Clinical Significance of Subjective Foamy Urine

Abstract

Foamy urine is widely regarded as a sign of proteinuria. However, there is no objective definition of foamy urine and there are no reports on the proportion of involved patients who have overt proteinuria or microalbuminuria. We performed this study to investigate this proportion and to identify possible risk factors for these two conditions. We reviewed all new outpatients from 1 November 2011 to 30 April 2012 and identified patients complaining of foamy urine. Their demographic data and medical records were examined. In particular, we tabulated the patients' spot urinary protein to creatinine ratio, spot urinary microalbumin to creatinine ratio (ACR), blood urea nitrogen (BUN), and serum levels of creatinine (Cr), uric acid, calcium, phosphate, and glucose. In addition, we calculated estimated glomerular filtration rates (eGFRs) by using the CKD-EPI equation. We also performed risk factor analysis with the Chi-squared test and by logistic regression. Seventy-two patients (6.3% of total new outpatients) complained of foamy urine; of these, there were 59 males with a median age of 65.5 years (range, 36-87 years). Of the 72 patients, 16 (22.2%) had overt proteinuria. We found that diabetes, poor renal function (high Cr, BUN, low eGFR), increased serum phosphate, and increased serum glucose were associated with overt proteinuria. Multiple logistic regression analysis showed that serum Cr and serum phosphate were associated with overt proteinuria. The ACR was available for 38 patients, and in this subgroup, 12 (31.6%) showed microalbuminuria or overt proteinuria. In this subgroup, a high serum Cr was the only statistically significant risk factor. Among patients who complained of foamy urine, approximately 20% had overt proteinuria, and increased serum Cr and phosphate were statistically significant risk factors.

Foamy Urine

“…In fact, it is listed by most electronic health records in their customizable specialty templates as a symptom of kidney disease. Only about one third of patients volunteering this complaint will be found to have abnormal proteinuria, so most cases of "foamy" urine remain unexplained (1). We found no studies specifically examining the physio-chemical characteristics of urine that foams upon voiding.…”

The Urine Foaming Test in COVID19 as a Useful Tool in Diagnosis, Prognosis and Follow-up: Preliminary Results

“…Proteinuria is a cardinal sign of diverse renal diseases and may result in foamy urine. Foaming occurs because albumin has a soap-like effect that reduces the surface tension of urine [ 11 ]. Foam forms by trapping pockets of gas in liquid with the help of surfactant.…”

Schistosoma haematobium infection is associated with increased urine foam

“…7 Increased urine foam is a poorly understood and reported phenomenon, but may result from renal disease. 8 The presence of urine albumin may reduce the surface tension of urine, allowing for the development of foam although the association with proteinuria is unclear. 8,9 There are no reports of an association between urine foam and schistosomiasis, but proteinuria has been associated with S. haematobium infection.…”

“…Increased urine foam is a poorly understood and reported phenomenon, but may result from renal disease . The presence of urine albumin may reduce the surface tension of urine, allowing for the development of foam although the association with proteinuria is unclear .…”