Role of routine pre-operative screening venous duplex ultrasound in morbidly obese patients undergoing bariatric surgery.

BACKGROUND/AIMS: It is well established that obesity is a strongly associated risk factor for post-operative deep vein thrombosis (DVT). Physical effects and pro-thrombotic, pro-inflammatory and hypofibrinolytic effects of severe obesity may predispose to idiopathic DVT (pre-operatively) because of which bariatric patients are routinely screened before surgery. The aim of this study was to audit the use of routine screening venous duplex ultrasound in morbidly obese patients before undergoing bariatric surgery.
METHODS: We retrospectively reviewed 180 patients who underwent bariatric surgery from August 2013 to August 2014 who had undergone pre-operative screening bilateral lower-extremity venous duplex ultrasound for DVT. Data were collected on patient's demographics, history of venous thromboembolism, prior surgeries and duplex ultrasound details of the status of the deep veins and superficial veins of the lower limbs.
RESULTS: No patients had symptoms or signs of DVT pre-operatively. No patient gave history of DVT. No patient was found to have iliac, femoral or popliteal vein thrombosis. Superficial venous disease was found in 17 (8%). One patient had a right lower limb venous ulcer.
CONCLUSION: Thromboembolic problems in the morbidly obese before bariatric surgery are infrequent, and screening venous duplex ultrasound can be done in high-risk patients only.

INTRODUCTION

Venous thromboembolism (VTE) is a recognised and significant cause of morbidity and mortality, especially in the post-operative setting. Risk factors for post-operative deep vein thrombosis (DVT) are well established and include older age, malignancy, major surgery, hip and pelvic surgery, prior VTE, multiple trauma, prolonged immobilisation, cardiac and neurologic disorders, hypercoagulable disorders, oral contraceptives pills, oestrogen replacement therapies and obesity.[123] VTE occurs in <2% of open and laparoscopic bariatric procedures.[4] Aside from a post-operative setting, numerous studies have implied that there is a strong association with obesity and the risk of idiopathic DVT independent of other recognised risk factors, which is of importance in a pre-operative setting.[567] This has been linked to chronically raised intra-abdominal pressure, decreased blood velocity in the common femoral vein, inactivity, osteoarthritis and poor gait, which impair venous return from the lower limbs possibly predisposing to VTE.[891011] This forms the basis of routine pre-operative screening for DVT in all morbidly obese patients being submitted to bariatric surgery because of medico-legal implications. However, there is a lack of clinical knowledge regarding the actual incidence of idiopathic DVT in the severely obeses. Few studies and experience from routine practice show that idiopathic DVT (pre-operatively) in morbidly obese is uncommon and question the practice of routine screening before bariatric surgery.[4]

With this study, we aimed to audit the use of routine screening venous duplex ultrasound in morbidly obese patients before undergoing bariatric surgery.

METHODS

Study population

We retrospectively reviewed 180 patients who underwent bariatric surgery from August 2013 to August 2014 in whom a pre-operative screening bilateral lower-extremity venous duplex ultrasonography (USG) for DVT was performed. Mean age was 43.45 ± 12.64 (range 18–75) years. Mean body mass index (BMI) was 45.81 ± 7.52. Surgical procedures included 133 sleeve gastrectomies and 45 Roux-en-Y gastric bypasses. Two were revisional bariatric procedures (sleeve gastrectomy to Roux-en-Y bypass).

Clinical evaluation

History enquired included pain, redness or swelling of legs, drugs history, history of DVT and prior surgeries. Signs of venous disease looked for included pretibial oedema, induration of the skin, hyperpigmentation, venous ectasia, redness, pain during calf compression and ulceration of the skin.

Venous duplex ultrasonography

All patients were examined with duplex scanning using Acuson S2000 (Acuson, Mountain view, CA, USA) with 7 and 10 MHz probes. Iliac, femoral, popliteal and crural veins were scanned in the longitudinal planes with color flow imaging. Compression tests and augmentation of venous flow by distal compression were routinely used to demonstrate patency of the veins. Lack of compressibility and absence of flow augmentation in distended veins were interpreted as venous thrombosis.

