Results

RVT was suspected in most patients because of the presence of recent development of heavy proteinuria, peripheral oedema, or concomitant antiphospholipid antibody syndrome symptoms, or all three (table 1). No obvious clinical symptoms were detected except very mild flank soreness and knocking pain in two patients during the physical examination. At the time of RVT development, active lupus features (pleural effusion, arthritis, haemolytic anaemia, vasculitis, malar rash, pericardial effusion) and/or active lupus nephritis were noted in clinical evaluation. Characteristically, all patients had nephrotic syndrome with a mean duration of antecedent nephrotic syndrome history for 3.2 months (range 2–4). A renal biopsy, performed at the time of diagnosis of RVT, showed WHO class V lupus membranous glomerulonephritis in two patients, class IV in three patients, and class III in one patient. In addition, microthrombosis in glomerulus were also identified in patients 4 and 5. Evaluation of renal function showed transient abnormality with increase in serum creatinine and decrease in the renal glomerular filtration rate in patient 1 and 3. Patient 6, however, had acute renal failure and needed haemodialysis twice. The serum creatinine decreased from 6.2 mg/dl and was maintained at 3.9 mg/dl after the start of treatment. All our lupus patients with RVT were women.

Discussion

Since the 1950s, numerous studies of renal biopsy in patients with SLE have been done in an attempt to define its pathological features and to determine the prognostic value of the pathological findings. The intrarenal vascular changes in patients with SLE have, however, received little attention. A recent study of clinicopathological necropsy data of vascular changes in the kidneys of 100 patients with SLE has shown that vascular changes (necrotising arteritis, mucinous intimal thickening, and RVT) seen in patients with SLE often modify the clinical course. The incidence of RVT was almost 2%.1 The findings from Kant suggest that glomerular thrombi occur frequently and are a singularly important factor in determining whether glomerulosclerosis develops subsequently.10 Although rare, the intrarenal vascular changes may be responsible for the sudden deterioration of renal function in some lupus patients, factors that cannot be explained by the presence of lupus glomerulonephritis alone. Clinically, early reports of RVT emphasised the presence of flank pain, microscopic haematuria, flank tenderness, rapid deterioration of renal function, and worsening of proteinuria.11 However, Harrisonet al in 1956 described two groups of patients with RVT.12 The first group had a sudden onset of the above mentioned symptoms, while the second group had only the nephrotic syndrome and absence of any acute symptoms. The only clinical manifestation in these patients was peripheral oedema. Our patients belonged to the second group of RVT, with predominant clinical symptoms of nephrotic syndrome as classified by Harrison et al. High suspicion is essential for early diagnosis of this potentially treatable condition.

In a large scale evaluation of the risk factors in developing RVT in SLE patients,8 the results showed that SLE patients with peripheral thrombophlebitis had a high risk of developing RVT (61.5%). Patients with nephrotic syndrome have a smaller risk (27%). In their study, RVT in SLE patients who have nephrotic syndrome is just as frequent as in patients who have nephrotic syndrome of other aetiology. Our data, on the contrary, delineate a different clinical picture in Chinese SLE patients with RVT. It might be indicated that RVT in SLE patients was related to nephrotic syndrome, regardless of renal histopathological type. Furthermore, four patients had a positive antiphospholipid antibody syndrome profile at the time of diagnosis of RVT. Whether or not these ACA played a part in the development of RVT was not confirmed definitely. The reason for this disparity is still unknown, but ethnic difference (white versus Chinese), study design (prospective versus retrospective) are all possible.

RVT is frequently reported to be associated with membranous glomerulonephritis.13 The earliest findings showing that RVT occurred only in membranous glomerulonephritis led to the suggestion that RVT was the primary event in causing membranous glomerulonephritis and nephrotic syndrome by releasing renal tubular antigens. In contrast with this view, after a review of all the cases with nephrotic syndrome, Dr Zucchelli provided the tentative conclusion that RVT does not occur exclusively with membranous glomerulonephritis,14 even though the prevalence seems to be more common in membranous glomerulonephritis. In this study, RVT was found both in WHO class V, class III, and class IV lupus nephritis. Therefore, in agreement with Zucchelli, our data suggest that RVT is caused by nephrotic syndrome, particularly when complicated with increased blood viscosity, hypercoagulation state resulting from nephrotic syndrome (increased protein synthesis, including coagulation factors, and/or increased urinary loss of anti-thrombotic proteins such as anti-thrombin III during nephrotic syndrome),5intravascular volume depletion, and other treatments such as high dose corticosteroid use. Although the retrospective nature of the study and the lack of detail information about the background SLE and RVT population weakens conclusions made about pathogenesis of RVT in this population, it is important to recognise these triggering factors in the treatment of RVT in SLE patients.