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Abstract: PO2316

Missed Diagnosis: A Case of Asymptomatic Isolated Orthostatic Proteinuria from Nutcracker Phenomenon

Session Information

Category: Trainee Case Report

  • 1700 Pediatric Nephrology

Authors

  • Gaddy, Anna R., Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Moorthi, Ranjani N., Indiana University School of Medicine, Indianapolis, Indiana, United States
Introduction

In children, proteinuria which exceeds 100 mg/m2 per day or 150 mg per day is considered abnormal. Isolated proteinuria is relatively common, but persistent proteinuria is abnormal and should be investigated. Persistent proteinuria can be further divided into orthostatic subtype if the recumbent Pr/Cr is <0.2mg/mg but this rises to abnormal (>0.2mg/mg) after standing.
One cause of orthostatic proteinuria is entrapment of the left renal vein, which is known as the Nutcracker Syndrome.
Orthostatic proteinuria, isolated hematuria and pelvic congestion pain are the most common manifestations, however Nutcracker Syndrome is highly heterogeneous and frequently missed.

Case Description

We present an 18 year-old female with intermittent proteinuria, hematuria and occasional flank pain for nine years. The patient had proteinuria on dipstick at age eight. At age 15, she again was noted to have proteinuria on serial urinalyses with up to 500mg/dL protein. ANA, anti-dsDNA, C3, and C4 were normal. Renal ultrasound was performed with unremarkable kidneys and urinary bladder. For several years, proteinuria was mild and intermittently negative and no further workup was done. Split urine collection demonstrated minimal protein on first morning void but over 1g/g Pr/Cr by afternoon. We ordered renal ultrasound with Doppler, which demonstrated Doppler ultrasonography showed the left renal vein had significantly increased flow velocity and appeared to be compressed between the AO and SMA.

Discussion

Differential for etiology of orthostatic proteinuria should include Nutcracker Syndrome as this diagnosis requires a high degree of suspicion.
Nutcracker Syndrome can involve proteinuria as well as hematuria but also pelvic pain, back pain, and pelvic congestion symptoms.

Elevated flow velocity in the LRV of 342 cm/s