IDIOPATHIC RETROPERITONEAL FIBROSIS: A RARE CAUSE OF ABDOMINAL PAIN AND OBSTRUCTIVE UROPATHY

Abstract

SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Retroperitoneal fibrosis (RPF) is a rare disorder that presents with subtle symptoms. It may be idiopathic or secondary to other causes; with the idiopathic form being either immunoglobulin G4 (IgG4) or non-IgG4 related. The incidence of idiopathic RPF has been reported to be 0.1 per 100,000 person-years with a male-to-female ratio of 1.9:1. Our case aims at highlighting this rare disorder as a cause of abdominal pain in a middle-aged man. CASE PRESENTATION: A 48-year-old man presented with persistent lower abdominal pain, decreased appetite and weight loss for three months. Physical exam was remarkable for mild abdominal tenderness. Laboratory results were remarkable for creatinine 1.6 mg/dL, BUN 56 mg/dL, CRP 35.7 mg/L and ESR 95 mm/hr. CBC, infectious workup, autoimmune panel, serum protein electrophoresis and tumor markers were unremarkable. Serum IgG and immunoglobulin G4 (IgG4) were normal. CT abdomen and pelvis revealed a soft tissue mass surrounding the distal abdominal aorta and inferior mesenteric artery; entrapping the left ureter accounting for left-sided hydroureteronephrosis. The patient underwent left uterolysis and DJ stent placement. Histopathology (H/P) of the mass showed an abundance of fibro-adipose tissue and lympho-plasmacytic infiltration with rare IgG4 positive plasma cells; negative for infection or malignancy. The patient was started on high dose prednisone leading to resolution of clinical symptoms. Serum creatinine level, ESR and CRP also returned to normal. A follow up CT scan showed regression of the mass. DISCUSSION: RPF is a rare fibro-inflammatory disease with poorly understood pathogenesis. Idiopathic RPF accounts for more than 70% of cases, with secondary causes related to retroperitoneal injury, malignancy, infection, drug therapy or genetic factors. Interestingly, a recent study (Zen et al) found a positive correlation between immunoglobin G4 (IgG4) on H/P and idiopathic RPF in 10 cases out of 17 patients. These cases were hallmarked by a unique H/P pattern and elevated serum IgG4 concentration. Our case, however, was the non-IgG4 related type. Patients with IRF most frequently present with abdominal pain, weight loss and features of obstructive uropathy. Elevated inflammatory markers and imaging studies aid in the diagnosis but biopsy is the gold standard. Goals of treatment for RPF is relief of ureteral obstruction and disease regression with glucocorticoids with or without other immunosuppressants. Tamoxifen has been used with success in patients who cannot tolerate glucocorticoids. Biologic therapies such as rituximab and tocilizumab have shown promise in select patients with refractory disease but further research is warranted. CONCLUSIONS: Idiopathic retroperitoneal fibrosis should be kept in the differential diagnosis of a patient presenting with abdominal or flank pain, obstructive uropathy and elevated markers of inflammation. Reference #1: Idiopathic retroperitoneal fibrosis: clinicopathologic features and outcome analysis. Yachoui R, Sehgal R, Carmichael B. Clin Rheumatol. 2016 Feb;35(2):401-7. https://doi.org/10.1007/s10067-015-3022-y. Epub 2015 Jul 25. Reference #2: Idiopathic and secondary forms of retroperitoneal fibrosis: a diagnostic approach. Urban ML, Palmisano A, Nicastro M, Corradi D, Buzio C, Vaglio A. Rev Med Interne. 2015 Jan;36(1):15-21. https://doi.org/10.1016/j.revmed.2014.10.008. Epub 2014 Nov 18. Reference #3: Idiopathic retroperitoneal fibrosis and its overlap with IgG4-related disease. Rossi GM, Rocco R, Accorsi Buttini E, Marvisi C, Vaglio A. Intern Emerg Med. 2017 Apr;12(3):287-299. https://doi.org/10.1007/s11739-016-1599-z. Epub 2017 Jan 9. DISCLOSURES: No relevant relationships by Moses Bachan, source=Web Response No relevant relationships by Muneer Khan, source=Web Response No relevant relationships by Zinobia Khan, source=Web Response No relevant relationships by Mariam Saeed, source=Web Response