A patient with a floating kidney and nephrotic syndrome.

Asymptomatic retroperitoneal fluid is rarely detected. We encountered a young man with known nephrotic syndrome who presented with left-sided abdominal pain. He had very little peripheral edema, but a massive fluid collection around a "floating" left kidney, as determined by three different imaging studies. Large amounts of fluid and a cyst surrounding the kidney were removed laparascopically and malignancy was excluded. The patient had a rare benign cystic mesothelioma together with focal-segmental glomerulosclerosis. Both diseases do not seem to be causally related. Complete surgical resection of the mesothelioma is the definitive treatment. If resection is incomplete, recurrence is frequent. Indeed, when our patient returned some years later for an elective hernia repair, the fluid collection had recurred.