, the liver loses approximately two-thirds of its blood supply. In the acute phase, several compensatory mechanisms occur, including dilation of the hepatic artery to increase blood supply, the development of variceal collaterals between the portal and systemic venous systems, and collateral cavernoma formation. The cavernomas are a matted plexus of collateral vessels that form at the porta hepatis, often leading to secondary biliary effects including cholecystitis, biliary obstruction, and jaundice. Although collateral formation ultimately restores some degree of splanchnic circulation, hepatocytes often continue to be underperfused, leading to ongoing ischemia and cell death.^32,35

Acute portal vein thrombosis may present with abdominal pain (which may be localized in the right upper quadrant, but is frequently diffuse), nausea, and fever. Signs of intestinal ischemia (discussed later), which is a secondary effect of acute portal vein thrombosis, may also be present.^32,34 With chronic thrombosis, patients may remain clinically silent until the secondary effects of the thrombosis occur. These effects include worsening hepatic function, worsening portal hypertension, and hematemesis from esophageal varices.^32,34,36

Ultrasound with Doppler is the diagnostic modality of choice for portal vein thrombosis. The absence of flow within the lumen and, in some cases, the presence of a cavernoma identifies the disease. If suspicion exists for extension of the clot into the mesenteric venous system, CT with intravenous contrast is indicated to evaluate the vasculature and intestines.

Patients with portal vein thrombosis without complications of bleeding or intestinal ischemia are managed with systemic anticoagulation.^31,32,37 Empiric thrombolytic therapy in cases of acute thrombosis may be indicated in severely ill patients in consultation with a gastroenterologist, although there may be significant complication rates.³⁸ Thrombolytics are also considered when standard anticoagulation does not lead to recanalization.³² A transjugular intrahepatic portosystemic shunt (TIPS) procedure may be considered in patients having liver transplants or as an alternative to thrombolytic therapy.

Mesenteric arterial and venous thromboses are discussed later.

Atherosclerosis is the major cause of arterial thrombosis leading to ischemia of the SMA and is the cause of mesenteric ischemia in 25% of patients.^39,42 The onset of pain is usually more insidious and may be initially intermittent and eventually becoming constant. Other causative factors are hypercoagulability, estrogen therapy, and prolonged hypotension.⁵⁰ Patients with chronic ischemia may present with intestinal angina (typically epigastric pain precipitated by eating) and describe food fear and ensuing weight loss.⁴² Chronic mesenteric ischemia is usually caused by atherosclerosis and is more common in women and smokers. It is also associated with radiation arteritis, autoimmune arteritides, and fibromuscular dysplasia.⁵² Mortality is high for this disorder and, following surgical treatment, is reportedly 77% (Fig. 3).⁴⁴

Fig. 3 Selective conventional angiography shows an abrupt cutoff of the SMA secondary to embolus (arrow).

(From Martinez JP, Hogan GJ. Mesenteric ischemia. Emerg Med Clin North Am 2004;22(4):912; with permission.)

Mesenteric venous thrombosis accounts for 10% to 15% of mesenteric ischemia cases. Risk factors for mesenteric venous thrombosis include oral contraceptives or estrogen therapy, malignancy, hypercoagulability, portal hypertension, portal vein thrombosis or other deep vein thrombosis, sickle cell disease, clotting disorders, hepatosplenomegaly, hepatitis, pancreatitis, coagulopathic states, sepsis, cigarette smoking, prior abdominal surgery, and alcohol use.^{42,50,52–56} Twenty percent of mesenteric venous thrombosis cases are found to be idiopathic. Patients may present in a subacute fashion with abdominal pain and diarrhea. Clinical findings are likely to be more severe, with frank peritonitis and bleeding in patients with extensive transmural ischemia. With chronic mesenteric vein thrombosis, the collateral circulation usually allows for adequate venous drainage, limiting symptoms and consequent secondary effects of portal hypertension and varix formation. Mesenteric venous thrombosis is usually diagnosed by CT with intravenous contrast. This modality has the advantage compared with color Doppler ultrasound of also allowing for assessment of the bowel and other intra-abdominal conditions. Most mesenteric venous ischemia is treated nonoperatively with anticoagulation. As with portal vein thrombosis, a consideration of the harm-to-benefit profile of thrombolytics can be undertaken in consultation with a gastroenterologist as clinical indications dictate. The pooled reported mortality following surgical treatment of venous thrombosis is 32%.⁴⁴