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Screening post-surgical high risk groups for proximal deep venous thrombosis with ultrasound: a practical alternative to venography
KNEE
The Knee 4 (1997) 77-79
Screening post-surgical high risk groups for proximal deep venous thrombosis with ultrasound: a practical alternative to venography B. Morgan* a, G. Tudorb, J. Greenb, D. Markhamb, “Academic
Department bDepatiment
of Radiology,
of Radiology,
Leicester Glenfield
A. Crozierb
Royal Injirmaly N.H.S. Trust, Leicester LEl5m Hospital NHS Trust, Glenfield, Leicester, UK
UK
Accepted 27 September 1996
Abstract Many orthopaedic centres screen the proximal leg veins for occult deep venous thrombosis (DVT) in post-operative patients. This paper studies the practical implications of ultrasound screening. Venography and ultrasound with colour Doppler was performed in 51 patients. The time taken and results were recorded. There were seven cases (14%) of proximal DVT. The sensitivity of ultrasound was 86% with a specificity of 100%. There was one false negative (a small, < 1 cm, thrombus of uncertain significance). Both techniques were of similar duration. The results support the use of ultrasound for screening in high risk groups. 0 1997 Elsevier Science B.V. Keywords:
DVT; Venography; Colour doppler ultrasound
I. Introduction With increasing awareness bosis (DVT) as a potentially
of deep venous throm-
serious complication of surgery both in terms of possible pulmonary embolism [l] or long term venous insufficiency [2] there has been greater emphasis in its prevention, detection and treatment. Patients undergoing hip and knee replacements have been recognised as having high risk for the formation of DVT (rates of proximal DVT up to 10% with pre-operative prophylaxis) [3]. The detection of DVT clinically is unreliable in this group of patients and many centres are becoming increasingly interested in screening all patients for DVT in the early post-operative period either as management or to evaluate different prophylactic regimes. The screening technique must be both sensitive (allowing recognition and treatment of those with significant DVT) and specific (avoiding unnecessary treatment which may cause significant post-operative problems).
* Corresponding author. 0968-0160/97/$17.00 0 1997Elsevier ScienceB.V. All rights reserved PII SO968-0160(96>00241-4
With increasing numbers of hip and knee replacements performed screening has considerable implications for the workload of radiology departments. Ultrasound with compression and colour Doppler flow imaging has been suggested as the method of choice in the diagnosis of DVT [4] and would be a suitable method for the screening of post operative patients being cheaper and less painful than bilateral contrast venography. Ultrasound is well recognised in the diagnosis of proximal DVT in symptomatic subjects and also for the diagnosis of symptomatic calf vein DVT (in skilled hands) [5]. The diagnosis of DVT in asymptomatic high risk groups, however, has been surprisingly disappointing [6,71 although some groups show promising results [8,9]. In many centres where post operative screening is performed the emphasis of diagnosis is on proximal DVT (femoral and popliteal veins) as it is felt that the complications of treatment of DVT in the calf may outweigh benefit [lo]. The objective of this study is therefore to look at the practical implications of ultrasound in screening for proximal DVT. This trial differs from previous
78
B. Morgan
et al. /The
trials in that the examinations are all performed by junior radiologists with l-2 years ultrasound experience (including vascular ultrasound). The trial assesses the accuracy of ultrasound and also the time implications involved, taking into account that venograms will be necessary as an adjunct in difficult cases. 2. Method
It is local practice for all patients undergoing hip or knee replacement from hvo orthopaedic teams to be screened for DVT with a post-operative screening venogram. Patients with clinical symptoms or signs of DVT are investigated immediately whilst patients asymptomatic for DVT are screened on a separate routine list (between 5 and 7 days post-operatively). All ‘asymptomatic’ patients over a 9-month period were included in the trial. Patients had the venogram technique explained and were asked for consent to an ultrasound examination prior to the procedure. Ultrasound scans were performed of the distal external iliac and femoral veins in the supine position. In patients post-hip replacement the popliteal vein was scanned with a bent knee in the supine position whilst those post-knee replacement were scanned on their side. Scans were performed using both compression and colour Doppler techniques in the transverse and longitudinal plane using a Hitachi EUB 515 scanner, probe frequency was between 3.5 and 10 MHz depending on patient size. The result of the scan and the time taken were recorded. The operator recorded their confidence in the result by stating if they would proceed to venogram. Venography was performed using a standard technique examining all the deep leg and iliac veins. The result and time taken were again recorded. At the onset of the trial both legs were studied but venograms of the non-operated leg were abandoned during the trial due to the low rate of DVT.
