What is CKD of Uncertain Cause (with Small Kidneys)?

What is CKD of Uncertain Cause (with Small Kidneys)?

CKD of uncertain cause with small kidneys means:

1. The exact cause isn’t known, and

2. Imaging (usually ultrasound) shows the kidneys are smaller than normal, which tells doctors the damage is long-standing and irreversible.

Note. Interestingly, uncertain cause is the commonest ’cause’ of patients being on dialysis (diabetes is the second commonest)

What “small kidneys” mean

Normal adult kidney length: ~10–14 cm. Bigger people have bigger kidneys. The average length = 12 cm

• Length < 10 cm (<9 cm in smaller people, especially older ladies). It is usually bilateral
• Chronic scarring and loss of kidney tissue
• Other known, reversible or acute kidney problems have been ruled out
• It usually means the disease has been present for years, often silently
• Some patients will deteriorate (usually slowly) and end up on dialysis or with a kidney transplant

Why the cause is “uncertain”

Common causes of CKD like:

• Diabetes
• Long-standing high blood pressure
• Polycystic kidney disease (PKD)
• Obstructive nephropathy
• Tubulointerstitial disease (TID) – e.g. reflux nephropathy
• Renovascular disease (RVD)
• Autoimmune diseases – e.g. chronic glomerulonephritis and vasculitis

 .. have either been ruled out or don’t fully explain the findings.

Because the kidneys are small, biopsy is usually not helpful or safe, which limits the ability to identify a precise diagnosis—hence ‘uncertain cause.’

So, what is the cause?

Well, by definition, we don’t know. Possible causes – even if doctors can’t prove it definitively – include a late stage of other (known) causes like:

• Diabetes
• Tubulointerstitial disease (TID) – including, possibly, childhood TB in Asian people
• Renovascular disease (RVD)
• Autoimmune diseases – e.g. chronic glomerulonephritis and vasculitis
• Congenital/dysplastic kidneys (you are born with)

Note. Sometime doctors get the hint of the original cause through blood or urine tests. They can then be labelled somthing like ‘CKD ?cause (??IgA nephropathy)’.

What this diagnosis implies

• The damage is not reversible
• Focus shifts to slowing progression rather than finding the cause
• Kidney size usually will not increase
• Risk of progression to kidney failure depends on:
  • Current GFR, and rate of decline
  • Level of protein in urine (higher levels have a worse outlook)
  • Blood pressure control
  • Lifestyle and medication adherence

Treatment

• Strict blood pressure control – as low as possible = under 130/80 all the time, at home, GP and hospital
• Avoiding NSAIDs and nephrotoxic drugs
• Treating complications like anaemia, and bone/mineral issues
• Regular nephrology follow-up
• Planning ahead  (dialysis and/or a kidney transplant), if kidney function declines