¹Turkiya Abdulla AL Mamari, ²Tariq Al-Araimi, ²Ahmed Al Kindi, ³Yarab Al Bulushi

¹Al Nahdha hospital, ²Royal Hospital, ³Sultan Qaboos University Hospital

Background(s): Vasculitis encompasses a group of disorders characterized by blood vessel inflammation and injury, with classifications based on vessel size and associated conditions. Diagnosing vasculitis poses significant challenges, particularly in isolated vasculitis cases lacking systemic disease diagnostic manifestations. This case discusses a unique presentation of renal artery vasculitis initially appearing as acute renal artery thrombosis masking the underlying diagnosis.

Method(s): A 56-year-old male without prior medical history presented with five days fever, severe abdominal pain, and hematuria. Abdominal examination revealed flank tenderness. His CPR was 68 mg/l (<10 mg/l ) but had normal ESR.  Initial creatinine revealed a creatinine of 113 umol/L (62-110) and urine was bland for protein. Initial CT scans showed right renal artery thrombosis and infarctions in both kidneys. He subsequently was anticoagulated with Low molecular weight heparin but returned to the emergency room one day later with worsening abdominal pains. CT angiogram showed this time circumferential wall thickening of different segments of renal arteries and their branches at renal hila bilaterally with worsening infarcts as well as renal artery segmental occlusions extending to branches. He had an normal ECHO and blood work was not suggestive of thrombophilia, malignancies and infections. An extensive autoimmune investigation all turned back to be negative not limited to ANCA, RF, Antiphoslipid workup, Anti-CCP, Complements, HLA-B27 and HLAB-51.  His abdominal symptoms worsened accompanied with slight rise of creatinine to 121 umol/L (62-110) and slight decreased urine output. A multidisciplinary team meeting consisted of rheumatologists, radiologists and hematologists concluded that his presentation and imaging findings are consistent with vasculitis. Treatment commenced with high-dose IV methylprednisolone, IV cyclophosphamide for induction, and continued prednisolone taper, followed by maintenance with azathioprine and anticoagulation with Rivaroxaban due to labile INRs.

Result(s): The patient’s response to the treatment regimen was positive, with complete relief of pains, normalization of creatinine levels and CT angiogram showing improvement in perivascular inflammatory changes within three months.At eight-month follow-up confirmed sustained recovery and stable kidney function.

Conclusion(s): This case exhibits an unusual presentation of medium vessel vasculitis, concealed initially by bilateral renal artery thrombosis. Comprehensive testing excluded common mimics and secondary causes, yet a definitive systemic vasculitis diagnosis remained elusive. The patient’s quick and consistent improvement with immunosuppressive treatment underscores the benefit of prompt intervention in complex cases. To our knowledge, this represents a distinct case of an acute idiopathic renal vasculitis with a favorable response, unlike the few reported instances in literature, such as granulomatous necrotizing renal artery vasculitis associated with myelodysplasia, Behçet’s disease, or polyarteritis nodosa.

These conditions typically follow a chronic course, often featuring microaneurysms and occasionally stenosis, usually alongside hypertension or major systemic disease specific signs and symptoms.

Diagnosing vasculitis without major chronic systemic signs demands increased awareness and teamwork. This case underscores considering vasculitis in unexplained arterial thrombosis and calls for more research on renal artery vasculitis. Regular follow-up is crucial for early detection of systemic disease progression and effective treatment.