Open thrombectomy for mesenteric vein injury and acute thrombosis. Is it the right way? A case report and review of literature

Abstract

Mesenteric vein thrombosis following injury to the superior mesenteric vein (SMV) during abdominal surgery is rare but it is associated with poor outcome. Late detection of mesenteric vein thrombosis results in extensive bowel gangrene resulting in poor patient outcome. Thrombectomy is rarely attempted at the time of re exploration even if the SMV is found to have a thrombus. But evidence suggests that performing thrombectomy at the time of re exploration will reduce the length of bowel resection. In addition venous thrombectomy will also result in better patient outcome. This case describes a patient who developed superior mesenteric vein thrombosis in the immediate post laparotomy period following SMV injury. She was managed successfully with open thrombectomy and bowel resection.

Open thrombectomy for mesenteric vein injury and acute thrombosis. Is it the right way? A case report and review of literature

Mesenteric vein thrombosis (MVT) is a rarely suspected and a rarely diagnosed entity following intra-abdominal surgery. It is a rare cause for acute intestinal ischaemia (5- 15%)   resulting in venous gangrene of the bowel. MVT is associated with a very high mortality (1).

With early diagnosis and appropriate intervention, the bowel gangrene and the mortality can be reduced. The guidelines for optimal management for MVT are lacking due to the rarity of acute MVT following injuries to the Superior Mesenteric Vein (SMV) during surgery and delay in diagnosis of MVT. This case report describes a patient who developed superior mesenteric vein thrombosis following laparoscopic right hemi colectomy and injury to the SMV due to avulsion of the middle colic vein. She was managed successfully with open thrombectomy and SMV repair.

Case

A 59 year old female underwent laparoscopic right hemi colectomy. During colonic mobilisation heavy bleeding was encountered at the route of the mesentery due to avulsion of the middle colic vein. Procedure was converted to laparotomy and the haemostasis was achieved with difficulty with suture ligation. The colectomy was completed. An end to end distal ileum to transverse colon anastomosis was done. Towards the end of the surgery dusky discoloration of the distal end of the ileum was noted.  However the small intestine was well perfused with visible pulsation of the terminal branches of the mesenteric artery at the intestinal border of the mesentery. The peristalsis was present. Therefore no further action was taken and the abdomen was closed.

About 6 hours after the surgery the patient became haemodynamically unstable with increasing need for inotropes and the serum lactate level was rising (serum lactate level was 7.9 mmol/l on arterial blood gas analysis- normal range 0.5 to 1.3).  There was large amount of blood stained drainage (1130 ml in the first 2 hours) from the abdominal drain. A decision was taken to perform an urgent relaparotomy suspecting a reactionary haemorrhage. At the relaparotomy, the whole length of the small intestine other than the initial few centimetres of the jejunum was found to be dark red in colour with absent peristalsis (Figure 1).  On further exploration the mesenteric vein was found to be thrombosed at the site of middle colic vein injury.

Superior mesenteric vein (SMV) was mobilised proximally and distally. Proximal and distal control was achieved. A bolus dose of unfractionated heparin (100u/kg) was administered. The SMV wall was found to be lacerated due to avulsion of middle colic vein from its junction with the SMV (Figure 2). The haemostatic sutures applied during the initial surgery were found to be constricting the vein. The previously applied sutures were removed. Thrombectomy was done. The lacerated venous edges were trimmed. And the defect was repaired with 6/0 Polypropylene sutures transversely. And the venous flow was re-established. Following thrombectomy and venous wall repair, the jejunum and the proximal ileum returned to normal colour (Figure 3). Peristalsis reappeared. The arterial pulsation was noticed in the terminal branches of the superior mesenteric artery. The colour of the distal ileum did not improve. Therefore the ileocolic anastomosis was disconnected and the distal end of the ileum was resected.  The end of the ileum and the transverse colon were brought out as two separate stomas on either side of the midline incision. Following the surgery the lactate level returned to normal level gradually. The ileostomy started to function, the colour of the stoma was normal. At present the patient is recovering slowly and managed with supplemental parenteral nutrition.

Discussion and conclusion 

Mesenteric vein thrombosis is rarely encountered due to injuries to the SMV during abdominal surgeries and difficult to diagnose in the immediate postoperative period. But it is a very serious complication associated with very high mortality. The mortality following MVT varies from 12.5% to 50% (1) (2) (3) (4).