Knee 4 (1997)
77-79
The percentage of requests for adjunct venogram reduced with increasing experience. All these cases were correctly diagnosed as normal. The results show one ultrasound false negative which was a small (< 1 cm> thrombus adjacent to a valve in the proximal superficial femoral vein. There were no false positives in either group. In the operated leg the sensitivity was 86%, specificity lOO%, positive predictive value lOO%, negative predictive value 98% and the accuracy 98%. Table 2 gives the average times taken for the techniques. This takes into account the extra time required in the ultrasound group if a venogram is required to confirm the diagnosis in some of the cases. 4. Discussion
Of 68 legs scanned by ultrasound all normals were successfully identified and there was only one false negative. In this case a small thrombus adjacent to a venous valve was present on the venogram and was of uncertain significance. No substantial proximal DVTs were missed. The average time for an ultrasound scan, taking into account the proportion of cases that adjunct venogram is necessary, is greater than that of a venogram alone but this is not felt to be significant taking into account the often longer time taken in Table 1 Comparison of ultrasound versus venogram in the proximal DVT in asymptomatic high risk groups
detection
Venogram
Operated leg Ultrasound Non-operated Ultrasound
+
-
6 1
0 44
0 0
0 17
leg
3. Results
Fifty-two patients were included in the trial, one was excluded due to unsuccessful venogram. Of 51 patients 22 were male and 29 female. Twenty-eight patients were post-hip replacement and 23 post-knee replacement. In 17 patients both legs were studied. In the operated leg there were seven cases (14%) of proximal DVT and 18 cases (36%) of distal DVT. In the non-operated leg there were no cases of proximal DVT and one (6%) case of distal DVT. Results are given in Table 1. In 11 cases the operator felt an adjunct venogram was necessary to exclude DVT (nine in the operated leg and two in the non-operated leg).
Table 2 Average time taken to perform ing those cases where venogram Operated
leg
Hips Knees
Non-operated
leg
Hips Knees
Overall
us
ultrasound is required
and venograms as an adjunct
includ-
US Venogram US Venogram
13 min 9 min 13 min 9 min
us Venogram us Venogram
11 min 6.5 min 13 min 8 min
13 min Venogram
8.5 min
of
B. Morgan
et al. /The Knee 4 (1997) 77-79
getting post operative patients on and off the X-ray examination table and the time taken for cannula removal which was not assessed in this trial. Post operative patients often stated that they had ‘had enough’ of painful procedures by the date of the venogram and therefore found the procedure distressing. Ultrasound, however, was well tolerated in all cases. We feel that these results support the use of ultrasound in screening for proximal DVT in high risk groups. It provides a quick, painless and accurate result without the need for contrast media. References 111 Huisman MV, Buller HR, Cate JW, van Royen EA, Vreeken J, Kersten MJ, Bakx B. Unexpected high prevalence of silent pulmonary embolism in patients with deep venous thrombosis. Chest 1989; 9.5(3): 498-502. I21 Andersen M, Wille-Jorgensen P. Late complications of asymptomatic deep venous thrombosis. Eur J Surg 1991; 157(g):
[6]
[7]
[81
[9]
527-530.
Levine et al. Prevention of DVT after elective hip surgery. Ann Intern Med 1991; 114: 545-551. [4] van Schaik CC, Verzijlbergen F, van Ramshorst B, Eikel[3]
151
boom BC, Meuwissen OJ. Contrast venography: from gold standard to ‘golden backup’ in clinically suspected deep vein thrombosis. Eur J Radio1 1990; H(2): 131-137. Baxter GM, Duffy P, Partridge E. Colour flow imaging of calf vein thrombosis. C&z Radial 1992; 46(3): 198-120. Davidson BL, Elliott CG, Lensing AW. Low accuracy of color doppler ultrasound in the detection of proximal leg vein thrombosis in asymptomatic high-risk patients. The RD hairpin arthroplasty group. Ann Intern Med 1992; 117(9): 735-738. Monreal M, Montserrat E, Salvador R, Bechini J, Donoso L, MaCallejas J, Foz M. Real-time ultrasound for diagnosis of symptomatic venous thrombosis and for screening of patients at risk: correlation with ascending conventional venography. Angiolog~ 1989; 40(6): 527-533. Woolson ST, McCrory DW, Walter JF, Maloney WJ, Watt JM, Cahill PD. B-mode ultrasound scanning in the detection of proximal venous thrombosis after total hip replacement. J Bone Joint Surg [Am] 1990; 72(7): 983-987. Vanninen R, Manninen H, Soimakallio S, Katila T, Suomalainen 0. Asymptomatic deep venous thrombosis in the calf: accuracy and limitations of ultrasonography as a screening test after total knee arthroplasty. Br J Radio1 1993; 66(783):
[lo]
79
199-202.
Moser KM, LeMoine JR. Is embolic risk conditioned by location of deep venous thrombosis. Ann Intern Med 1981; 94(l):
439-444.
