Diagnosing chronic kidney disease (CKD) is done through a careful process. Because CKD often develops slowly and may not cause any symptoms in the early stages, Nephrologists use different methods to detect it. The goal is to find out whether the kidneys are damaged, how much they are affected, and what might be causing the problem.
The diagnostic evaluation includes the following:
- Risk assessment – to find out if a person has any conditions or habits that increase their chances of kidney disease, such as
diabetes, high blood pressure (Hypertension), older age, or a family history of kidney problems.
- Medical history – to understand past health problems, family history, or medications that could affect the kidneys.
- Physical examination – to look for signs like swelling, high blood pressure, or pale skin that may suggest kidney problems.
- Diagnostic tests – to confirm kidney damage, check how well the kidneys are working, and identify possible causes or complications.
- Staging – to determine how advanced the kidney disease is, based on test results like kidney function (eGFR) and protein in the urine. Staging helps doctors plan treatment and predict the risk of further damage.
Risk Assessment
Before beginning a formal diagnosis, it is important to identify people who may be at a higher risk of developing chronic kidney disease (CKD). Many individuals with CKD remain undiagnosed because the condition progresses silently in its early stages. Recognizing risk factors allows for early screening, which can catch kidney problems before they become severe.
The most common risk factor for CKD is diabetes, especially if blood sugar levels have not been well controlled over time. High blood pressure is another major contributor, as it can damage the blood vessels in the kidneys. People with heart disease or a history of stroke are also more likely to have reduced kidney function. Age is another important factor. CKD becomes more common among individuals over 60 years old, even without other medical problems.
Family history also plays a role. If someone has a close relative with kidney disease, particularly conditions like
polycystic kidney disease or Alport syndrome (a genetic disorder that primarily affects kidneys), their own risk is higher. Recurrent
urinary tract infections (UTI), a history of
kidney stones, or blockages in the urinary tract may also contribute to long-term kidney damage. Use of certain medications, especially non-steroidal anti-inflammatory drugs (NSAIDs) over long periods, can gradually harm the kidneys without causing immediate symptoms.
In some regions, people from certain ethnic background such as African, South Asian, or Indigenous communities are more likely to develop CKD. For these individuals, Nephrologists may recommend regular kidney checkups, even if they feel healthy.
By identifying risk factors early, healthcare providers can take preventive steps or start screening tests to catch CKD in its earliest stages, when it is most manageable.
Medical History
Taking a comprehensive medical history is the cornerstone of CKD diagnosis. The purpose of this step is to uncover potential causes of kidney damage, identify risk factors, and determine the chronicity of symptoms. CKD is most commonly caused by long-standing conditions such as diabetes mellitus and hypertension. Therefore, the nephrologist begins by assessing whether the patient has been diagnosed with these conditions, for how long, and whether they have been adequately managed. A history of poor glycemic control or uncontrolled blood pressure significantly raises suspicion for chronic kidney involvement.
The patient’s family history is another important component. A positive family history of kidney disease may point to hereditary conditions such as autosomal dominant polycystic kidney disease, Alport syndrome, or other inherited nephropathies (kidney diseases). The nephrologist will also ask about the history of recurrent urinary tract infections, nephrolithiasis (kidney stones), or urinary obstruction, all of which can contribute to kidney damage over time.
Medication history plays a vital role in evaluating nephrotoxic exposures. Patients are asked about long-term use of over-the-counter drugs like NSAIDs, proton pump inhibitors, or herbal supplements, which are known to cause chronic interstitial nephritis. In addition, prior exposure to contrast agents, chemotherapeutic drugs, or immunosuppressants may also be significant. The clinician may investigate occupational or environmental exposures that could potentially harm the kidneys, such as heavy metals or solvents.
History also seeks symptoms that may suggest impaired kidney function or its complications. These may include fatigue, decreased appetite, swelling in the legs or around the eyes, muscle cramps, or nocturia. Patients may describe frothy urine, which indicates proteinuria, or complain of dark-colored or blood-tinged urine, which may suggest hematuria (blood in urine) or glomerular disease. Importantly, CKD often presents without symptoms in the early stages, and many cases are detected incidentally during routine health screenings.
