Postgraduate Medical Journal (1985) 61, 23-27

The swollen leg: ultrasonographic demonstration ofnon-thrombotic causes

Jonathan M. Bell, F.G.M. Ross, S. Mackenzie and Paul R. Goddard

The Imaging Research Unit, UniversitY Dept. ofRadiodiagnosis and Dept. ofMedical Physics, Bristol RoyalInfirmary, Bristol, UK.

Summary: Grey-scale ultrasound is a useful investigation in selected patients with a painful swollenleg. It is of particular value in cases in which there is a clinical suspicion ofdeep vein thrombosis (DVT') butother features, such as an atypical history or equivocal radiology, suggest alternative pathology. Five suchcases are presented in which ultrasound showed transonic lesions. The cause of the swelling of the leg wasthus shown to be 'cystic' in nature and therefore not due to DVT. This enabled inappropriate andpotentially harmful therapy to be avoided and the correct therapy, such as surgical drainage, to beundertaken.

Introduction

The investigation ofpatients with a painful swollen legis of considerable importance since the treatmentregimes for the different diagnoses are conflicting. Themain differential diagnoses include deep venousthrombosis (DVT), ruptured Baker's cyst, haematomaor abscess formation. All ofthese can be confused witheach other (Hughes & Pridie, 1970; Rosewarne, 1978;Gompels & Darlington, 1979). This paper reports theuse ofgrey-scale ultrasound in 5 patients with a painfulswollen leg.

Materials and methods

Grey-scale ultrasound was performed on five patientsaged 37 to 89 years, who presented to the Bristol RoyalInfirmary or Weston General Hospital with pain andswelling in the leg. Examination in each case hadconfirmed that their legs were swollen and painful butinvestigations had not established a diagnosis.

Grey-scale ultrasound was performed with thepatients lying supine in one case and prone in the otherfour cases. Longitudinal and transverse scans weredone using a variety of ultrasound machines (Diason-ograph, Phosonic, Philips and A.T.L.).

Case histories

Case I

A 37 year old man sustained lacerations and con-tusions to the right leg in a road accident. Eight dayslater he was admitted with a suspected DVT, his leghaving become very swollen and tender. Plainradiographs showed no bone injury. Ultrasoundshowed a transonic area superficially in the right calf.The calfmuscles were also shown to be enlarged due tobruising (Figures 1 a and 1 b). The transonic area wasdiagnosed as a haematoma. Computed tomographythe following day showed a homogeneous mass lyingsuperficially in the calf (Figure 2). 50 ml of liquidhaematoma were subsequently drained surgically,confirming the diagnosis.

Case 2

A 45 year old man, neutropaenic due to acute myelo-monocytic leukaemia developed severe, painful swell-ing ofhis left thigh and knee. He had a previous historyof DVT. On examination he was in addition found tohave a knee joint effusion. The initial diagnosis ofleukaemic infiltration was soon abandoned in favourof that of DVT and he was anticoagulated. The painand swelling, however, became worse. Plainradiographs confirmed the presence ofajoint effusion.Ultrasound showed a large transonic area in the backof the lower thigh extending laterally. A few echoeswere present within this area. It was thought probably

) The Fellowship of Postgraduate Medicine, 1985

Jonathan M. Bell, M.B., Ch.B., M.R.C.P. (UK); F.G.M.Ross, F.R.C.R., F.F.A.R.C.S.I.; S. Mackenzie, F.R.C.R.;and Paul R. Goddard, M.D., F.R.C.R.Accepted: 23 May 1984

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24 J.M. BELL et al.

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Figure la Case 1. Ultrasound of the calf, midlinelongitudinal scan with the patient prone. There is atransonic mass superficially and increased echogenicity ofthe underlying muscle. (PF: popliteal fossa, H:haematoma, A: towards the ankle).

b Left Leg Right Leg

Figure lb Cross-sectional ultrasound scans of both legs of the same patient. The appearances in the right legrepresented a superficial haematoma and bruising of the underlying muscles. (H: haematoma, T: tibia, F: fibula).

to be an abscess containing necrotic tissue, althoughthe alternative of a haematoma containing somethrombus was also considered.The lesion was subsequently drained producing

700 ml ofgreen pus from which Staphylococcus aureuswas grown.

Case 3

A 73 year old man with ankylosing spondylitis affect-ing his spine presented with a one week history ofincreasing pain, swelling and stiffness in his right calf.There was no previous involvement of his right kneewith ankylosing spondylitis. The calf was found to be

hot, tender and indurated with distended superficialveins. A diagnosis of DVT was made and he wasanticoagulated. Over the following week his legbecame worse and further investigations were ins-tigated. A knee arthrogram was reported as normaland a venogram showed a small thrombus in one ofthedeep veins of the calf. The DVT was too small to fullyaccount for the clinical picture. Ultrasound wastherefore performed and showed a large collection offluid posteriorly extending above and below the knee.The abscess was surgically drained producing a

large quantity of pus from which S. aureus wascultured.

