CHICAGO – Treatment of isolated acute mesenteric venous thrombosis remains a topic of controversy, with no established guidelines available, Thomas S. Maldonado, MD, observed at a symposium on vascular surgery sponsored by Northwestern University.
“There has been a pendulum swing. Earlier on there was a lot of excitement about surgical thrombectomy, then we tended to become more nonoperative and conservative, using just anticoagulation. But in recent years endovascular therapy has been gaining some traction and shows good preliminary results,” according to Dr. Maldonado, professor of surgery at New York University.
Today MVT accounts for 1 in 1,000 emergency department visits and 6%-9% of cases of acute mesenteric ischemia. Dr. Maldonado cited two reasons for the increasing incidence. One is the widespread recognition that contrast-enhanced helical CT is the diagnostic imaging method of choice; it is being employed more liberally because of its ready availability and overall 95%-100% accuracy, which allows for rapid and reliable diagnosis with precise location of the thrombus.
The other factor is that bariatric surgery is booming. While the most common local etiologies of the hypercoagulable state predisposing to MVT remain cancer and intra-abdominal inflammatory diseases such as pancreatitis, there is no doubt that laparoscopic bariatric surgery is emerging as another contributing factor, according to the surgeon.
MVT is an insidious and lethal disease. In most series, it has a mortality of at least 25%, and it doesn’t appear to be going down in recent years. This is probably because of difficulty in making a prompt diagnosis before bowel ischemia occurs. Multiple studies show that onset of symptoms typically occurs 6-14 days before patients present for care.
“I think this is really the Achilles heel of this diagnosis – that it can be delayed. The diagnosis can be elusive. There is no constellation of signs or symptoms that is pathognomonic for MVT. This is where prompt recognition and a CT scan can really play an important role,” Dr. Maldonado said.
He and a coworker conducted a review of 37 studies on MVT published in 1997-2016 which underscored the challenges in making a prompt diagnosis. The most common presenting symptom was nonspecific abdominal pain out of proportion to findings on physical exam. Other possible symptoms included anorexia, nausea, vomiting, constipation, and/or passage of blood through the anus. The disease occurred most often in men aged 40-60. A history of unprovoked venous thromboembolism was often present ().
The three-phase CT scan – arterial, venous, and delayed venous – not only locates the thrombus with precision, it also shows whether the occlusion is partial or complete, which is important information prognostically (see below). The scan also provides information on bowel ischemia with at least 90% sensitivity and specificity. Bowel compromise shows up on CT as a thickened bowel wall with dilated lumen, mesenteric fat stranding, and ascites.
CT imaging has become so useful for rapid diagnosis of MVT that duplex ultrasound, although considerably less costly and radiation-free, has become relegated to a secondary role. At most centers its use is restricted to follow-up surveillance to assess for thrombus resolution and vascular recanalization after the acute episode has been treated. Duplex ultrasound simply can’t match CT in the crucial task of assessment for bowel ischemia.
The mainstay of treatment in patients with MVT without bowel ischemia is medical management: immediate anticoagulation with unfractionated or low-molecular-weight heparin bridging to warfarin, bowel rest, aggressive fluid resuscitation, and correction of electrolyte imbalances. Most patients with nonocclusive MVT and no ischemic bowel can be managed in this way without surgical intervention. The newer oral anticoagulants haven’t yet been studied in patients with MVT.
How long to continue oral anticoagulation is an unresolved issue. In Dr. Maldonado’s literature review, the median duration was 90 days. In his own practice, anticoagulants aren’t stopped until duplex ultrasound demonstrates recanalization of the mesenteric venous system. If residual thrombus is present or a patient has an underlying hypercoagulable state, treatment continues indefinitely.
In a series of 50 noncirrhotic MVT patients treated at New York University using various strategies, 19, or 38%, were completely recanalized. Recurrence of MVT after successful treatment occurred in only 2 of these 19 patients, in both cases upon discontinuation of anticoagulation.
“It speaks to the issue of length of treatment – or should it be discontinued at all?” the surgeon said.
Open surgical thrombectomy has fallen into disfavor because the thrombus tends to recur within 7 days post surgery. It is now best reserved for patients with acute MVT with a contraindication to thrombolytic therapy, such as cirrhosis or recent major surgery, according to Dr. Maldonado.
Multiple patient series using endovascular catheter-directed thrombolytic therapy with a transhepatic, transvenous, transarterial, or combined approach have reported high rates of successful recanalization – even in the 90% range – with low recurrence rates and fewer bowel resections than with anticoagulation alone.
Indeed, Dr. Maldonado and his fellow vascular surgeons at New York University have recently developed a management algorithm whereby patients with occlusive MVT and no bowel ischemia undergo catheter-directed thrombolysis provided there are no contraindications, such as uncontrolled hypertension or a recent hemorrhagic stroke. The surgeons will also seriously consider catheter-directed lytic therapy in MVT patients with bowel ischemia who show no improvement after laparotomy, bowel resection, and open thrombectomy.