In addition to direct kidney-related symptoms, systemic features such as joint pains, rashes, or fever may indicate autoimmune or inflammatory conditions affecting the kidneys, such as systemic lupus erythematosus or vasculitis. Travel history, high-risk behavior, or past infections are relevant when considering infectious causes like HIV-associated nephropathy or hepatitis-related glomerulonephritis.
Physical Examination
The physical examination in suspected CKD serves two main purposes: to detect clinical signs of renal dysfunction and to evaluate complications or systemic conditions that may contribute to or result from CKD. Although many patients with early-stage CKD may appear well, the physical exam becomes increasingly informative as the disease progresses.
Measurement of blood pressure is an essential part of the examination, as hypertension is both a common cause and a frequent complication of CKD. The physician will look for persistently elevated readings or evidence of hypertensive damage, such as retinopathy or left ventricular hypertrophy. Orthostatic blood pressure measurements may also be taken in some patients to assess autonomic dysfunction or volume depletion.
Edema is another key finding. Patients with moderate to advanced CKD often exhibit peripheral edema, particularly in the lower limbs, due to sodium and fluid retention. Periorbital puffiness may be noted in the mornings, especially in cases of heavy proteinuria as seen in nephrotic syndrome. Generalized swelling (anasarca) may suggest severe hypoalbuminemia or advanced kidney failure.
Pallor is a common sign of anemia resulting from reduced erythropoietin production by the diseased kidneys. It may be visible in the conjunctiva, nail beds, or oral mucosa. In more advanced cases, uremic symptoms such as dry, itchy skin, uremic frost, or yellowish skin hue may be observed, although these are rare in the era of early intervention.
The cardiovascular examination is particularly important, as CKD is closely linked to heart disease. The clinician may detect signs of volume overload such as jugular venous distension, displaced apical impulse, or basal lung crepitations. A pericardial friction rub, although uncommon, may indicate uremic pericarditis in severe renal failure.
The abdominal examination may reveal enlarged kidneys in polycystic kidney disease or a palpable bladder in cases of outflow obstruction. A bruit over the renal arteries may suggest renal artery stenosis, a potentially reversible cause of hypertension and kidney dysfunction.
Lastly, the physical exam includes a search for extra-renal signs that may point to a systemic etiology. Rashes, oral ulcers, or synovitis can support a diagnosis of lupus nephritis. Purpura or livedo reticularis might raise suspicion for vasculitis or cryoglobulinemia.
In essence, the physical examination in CKD is a powerful tool for reinforcing clinical suspicion, assessing disease severity, identifying complications, and providing clues to the underlying etiology. It complements the history and sets the stage for appropriate diagnostic testing.
Diagnostic Tests
To confirm the diagnosis of chronic kidney disease (CKD), assess its severity, identify the underlying cause, and detect complications, a range of diagnostic tests is utilized
The key diagnostic tests for CKD include:
- Serum creatinine and estimated glomerular filtration rate (eGFR)
- Blood urea nitrogen (BUN)
- Electrolyte panel (sodium, potassium, chloride, bicarbonate)
- Calcium, phosphate, and parathyroid hormone (PTH) levels
- Hemoglobin and
complete blood count (CBC)
- Urine albumin-to-creatinine ratio (ACR)
- Urinalysis (dipstick and microscopy)
- 24-hour urine protein or creatinine clearance (when needed)
- Renal ultrasound
- Kidney biopsy (in selected cases)
Serum Creatinine and eGFR
Serum creatinine is a byproduct of muscle metabolism and is filtered by the kidneys. An elevated serum creatinine level often reflects reduced kidney function. However, because creatinine levels can vary depending on muscle mass, age, sex, and race, they are used to calculate the estimated glomerular filtration rate (eGFR). The eGFR provides a more accurate measure of kidney function and is used to stage CKD. A persistently reduced eGFR below 60 mL/min/1.73 m² for at least three months is one of the key diagnostic criteria for CKD.
Blood Urea Nitrogen (BUN)
BUN is another marker of renal excretory function. Like creatinine, it can be elevated when kidney function declines. However, BUN is less specific than creatinine because it can also be influenced by factors such as dehydration, high protein intake, or gastrointestinal bleeding. It is usually interpreted alongside serum creatinine.
Electrolyte Panel
Electrolyte levels provide important information about the kidney’s ability to maintain internal balance. Patients with CKD may develop hyperkalemia due to impaired potassium excretion, and metabolic acidosis because of decreased bicarbonate retention. Sodium and chloride levels are usually stable but may vary depending on volume status or medication use.
