From the Guidelines
Proteinuria in young women is most commonly caused by urinary tract infections, with Escherichia coli accounting for more than 90% of acute pyelonephritis cases in this population. The causes of proteinuria in young women can be multifaceted, including:
- Urinary tract infections, which cause protein leakage due to inflammation of the urinary tract 1
- Exercise-induced proteinuria, a temporary condition that resolves after rest
- Orthostatic (postural) proteinuria, which occurs when standing but disappears when lying down, typically benign in young adults
- Pregnancy-related conditions like preeclampsia, due to changes in kidney function and blood pressure
- Glomerular diseases like lupus nephritis, IgA nephropathy, and minimal change disease, which damage the kidney's filtering units, allowing protein to leak into urine
- Other causes, such as diabetes, hypertension, certain medications (NSAIDs, antibiotics), and genetic conditions
Evaluation of proteinuria typically includes urinalysis, protein-to-creatinine ratio, blood tests, and sometimes kidney biopsy 1. The National Kidney Foundation recommends a cutoff value for an albumin–creatinine ratio greater than 30 mg/g in men and women to detect proteinuria 1. Treatment depends on the underlying cause, ranging from antibiotics for infections to specific medications for glomerular diseases. Any persistent proteinuria warrants medical evaluation to prevent potential kidney damage.
Key risk factors for developing acute pyelonephritis, a common cause of proteinuria in young women, include sexual activity, new sexual partner, spermicide exposure, personal or maternal history of UTIs, genetic predisposition, and diabetes mellitus 1. Factors that disrupt urinary flow, such as vesicoureteral reflux, congenital urinary tract anomalies, altered bladder function, pregnancy, renal calculi, or mechanical obstruction, also increase the risk of developing acute pyelonephritis 1.
From the Research
Causes of Proteinuria
- Proteinuria can result from nonpathological processes such as posture, fever, or exercise, as well as pathological processes including glomerular or tubular disorders 2
- Glomerular proteinuria is an early sign of kidney disease and may play a role in the progression of glomerular damage 2
- Persistent proteinuria can be caused by disorders associated with increased glomerular permeability, such as nephrotic syndrome, glomerulonephritis, and genetic defects like Alport syndrome and mesangial sclerosis 2
- Tubular disorders should also be considered as a potential cause of proteinuria 2
Types of Proteinuria
- Functional proteinuria can occur in disorders with altered renal hemodynamics and usually resolves without progressive renal disease 3
- Idiopathic transient proteinuria is typically discovered on routine screening and usually disappears on subsequent testing 3
- Orthostatic proteinuria is a benign condition where the rate of protein excretion normalizes in the recumbent position 3
- Persistent isolated proteinuria represents a heterogeneous group, but a significant proportion of these patients have prominent renal pathologic findings and may progress to serious renal disease 3
Proteinuria in Young Women
- Persistent proteinuria in adolescents should be regarded seriously, as it may be associated with chronic kidney disease 4
- However, most adolescents with proteinuria on screening urinalysis do not have renal disease, and the proteinuria usually resolves on repeat testing 4
- Urinary tract infections are common in adolescents and young adults, and may be associated with proteinuria or hematuria 5
Mechanisms of Proteinuria
- Proteinuria can result from dysfunction of the glomerular filtration barrier, including damage to the endothelium, glomerular basement membrane, or podocytes 6
- Increased intraglomerular hydraulic pressure or damage to the glomerular filtration barrier can elicit glomerular or overload proteinuria 6
- Albuminuria can induce expression of inflammatory and fibrogenic mediators, resulting in inflammation and fibrosis, and ultimately leading to loss of renal function 6