A 73 year old female was diagnosed with Giant Cell Arteritis (GCA), confirmed on temporal artery biopsy. She was treated with prednisone for many years but steroid therapy was recently discontinued. 8 months after discontinuation of prednisone, she presented to the emergency department with a 3 day history of nausea, lower abdominal pain and decreased urine output. She denied vomiting, diarrhea, dysuria, urgency or frequency. On initial evaluation, her blood pressure was elevated at 188/90 mmHg, otherwise she appeared well. On physical examination, abdomen was soft but mildly tender on deep palpation in all the four quadrants without any signs of acute abdomen. Cardiovascular, respiratory and neurological examination was unremarkable. Laboratory studies revealed elevated creatinine of 9.6 mg/dl, blood urea nitrogen of 70 mg/dl, K 7.4. ESR and CRP were elevated. Ultrasound of the kidney was ordered which showed bilateral hydronephrosis with hydroureter. Urology was consulted and the patient underwent bilateral percutaneous nephrostomy tube placement. Subsequently, a CT abdomen and pelvis was ordered to further evaluate the etiology of hydronephrosis. The imaging clearly demonstrated moderate amorphous soft tissue encapsulating the abdominal aorta and iliac vessels consistent with retroperitoneal fibrosis. Secondary causes of retroperitoneal fibrosis such as drugs, malignancy, infections and autoimmune diseases like IgG4 were ruled out. The patient was diagnosed with idiopathic retroperitoneal fibrosis. She was initiated on prednisone 1mg/kg for 1 month followed by gradual taper. Repeat abdominal CT scan a few months later showed resolution of the fibrosis.
Discussion:
GCA is a large vessel vasculitis which primarily involves the external carotid arteries and its branches. Inflammation of the aorta occurs in a few patients, although the signs of aortic involvement may occur years later the initial diagnosis of GCA. The incidence of aortic involvement in GCA may be more frequent than suspected. Review of the literature revealed only a few reported cases of retroperitoneal fibrosis due to GCA. Pathogenesis of idiopathic retroperitoneal fibrosis is unclear but large vessel vasculitis and chronic periaortitis, as seen in retroperitoneal fibrosis, share common pathological mechanism.
Conclusions:
In patients with GCA, early identification of retroperitoneal fibrosis and more specifically, aortic involvement is imperative in order to prevent life threatening emergencies. Current guidelines have no mention of screening in this particular group of patients. Clinicians treating patients with GCA should have a high index of suspicion to identify those who are at risk of retroperitoneal fibrosis.