Intermittent White Urine With Nephrotic-Range Proteinuria and Preserved Renal Function: A Diagnostic Dilemma Between Chyluria, Pseudochyluria, and Amyloidosis.

Milky or "white" urine is usually attributed to chyluria but may also result from lipid-rich proteinuric urine or crystals ("pseudochyluria"). We describe a 47-year-old woman with a 6-month history of intermittent white urine, bilateral edema, nephrotic-range proteinuria (20.3 g/24 h), preserved renal function, near-normal serum albumin, and chronic bronchiectasis. Evaluation for parasitic and non-parasitic chyluria, tuberculosis, and systemic amyloidosis was repeatedly negative. A fasting urine sample showed markedly raised triglycerides but negative tests for chyle. The kidney biopsy was non-representative, and the abdominal fat-pad biopsy was Congo-red-negative. Serum anti-PLA2R antibodies and free light chains were normal. The case illustrates the gray zone between chyluria and pseudochyluria and the challenge of defining the underlying glomerular lesion when tissue diagnosis is limited.