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Proteinuria

Proteinuria causes, symptoms and treatments

Healthy individuals pass frothy or bubbly urine every now and then. This may be caused by the speed and force that urine is passed out and the proteins that occasionally come with it. This transitory proteinuria (“protein in urine”), also sometimes called albuminuria, is normal and can be found in a number of benign conditions such as fever and pregnancy. However, persistence can be an early warning sign of impending or ongoing kidney disease. Medically defined, proteinuria is excretion of more than 150 mg daily of protein in the urine and warrants further investigation. 

 

Types and causes of proteinuria 

Proteinuria can be divided into transient or temporary and persistent. The former does not necessarily require more comprehensive evaluation, and the proteinuria resolves once the inciting event is addressed; the latter is pathological proteinuria, and patients need thorough medical evaluation to manage the cause and prevent further deterioration. 

 

Transient or Temporary 

Persistent 

  • Dehydration 
  • After strenuous exercise 
  • High fever 
  • Postural or orthostatic proteinuria: Related to changes in body posture, common in children. Usually, there is no proteinuria in the morning, but it will be detected after activities during the day 
  • Pregnancy 
  • Vaginal mucus 
  • Urinary tract infection 
  • Glomerular proteinuria: most common cause of persistent proteinuria; glomerular lesions increase the excretion of albumin in the urine, often resulting from conditions such as diabetes (most common), dyslipidemia, drug-induced nephropathy (NSAIDs, lithium, heavy metals), malignancies & connective tissue disease (e.g. SLE) 
  • Renal tubular proteinuria: Renal tubular disease reduces the proximal tubule’s ability to re-absorb filtered proteins, which can be caused by drugs such as immunosuppressants (cyclosporin, tacrolimus) and analgesics (NSAIDS) and hypertension (hypertensive nephrosclerosis) 
  • Overflow proteinuria: An abnormal increase in low molecular weight protein exceeds the reabsorbing capacity of the renal tubules;  common in conditions such as amyloidosis, multiple myeloma and myoglobinuria 
  • Secretory proteinuria: usually from oversecretion of specific proteins in the tubules, most notably Tamm-Horsfall proteins in interstitial nephritis 

 

Symptoms Commonly Associated with Proteinuria 

Proteinuria is usually asymptomatic in the early stages, but it can still be identified through urine analysis. As the disease becomes more serious, more symptoms may appear: 

  • Urine is persistently foamy due to high protein content 
  • Edema of the hands, feet, abdomen, and face 
  • Frequent urination 
  • Shortness of breath 
  • Eyes that are puffy especially in the morning 
  • Loss of appetite 
  • Fatigue 
  • Muscle pain especially at night 
  • Chronic low-grade fevers 
  • Unexplained weight loss 

Proteinuria is a warning sign for kidney disease and other chronic diseases. If the condition persists, it can lead to acute renal failure, fluid accumulation in the lungs, and an increased risk of cardiovascular disease, bacterial infection, and arterial or venous embolism. 

 

High-risk group for proteinuria 

 The following conditions predispose people to proteinuria: 

  • Hypertension 
  • People with type 1 and type 2 diabetes 
  • Obesity 
  • Primary nephropathy (kidney dysfunction) 
  • Aged 65 and above 
  • Family history of kidney disease 
  • Pregnancy toxemia (hypertension due to pregnancy) 
  • Individuals with autoimmune connective tissue disorders such as SLE, rheumatoid arthritis (RA) and Sjögren’s disease 

  

Diagnostic methods for proteinuria 

To determine whether there is proteinuria, the most direct way is to conduct a urine test (Urinalysis); 24-hour albumin content and serum creatinine testing can also be used to test the albumin content and kidney function respectively. In addition, a complete blood count, urine bacterial culture, and other blood tests are ways to detect proteinuria. 

The following are different types of proteinuria based on laboratory findings:  

Normal Level 

Moderately Elevated 

(also called microalbuminuria) 

Severe Elevation (also called macroalbuminuria) 

Urinary protein excretion <150mg/day 

or  

Median albumin excretion rate is 5-10mg/day 

Albumin excretion rate is 30-300mg/day 

Albumin excretion rate>300mg/day 


  

Treatment of proteinuria 

Since proteinuria is interrelated with kidney disease and other chronic medical conditions, the treatment is mainly directed at the root causes of persistent proteinuria enumerated in the table above. For chronic medical conditions such as diabetes, hypertension and obesity, lifestyle modification (i.e. diet, exercise, sleep/rest, smoking cessation) coupled with medication and regular monitoring are the mainstays of management. Prior awareness of nephrotoxic effects of different medications especially common ones like (non-steroidal anti-inflammatory drugs) NSAIDs, beta-lactam antibiotics (e.g. co-amoxiclav) and quinolones (e.g. levofloxacin) can prevent kidney damage. And malignancies and auto-immune connective tissue disorders can be discussed with medical experts and family members for optimum approach to multi-modal management.  

 

Prevention of proteinuria 

In Hong Kong, two studies, namely, the Screening for Hong Kong Asymptomatic Renal Population and Evaluation program (The SHARE program 2003) and Relatives in silent kidney disease screening study in Hong (The RISKS study 2009), emphasized that: (1) simple screening methods such as urinalysis and blood pressure measurement, and (2) screening asymptomatic first-degree relatives of patients with chronic kidney disease (CKD), are means by which the populace can be proactively advised of their risks of developing kidney disease even without overt symptoms.   

OT&P Medical Advice 

When it comes to kidney disease, the earliest awareness through personal or family history and professional medical advice provides the greatest benefit for at-risk individuals who can start with a simple urine test. At OT&P Healthcare, we aim to help you understand your health better. We offer a range of services, including a general practice clinic. Contact us today to book an appointment.

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References 

Johns Hopkins Medicine. Proteinuria.7 Dec 2023 Retrieved from https://www.hopkinsmedicine.org/health/conditions-and-diseases/proteinuria  
Cleveland Clinic. Proteinuria.7 Dec 2023 Retrieved from https://my.clevelandclinic.org/health/diseases/16428-proteinuria  
WebMD. Protein in Urine (Proteinuria). 7 Dec 2023 Retrieved from https://www.webmd.com/a-to-z-guides/proteinuria-protein-in-urine  
Mobeen Z. Haider; Ahsan Aslam. Proteinuria. NIH National Library of Medicine, National Center for Biotechnology Information StatPearls, September 4, 2023. from https://www.ncbi.nlm.nih.gov/books/NBK564390/, retrieved on 16 February 2024. 
Li PKT, Kwan BC, Leung CB, Kwan TH, Wong KM, Lui SL, Tsang WK, Mak CC, Mak SK, Yu AW, Tang S; Hong Kong Society of Nephrology. Prevalence of silent kidney disease in Hong Kong: the screening for Hong Kong Asymptomatic Renal Population and Evaluation (SHARE) program. Kidney Int Suppl. 2005; 67 (s94): S36-S40  
Li PKT, Cheng YL, Kwan TH, Leung CB, Lau MF, Choi KS, Fung SKS, Ho YW, Mak SK, Tang SC, Wong KS, Yong D, Lui SL; for The Hong Kong Society of Nephrology. RISKS Study: Relatives in Silent Kidney-disease Screening Study. Nephrology. 20 November 2017, from https://pubmed.ncbi.nlm.nih.gov/29155503/ retrieved on 16 February 2024.  

Please note that all medical articles featured on our website have been reviewed by qualified healthcare doctors. The articles are for general information only and are not medical opinions nor should the contents be used to replace the need for a personal consultation with a qualified medical professional on the reader's medical condition.

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