The key difference between glomerular and tubular proteinuria is that in glomerular proteinuria, the body excretes approximately 20g of proteins in 24 hours through glomeruli, while in tubular proteinuria, the body excretes less than 1–2g of proteins in 24 hours through tubules.
Proteinuria is a medical condition that causes high levels of protein in the urine. Usually, proteins get added to urine if the kidneys do not work properly. Proteins may flow into the urine if there is damage to the glomeruli (glomerular proteinuria) or tubules (tubular proteinuria) and a problem with the reabsorption process of the proteins.
CONTENTS
1. Overview and Key Difference
2. What is Glomerular Proteinuria
3. What is Tubular Proteinuria
4. Similarities – Glomerular and Tubular Proteinuria
5. Glomerular vs Tubular Proteinuria in Tabular Form
6. Summary – Glomerular vs Tubular Proteinuria
What is Glomerular Proteinuria?
Glomeruli are groups of tiny blood vessels in the kidneys of humans. They perform a pivotal role in ultrafiltration. They participate in the first stage of filtering waste products and excess water from the blood. Generally, waste products and excess water leave the body through urine. However, glomeruli do not allow the passage of larger proteins or blood cells into the urine through their tiny blood vessels. If smaller proteins escape through the glomeruli, then long, thin tubes called tubules in the kidneys recover these proteins and send them back to the blood of the body.
Glomerular proteinuria happens when the body excretes approximately 20g of proteins in 24 hours through glomeruli. These proteins mainly consist of albumins. Glomerular proteinuria can be caused by a damaged glomerular filtration barrier or increased hydrostatic pressure due to factors like diabetic nephropathy, drug-induced nephropathy, lymphoma, Infections (HIV, hepatitis B, and C), primary glomeruli nephropathies, amyloidosis, malignancies, dyslipidemia, reactive oxygen species, inflammatory cytokines, activation of the renin-angiotensin system, and diseases in connective tissue.
Figure 01: Glomerular Proteinuria
The typical symptoms of this condition may include pink-colored urine (red blood cells in the urine), foamy or bubbly urine due to excess protein urine, high blood pressure, fluid retention or edema in different parts of the body, frequent urination at nighttime, nausea, vomiting, muscle cramps, weakness or fatigue.
Glomerular proteinuria can be diagnosed through physical examination, blood tests, and urine tests. Furthermore, glomerular proteinuria can be treated by controlling blood pressure through ACE inhibitors or ARBs, taking diuretics to manage edema, making changes to the diet (ex: eating less salt), and taking medications such as corticosteroids to keep the immune system less active.
What is Tubular Proteinuria?
Tubular proteinuria is a type of proteinuria that excretes less than 1–2g proteins in 24 hours through tubules. This condition is caused due to damage or problems in the tubules of the kidney by inherited diseases such as RTA (renal tubular acidosis), cystinosis, Wilson disease, Fanconi syndrome, Lowe syndrome, Dent disease, nephronophthisis, and acquired diseases nephrotoxic drugs disease, interstitial nephritis, reflux nephropathy, acute tubular necrosis, and heavy metal poisoning. The symptoms of this condition may include foamy, frothy, or bubbly urine due to proteins in the urine, swelling in the hands, feet, abdomen, or face, urinating frequently, throwing up, and muscle cramps at night.
Figure 02: Tubular Proteinuria
Moreover, tubular proteinuria is diagnosed through physical examinations, blood tests, urinary protein electrophoresis showing predominant globulin excretion (measurement of β2-microglobulin), imaging tests (CT and ultrasound), and kidney biopsy. Furthermore, tubular proteinuria is treated with anti-proteinuric medications such as ACE inhibitors or ARBs, lifestyle changes (eating fewer proteins, limiting salt, taking more fiber, exercising, and quitting smoking), and avoiding nonsteroidal anti-inflammatory drugs (NSAIDs) unless recommended by a doctor.
What are the Similarities Between Glomerular and Tubular Proteinuria?
- Glomerular and tubular proteinuria are two types of proteinuria due to problems in the parts of the kidney.
- Both conditions may have similar symptoms, such as foamy or bubbly urine, frequent urination, fatigue, etc.
- Both conditions can be diagnosed through physical examinations, blood tests, and urine tests.
- They are mainly treated through specific medications.
What is the Difference Between Glomerular and Tubular Proteinuria?
In glomerular proteinuria, the body excretes approximately 20g of proteins in 24 hours through glomeruli, while in tubular proteinuria, the body excretes less than 1–2g of proteins in 24 hours through tubules. Thus, this is the key difference between glomerular and tubular proteinuria. Furthermore, in glomerular proteinuria, the body mainly excretes higher molecular weight proteins such as albumins, while in tubular proteinuria, the body excretes both higher molecular weight proteins such as albumins and lower molecular weight proteins (<60 000 Da).
The infographic below presents the differences between glomerular and tubular proteinuria in tabular form for side-by-side comparison.
Summary – Glomerular vs Tubular Proteinuria
In proteinuria, there is a high level of proteins in the urine. It can cause complications. It is caused by relatively harmless conditions like dehydration, intense exercise, or more severe conditions like kidney disease or immune disorders. Glomerular and tubular proteinuria are two types of proteinuria due to problems in the parts of the kidney. In glomerular proteinuria, the body excretes approximately 20 g of proteins per 24 hours through glomeruli. In tubular proteinuria, the body excretes less than 1-2 g of proteins per 24 hours through tubules. So, this summarizes the difference between glomerular and tubular proteinuria.
Reference:
1. Garg, Puneet, and Ton Rabelink. “Glomerular Proteinuria: A Complex Interplay between Unique Players.” Advances in Chronic Kidney Disease.
2. “Tubular Proteinuria.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Histopathology of hypertensive glomerular lesion of hypertensive nephropathy” By Rishi Sharma, Surineni Kamalakar, Ellen McCarthy, Timothy A. Fields, Kamal Gupta, Rajat Barua, Virginia Savin – (2014). “Proteinuria in Hypertensive Nephropathy: A Review.” Open Journal of Nephrology 04 (02): 92–99. DOI:10.4236/ojneph.2014.42013. ISSN 2164-2842. (CC BY 4.0) via Commons Wikimedia
2. “Histopathology of renal interstitial fibrosis of hypertensive nephropathy” By Rishi Sharma, Surineni Kamalakar, Ellen McCarthy, Timothy A. Fields, Kamal Gupta, Rajat Barua, Virginia Savin – (2014). “Proteinuria in Hypertensive Nephropathy: A Review.” Open Journal of Nephrology 04 (02): 92–99. DOI:10.4236/ojneph.2014.42013. ISSN 2164-2842. (CC BY 4.0) via Commons Wikimedia