Abstract
Background: Foamy urine is often reported to be associated with proteinuria and kidney diseases. There is no objective measure on the nature and correlation of this relationship. Literature reviews revealed very few studies that can confirm or refute this relationship. This study hypothesized that the severity and persistence of urinary foam were associated with the degree of proteinuria (as determined by urine protein-creatinine ratio and dipstick). Methods: We analyzed urine samples of patients from our chronic kidney disease (CKD) clinics for urine protein and foam. The urine samples were shaken in a standardized way and heights of resting foam (in millimeters) were measured after a pre-determined resting time. The foam heights were correlated with clinical variables including proteinuria, stages of CKD, gender, age, co-morbidities and urine specific gravity. Results: A total of 160 urine samples were analyzed. Greater foam height was significantly associated with advanced CKD stages (p=0.015), urine dipstick protein (p<0.001), urine PCR (p=0.005) and diabetes mellitus (p=0.013). Urine specific gravity (p=0.053) and hypertension (p=0.91) did not achieve statistically significant results with foam height. Further analyses were performed on 54 urine samples with no or low protein level (defined as urine PCR of less than <100 mg/mmol AND urine protein dipstick result of ≤ 1+). In these samples, there was no statistically significant relationship between foam height and CKD stages (p=0.403), specific gravity (p=0.564), diabetes mellitus (p=0.909) and hypertension (p=0.08). Conclusion: Our study showed that urinary foam can be used as a rudimentary surrogate marker for proteinuria in patients with CKD. It provides extra leverage to the age-long assumptions that urinary foam is associated with kidney disease and proteinuria. More research will be needed to ascertain and investigate the nature of this relationship.
Highlights
Foamy or frothy urine is often associated with proteinuria
All early morning urine samples sent for urine protein creatinine ratio (PCR) from the chronic kidney disease (CKD) clinics during a three-month time frame were included in the study
Advanced CKD stages and diabetes mellitus were significantly associated with increased age, dilute urine and higher level of serum creatinine and urinary protein
Summary
Foamy or frothy urine is often associated with proteinuria. Most clinicians and laymen will associate the presence of foam in the urine with some form of kidney diseases. There is no evidence to correlate nature or degree of foaming with clinically proven proteinuria. Our literature review revealed a dearth of reports or research on the subject matter, likely due to the absence of an accepted clinical definition for the condition and a validated approach for assessing foam. The identification and quantification of urinary protein are important investigations in the management of renal diseases. These investigations play an important role in determining the diagnosis and prognosis of various renal pathologies. Foamy urine is often reported to be associated with proteinuria and kidney diseases. This study hypothesized that the severity and persistence of urinary foam were associated with the degree of proteinuria (as determined by urine protein-creatinine ratio and dipstick)
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