The Superior Mesenteric vein (SMV) drains blood from the duodenum through the inferior pancreaticodudenal veins. It also drains blood the jejunum and ileum via jejunal and ileal branches. In addition it also drains blood from the caecum and the ascending colon through the ileocolic and the right colic branches. Additionally it drains right 2/3 of the transverse colon through the middle colic branch. In addition the large bowel and the duodenum have alternative venous drainage pathways through the inferior mesenteric and portal vein tributaries.  Finally the SMV joins the splenic vein behind the neck of the pancreas to form the portal vein that eventually drains into the liver. Mesenteric vein thrombosis usually leads to distal jejunal and ileal infarction and gangrene, perforation, sepsis and finally death. In addition the patient can develop short bowel syndrome as a result of extensive bowel resection. The large bowel and the duodenum are usually spared because of the alternative venous drainage pathways as explained above.

Causes of mesenteric venous thrombosis can be divided into three categories i.e. Virchow’s triad. Those are;

• Venous wall injury
• Stagnation
• Hypercoagulable state

Venous wall injury can occur during intra-abdominal surgeries as in the case described above and also in pancreatectomy, splenectomy, in abdominal trauma, etc. In addition the risk of SMV thrombosis increases with peritoneal inflammation e.g. in peritonitis.

Hypercoagulable States occurs secondarily in various conditions like myeloproliferative diseases and primarily in primary thrombophilias.

Stagnation to the flow occurs following accidental ligation of the vein as in the current case. Stagnation also occurs in conditions like cirrhosis due to increase in the liver resistance resulting in slow flow in the portal and mesenteric vein.  Furthermore stagnation can occur following splenectomy. During splenectomy the splenic artery is ligated. This results in reduction of the blood flow in the splenic vein. This in turn results in reduced blood flow in the portal vein leading to a state of stagnation producing portal vein as well as superior mesenteric vein thrombosis.

Local factors like venous wall injury e.g. during pancreatectomy and splenectomy generally leads to proximal mesenteric vein thrombosis whereas hypercoagulable state leads to small tributary vein thrombosis (5).

When mesenteric vein thrombosis occurs there will be stagnation and increased hydrostatic pressure at the venous end of the capillaries. This will lead to leakage of fluid through the capillary wall into the interstitial space of the bowel wall. This results in bowel wall edema. In addition due to increased venous end pressure at the capillaries, there will be reduced perfusion pressure to the bowel wall resulting in ischemia and necrosis leading to bowel wall gangrene. In chronic mesenteric vein thrombosis, due to establishment of venous collateral pathways, the capillary venous pressure does not rise high enough to cause bowel wall ischemia and gangrene.

Clinical features will depend on the acuity of the onset and the extent of the thrombosis.

The patient often presents with nonspecific central abdominal pain. Only vague signs are detected on abdominal examination. Due to the nonspecific nature of the pain and lack of abdominal signs, the diagnosis may be missed initially. In addition during the immediate postoperative period like in the patient described above, recognising the pain due to the mesenteric vein thrombosis is difficult.

If the diagnosis is missed in the initial period, bowel gangrene results. There will be acidosis with a rise in the serum lactate level and leucocytosis (white cell count of more than 20000 /mm³) (6) (7). Eventually the patient develops bowel perforation, peritonitis and sepsis with multi organ failure. Finally the death results (5).

In postoperative mesenteric vein thrombosis like in the case described above, the patient develops severe abdominal pain and tachycardia.  If there is a small intestinal stoma, the stoma effluent will be heavily blood stained. There will be a bluish discoloration of the stoma mucosa. Patient develops severe acidosis and multiorgan failure.

Imaging is used to confirm the diagnosis and to assess the extent of the thrombosis. Imaging is also used to assess the complications of the mesenteric vein thrombosis e.g. bowel gangrene. The main imaging modalities available are ultrasound scan (USS) and Computerised tomography (CT).

Ultrasound scan with Doppler will confirm the presence of thrombus. But USS is not suitable to assess the extent of the thrombosis.  In addition USS will not adequately demonstrate the bowel complications. In addition during the postoperative period it is difficult to perform a USS.