The Knee 4 (1997) 77-79
Screening post-surgical high risk groups for proximal deep venous thrombosis with ultrasound: a practical alternative to venography B. Morgan* a, G. Tudorb, J. Greenb, D. Markhamb, “Academic
Department bDepatiment
of Radiology,
of Radiology,
Leicester Glenfield
A. Crozierb
Royal Injirmaly N.H.S. Trust, Leicester LEl5m Hospital NHS Trust, Glenfield, Leicester, UK
UK
Accepted 27 September 1996
Abstract Many orthopaedic centres screen the proximal leg veins for occult deep venous thrombosis (DVT) in post-operative patients. This paper studies the practical implications of ultrasound screening. Venography and ultrasound with colour Doppler was performed in 51 patients. The time taken and results were recorded. There were seven cases (14%) of proximal DVT. The sensitivity of ultrasound was 86% with a specificity of 100%. There was one false negative (a small, < 1 cm, thrombus of uncertain significance). Both techniques were of similar duration. The results support the use of ultrasound for screening in high risk groups. 0 1997 Elsevier Science B.V. Keywords:
DVT; Venography; Colour doppler ultrasound
I. Introduction With increasing awareness bosis (DVT) as a potentially
of deep venous throm-
serious complication of surgery both in terms of possible pulmonary embolism [l] or long term venous insufficiency [2] there has been greater emphasis in its prevention, detection and treatment. Patients undergoing hip and knee replacements have been recognised as having high risk for the formation of DVT (rates of proximal DVT up to 10% with pre-operative prophylaxis) [3]. The detection of DVT clinically is unreliable in this group of patients and many centres are becoming increasingly interested in screening all patients for DVT in the early post-operative period either as management or to evaluate different prophylactic regimes. The screening technique must be both sensitive (allowing recognition and treatment of those with significant DVT) and specific (avoiding unnecessary treatment which may cause significant post-operative problems).
* Corresponding author. 0968-0160/97/$17.00 0 1997Elsevier ScienceB.V. All rights reserved PII SO968-0160(96>00241-4
With increasing numbers of hip and knee replacements performed screening has considerable implications for the workload of radiology departments. Ultrasound with compression and colour Doppler flow imaging has been suggested as the method of choice in the diagnosis of DVT [4] and would be a suitable method for the screening of post operative patients being cheaper and less painful than bilateral contrast venography. Ultrasound is well recognised in the diagnosis of proximal DVT in symptomatic subjects and also for the diagnosis of symptomatic calf vein DVT (in skilled hands) [5]. The diagnosis of DVT in asymptomatic high risk groups, however, has been surprisingly disappointing [6,71 although some groups show promising results [8,9]. In many centres where post operative screening is performed the emphasis of diagnosis is on proximal DVT (femoral and popliteal veins) as it is felt that the complications of treatment of DVT in the calf may outweigh benefit [lo]. The objective of this study is therefore to look at the practical implications of ultrasound in screening for proximal DVT. This trial differs from previous
78
B. Morgan
et al. /The
trials in that the examinations are all performed by junior radiologists with l-2 years ultrasound experience (including vascular ultrasound). The trial assesses the accuracy of ultrasound and also the time implications involved, taking into account that venograms will be necessary as an adjunct in difficult cases. 2. Method
It is local practice for all patients undergoing hip or knee replacement from hvo orthopaedic teams to be screened for DVT with a post-operative screening venogram. Patients with clinical symptoms or signs of DVT are investigated immediately whilst patients asymptomatic for DVT are screened on a separate routine list (between 5 and 7 days post-operatively). All ‘asymptomatic’ patients over a 9-month period were included in the trial. Patients had the venogram technique explained and were asked for consent to an ultrasound examination prior to the procedure. Ultrasound scans were performed of the distal external iliac and femoral veins in the supine position. In patients post-hip replacement the popliteal vein was scanned with a bent knee in the supine position whilst those post-knee replacement were scanned on their side. Scans were performed using both compression and colour Doppler techniques in the transverse and longitudinal plane using a Hitachi EUB 515 scanner, probe frequency was between 3.5 and 10 MHz depending on patient size. The result of the scan and the time taken were recorded. The operator recorded their confidence in the result by stating if they would proceed to venogram. Venography was performed using a standard technique examining all the deep leg and iliac veins. The result and time taken were again recorded. At the onset of the trial both legs were studied but venograms of the non-operated leg were abandoned during the trial due to the low rate of DVT.