Venous thromboprophylaxis

Venous thromboprophylaxis was given to all patients. Injection enoxaparin 0.6 ml U or injection fondaparinu × 2.5 mg U single daily dose was administered subcutaneously day before the operation and was continued after the operation with graded compression stockings throughout hospitalisation. Low-molecular-weight heparin was administered for a total of 10 days after surgery being continued after discharge from the hospital. Ambulation was instituted on post-operative day 1.

Data collection

Data were collected on patient's demographics, history of DVT, prior surgeries and duplex USG details of the status of the deep veins and superficial veins of the lower limbs.

RESULTS

No patients had symptoms or signs of DVT pre-operatively. No patient gave a history of DVT. Prior abdominal, pelvic, orthopaedic and venous surgeries included 34 caesarean sections, 9 hysterectomies, 5 tubal ligations, 2 salpingo-oophorectomies, 1 myomectomy, 17 appendicectomies, 7 ventral hernia repairs, 4 prior bariatric procedures, 4 abdominoplasties, 4 liposuctions, 3 endourological interventions, 5 lower limb and spinal orthopaedic procedures and 1 varicose vein laser ablation.

No patient was found to have any sign of iliac, femoral, popliteal vein thrombosis. Superficial venous disease was found in 17 (8%) of the patients, of which 9 had unilateral or bilateral sapheno-femoral incompetence, 1 had bilateral sapheno-popliteal incompetence and 12 had multiple incompetent perforators. One patient had a right lower limb venous ulcer.

DISCUSSION

Obesity is associated with various comorbid factors. In particular, Type 2 diabetes mellitus, arterial hypertension, dyslipidaemia, obstructive sleep apnoea, polycystic ovary disease, non-alcoholic fatty liver disease and gastro-oesophageal reflux have a well-established association.[12] Evidence already exists linking obesity with VTE.[567] Elevated levels of leptin, tissue factor, coagulation factors VII and VIII, thrombin, fibrinogen, von Willebrand factor and fibrinogen plasminogen activator inhibitor 1 are observed which lead to hypercoagulability which leads to changes in the haemostatic and fibrinolytic activity.[11] Dyslipidaemia, hyperglycaemia, increased inflammation, oxidative stress and endothelial dysfunction with obesity may also be contributory.[13] However, VTE manifests mostly when obesity is associated with abdomino-pelvic, orthopaedic and bariatric procedures which form the basis of venous thromboprophylaxis in such settings.[2] It is not known if obesity acts alone causing idiopathic DVT before surgery and it remains controversial if patients need to be rigorously screened before these procedures though this is routinely done because of medico-legal implications. Our audit shows that the incidence of venous thromboembolic problems before bariatric surgery in morbidly obese patients is very infrequent. This has also been noted in few other studies in literature.[4] This would support the practice of performing pre-operative screening bilateral lower-extremity venous duplex USG for DVT only in high-risk patients. Classifying high risk in morbidly obese patients is complex. However, a simple way of classifying morbidly obese patients into high-risk groups pre-operatively can be based on certain well-established risk factors in the post-operative settings. Very severely obese people, elderly patients, presence of heart failure or a history of prior VTE are at very high risk.[13141516] Furthermore, morbidly obese patients with prior abdomino-pelvic surgery, bariatric surgery or venous surgery may also face increased risk.[217] Dilated superficial veins may be a sign of an underlying DVT and venous insufficiency itself increases risk.[18] Based on this, high risk may be defined as super-obese patients with a BMI > 50 kg/m2, elderly, prior history of DVT, history of cardiac failure, prior abdomino-pelvic, bariatric or venous surgery and presence of superficial venous disease. Most of these factors can be determined by a thorough history on admission and in pre-operative planning.

CONCLUSION

Thromboembolic problems in obese individuals are infrequent before surgery and screening duplex USG can be done in high-risk patients only.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.