Portomesenteric thrombosis after robotic sleeve gastrectomy

Abstract

Portomesenteric thrombosis is an important but rarely reported complication following bariatric surgery. It has been suggested that the incidence of portal vein thrombosis is directly related to many risk factors inherent in the bariatric population as well as factors related to local and systemic effects of laparoscopic surgery. Possible aetiologies vary from systemic inherited hypercoagulable states to a direct inflammatory reaction of portosystemic vessels. Here we present a case report of a 47-year-old obese women who underwent a robotic sleeve gastrectomy with subsequent development of a main portal vein, complete right intrahepatic portal vein and splenic vein thrombosis ultimately found to have a compound mutation of the methylenetetrahydrofolate reductase C677T and A1298C alleles.

Background

Bariatric surgery has become an increasingly used and efficient treatment modality for our enlarging morbidly obese population. Despite the many health benefits of bariatric surgery, the overall incidence of complications is reported to be as high as 7%.¹ Of these complications, venous thromboembolism (VTE) is a leading cause of morbidity and mortality due to inherent risk factors as well as the prothrombotic effects of abdominal surgery.²

Case presentation

We present a 47-year-old woman with a previous medical history of migraines, obstructive lung disease and obesity (body mass index (BMI) 49.13 kg/m²) who presented for robotic sleeve gastrectomy (RSG). The patient underwent an uncomplicated procedure (total operative time was 104 min) and was admitted postoperatively per protocol. Her immediate postoperative course was uncomplicated; she was ambulatory, tolerated a clear liquid diet and reported adequate postoperative pain control. She was cleared for discharge home on daily 81 mg Aspirin per our sleeve gastrectomy discharge protocol. At her 1-week follow-up, she was also found to be doing well, maintaining her diet and reporting improvement to her surgical pain. On postoperative day (POD) 12, she presented to the emergency room with 4 days of progressive sharp left-sided abdominal pain that was made worse with movement and coughing; she also reported fever, headache and constipation.

Investigations

A CT of the abdomen and pelvis was obtained and was significant for partial main portal vein, complete right intrahepatic portal vein and splenic vein thrombosis. (figure 1A–C) A basic metabolic panel, complete blood count, hepatic panel, lipase and venous blood gas were obtained without significant findings.

Figure 1.

A (coronal), B (sagittal) and C (axial): CT of the abdomen demonstrating partial main portal vein thrombosis (A), complete thrombosis of the intrahepatic right portal vein (B) as well as splenic vein (C).

Treatment

The patient denied any hypercoagulable risk factors including smoking history and contraceptive pill use. She was admitted and was started on a heparin infusion; haematology was consulted and recommended a hypercoagulable workup as well as apixaban on discharge. On POD 14, the patient reported improvement to her abdominal pain with normal bowel movements and dietary tolerance and was cleared for discharge home.

Outcome and follow-up

She underwent outpatient hypercoagulable workup, which was significant for a compound mutation in the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C alleles for which she was advised to continue apixaban for 6 months. She remains asymptomatic, has been reported with nutrition follow-up and has been tolerating a regular diet well with an overall 25-pound weight loss at her 6-month follow-up appointment.

Discussion

Nearly 900 000 VTE events occur in the USA yearly making this an important cause of preventable deaths in patients.² There are several traditional risk factors that have been implicated in VTE events. These risk factors include previous VTE, advanced age, general anaesthesia, major surgery, relative immobility, malignancy, tobacco use, oral contraceptive agents and coagulation disorders.² The bariatric population is particularly vulnerable as obesity serves as an independent risk factor for VTE; bariatric surgery, therefore, takes an already at-risk individual and exposes them to the risks associated with major surgery, general anaesthesia and relative immobility, which may extend far beyond initial hospitalisation.²

A rare but potentially lethal condition can result when thrombotic events involve the portal venous system.² The portal vein accounts for 75% of the hepatic blood supply; portal vein thrombosis accounts for approximately 5%–15% of all mesenteric ischaemia.^{3 4} Thrombus may extend both distally towards splenic mesenteric veins as well as proximally towards the liver.⁵ The mechanism by which laparoscopic surgery increases the risk of developing splanchnic vessel thrombosis remains unclear. Proposed mechanisms include mechanical and systemic capnoperitoneum-related interactions that result in a variety of changes in coagulation and haemodynamics.⁵ Studies have demonstrated that laparoscopic surgery is associated with a statistically significant decrease in hepatic microcirculation along with decreased gastric intraluminal pH.⁶ It has also been suggested that, similarly to the overall risk of VTE in bariatric surgery, the incidence of portomesenteric vein thrombosis (PMVT) may be directly related to the inherent risk of obesity as well as factors related to local and systemic effects of laparoscopic surgery.⁵

