Case Presentation:
A 59‐year‐old man presented to the emergency department with new‐onset right testicular pain in the setting of back pain and abdominal distention. After evaluation by his primary care physician 2 weeks prior, he was diagnosed with musculoskeletal back pain that was minimally controlled with ibuprofen. He described the testicular pain as a constant, nonradiating ache. Additionally, he noted frequent urination, decreased urine production, and the sensation of incomplete voiding. Most worrisome to the patient was the abdominal distention that had required adjustment of his belt 4 “notches up” over the past 10 days. His medical history was significant for a stable 3‐cm abdominal aortic aneurysm. Physical examination revealed a distended, tympanic abdomen with rebounding in the right and left lower quadrants. Laboratory evaluation revealed a BUN of 73 mg/dL, a creatinine of 5.3 mg/dL, and more than 100 red blood cells in his urine. Two months earlier, at the patient's general medical examination, his BUN was 15 mg/dL, and his creatinine was 1.0 mg/dL. Dopplerultrasound of the kidney showed no evidence of renal artery stenosis or hydronephrosis. Intrinsic renal and autoimmune diseases were also ruled out. A CT scan of the abdomen and pelvis revealed a periaortic inflammatory process encasing both ureters proximally. Pathologic examination of a biopsy showed fibrosis and chronic inflammation consistent with idiopathic retroperitoneal fibrosis.
Discussion:
The incidence of acute renal failure in hospitalized patients is 2%‐6%. Most cases are a result of either pre‐renal azotemia or acute tubular necrosis. Obstructions are the cause of acute renal failure in 8%‐10% of hospitalized patients, with the obstructions usually a result of medications that impair bladder function, prostate cancer or hyperplasia, in men, and pelvic malignancy, in women. In 1% of cases of acute renal failure with an obstructive etiology, idiopathic retroperitoneal fibrosis is the cause of the obstruction. We describe a classic presentation of a rare cause of post‐renal azotemia. Initial symptoms are vague such as abdominal discomfort, back pain, and malaise. Ultrasound typically shows evidence of hydronephrosis; however, in a small subset of patients (2.5%), it does not. The disease process is insidious, and the diagnosis is often made after the onset of acute renal failure. Treatment modalities such as ureteral stents in combination with immunosuppressive therapy are very successful. Most patients recover 90%‐95% of their baseline kidney function.
Conclusions:
Acute renal failure is a common clinical entity hospitalists encounter, and in 8%‐10% of the cases it has obstructive causes. Retroperitoneal fibrosis is a rare cause of obstructive acute renal failure. Hospitalists should be aware of this condition given its response to treatment and the excellent recovery of kidney function.
Author Disclosure:
R. K. Patch, None; K. M. Swetz, None.