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PubMed This is a summary of 10 peer-reviewed journal articles Updated
Nephrology

Recognizing Symptoms and Managing Red Flags

At a Glance

FSGS commonly causes nephrotic syndrome, with protein in the urine, low blood albumin, and swelling. Sudden breathlessness, chest pain, very low urine output, severe infection symptoms, or new confusion and vision changes require immediate medical attention.

Living with Focal Segmental Glomerulosclerosis (FSGS) means monitoring your body for changes that can happen slowly or quite suddenly. Most symptoms of FSGS are caused by Nephrotic Syndrome, a group of signs that occur when the kidney’s filters are so damaged they leak large amounts of protein into the urine [1].

Signs of Nephrotic Syndrome

When your kidneys are losing a significant amount of protein—specifically albumin—your body’s chemistry changes. This leads to hallmark features [1][2]:

  • Heavy Proteinuria: This is often the first sign, commonly defined as nephrotic-range proteinuria of roughly 3.5 g/day (or an equivalent UPCR). While you may notice your urine looks unusually foamy, laboratory testing is required because appearance alone does not track disease severity reliably [1].
  • Hypoalbuminemia: This means you have low levels of albumin in your blood because it is being lost in your urine. Albumin is essential for keeping fluid where it belongs—inside your blood vessels [2].
  • Edema (Swelling): When albumin levels drop, fluid leaks out of the blood vessels and into your tissues. This most commonly causes swelling in the legs, ankles, and feet, but it can also cause puffiness around the eyes (especially in the morning) or a swollen abdomen (ascites) [1][3].
  • Hyperlipidemia: As the liver tries to compensate for the loss of protein, it overproduces fats and cholesterol, leading to high levels in the blood [1].

Serious Complications

Nephrotic syndrome is not just about swelling; it changes how your body functions in ways that can be dangerous [2].

  • Blood Clots (VTE): Proteins that help prevent clotting are also lost in the urine, making your blood “stickier.” This increases the risk of Venous Thromboembolism (VTE), including deep-vein thrombosis (DVT) in the legs or a pulmonary embolism (PE) in the lungs [4][5]. The decision to start preventive anticoagulation is not automatic and depends on your serum albumin, degree of proteinuria, kidney function, and bleeding risk. Do not start an over-the-counter or prescribed blood thinner without medical advice.
  • Infections: You also lose proteins called immunoglobulins that help fight germs. This makes you more vulnerable to serious infections, such as pneumonia or peritonitis (infection in the abdominal lining) [2][6].
  • Acute Kidney Injury (AKI): Sometimes the kidney’s function can drop very quickly due to severe inflammation, infection, or lack of blood flow, leading to a sudden rise in waste products like creatinine [7][8].

When to Seek Emergency Care

While mild swelling and fatigue are common parts of living with FSGS, certain “Red Flag” symptoms indicate a medical emergency. If you experience any of the following, seek urgent medical attention (such as calling emergency services) immediately [4][8][6]:

Signs of a Blood Clot (Thrombosis)

  • In the Lungs (Pulmonary Embolism): Sudden shortness of breath, sharp chest pain (often worse when breathing deeply), coughing up blood, or feeling faint or lightheaded [5].
  • In the Leg (Deep Vein Thrombosis): New pain, swelling, warmth, or redness. While it often affects one leg, it can affect both, so bilateral symptoms should not be ignored [4].

Signs of Acute Kidney Injury (AKI)

  • A marked or sudden drop in the amount of urine you produce (oliguria), or stopping urinating entirely [9].
  • Rapidly worsening generalized swelling that does not respond to your usual medications [10].

Signs of Serious Infection

  • A fever. Keep in mind that a fever cutoff of 101°F/38.3°C should not be the sole determinant of urgency, particularly if you are taking immunosuppressive medications that can mask a high fever [6].
  • Severe abdominal pain, especially if the abdomen feels hard or very tender to the touch (possible peritonitis) [6].

Signs of Hypertensive Emergency

  • A sudden, severe headache, confusion, new neurological symptoms, or changes in your vision (such as blurring or seeing spots), especially if combined with very high blood pressure (for example, 180/120 mmHg or higher) [4].

Daily Monitoring vs. Emergencies

It is helpful to distinguish between the “slow” changes of FSGS and “fast” emergencies.

  • Daily Monitoring: You may notice your socks leave deeper indentations or you have slightly more fatigue than yesterday. These are important to discuss with your doctor at your next appointment or via a same-day phone call.
  • Emergencies: The symptoms listed in the “Red Flag” section represent a sudden, severe change from your baseline. These require an immediate trip to the emergency room or a call to emergency services [2][4].

