High Creatinine: How to interpret?

Creatinine is a waste product of muscle breakdown. It is removed from the blood through your kidneys and high levels can signal kidney issues. This test therefore helps assess kidney function.

Some people with a “normal” creatinine levels can also have kidney disease. This is because a “normal” creatinine level can change depending on multiple factors like age, sex and body size0.

The best way to understand how well your kidneys are functioning is to look at eGFR (estimated glomerular filtration ratio) which is calculated using serum (blood) creatinine level, age and sex, height and weight.

The serum (blood) creatinine derived eGFR is used:

• To establish a diagnosis of kidney dysfunction - AKI (acute kidney injury) or CKD (chronic kidney disease)
• To classify the stage of CKD
• To monitor changes in kidney function over time in people with CKD
• To decide if any medication needs to be stopped or modification of dose

Evaluation of kidney functions includes a combination of history, clinical examination and laboratory tests.

The baseline blood tests range from CBC, blood urea/ creatinine, electrolytes (Na/K), calcium/ phosphorus/ uric acid, serum protein/ albumin etc. Urine examination involves physical examination for colour/ turbidity, chemical analysis for protein/ blood/ sugar, microscopic evaluation for WBC/ RBC/ Casts/ Crystals etc and urine culture. Radiological studies include USG, X Ray, CT scan & Radionuclide scan. Specialized tests like iPTH, iron studies and serological/ immunological tests may also be required depending on associated illness.

Kidney biopsy may be indicated in certain situations. It is a bedside procedure done under L/A using real-time USG guidance. Tissue is examined after staining with special stains.

Therefore only looking at a creatinine level is not the best way to completely understand kidney health.

 

Chronic Kidney Disease - An introduction

 

Chronic Kidney Disease (CKD) is a progressive, irreversible decline in kidney function occurring over months to years. Globally, CKD affects nearly 10–15% of adults. In India, prevalence estimates range from 8–12%.

Definition and Classification: CKD is defined as abnormalities of kidney structure or function present for more than 3 months.

Classified into 5 stages based on

a. Glomerular Filtration Rate (GFR): G1 to G5, with G3 split into 3a and 3b

b. Subcategorized according to the spot urinary albumin-creatinine ratio : 3 levels of albuminuria (A1, A2, and A3), with each stage of CKD

CKD classification also recommends specifying the cause of CKD (e.g., diabetic nephropathy, hypertensive nephrosclerosis)

Etiology

Diabetes Mellitus (Diabetic Nephropathy)

Hypertension (Hypertensive Nephrosclerosis)

Glomerulonephritis

Polycystic Kidney Disease

Obstructive Uropathy

Prolonged use of nephrotoxic drugs (NSAIDs, certain antibiotics)

Risk factors:

Age >60 years

Family history of CKD

Cardiovascular disease

Obesity and metabolic syndrome

Smoking

Recurrent urinary tract infections

Low birth weight (predisposing to reduced nephron number)

 

Pathophysiology: CKD results from chronic and sustained insults leading to a gradual loss of functioning nephrons. The remaining nephrons undergo hyperfiltration to compensate, which increases intraglomerular pressure. This intraglomerular hypertension in turn leads to increased glomerular permeability and filtration resulting in proteinuria. Increased tubular resorption of protein results in tubulointerstitial inflammation & fibrosis. Over time, this leads to glomerulosclerosis, tubulointerstitial fibrosis, vascular sclerosis and further nephron loss - a vicious cycle culminating in end stage kidney disease (ESKD).

 

Clinical Features:

CKD often remains asymptomatic until advanced stages. Symptoms do not appear till more than 50% kidney function is lost.

Early (nonspecific) manifestations:

Fatigue and malaise

Loss of appetite/ Nausea or vomiting

Nocturia or polyuria

Mild edema

Late manifestations:

Generalized swelling

Shortness of breath

Generalised Pruritus

Cardiovascular manifestations- Arrhythmias, Ischaemic heart disease.

Bone pain or fractures (renal osteodystrophy)

Cognitive impairment or drowsiness (uremic encephalopathy)

 

Diagnosis:

CKD is diagnosed through a combination of laboratory tests and imaging studies.

Laboratory Evaluation:

a.       Serum Creatinine and eGFR: cornerstone for staging kidney function.

b.       Urinalysis: to detect protein, sugars, RBC, WBC or casts

c.       Urine Albumin Creatinine Ratio (UACR): quantify albuminuria, an early marker.

d.       Serum Electrolytes: Na, K, Ca, Phosphorus

e.       iPTH, Sr HCO^3-

f.         Hemoglobin

g.        Lipid profile: to assess metabolic risk factors

h.       HbA1c: to assess degree of blood sugar control.

Imaging Studies:

a.       Ultrasonography: to check size, alteration in echogenicity & corticomedullary differentiation, to detect obstruction etc.

b.       CT/MRI: in selected cases to evaluate structure or vascular causes.

Renal Biopsy: Indicated when the cause is uncertain or glomerulonephritis is suspected.

 

Complications: CKD is a systemic disorder with multiple complications:

1.       Cardiovascular disease: present in approx. 75% patients.

2.       Anemia

3.       Mineral and Bone Disorder (CKD-MBD

4.       Metabolic acidosis

5.       Electrolyte disturbances: hyperkalemia, hyperphosphatemia, hypocalcemia.

6.       Fluid overload

7.       Uremic complications: pericarditis, encephalopathy, neuropathy.

 

Management: The goals of CKD management are to treat the underlying disease, slow disease progression, treat complications, and prepare for renal replacement therapy.

Treat the Underlying Cause:

1.       Glycemic control: maintain HbA1c <7%.

2.       Blood pressure control: target <130/80 mmHg.

3.       Control of proteinuria

4.       Avoid nephrotoxic drugs: NSAIDs, contrast agents, and certain antibiotics.

Lifestyle Modifications:

1.       Dietary salt restriction (3-5 g/day).

2.       Moderate protein intake (0.8 g/kg/day).

3.       Maintain ideal body weight.

4.       Avoid smoking and alcohol.

5.       Encourage regular physical activity.

Prepare for Renal Replacement Therapy: Options include

1.       Hemodialysis,

2.       Peritoneal dialysis

3.       Kidney transplantation

 

Prognosis: The prognosis depends on the stage at diagnosis and control of underlying conditions. Earlier diagnosis helps prevent further damage to kidneys and also slow down progression of disease. Patients with well controlled diabetes and blood pressure can stabilize for years. Newer medications to slow progression of kidney damage can help improve outcomes. In patients with End Stage Kidney disease kidney transplant is the renal replacement therapy of choice.