Excessive urinary tract dilatation and proteinuria in pregnancy: a common and overlooked association?

BACKGROUND Proteinuria and dilatation of the urinary tract are both relatively common in pregnancy, the latter with a spectrum of symptoms, from none to severe pain and infection. Proteinuria is a rare occurrence in acute obstructive nephropathy; it has been reported in pregnancy, where it may pose a challenging differential diagnosis with pre-eclampsia.The aim of the present study is to report on the incidence of proteinuria (≥ 0.3; ≥ 0.5 g/day) in association with symptomatic-severe urinary tract dilatation in pregnancy. METHODS Case series. SETTING Nephrological-Obstetric Unit dedicated to pregnancy and kidney diseases (January 2000-April 2011). SOURCE database prospectively updated since the start of the Unit. Retrospective review of clinical charts identified as relevant on the database, by a nephrologist and an obstetrician. RESULTS From January 2000 to April 2011, 262 pregnancies were referred. Urinary tract dilatation with or without infection was the main cause of referral in 26 cases (predominantly monolateral in 19 cases): 23 singletons, 1 lost to follow-up, 1 twin and 1 triplet. Patients were referred for urinary tract infection (15 cases) and/or renal pain (10 cases); 6 patients were treated by urologic interventions ("JJ" stenting). Among them, 11 singletons and 1 triple pregnancy developed proteinuria ≥ 0.3 g/day (46.1%). Proteinuria was ≥ 0.5 g/day in 6 singletons (23.1%). Proteinuria resolved after delivery in all cases. No patient developed hypertension; in none was an alternative cause of proteinuria evident. No significant demographic difference was observed in patients with renal dilatation who developed proteinuria versus those who did not. An association with the presence of "JJ" stenting was present (5/6 cases with proteinuria ≥ 0.5 g/day), which may reflect both severer obstruction and a role for vescico-ureteral reflux, induced by the stent. CONCLUSIONS Symptomatic urinary tract dilatation may be associated with proteinuria in pregnancy. This association should be kept in mind in the differential diagnosis with other causes of proteinuria in pregnancy, including pre-eclampsia.