Chyluria associated with nephrotic-range proteinuria: pathophysiology, clinical picture and therapeutic options.

Chyluria denotes the urinary excretion of chyle, which is a lymphatic fluid rich in chylomicrons. Chyle flows from the intestinal lacteals to the left subclavian vein through the thoracic duct. When an abnormal connection between these structures and the urinary tract develops, chyluria appears. The syndrome is often associated with a nephrotic-range proteinuria, and this could be a wrong indication to perform renal biopsy. Chyluria is classified as parasitic or nonparasitic, the former being induced by lymphatic filariasis, whereas the latter is caused by medical, traumatic or inherited diseases. The patient usually reports excretion of milky urines, monolateral flank pain, malnutrition, weight loss and weakness. Urinalysis demonstrates lymphocyturia associated with chylomicrons and triglycerides in the supernatant. The diagnostic approach is aimed to define the site of lymphourinary fistula. A selective ureteral catheterization allows to collect urine samples from each kidney, demonstrating a monolateral source of proteins and lipids and making renal biopsy superfluous. Other diagnostic tools include nuclear magnetic resonance urography and lymphoangiography. Many therapeutic options have been proposed. Sclerosing solution instillation into the renal pelvis and laparoscopic renal pedicle disconnection are the invasive procedures most commonly employed. Among the medical alternatives, a low-fat diet supplemented with medium-chain triglycerides is often followed by complete clinical and biochemical remission.