It has also been proposed that robotic surgery may expose patients to additional risk factors that could contribute to PMVT.⁷ While case reports of robotic bariatric procedures have demonstrated similar cases of PMVT among patients with risk factors such as antiphospholipid syndrome and factor 5 Leiden, a recent multicenter case–control study found the highest rate of PMVT to be at a centre that primarily performs RSGs (0.5% compared with 0.1% at the other centres reviewed).^7–9 While the study had several limitations and was not designed to determine a significant difference between robotic and laparoscopic sleeve gastrectomy, one mechanism proposed was that during the procedure, the robotic arms may unintentionally retract on the pancreas and the retroperitoneum, which may result in thrombosis of the splenic vein.⁷

Portomesenteric thrombosis has also been reported in obese patients undergoing many non-bariatric surgical procedures. In a retrospective review, Robinson et al found a PMVT rate of 3% among patients who underwent colon and rectal surgery while demonstrating BMI >30 kg/m² as a significant predictor.¹⁰ In a study of patients undergoing orthotopic liver transplants, Ayala et al found a 16.3% incidence of pretransplant portal vein thrombosis with obesity serving as the only identified independent risk factor.¹¹ Interestingly, Bureau et al found central obesity to be associated with PMVT in a study which reviewed consecutive patients with non-cirrhotic portal vein thrombosis including both patients with idiopathic and secondary portal vein thrombosis.¹² These findings suggest that obesity may serve an independent risk factor for PVMT regardless of surgical intervention.

The diagnosis of postoperative PMVT is difficult to make. Many patients may be asymptomatic while others may demonstrate non-specific symptoms such as fever, abdominal pain, back pain, nausea, emesis, diarrhoea or constipation. The average onset is estimated to be 14 days postoperatively. Laboratory workup may demonstrate a non-specific leukocytosis as well as lactic acidosis, and therefore a CT of the abdomen and pelvis with intravenous contrast is recommended for definitive diagnosis.¹

A hypercoagulable workup may identify one of several possible abnormalities in blood coagulation, such as the 5,10-MTHFR mutation in our patient. 5,10-MTHFR is a catalyst for the methylation of homocysteine to methionine.¹³ Mutations at MTHFR at the C677T and A1298C alleles may result in elevated levels of homocysteine, which has been identified as a risk factor for thrombosis.¹³ MTHFR mutations have also been implicated in the possible prothrombotic aetiology of idiopathic portal hypertension (IPH) due to an estimated twofold increased risk of IPH in patients with both C677T and A1298C mutations.¹⁴ Interestingly, a prior case report by Gursoy et al presented a combined portal, splenic and mesenteric venous thrombosis in a patient with ulcerative colitis who was also found to have a heterozygous mutation of the MTHFR gene at the C677T and A1298C alleles.¹⁴ Further support of this prothrombotic state is evidenced by the increased risk of thrombotic ischaemic stroke by 3.39-fold with the presence of both MTHFR C677T and A1298C.^{13 14}

Management of PMVT is dictated by the risk factors and the severity of the thrombosis. Treatment options include systemic anticoagulation alone while severe cases require further thrombolytic agents and/or thrombectomy. In patients with severe secondary ischaemia, laparotomy may be indicated to best evaluate bowel viability and allow for open thrombectomy.

Genetic counselling may also be advised for the patient with prothrombotic genetic mutations.^{1 6 14} Guidelines for the prevention of perioperative thromboembolic events vary greatly. Some conservative protocols recommend mechanical compression devices along with early ambulation while others recommend chemoprophylaxis and inferior vena cava filters.^{1 15} For high-risk patients undergoing chemoprophylaxis, prolonged anticoagulation in addition to higher than standard dosages may be required.^{16 17} At our institution, the current VTE regimen consists of heparin subcutaneous (5000 units every 8 hours or 7500 units every 8 hours for patients with BMI >50. On discharge, patients who underwent sleeve gastrectomy are prescribed Aspirin 81 mg/day for 30 days with the addition of enoxaparin for patients who are deemed high risk (history of VTE, thrombophilia or limited ambulation).

Learning points.

• Thrombotic events involving the portal venous system, while rare, can be potentially lethal.

• The mechanism by which postoperative portomesenteric vein thrombosis occurs remains unclear; however, proposed mechanisms include mechanical and systemic capnoperitoneum-related interactions.

• Prolonged postoperative venous thromboembolism (VTE) prophylaxis should be considered in patients with risk factors such as obesity, previous VTE, advanced age, relative immobility, malignancy, tobacco use, oral contraceptive agents and coagulation disorders.