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THE SWOLLEN LEG: ULTRASONOGRAPHIC DEMONSTRATION 25

Case 4

A 69 year old woman presented with a five day historyof a painful swollen right calf. This was found onexamination to be slightly red with some pittingoedema. She had a history ofa Charnley hip prosthesissome years previously and a vaginal hysterectomy onemonth before admission. A diagnosis of DVT wasmade but following anticoagulation her leg becameworse. A knee arthrogram was then performed andshowed a ruptured Baker's cyst. Bloody pus wasaspirated and S. aureus was subsequently grown. Thepain and swelling became worse despite appropriateantibiotics. Ultrasound was then performed andshowed a mass of mixed echogenicity between thegastrocnemius and soleus muscles which was thoughtto be an abscess (Figures 3a and 3b). Computedtomography also clearly showed a mass with a centraldenser part and surrounding lower attenuation(Figure 4). The abscess was surgically drained.

Case S

An 89 year old woman was admitted with a two weekhistory of a painful swelling in the left thigh. She had 2months previously had a dynamic hip screw insertedfor an inter-trochanteric fracture of the left hip. On

examination the thigh was hot and swollen with bluediscolouration of the skin. There was also peripheraloedema ofthe lower leg. Clinically a DVT was initiallysuspected and a venogram requested. Ultrasound ofthe thigh was, however, considered to be a morevaluable first examination and this showed a largelesion with mixed echogenicity and some transonicareas. This was thought to be a haematoma containingthrombus, a diagnosis favoured by the profoundanaemia which had developed since her hip operation.As the cause of the haematoma was uncertain anarteriogram was performed. This showed a leakingfalse aneurysm of one of the branches of the profundafemoris artery just distal to the fracture site.The leg was explored, the haematoma drained and

the feeding vessel ligated. The aneurysm was found tohave been caused by a small bone spicule from thefracture site.

Results

In all 5 patients ultrasound demonstrated partially orcompletely transonic lesions at the site of the legswelling. This confirmed that all of the lesions werewholly or partially cystic and therefore not likely to bedue to DVT. In the two cases in which echoes were

Posterior

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Figure 2 Computed tomography of both lower legs at the same anatomical level as that shown in Figure lb(L20,W400 HU). The haematoma is seen as a superficial swelling ofhomogeneous density. Although the scans wereperformed with the patient supine they have been inverted for easier comparison with the ultrasound.

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26 J.M. BELL el al.

Figure 3a Case 4. Longitudinal ultrasound scan of thecalf with the patient prone. There is a mass of mixedechogenicity, being mainly transonic but containing a fewscattered echoes. (PF: popliteal fossa, A: towards theankle, Ab: abscess).

Left Leg Right Legb

A

Figure 3b Cross-sectional u ltrasound scans of the samepatient (case 4). The appearances represented an abscessdeep in the calf muscles. (Ab: abscess, T: tibia).

present within the lesion the ultrasound appearancessuggested either an abscess containing necrotic debrisor a partially liquefied haematoma. In all cases theinformation obtained by ultrasound was considered assufficient justification for surgical intervention. In 2patients already anticoagulated, this therapy wasstopped following ultrasound. In all cases surgeryconfirmed the lesion to be due to either abscess orhaematorma.

Discussion

Confusion between different conditions that maycause a painful swollen leg is not uncommon (Tait etal., 1965; Rosewane, 1978; Clamn, 1980). The maindifferential diagnoses to be considered are DVT,ruptured Baker's cyst, haematoma and abscess.However the treatment for these conditions differwidely and appropriate therapy for one may beinappropriate or even dangerous in another. It is

therefore of paramount importance to establish thecorrect diagnosis as early as possible. Several of thepossible causes of a swollen leg (Baker's cyst, abscessand haematoma) are likely to contain cystic areas andmay thus be easily demonstrated by ultrasound (Ham-ments, 1982).

In cases of swollen legs where DVT is a possiblediagnosis a variety of radiological investigations areavailable. Venography carries a risk of causing deepvein thrombosis (Berge et al., 1978) although recentevidence suggests this may be minimized by using thenew low-osmolality contrast media (Thomas et al.,1984). In patients with a swollen, oedematous foot,cannulation of a foot vein may prove very difficult, aproblem also encountered in isotope venography.Doppler ultrasound is often inaccurate and requiressudden firm pressure on the affected part causingconsiderable pain. Arthrography for suspected Bak-er's cyst rupture can prove of value (Tait et al., 1965;Rosewarne, 1978) but in patients with a very painfulleg flexion may be difficult and the arthrographyequivocal. Grey-scale ultrasound has the advantagesof being non-invasive, painless and free from sideeffects.

It is clear that ultrasound has a valuable role in theassessment of the painful swollen leg. While it was notpossible in this series to be entirely tissue-specificvaluable information was obtained which enabledappropriate treatment to be undertaken and potential-ly dangerous treatment to be stopped. It is of par-ticular use in cases where DVT had been suggested as apossible cause of the swelling of the leg, but there areatypical features in the history or on examinationwhich cast doubt on the diagnosis.

Posi1r or

Figure 4 Computed tomography of both lower legs atthe same anatomical level as that shown in Figure 3b(LOO,W800 HU). The abscess is again seen between thegastrocnemius and soleus muscles. (Ab: abscess, T: tibia,F: fibula).

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Acknowledgements

We would like to thank the radiographers of Bristol RoyalInfirmary and Weston General Hospital. Acknowledgments

are also due to Dr H.A. Andrews and Dr G. Stoddart forconstructive suggestions and help, to Miss J. Hugh and MrsR. Amesbury for valued secretarial work and to the Depart-ment of Medical Illustration (BRI).

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