Contrast enhanced CT angiography in portal venous phase (70s delay) is done to confirm the diagnosis. The CT scan has a sensitivity of 90%. If mesenteric vein thrombosis is suspected there CT scan should be done immediately (8).  The CT appearances include filling defects in the lumen of the SMV, dilatation proximal to the occluded vein,  bowel wall edema resulting in “halo sign” or “target sign”, oedema of the mesentery (mesenteric fat stranding) (9) and altered bowel wall enhancement (10). If there are any doubts about bowel wall gangrene, urgent laparoscopic assessment should be performed.

In all patients with acute MVT, intravenous heparin infusion should be started immediately, with a bolus dose of 100 IU per kg intravenously followed by 18U per kg per hour intravenous infusion. The activated partial thromboplastin time (APTT) is maintained at twice the normal range. Early anticoagulation is shown to improve the outcome and it also facilitates recanalisation of the vein. Studies have shown that early anticoagulation results in 61% to 80% recanalisation rate in cases of acute MVT (11) (12). Subsequently the patients are converted to oral anticoagulants i.e. Warfarin. Warfarin is continued for 6 months if there are no further risk factors for recurrence. If there are thrombophilic conditions and in idiopathic cases causing the MVT, warfarin is continued with the advice from the haematologist for lifelong period (11). The international normalised ratio (INR) is maintained in between 2 to 3 while on warfarin.

The patients with bowel gangrene should be prepared for emergency laparotomy. At laparotomy the extent of the bowel gangrene and the presence of thrombosis in the mesenteric vein are confirmed. When abdominal exploration is done early as in the above described case, open thrombectomy should be attempted. Open thrombectomy is effective in removing large amount of thrombus. Only few series reported the outcome of open thrombectomy. In one series of mesenteric vein thrombosis, the mortality was less in patients who underwent thrombectomy and bowel resection than in patients who underwent bowel resection alone (13).

Endovascular options include catheter-directed administration of thrombolytic agents (e.g. tissue plasminogen Activator (TPA) and Streptokinase) and mechanical thrombectomy. In catheter-directed administration of thrombolytic agents the thrombolytic agent is injected via a catheter either into the superior mesenteric artery (indirect lysis) or into the superior mesenteric vein (direct lysis).

To access the SMV, the catheter is inserted through the internal Jugular vein into the hepatic veins. Then it is directed through trans hepatic route into the portal vein and subsequently into the SMV. Studies have shown good outcomes with direct thrombolysis. In one study done among 20 patients with superior mesenteric vein thrombosis, 15 (75%) had either complete or partial resolution of the thrombus. The major complications reported in this study were gastrointestinal haemorrhage and septic shock (14). Similarly in another study among 12 patients with superior mesenteric vein thrombosis, 7 (58.3%) had either complete or partial resolution of thrombus. This study also reported a 50% major haemorrhagic event (15).

Catheter-directed injection of thrombolytic agents into the artery (indirect lysis) is aimed at achieving the thrombolysis in the small venules. But it is less effective compared to direct injection into the vein. The reason being that the thrombolytic agent may pass through the collateral veins bypassing the thrombosed venules. This results in sub-optimal thrombolysis. Therefore a larger dose of thrombolytic agent and longer duration of infusion is needed to achieve thrombolysis (16).

Mechanical thrombectomy can be attempted in patients who have contra indications to the thrombolytic agents e.g. in the immediate postoperative period like the patient described above.

Endovascular options are indicated in patients who remain symptomatic after 48 to 72 hours of anticoagulation, in patients with worsening abdominal signs and in patients who are not fit for surgical interventions.  But in the patient described above endovascular options were not attempted due to non-availability and the patient’s condition required and open surgery due to the presence of large volume of blood stained drainage.

Therefore in a patient with mesenteric vein thrombosis, if the patient is subjected to laparotomy i.e. for bowel resection, open thrombectomy should also be attempted as in the case described above. However  the current tendency  in local setting is to do only  bowel resection and not attempting open thrombectomy. However the evidence suggests that performing thrombectomy at the time of surgery will reduce the length of bowel resection. In addition venous thrombectomy will also result in better patient outcome (13).

Figure 1 Image showing congested small bowel

Figure 2 Image showing damaged wall of the superior mesenteric vein

Figure 3 Image showing the recovery in congestion of the small bowel after thrombectomy

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