LAUSR

A 48-year-old woman presented with right flank pain and fever with past medical history of Henoch Schönlein purpura, cold urticaria and untreated hypertension. She was hypertensive (170/110 mmHg) and had an unremarkable examination other than minimal right flank tenderness. Her pathology showed elevated inflammatory markers including mild leucocytosis with neutrophilia, raised C-reactive protein, negative cultures and elevated lactate dehydrogenase (LDH). Her renal functions were normal with a bland urinary sediment and normal ultrasound. Computed tomography (CT) scan revealed patchy heterogeneous wedge-shaped areas within the right kidney. Follow-up CT angiogram identified a wedgeshaped vascular defect in the renal parenchyma, confirming infarction (Fig. 1). Other renal vascular changes seen included focal abrupt tapering, beading and irregularity of some areas bilaterally and a small microaneurysm, all suggestive of fibromuscular dysplasia (FMD). There was no extrarenal involvement. Renal digital subtraction angiography revealed ostial dissection of the superior branch of the right renal artery causing occlusion. FMD is a rare non-inflammatory, non-atherosclerotic vascular disease with a wide variety of clinical presentations, from asymptomatic to devastating cerebrovascular accidents. It can affect small and medium sized arteries, and has been reported in almost all vascular territories. Renal infarction is a rare complication of FMD with only 29 case reports published in English literature. Renal infarction most often presents with flank pain, with or without fever, vomiting and oliguria, so it is important to consider the diagnosis after more common diagnoses like renal calculi and pyelonephritis are excluded. The diagnosis is easily missed, as many features are non-specific, such as the presence of leucocytosis, haematuria and LDH elevation (elevated in 95% of cases). Investigations should be done to rule out other differential diagnosis including medium vessel vasculidities and thromboembolic causes. This patient returned negative autoimmune and thrombophilia screens and normal echocardiograph. The diagnosis of FMD can now be made on angiography (either non-invasive or invasive) rather than requiring tissue sample for histological diagnosis. There are two classifications: multifocal FMD, which is characterised by the classical ‘string of beads’ appearance, and focal FMD,with a single concentric band-like stenosis. Current guidelines recommendCThead to pelvis to identify extrarenal disease, which thispatientdidnothave. This case highlights the importance of recognising and treating FMD as renal artery dissection and subsequent renal infarction is a rare but under-recognised complications of FMD.