Chronic kidney disease Flashcards
What is chronic kidney disease?
Chronic kidney disease is defined by either, or both, of the following:
- Kidney damage (as evidenced by proteinuria, haematuria, or an anatomical abnormality)
- An estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2 present on at least two occasions over at least a three month period.
This means that an individual can be classified as having CKD as a consequence of a minor renal tract abnormality, for example a renal scar or a simple renal cyst.
CKD staging
CKD is classified by eGFR and amount of proteinuria. The prognosis of CKD is colour-coded as shown in Figure 1
eGFR Test result variability
Intra-test variability for eGFR can be up to 20%. Therefore, an eGFR as low as 51 ml/min/1.73 m2 as a single reading may represent an actual GFR of 60 ml/min/1.73 m2 or more
eGFR interpretation based on body characteristics
eGFR should be interpreted with caution in extremes of muscle mass; eg eGFR may be overestimated in a frail elderly woman with little muscle mass or a patient with a leg amputation and underestimated in a bodybuilder
Causes of CKD
Diabetes and hypertension are the most common causes of CKD in the UK. Other rarer causes may include:
- Glomerulonephritis
- Inherited renal diseases such as polycystic kidney disease
- Heart failure
- Drug toxicity
- Obstructive uropathy or reflux nephropathy
Pathophysiology of CKD
- Chronic kidney disease is the end-stage for any cause of severe and/or long-standing kidney injury. Regardless of the cause, once half the nephrons are damaged CKD will progress.
- Damage to the kidneys reduces the number of functioning nephrons, which leads to several adaptations. There is hyperfiltration at the glomeruli, and the increased glomerular permeability contributes to the development of proteinuria.
- Another adaptation is the activation of the renin-angiotensin-aldosterone system causing an increase in blood pressure, which furthers the hyperfiltration at the glomerular level. Other adaptations include the release of cytokines and growth factors.
- The increase in capillary pressure within the glomerulus and inflammatory mediators cause chronic inflammation. This reduces the filtration ability of the glomerulus, which manifests as a reduced glomerular filtration rate (eGFR). This can lead to systemic complications, which are discussed later in this article.
Risk factors for CKD
Risk factors for chronic kidney disease include:
Age greater than 50 years
History of acute kidney injury
History of childhood kidney disease
Family history of CKD stage 5
Diabetes mellitus
Cardiovascular disease
Hypertension
Obesity with metabolic syndrome
Gout
Solitary functioning kidney
Smoking
Black or Hispanic ethnicity
Male gender
Symptoms of CKD
- CKD is usually asymptomatic, and symptoms usually only start developing when it is advanced (stages 4-5).3
- CKD is usually detected through the presence of hypertension, haematuria and/or proteinuria upon urinalysis, or a reduction in GFR with increased serum creatinine.6
- In advanced CKD, typical symptoms may include:
- General symptoms: such as fatigue, nausea and vomiting, cramps, insomnia, restless legs, taste disturbance, bone pain, and pruritus
- Abnormal urine output: such as polyuria, oliguria, or nocturia
- Fluid overload: may present as dyspnoea and orthopnoea
- Sexual dysfunction
- Severe uraemia may also cause hiccups, pericarditis, coma and seizures
Diagnosis of CKD
- Most patients with CKD are identified from renal function blood tests and/or urine tests in at-risk patients
- A diagnosis of CKD requires evidence of kidney damage and/or a persistent reduction in renal function.
Clinical examination findings in CKD
Typical clinical findings in CKD may include:
- Uraemic fetor: ammonia-like smell of the breath
- Pallor: due to anaemia
- Cachexia
- Cognitive impairment: specifically affecting language, orientation and attention
- Tachypnoea: may be due to fluid overload, anaemia
- Hypertension
- Volume disturbance: volume overload (e.g. peripheral oedema, pulmonary oedema, pleural effusions, ascites) or volume depletion
- Peripheral neuropathy
- Fundoscopy may reveal microvascular damage in patients with diabetes or hypertension
There may be specific clinical findings depending on the underlying cause of CKD: - Bilateral masses upon palpation of flanks, suggestive of adult polycystic kidney disease. May be accompanied by hepatomegaly due to liver cysts.
- Palpable bladder: may suggest obstructive uropathy, often accompanied by prostatic enlargement in men
How is kidney transplantation done?
- The patient’s native kidneys are normally left in situ, and the donor kidney is placed in the iliac fossa.
- Patients receive induction and maintenance immunosuppression to prevent graft rejection