Calcium, Phosphate, and Parathyroid Hormone (PTH)
As CKD progresses, the kidneys lose their ability to regulate calcium and phosphate levels. This can lead to hyperphosphatemia, hypocalcemia, and secondary hyperparathyroidism. Measuring these values helps identify and manage chronic kidney disease mineral and bone disorder (CKD-MBD), a common and serious complication of CKD.
Hemoglobin and Complete Blood Count (CBC)
Anemia is common in CKD due to decreased erythropoietin production by the kidneys. A complete blood count helps assess hemoglobin levels and detect normocytic, normochromic anemia, which is typical in CKD. Early identification and treatment of anemia are crucial to reduce symptoms and improve quality of life.
Urine Albumin-to-Creatinine Ratio (ACR)
The ACR is a simple and sensitive test that detects albuminuria (presence of albumin in urine), one of the earliest signs of kidney damage. It is performed on a spot urine sample and adjusts for urine concentration. An ACR greater than 30 mg/g is abnormal and helps in both the diagnosis and staging of CKD. Persistent albuminuria also indicates a higher risk of cardiovascular events and disease progression.
Urinalysis
A general urinalysis includes a dipstick test followed by microscopic examination. The dipstick may detect protein, blood, glucose, and specific gravity. Microscopy can reveal red blood cells, white blood cells, casts, and crystals. The presence of red blood cell casts or dysmorphic red cells can suggest glomerulonephritis, while white cell casts may indicate interstitial nephritis.
24-Hour Urine Collection
Though less commonly used in routine practice, a 24-hour urine collection can provide a more accurate measurement of total protein excretion or creatinine clearance. It is particularly useful in cases where precise quantification of proteinuria is needed or when the accuracy of eGFR is in doubt.
Renal Ultrasound
Ultrasound imaging is a non-invasive and essential tool in evaluating CKD. It provides information about kidney size, cortical thickness, echogenicity, and the presence of structural abnormalities such as cysts, stones, or
hydronephrosis. Small, shrunken kidneys with increased echogenicity typically indicate chronic and irreversible damage.
Kidney Biopsy
In selected cases, when the cause of CKD is unclear or a glomerular disease is suspected, a kidney biopsy may be necessary. This invasive procedure involves obtaining a small tissue sample from the kidney under ultrasound guidance. Histological examination can confirm specific diagnoses such as lupus nephritis, IgA nephropathy, or vasculitis, and guide immunosuppressive therapy. Biopsies are usually reserved for patients with preserved kidney size, significant proteinuria, or unexplained active urinary sediment.
Staging of Chronic Kidney Disease
After a diagnosis of CKD is made, the next step is to determine how advanced the disease is. This process is called staging. CKD is divided into stages based on how well the kidneys are working and how much damage is present. Staging helps nephrologists to understand the severity of the disease, predict how fast it may progress, and decide the best course of treatment.
The main factor used to stage CKD is the estimated glomerular filtration rate (eGFR), which shows how well the kidneys are filtering waste from the blood. CKD is categorized into five stages, from G1 to G5. Stage G1 means kidney function is normal or only slightly reduced, while stage G5 represents kidney failure, which may require
dialysis or
Kidney transplantation. For example, a person with an eGFR above 90 is in stage G1, while an eGFR below 15 indicates stage G5.
Another important part of staging is the amount of albumin in the urine, measured by the urine albumin-to-creatinine ratio (ACR). Albumin is a protein that normally stays in the blood, and its presence in urine is a sign of kidney damage. Albuminuria is divided into three categories: A1 (normal to mildly increased), A2 (moderately increased), and A3 (severely increased). The higher the level of albumin in the urine, the greater the risk of disease progression and complications.
Nephrologists often use a chart called the KDIGO heat map to combine eGFR and albumin levels into a single risk category. This helps them decide how closely a patient should be monitored and what treatments may be necessary. For example, someone in stage G3a with A1 albuminuria might only need regular checkups, while a patient in stage G3b with A3 albuminuria could require specialist care and aggressive treatment.
Proper staging of CKD is essential for planning care, managing symptoms, and preventing complications such as heart disease, anemia, and bone problems. It also helps patients understand their condition and what steps they can take to protect their kidney health.
