Over the past 20 years, high-resolution ultrasound (US) has become an essential tool to aid the diagnosis and administration of treatment in rheumatological practice. As an imaging modality that involves no radiation, is well tolerated and can be readily available in the clinical/bed-side setting, it has been shown to be generally more accurate than clinical examination in identifying synovitis, tenosynovitis and bursitis and more sensitive than plain radiographs, in identifying bony erosions.

Using information provided by power Doppler on hyperaemia of the synovial tissue compartment in combination with the grey-scale image information about synovial thickening and/or effusion, US is generally accepted as not only sensitive but also specific for active synovitis. Figure 1 shows an example of an active synovitis in a metacarpo-phalangeal joint.

Fig 1: showing a longitudinal (left image) and transverse (right image) view across the dorsal aspect of a mid-finger MCPJ with synvial thickening and effusion, associated with moderately increased power Doppler hyperaemia.

Arthralgia is a very common feature of patients with lupus. It is, however, recognised that arthritis (i.e. synovitis) can be elusive on clinical assessment. The latest international disease classification criteria by the Systemic Lupus International Collaborating Clinics (SLICC) group in 2012 reflect this: while synovitis with swelling in two or more joints is one of the criteria, the clinical finding of two or more tender joints in the context of inflammatory arthralgia (i.e. morning stiffness of more ≤ 30 minutes) is considered a valid alternative to fulfil the criterion ‘synovitis’1.

Ultrasound changes indicating synovial pathology can be demonstrated in the joints of hands, wrists and forefeet, even in asymptomatic lupus patients 2, although it is not clear whether this should lead to a re-classification of any patients with borderline criteria for SLE. A systematic review showed that US findings in joints of lupus patients show a very variable prevalence of synovitis (25 94 %), tenosynovitis, power Doppler hyperaemia and even bone erosions - even though SLE is usually considered a non-erosive joint disease 3. What is clear from these studies is that further systematic research is needed to evaluate well characterised, larger cohorts in terms of their sonographic joint disease manifestations. It is currently not known whether treatment decisions based on such findings, i.e. treatment escalation for US-active joint disease, is superior in terms of clinical outcome than treatment decisions based on clinical findings without US information. For the management of early rheumatoid arthritis, such US directed treatment escalations have proved not superior in the published studies so far. It should be appreciated that beyond the use for suspected joint disease, US can also be used to identify pleural and pericardial effusion (to diagnose the serositis of SLE, another SLICC criterion); and assess salivary gland inflammation in patients with Sjögren’s syndrome 4, a condition recognised to overlap with SLE from time to time. This illustrates further the versatility of US as a bed-side imaging modality, in the comprehensive assessment of patients with SLE.

References:
1. Petri M et al. Arthritis Rheum. 2012 August ; 64(8): 2677–2686.
2. Iagnocco A et al. Rheumatology 2014;53:465_472.
3. Zayat AS et al. Rheumatology 2016;55:485_494.
4. Mossel E et al. Ann Rheum Dis. 2017 Nov;76(11):1883-1889.

Dr Rainer Klocke
Consultant Rheumatologist & Honorary Senior Lecturer
Musculoskeletal and Dermatological Science
School of Biological Sciences
University of Manchester

Dudley Group NHS Foundation Trust
Department of Rheumatology
Russells Hall Hospital
Pensnett Road
Dudley
West Midlands, DY1 2HQ