Knee 4 (1997)
77-79
The percentage of requests for adjunct venogram reduced with increasing experience. All these cases were correctly diagnosed as normal. The results show one ultrasound false negative which was a small (< 1 cm> thrombus adjacent to a valve in the proximal superficial femoral vein. There were no false positives in either group. In the operated leg the sensitivity was 86%, specificity lOO%, positive predictive value lOO%, negative predictive value 98% and the accuracy 98%. Table 2 gives the average times taken for the techniques. This takes into account the extra time required in the ultrasound group if a venogram is required to confirm the diagnosis in some of the cases. 4. Discussion
Of 68 legs scanned by ultrasound all normals were successfully identified and there was only one false negative. In this case a small thrombus adjacent to a venous valve was present on the venogram and was of uncertain significance. No substantial proximal DVTs were missed. The average time for an ultrasound scan, taking into account the proportion of cases that adjunct venogram is necessary, is greater than that of a venogram alone but this is not felt to be significant taking into account the often longer time taken in Table 1 Comparison of ultrasound versus venogram in the proximal DVT in asymptomatic high risk groups
detection
Venogram
Operated leg Ultrasound Non-operated Ultrasound
+
-
6 1
0 44
0 0
0 17
leg
3. Results
Fifty-two patients were included in the trial, one was excluded due to unsuccessful venogram. Of 51 patients 22 were male and 29 female. Twenty-eight patients were post-hip replacement and 23 post-knee replacement. In 17 patients both legs were studied. In the operated leg there were seven cases (14%) of proximal DVT and 18 cases (36%) of distal DVT. In the non-operated leg there were no cases of proximal DVT and one (6%) case of distal DVT. Results are given in Table 1. In 11 cases the operator felt an adjunct venogram was necessary to exclude DVT (nine in the operated leg and two in the non-operated leg).
Table 2 Average time taken to perform ing those cases where venogram Operated
leg
Hips Knees
Non-operated
leg
Hips Knees
Overall
us
ultrasound is required
and venograms as an adjunct
includ-
US Venogram US Venogram
13 min 9 min 13 min 9 min
us Venogram us Venogram
11 min 6.5 min 13 min 8 min
13 min Venogram
8.5 min
of
B. Morgan
et al. /The Knee 4 (1997) 77-79
getting post operative patients on and off the X-ray examination table and the time taken for cannula removal which was not assessed in this trial. Post operative patients often stated that they had ‘had enough’ of painful procedures by the date of the venogram and therefore found the procedure distressing. Ultrasound, however, was well tolerated in all cases. We feel that these results support the use of ultrasound in screening for proximal DVT in high risk groups. It provides a quick, painless and accurate result without the need for contrast media. References 111 Huisman MV, Buller HR, Cate JW, van Royen EA, Vreeken J, Kersten MJ, Bakx B. Unexpected high prevalence of silent pulmonary embolism in patients with deep venous thrombosis. Chest 1989; 9.5(3): 498-502. I21 Andersen M, Wille-Jorgensen P. Late complications of asymptomatic deep venous thrombosis. Eur J Surg 1991; 157(g):
[6]
[7]
[81
[9]
527-530.
Levine et al. Prevention of DVT after elective hip surgery. Ann Intern Med 1991; 114: 545-551. [4] van Schaik CC, Verzijlbergen F, van Ramshorst B, Eikel[3]
151
boom BC, Meuwissen OJ. Contrast venography: from gold standard to ‘golden backup’ in clinically suspected deep vein thrombosis. Eur J Radio1 1990; H(2): 131-137. Baxter GM, Duffy P, Partridge E. Colour flow imaging of calf vein thrombosis. C&z Radial 1992; 46(3): 198-120. Davidson BL, Elliott CG, Lensing AW. Low accuracy of color doppler ultrasound in the detection of proximal leg vein thrombosis in asymptomatic high-risk patients. The RD hairpin arthroplasty group. Ann Intern Med 1992; 117(9): 735-738. Monreal M, Montserrat E, Salvador R, Bechini J, Donoso L, MaCallejas J, Foz M. Real-time ultrasound for diagnosis of symptomatic venous thrombosis and for screening of patients at risk: correlation with ascending conventional venography. Angiolog~ 1989; 40(6): 527-533. Woolson ST, McCrory DW, Walter JF, Maloney WJ, Watt JM, Cahill PD. B-mode ultrasound scanning in the detection of proximal venous thrombosis after total hip replacement. J Bone Joint Surg [Am] 1990; 72(7): 983-987. Vanninen R, Manninen H, Soimakallio S, Katila T, Suomalainen 0. Asymptomatic deep venous thrombosis in the calf: accuracy and limitations of ultrasonography as a screening test after total knee arthroplasty. Br J Radio1 1993; 66(783):
[lo]
79
199-202.
Moser KM, LeMoine JR. Is embolic risk conditioned by location of deep venous thrombosis. Ann Intern Med 1981; 94(l):
439-444.