A rare case of perinephric urinoma due to idiopathic retroperitoneal fibrosis.

Sir,

Urinoma as a consequence of urine extravasation is a rare complication of severe urinary tract obstruction, where it is most frequently in the fetus and the newborn [1]. However, urinoma in adults is usually developed by the traumatic urinary tract injuries [2]. Retroperitoneal fibrosis is an uncommon disease that is characterized by chronic inflammatory process with progressive fibrosis of retroperitoneal tissue and entrapment of ureteres and other structures located in the retroperitoneum [3,4]. We describe an uncommon case of perinephric urinoma secondary to idiopathic retroperitoneal fibrosis.

Case

A 33-year-old male was admitted to the hospital for severe back pain, general weakness and weight loss over the past 3-month duration. He had back pain continuously radiating to flanks, groins and thighs. His medical history was unremarkable. He had a family history of lymphoma. On examination, he presented with costo-vertebral angle tenderness and right upper abdominal tenderness. Laboratory findings revealed elevated erythrocyte sedimentation rate of 106 mm/h, C-reactive protein of 4.226 mg/dL and serum creatinine of 1.7 mg/dL. Urine analysis and its cytology were negative. Serologies and tumour markers were all negative. The chest X-ray and electrocardiogram were within normal. Computed tomography (CT) revealed bilateral hydronephrosis and right perinephric urinoma with retroperitoneal mass compressing both ureters and aorta (Figures 1 and 2). On the third hospital day, the patient's serum creatinine level was increased up to 2.2 mg/dL and urine output was markedly decreased. Bilateral percutaneous nephrostomy was performed to relieve both hydronephrosis. A CT-guided needle-punctured biopsy of the retroperitoneal mass was performed to confirm the diagnosis. On the pathological examination, the tissue showed chronic inflammation with large numbers of mononuclear cells within fibroblasts and collagen bundles (3). Tissue Tb PCR examination to exclude tuberculosis revealed to be negative. There was no evidence of malignancy. The radiologic and pathological findings were consistent with idiopathic retroperitoneal fibrosis with perinephric urinoma, which were completely resolved by oral prednisolone treatment. There has been no sign of relapse during the follow-up of 2 years.

Fig. 1

Computed tomographic images revealed extensive soft tissue infiltration (A, arrow) around abdominal aorta, both iliac arteries and both ureters, accompanied by perinephric urinoma (B, arrow) due to extrinsic compression of ureters and aorta.

Fig. 2

Abdominal aorta and both iliac arteries (arrow heads) were compressed by soft tissue mass, which also cause bilateral hydronephrosis improved by bilateral percutaneous nephrostomy (arrow).

Fig. 3

Tissue was stained with Masson's trichrome. It shows proliferation of fibroblasts and collagen fibre running in many directions with a diffuse cell infiltration of mononuclear cells (×200).

Discussion

Retroperitoneal fibrosis is a rare chronic inflammatory disease characterized by the progressive fibrosis of retroperitoneal tissue, which results in entrapment of ureters, and other retroperitoneal organs leading to an unusual back pain [3-5]. Approximately two-thirds of retroperitoneal fibrosis cases are considered to be idiopathic and to be related with autoimmune mechanisms, but the exact pathogenesis still remains uncertain. The other one-third is associated with many different causes such as use of medicines, malignancies, infections, radiotherapy and prior intra-abdominal surgery. Ureteral obstruction causing acute or chronic renal insufficiency is the most common complication of retroperitoneal fibrosis, which develops ureteral involvements in ∼80–100% of patients. However, this is uncommon in urinary leakage due to urinary tract obstruction of retroperitoneal fibrosis [6,7].

The patient in our case had no evidence of neoplasms, autominnue diseases and drugs related to secondary retroperitoneal fibrosis, where we could conclude that idiopathic retroperitoneal fibrosis was the most reasonable dianosis. The patient had bilateral ureteral involvement with hydronephrosis, which resulted in right perinephric urinoma. His major symptom was severe unusual low back pain, and it resulted from rapidly progressive hydronephrosis and urinoma. CT was the study of choice in the diagnosis of retroperitoneal fibrosis and urinoma (Figure 1). Treatment of retroperitoneal fibrosis is targeted to improve inflammatory process to slow down fibrosis and to relieve the obstruction of ureters or other retroperitoneal structures (Figure 2). Although there is no guideline about the treatment of idiopathic retroperitoneal fibrosis, there were many case reports and retrospective studies that recommend glucocorticoid as a primary treatment [3,8]. For those who are refractory to steroid therapy, immunosuppressants such as cyclophosphamide, azathioprine, methotrexate, mycophenolate mofetil and tamoxifen are recommended as an alternative [9].

In conclusion, urinoma is an uncommon complication of idiopathic retroperitoneal fibrosis, which develops acutely into unusual back pain. Either CT or magnetic resonance imaging (MRI) should be considered to define the cause of vague, non-specific and severe back pain or flank pain.

Conflict of interest statement. None declared.