What Is Kidney Disease?Learn more about the types, symptoms, and risk factors

Chronic kidney disease (CKD) includes any condition that causes reduced kidney function for more than 3 months.^{3, 11}

CKD is defined as the presence of kidney damage or an estimated glomerular filtration rate (eGFR) less than 60 mL/min per 1.73 m², persisting for 3 months or more.³

Early chronic kidney disease has no signs or symptoms as kidney function deteriorates slowly over time. For this reason, it has been referred to as the “silent killer.” Specific blood and urine tests are the only way to determine CKD.⁴

If kidney failure does occur, typical symptoms are weight loss and poor appetite, peripheral edema (swollen ankles, feet, or hands due to water retention), shortness of breath, blood or protein in urine, high blood pressure (hypertension), nausea, erectile dysfunction in men,⁵ vomiting, bone pain, headache, insomnia, itching, dry skin, malaise, fatigue with light activity, muscle cramps, high urine output or no urine output, recurrent urinary tract infections, urinary incontinence, pale skin, bad breath, hearing deficit, detectable abdominal mass, tissue swelling, irritability, poor muscle tone, change in mental alertness, and a metallic taste in the mouth.

The inclusion of the albumin-to-creatinine ratio for all GFR categories recognizes the importance of defining risk and individualizing treatment. Patients with ACR >30 mg/g have increased risk for CKD. Conversely, patients with ACR <30 mg/g are generally at lower risk.⁸

Your doctor will want to pinpoint your diagnosis and check your kidney function to help plan your treatment. The doctor may do the following:

• Calculate your Glomerular Filtration Rate (GFR). It is the best test to measure your level of kidney function and the determine stage of your kidney disease. Your doctor can calculate it from the results of your blood creatinine test, age, race, gender, and other factors.
• Calculate the albumin-to-creatinine ratio. Albumin is a protein that can pass into the urine when the kidneys are damaged.
• Perform an ultrasound or CT scan to get a picture of your kidneys and urinary tract. This tells your doctor whether your kidneys are too large or too small, whether you have a problem like a kidney stone or tumor, and whether there are any problems in the structure of your kidneys and urinary tract.
• Perform a kidney biopsy under image guidance, typically ultrasound. This is done in some cases to check for a specific type of kidney disease, see how much kidney damage has occurred, and help plan treatment. To do a biopsy, the doctor takes a sample from the region of interest. The pathologist than performs the histological analysis.

In complex cases, your doctor may also ask you to see a kidney specialist who will consult on your case and help manage your care.

In recent years, AKI has gained increasing recognition as a major risk factor for the development of chronic kidney disease (CKD). The clearest example of this relationship comes in cases of severe dialysis requiring AKI where patients fail to recover renal function. Indeed, acute tubular necrosis without recovery is the primary diagnosis for 2–3% of incident end‐stage renal disease (ESRD) cases annually. Yet this represents a small fraction of the renal disease burden resulting from AKI, as studies have demonstrated significantly increased long‐term risk of CKD and ESRD following AKI, even after initial recovery of renal function. Furthermore, this relationship is bidirectional, and CKD patients are at substantially greater risk of suffering an episode of AKI. As a result, AKI is frequently superimposed on CKD and therefore plays a key role in CKD progression.¹²

There are a variety of symptoms that may include swelling in legs, ankles, and around the eyes; too little urine output; fatigue or tiredness; shortness of breath; confusion; nausea; seizures or comma in severe cases; and chest pain or pressure.¹¹ Symptom onset can sometimes be correlated to events such as contrast application.

Other than chronic kidney disease or acute kidney injury, kidney disease may be characterized as end-stage renal disease or certain hereditary conditions.

There are many different types of hereditary kidney diseases, including congenital kidney and urinary tract malformations, congenital glomerulopathies, and tubular diseases.¹¹

The three hereditary diseases with the highest incidence include:

• Autosomal dominant polycystic kidney disease (ADPKD)
• Congenital nephrotic syndrome of the Finnish yype (CNF)
• Alport syndrome

End‐stage kidney or renal disease (ESRD) is the final stage of chronic kidney disease in which the kidneys no longer function well enough to meet the needs of daily life. People with diabetes or hypertension have the highest risk of developing ESRD.
It is important to note that one kidney can fail without any impact on overall renal function. MROI or nuclear medicine studies help to analyze renal function of left and right kidney separately. If kidney function is below 10% of normal and the damage is irreversible, the condition is called end‐stage renal disease or kidney failure. When the kidneys fail, the body retains fluid and harmful waste builds up. Two treatments are available for patients with ESRD: dialysis and transplantation.¹³

ADPKD is the most common hereditary kidney disease, with an incidence rate of about 1 in 1000. It is caused by mutations in the genes PKD1 and PKD2. A manifestation usually appears at age 30 to 50, and the clinical symptoms are hypertension, nephrolithiasis, and a progressive increase in the volume of both kidneys with appropriate accompaniments (e.g., impairment) due to massive cyst formation. Histologically, ADPKD is characterized by cysts in all areas in the nephron, which can vary in size and morphology. The most common extrarenal manifestations of the disease are cysts in the liver and pancreas.
The treatment of ADPKD is only symptomatic. Diseases that may negatively impair kidney function such as urinary tract infections, diabetes, and arterial hypertension are usually treated or managed effectively. The larger the kidney volume, the worse the prognosis for renal function. In advanced stages, dialysis is indicated. A complete cure can be achieved only through kidney transplantation.¹⁴

CNF is an autosomal recessive disease, genetically caused by mutation of the nephrin gene NPHS1. The highest incidence is in Finland (1:10,000). The disease is characterized prenatally with an increase in the amniotic fluid alpha‐fetoprotein; at birth by massive proteinuria; and by increasing renal insufficiency after 6 months.

Symptoms include general persistent edema, ascites, and infections, and nutritional disorders are common because of the enormous loss of protein.

CNF is difficult and proceeds until the onset of ESRD. Corticosteroids and immune‐suppressants are ineffective for treatment. Dialysis and transplantation are therapeutic options.

Alport syndrome is an inherited disease resulting in a progressive deterioration of renal function and can affect the inner ear and eye, leading to hearing and vision loss.

Its incidence is 1 in 10,000, and it is caused by mutations in the genes COL4A3, COL4A4, and COL4A5, which encode protein chains of collagen type IV. This leads to a  dysfunction of basal membranes, which is especially critical in the glomerulus, the inner ear, and the eyes.

The disease can be autosomal dominant (5%), autosomal recessive (15%), and is X‐linked in 80% of cases. Boys and men are more affected.

After birth, urinalysis is abnormal because of proteinuria and hematuria. This is an expression of an incipient chronic glomerulonephritis. Treatment options are ACE inhibitors or AT1 receptor antagonists. This therapy delays the manifestation of terminal kidney failure, but it cannot be stopped. The progressive renal failure may require hemodialysis or transplantation.

Siemens Healthineers supports the goals of the National Kidney Foundation to increase awareness, prevention, and treatment of kidney disease.

In this webinar, Dr. Amy Karger, Associate Professor, Dept. of Lab Medicine & Pathology, University of Minnesota, and Dr. O. Alison Potok, Assistant Professor, Clinical Medicine in the Division of Nephrology-Hypertension, University of California, San Diego, discuss:

• The current state of cystatin C assay performance and standardization, as well as the barriers and potential strategies to aid in more widespread implementation of cystatin C testing in clinical laboratories.
• The clinical evaluation of cystatin C results under the new recommendations, and differences in eGFR values compared to the former guidelines using serum creatinine values.