What kind of symptoms can I have?

The symptoms of LN in a person with SLE can be mild and aren’t the same in everyone. Many people do not have any obvious symptoms, so doctors use laboratory tests to monitor if a person with SLE has LN. For patients with SLE, doctors usually test for kidney problems every 3-6 months.

Here are some symptoms that a person with LN might have:

• Swelling of the legs and feet: the decline in the kidneys function can lead to a less effective liquid elimination and that leads to liquid retention and swelling.

• Swelling of the face and hands

• Weight gain: the retention of liquid also reflects as a weight gain which can be measured in check ups with your doctor.

• Fatigue

• High blood pressure

• Dark or foamy urine: glomerular disease and kidney damage can lead to presence of blood (pink or dark urine) or proteins (the urine can be foamy because of the leaked protein)

• The need to urinate frequently

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Swelling

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Weight gain

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Fatigue

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Increased need to pee

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Dark or foamy pee

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High blood pressure

How do you diagnose Lupus Nephritis?

Patients with a diagnosis of SLE should go to their doctor where they will perform a complete physical examination and request some lab tests that can help with the detection of LN in this context.

  Urine tests
Urine test to check for protein and blood:
 The laboratory findings in the urine of LN patients may differ from ‘silent’ LN (normal urine tests results, normal renal function and no protein in the urine, “proteinuria”) to severe proteinuria and nephrotic syndrome.
Nephrotic syndrome is when a very large amount of protein  leaks (more than 3.5 g of protein per day in the urine) through the damaged kidneys and it appears in a patients’ urine sample.
However, most LN patients usually present with mild proteinuria and/or blood in the urine.
Urinary protein-to-creatinine test:

For this test, the patient needs to collect all the urine they produce for 24 hours. Then the lab measures the amount of protein present in the sample and the amount of creatinine present. Creatinine is a waste product from activities of muscle fibers, and is normally filtered and removed from the blood by the kidneys.

The relationship between these two substances in the urine provides a very good idea of the functioning of the kidneys and can help make the diagnosis of LN.


For practical reasons, urinary protein-to-creatinine ratio in early morning or random daytime urine samples has replaced urinary protein excretion in 24 hour urine collection in many centres. Even if this approach might be easier, it can be less accurate than the 24 hour urine collection approach. So there are times when a 24 hour urine is still needed.

 

According to the 2012 Systemic Lupus International Collaborating Clinics (SLICC) [8] classification criteria, kidney involvement in patients with SLE is defined as a urinary protein-to-creatinine ratio or 24-h urinary protein excretion corresponding to 0.5 g daily or the presence of red blood cell casts in urinary sediment.

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  Blood tests
Serum Creatinine

The level of circulating creatinine in the blood is a marker of how well the kidneys are working. Creatinine is a waste product from activities of muscle fibers, and is normally filtered and removed from the blood by the kidneys. When the kidneys function worsens the creatinine serum levels rise. 

Serum creatinine is also used in the eGFR calculation.
Estimated Glomerular Filtration Rate (eGFR)

Estimated Glomerular Filtration Rate (eGFR):  

Using the blood creatinine concentration, age, body size and gender the doctor can calculate the eGFR for a patient. 

The eGFR is a commonly used test to estimate kidney function. It also allows for the monitoring of the disease progression and to plan treatment accordingly. 

The value of the eGFR decreases as lupus nephritis progresses: a lower eGFR score means that there is more damage to the kidneys and their function is lower.

eGFR can also be calculated using the concentration of another protein called cystatin C.
Other blood tests

Patients are also checked with regular blood tests such as blood counts, cholesterol, blood proteins, tests of liver function and measurement of the levels of some medication in the blood. They may also be tested for the presence of antibodies and other markers of disease activity. These are present in patients with SLE and indicate the involvement of the immune system in the mechanism of the disease.

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Kidney biopsy

 

Kidney biopsy involves taking a sample of the tissue of 1 or both kidneys with a needle and examining it under a microscope. This is the most accurate test for diagnosing and or confirming LN in SLE patients and it can also detect patients with LN that show no symptoms or altered lab results.

Findings in the kidney biopsy samples determine the grade or severity of the inflammation in the kidney which is a direct reflection of the severity of the disease.

It provides very important information regarding prognosis and treatment strategy moving forward for a particular patient and it helps to differentiate between LN and other types of autoimmune diseases that also can affect the kidneys.

Kidney biopsy is recommended in cases of persistent proteinuria with protein excretion of more than 0.5 g daily. [1]

 

Controls and screenings

 

Patients with SLE should be controlled and screened frequently.

During check-ups, SLE patients should be checked for the apparition of signs or symptoms of LN. Volume status, blood pressure, urine and blood tests to check for protein in the urine and to check the kidneys function should all be performed. [1]

 

References

 

1. Anders HJ, Saxena R, Zhao MH, Parodis I, Salmon JE, Mohan C. Lupus nephritis. Nat Rev Dis Primers. 2020 Jan 23;6(1):7. Doi: 10.1038/s41572-019-0141-9. PMID: 31974366.
2. Pons-Estel GJ, Alarcón GS, Scofield L, Reinlib L, Cooper GS. Understanding the epidemiology and progression of systemic lupus erythematosus. Semin Arthritis Rheum. 2010 Feb;39(4):257-68. doi: 10.1016/j.semarthrit.2008.10.007. Epub 2009 Jan 10. Review.
3. GfK Roper. (2012). Lupus Awareness Survey for the Lupus Foundation of America [Executive Summary Report]. Washington, DC.
4. Hong WANG, Yi-le REN, Jun CHANG, Luo GU, Ling-Yun SUN. A Systematic Review and Meta-analysis of Prevalence of Biopsy-Proven Lupus Nephritis
Arch Rheumatol. 2018 Mar; 33(1): 17–25. Published online 2017 Jul 25. doi: 10.5606/ArchRheumatol.2017.6127
5. Liu CC, Kao AH, Manzi S, Ahearn JM. Biomarkers in systemic lupus erythematosus: challenges and prospects for the future. Therapeutic Advances in Musculoskeletal Disease. 2013;5(4):210–233
6. Madhok R. Systemic lupus erythematosus: lupus nephritis. BMJ Clin Evid. 2015;2015:1123. Published 2015 Dec 18.
7. Hahn BH, McMahon MA, Wilkinson A, et al. American College of Rheumatology guidelines for screening, treatment, and management of lupus nephritis. Arthritis Care Res. 2012;64(6):797-808.
8. Emily J. Sutton, Julie E. Davidson, Ian N. Bruce. The Systemic Lupus International Collaborating Clinics (SLICC) damage index: A systematic literature review. Seminars in Arthritis and Rheumatism, Volume 43, Issue 3, 2013, Pages 352-361. ISSN 0049-0172. 

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