Differentials
Diabetic kidney disease
SIGNS / SYMPTOMS
History of poorly controlled diabetes for about 10 years. Often with co-existing diabetic retinopathy and other stigmata of diabetic microvascular disease.
INVESTIGATIONS
HbA1c is typically >53 mmol/mol (>7%).
Diagnostic tests include urinalysis for albuminuria and a serum creatinine for GFR assessment.
The quantification of proteinuria is variable over time and will decrease as the GFR declines.
Urine albumin is key for the diagnosis of early diabetic kidney disease.
Kidney ultrasound will typically show small, atrophic kidneys only in late stages of the disease, once substantial renal injury occurs.
Hypertensive nephrosclerosis
SIGNS / SYMPTOMS
History of poorly controlled hypertension for years. More common in black people than white people.
INVESTIGATIONS
Diagnostic tests include urinalysis for microalbumin or protein and a serum creatinine for GFR assessment.
The urine sediment is described as bland without formed elements or haematuria. Quantification of proteinuria is <2 g/24 hours.
Kidney ultrasound typically reveals small, atrophic kidneys.
Ischaemic nephropathy
SIGNS / SYMPTOMS
History of long-standing essential hypertension that is suddenly uncontrolled. More common in white people and older people.
Often will have a history of atherosclerotic disease such as coronary artery disease or peripheral vascular disease. There is also a history of tobacco abuse and hyperlipidaemia.
INVESTIGATIONS
The urine sediment is described as bland, without formed elements or haematuria. Quantification of proteinuria is <2 g/24 hours.
Kidney ultrasound reveals asymmetrical kidney size of ≥2.5 cm with unilateral disease, and duplex scan demonstrates an increase in the resistive index, suggesting obstruction.
ACE inhibitor renogram, CT angiogram, magnetic resonance angiogram, or renal arteriogram (test of choice) demonstrates luminal narrowing of the renal artery.
Obstructive uropathy
SIGNS / SYMPTOMS
More common in men and older people. Often due to prostatic enlargement or cancer.
Typical symptoms include urinary frequency, hesitancy, inability to empty the bladder completely, and decrease in urinary stream.
Urinary tract infections may develop.
Rectal examination may reveal prostatic enlargement or nodules.
INVESTIGATIONS
Kidney ultrasound is the diagnostic test of choice to document kidney obstruction. It would show hydronephrosis, and there may also be post-void residual volume in those cases when there is obstruction to bladder outflow.
Nephrotic syndrome
SIGNS / SYMPTOMS
Often associated with a more sudden onset of hypertension, or acceleration of essential hypertension and development of periorbital and peripheral oedema.
INVESTIGATIONS
Laboratory evidence may reveal hypoalbuminaemia, hyperlipidaemia and an increase in serum creatinine. Urinalysis has proteinuria as defined at >3.5 g/24 hours.
A kidney biopsy is required to determine the pathological lesion for nephrotic syndrome.
Serological tests for secondary causes of nephrotic syndrome such as anti-nuclear antibody in systemic lupus erythematosus, HIV in focal segmental glomerulosclerosis, and hepatitis B and C in membranous nephropathy, and serum protein electrophoresis for amyloidosis, are often helpful in confirming the diagnosis of the nephrotic syndrome.
Glomerulonephritis
SIGNS / SYMPTOMS
Often associated with a sudden onset of hypertension or acceleration of essential hypertension.
Patients with autoimmune disorders may have a skin rash or arthritis; post-infectious glomerulonephritis has a recent history of a pharyngeal or cutaneous infection; bloody diarrhoea is associated with haemolytic uraemic syndrome.
INVESTIGATIONS
Laboratory evidence reveals an increased serum creatinine, and urinalysis is significant for haematuria and proteinuria.
Urine sediment is evaluated for the presence of dysmorphic red blood cells (RBC) and RBC casts, which are diagnostic of glomerulonephritis.
Serological tests such as antinuclear antibody, complement levels, hepatitis B and C antibodies, anti-neutrophil cytoplasmic antibody, anti-glomerular basement antibody, and anti-streptolysin O titre are often helpful in confirming the diagnosis of glomerulonephritis.
A kidney biopsy is required to confirm the pathological lesion of glomerulonephritis.
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