Common questions in this guide

What symptoms commonly occur with FSGS?
FSGS often causes nephrotic syndrome, which means substantial protein loss in the urine. Common signs include foamy urine, low blood albumin, swelling in the legs or around the eyes, abdominal fluid buildup, high blood fats, and fatigue.
When is swelling or reduced urination an emergency with FSGS?
Rapidly worsening swelling that does not improve with your usual medicines, a marked drop in urine output, or stopping urination can signal a serious kidney problem. Seek urgent medical attention rather than waiting for a routine appointment.
What could a blood clot feel like if I have FSGS?
A clot in the lung may cause sudden shortness of breath, sharp chest pain, coughing up blood, or faintness. A clot in a leg may cause new pain, swelling, warmth, or redness, and these symptoms require immediate medical evaluation.
What are warning signs of a serious infection in FSGS?
Fever can signal infection, although medicines that suppress the immune system may prevent a high fever from developing. Severe abdominal pain, especially with a hard or very tender abdomen, may indicate an abdominal infection and needs urgent care.
Should everyone with FSGS take a blood thinner to prevent clots?
No. Preventive blood thinners are not automatic for everyone with FSGS; the decision depends on blood albumin, the amount of protein loss, kidney function, and bleeding risk. Do not start or stop a blood thinner without medical guidance.
Which FSGS symptoms may signal dangerously high blood pressure?
A sudden severe headache, confusion, new weakness or other neurological changes, or vision problems can be signs of a hypertensive emergency, especially with blood pressure around 180/120 mmHg or higher. Seek emergency care immediately.

Questions For You

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Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my current albumin level, and how does it affect my risk for blood clots or infections?
  2. 2.Is my protein loss high enough to put me in the 'nephrotic range'?
  3. 3.What should my specific daily urine output look like, and at what point should I be concerned that it is too low?
  4. 4.Given my FSGS diagnosis, should I be on a blood thinner or any specific preventive measures for blood clots?
  5. 5.How can I tell the difference between typical fluid weight gain and a more serious accumulation of fluid?

References

References (10)
  1. 1

    [Nephrotic syndrome].

    Braun DA, Pavenstädt HJ

    Innere Medizin (Heidelberg, Germany) 2025; (66(9)):917-926 doi:10.1007/s00108-025-01946-w.

    PMID: 40760331
  2. 2

    Nephrotic Syndrome.

    Wang CS, Greenbaum LA

    Pediatric clinics of North America 2019; (66(1)):73-85 doi:10.1016/j.pcl.2018.08.006.

    PMID: 30454752
  3. 3

    Nephrotic Syndrome in Adult Patients With COVID-19 Infection or Post COVID-19 Vaccine: A Systematic Review.

    Cancarevic I, Nassar M, Medina L, et al.

    Cureus 2022; (14(9)):e29613 doi:10.7759/cureus.29613.

    PMID: 36312654
  4. 4

    Risk factors of venous thromboembolism in focal segmental glomerulosclerosis with nephrotic syndrome.

    Li SJ, Tu YM, Zhou CS, et al.

    Clinical and experimental nephrology 2016; (20(2)):212-7 doi:10.1007/s10157-015-1149-4.

    PMID: 26220221
  5. 5

    Delayed Death Due to Saddle Pulmonary Thromboembolus in Child With Nephrotic Syndrome Induced by Focal Segmental Glomerulosclerosis.

    Guenther RA, Kemp WL

    The American journal of forensic medicine and pathology 2018; (39(4)):370-374 doi:10.1097/PAF.0000000000000432.

    PMID: 30234547
  6. 6

    Outcomes of Older Patients (≥60 years) with New-Onset Idiopathic Nephrotic Syndrome Receiving Immunosuppressive Regimen: A Multicentre Study of 116 Patients.

    Colliou E, Karras A, Boffa JJ, et al.

    Journal of clinical medicine 2019; (8(3)) doi:10.3390/jcm8030298.

    PMID: 30832362
  7. 7

    Minimal change disease and focal segmental glomerulosclerosis in adults: response to steroids and risk of renal failure.

    Moura LR, Franco MF, Kirsztajn GM

    Jornal brasileiro de nefrologia 2015; (37(4)):475-80.

    PMID: 26648497
  8. 8

    Primary focal segmental glomerulosclerosis in second trimester pregnancy presenting as rapidly progressive renal failure: diagnostic and therapeutic challenges: a case report.

    Petros A, Melkie A, Asrat Y, et al.

    Journal of medical case reports 2025; (19(1)):359 doi:10.1186/s13256-025-05408-7.

    PMID: 40696377
  9. 9

    Early Focal Segmental Glomerulosclerosis as a Cause of Delayed Graft Function With Combined Acute Antibody Rejection: A Case Report.

    Jung S, Park KM, Hah J, et al.

    Transplantation proceedings 2018; (50(8)):2579-2580 doi:10.1016/j.transproceed.2018.02.191.

    PMID: 30316402
  10. 10

    Complete Remission of Post-transplantation Recurrence of Focal Segmental Glomerulosclerosis With the Use of Adrenocorticotrophic Hormone Gel: Case Report.

    Mittal T, Dedhia P, Roy-Chaudhury P, et al.

    Transplantation proceedings 2015; (47(7)):2219-22.

    PMID: 26361683

This page explains FSGS symptoms and red flags for educational purposes only; it is not medical advice. Contact your healthcare team promptly, and seek emergency care for sudden or severe symptoms.