Proteinuria

You have a pair of kidneys in your body, that make urine, which takes away unwanted waste materials from the body. Normally, the urine contains only a little amount of proteins, up to 150mg/day. Due to some malfunctioning, excess proteins are excreted in the urine, known as proteinuria. Proteins are not only the building blocks for our body but are also essential to maintain body fluid, fight infections, and are supposed to remain in the body for all the vital functions. Proteinuria results in the loss of proteins causing fluid retention, foamy urine, tiredness, etc.

Your kidneys contain several tufts of small blood vessels called glomeruli. As your blood flows through the kidneys, the glomeruli sieve it, extracting what your body requires from what it does not. If some protein is left in the urine, there are special reabsorbing tubules in the kidneys that re-absorb the important substances, including protein. Conditions affecting this procedure at either step are responsible for proteinuria.

Mostly, proteinuria is caused by minor medical conditions like dehydration, inflammation, intense physical activity, severe emotional or physical stress, or excessive intake of fluids. Sometimes, proteinuria can be an early indication of kidney disease. Some of the conditions affecting kidneys are;

• Diabetes mellitus, causing diabetic nephropathy (most common cause)
• High blood pressure, causing nephrosclerosis
• Glomerular inflammation, called glomerulonephritis
• Nephrotic syndrome
• Infections like HIV, post-streptococcal infection, syphilis, hepatitis, urinary schistosomiasis
• Autoimmune diseases like lupus and Goodpasture’s syndrome
• Preeclampsia, development of hypertension and proteinuria in pregnancy
• Heart diseases
• Drugs: for example; penicillamine, NSAIDs, nicotine, lithium carbonate, antibiotics, gold and other heavy metals, ACE inhibitors, bevacizumab, or opiates
• Some systemic disorders like SLE, Wilson disease, rheumatoid arthritis, amyloidosis
• Cancers like multiple myeloma, chronic lymphocytic leukemia, renal tumors

In the US population, proteinuria was found to be 9.1% in females and 6.1% in males. Albuminuria was found to be 28.8% prevalent in diabetic patients and 16.0% in hypertensive patients. The starting age for proteinuria is 40 years. It is more prevalent in males than in females. It is found more in non-Hispanic blacks and Mexican Americans. 

Having some conditions can increase your chances of having proteinuria;

• High blood sugar, as in diabetes
• Systemic lupus,
  Amyloidosis,
• Reflux nephropathy,
• Other kidney disorders,
• Nonsteroidal anti-inflammatory medicines
• Some antibiotics
• HIV infection,
• Hepatitis B or C,  

Initially, proteinuria does not exhibit itself prominently. It is often found incidentally on routine blood tests. However, if the condition stays for a long duration, you may have the following signs and symptoms;

• Fluid retention leads to swelling, primarily present in the lower limbs and around the eyes.
• Increased urinary frequency
• Urine that looks foamy
• Shortness of breath
• Obesity due to fluid retention
• Nausea, vomiting
• Feeling tired
• Low appetite
• Cramps in the muscles, usually at night

Diagnosis of proteinuria is usually made by checking proteins in the urine. A patient is asked to submit a sample of urine in a bottle or a jar which is then tested in the lab or at the doctor's office for the presence of proteins, especially albumin, by inserting a dipstick, which is a piece of chemically processed material, into the urine. If protein is present in the urine, the dipstick turns color. This test is called a dipstick urine test. Albumin excretion rate between 30 to 300 mg/day is labeled as moderately increased albuminuria, while levels greater than 300 mg/day are categorized as severely increased albuminuria. If urine is found to have proteins after three successive tests performed three months apart, your doctor may suspect kidney disease, and you may be advised to undergo a few investigations, like;

• 24 hrs urine collection: for this type of test, you will need to obtain a urine specimen over 24 hours. After that, your medical practitioner will submit the samples to a laboratory for examination.
• Urine Albumin to Creatinine Ratio: This test estimates the quantity of albumin eliminated in 24 hours based on a single urine specimen. Albumin and creatinine are measured in this test.
• Blood tests can reveal low quantities of albumin, as well as a lower blood protein concentration altogether. Albumin loss is frequently linked with elevated blood cholesterol. The amounts of blood urea nitrogen in your blood may also be examined to determine how well your kidneys are working.
• Biopsy; In a biopsy of the kidney, a tiny piece of kidney tissue may be removed for examination by your physician. A needle is pushed into your dermis and then to your kidney, and a small specimen of tissue is taken and submitted to a laboratory for analysis.
• Imaging studies: a CT scan or Ultrasound may show abnormalities in the kidneys or the urinary tract. 

Other disorders that may need to be evaluated include;

• Heart failure
• Cirrhosis
• Drug toxicity
• Interstitial fibrosis
• HIV-Related Renal Disorders
• IgA Nephropathy
• Light Chain-Associated Renal Disorders
• Radiation Nephropathy
• Sickle Cell Nephropathy
• Transplant glomerulopathy
• Transplant Rejection

Treatment of proteinuria requires eliminating the root cause, controlling the symptoms with medications, and halting the progression towards end-stage kidney disease.

• Controlling blood sugar levels: if the proteinuria is caused by diabetes, then controlling adequate blood sugar levels may also slow the progression of proteinuria.
• Treating high blood pressure: In patients with hypertensive nephrosclerosis, controlling blood pressure with Angiotensin-converting enzyme (ACE) inhibitors is the best strategy. They also decrease the quantity of protein excreted in the urine. Lisinopril, captopril, and enalapril are examples of medicines in this group.
• Angiotensin II receptor blockers (ARBs): which include losartan and valsartan, are another class of medications that function in a comparable pattern. Additional drugs, like renin inhibitors, may be advised, although ACE inhibitors and ARBs are usually the first to be tried.
• Water content controlling pills. These increase the fluid production from your kidneys, which helps to decrease edema. Furosemide is a common diuretic medicine (Lasix). Spironolactone and thiazides (hydrochlorothiazide, metolazone) are two others.
• Medications to suppress the immune system: Sometimes, your physician might advise these drugs to lower inflammation in your body due to autoimmune or systemic diseases. They include corticosteroids, rituximab, and cyclophosphamide.

The outlook for proteinuria is usually favorable if timely care is given, but it varies depending on the actual reason and the patient's age.

Without therapy, it has an extremely poor prognosis, especially if the kidney disease progresses quickly, leading to abrupt kidney problems in a matter of months. Malnutrition can come from the depletion of too much protein. Weight loss can occur as a result of this, which can be concealed by edema. Anemia and vitamin D deficiency are further complications of end-stage kidney disease.

Ultimately, the kidneys lose their function and accumulate harmful products that need to be removed immediately using dialysis. Dialysis is an unnatural method of eliminating excess liquids and toxins from your blood that is usually performed using a kidney dialysis machine.

If your kidney function deteriorates sufficiently, you may require a kidney transplant.

Certain factors linked with proteinuria are unavoidable. However, you may take measures to protect your kidneys.

• If you have hypertension or diabetes, start taking medications for it.
• Eat healthy meals and drink plenty of water to keep your kidneys healthy.
• Get Vaccinated for contagious diseases, particularly if you deal with people who have hepatitis or some other conditions.
• Perform mild exercises regularly to keep you active.
• Follow the directions carefully and finish the whole course whenever your physician recommends antibiotics, even though you begin to feel well.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 01, 2023.

References

https://my.clevelandclinic.org/health/diseases/16428-proteinuria

https://link.springer.com/article/10.1007/s00467-019-04454-w