Chronic Kidney Disease – Help From Emedicine.Medscape.Com

The following are excerpts from Chronic Kidney Disease Updated: Jul 17, 2018 on emedicine.medscape.com:

Chronic kidney disease (CKD)—or chronic renal failure (CRF), as it was historically termed—is a term that encompasses all degrees of decreased renal function, from damaged–at risk through mild, moderate, and severe chronic kidney failure. CKD is a worldwide public health problem.

CKD is more prevalent in the elderly population. However, while younger patients with CKD typically experience progressive loss of kidney function, 30% of patients over 65 years of age with CKD have stable disease. [1]

Staging

The different stages of CKD form a continuum. The stages of CKD are classified as follows [5:

  • Stage 1: Kidney damage with normal or increased GFR (>90 mL/min/1.73 m2)

  • Stage 2: Mild reduction in GFR (60-89 mL/min/1.73 m2)

  • Stage 3a: Moderate reduction in GFR (45-59 mL/min/1.73 m2)

  • Stage 3b: Moderate reduction in GFR (30-44 mL/min/1.73 m2)

  • Stage 4: Severe reduction in GFR (15-29 mL/min/1.73 m2)

  • Stage 5: Kidney failure (GFR < 15 mL/min/1.73 m2 or dialysis)

In stage 1 and stage 2 CKD, reduced GFR alone does not clinch the diagnosis, because the GFR may in fact be normal or borderline normal. In such cases, the presence of one or more of the following markers of kidney damage can establish the diagnosis [5:

  • Albuminuria (albumin excretion >30 mg/24 hr or albumin:creatinine ratio >30 mg/g [>3 mg/mmol])
  • Urine sediment abnormalities
  • Electrolyte and other abnormalities due to tubular disorders
  • Histologic abnormalities
  • Structural abnormalities detected by imaging
  • History of kidney transplantation in such cases

In an update of its CKD classification system, the NKF advised that GFR and albuminuria levels be used together, rather than separately, to improve prognostic accuracy in the assessment of CKD. [45More specifically, the guidelines recommended the inclusion of estimated GFR and albuminuria levels when evaluating risks for overall mortality, cardiovascular disease, end-stage kidney failure, acute kidney injury, and the progression of CKD.

Here is a link to the Kidney Failure Risk Calculator.

Patients with CKD stages 1-3 are generally asymptomatic. Typically, it is not until stages 4-5 (GFR < 30 mL/min/1.73 m²) that endocrine/metabolic derangements or disturbances in water or electrolyte balance become clinically manifest.

See Signs and Symptoms, Laboratory Studies, and Imaging Studies [All on this page].

Pathophysiology

Factors other than the underlying disease process and glomerular hypertension that may cause progressive renal injury include the following:

  • Systemic hypertension

  • Nephrotoxins (eg, nonsteroidal anti-inflammatory drugs [NSAIDs], intravenous contrast media)

  • Decreased perfusion (eg, from severe dehydration or episodes of shock)

  • Proteinuria (in addition to being a marker of CKD)

  • Hyperlipidemia

  • Hyperphosphatemia with calcium phosphate deposition

  • Smoking

  • Uncontrolled diabetes

Aging and renal function

The biologic process of aging initiates various structural and functional changes within the kidney. [89Renal mass progressively declines with advancing age, and glomerulosclerosis leads to a decrease in renal weight. Histologic examination is notable for a decrease in glomerular number of as much as 30-50% by age 70 years. The GFR peaks during the third decade of life at approximately 120 mL/min/1.73 m2; it then undergoes an annual mean decline of approximately 1 mL/min/y/1.73 m2, reaching a mean value of 70 mL/min/1.73 m2 at age 70 years.

Genetics

Most cases of CKD are acquired rather than inherited, although CKD in a child is more likely to have a genetic or inherited cause. Well-described genetic syndromes associated with CKD include autosomal dominant polycystic kidney disease(ADPKD) and Alport syndrome. Other examples of specific single-gene or few-gene mutations associated with CKD include Dent disease, nephronophthisis, and atypical hemolytic uremic syndrome (HUS).

Hyperkalemia

Hyperkalemia usually does not develop until the GFR falls to less than 20-25 mL/min/1.73 m², at which point the kidneys have decreased ability to excrete potassium. Hyperkalemia can be observed sooner in patients who ingest a potassium-rich diet or have low serum aldosterone levels. Common sources of low aldosterone levels are diabetes mellitus and the use of ACE inhibitors, NSAIDs, or beta-blockers.

Etiology

Causes of chronic kidney disease (CKD) include the following:

  • Diabetic kidney disease

  • Hypertension

  • Vascular disease

  • Glomerular disease (primary or secondary)

  • Cystic kidney diseases

  • Tubulointerstitial disease

  • Urinary tract obstruction or dysfunction

  • Recurrent kidney stone disease

  • Congenital (birth) defects of the kidney or bladder

  • Unrecovered acute kidney injury

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