There was some discussion about the very wide discrepancy between urea and
creatinine values seen in Case 70. Quite by chance this one turned up on my
desk a couple of weeks ago.
A 53 year old lady, seen by a Registrar (relatively junior member of the
Medical team) in the Renal Outpatient Clinic.
Clinical information on the request card is 'low albumin. Why?' Serum
results are
Sodium: 134 mmol/L
Potassium: 3.9 mmol/L
Bicarbonate: 28 mmol/L
Urea: 6.0 mmol/L
Creatinine: 378 umol/L (62 - 133)
Albumin: 20 g/L (35 - 49)
Globulins: 36 g/L (17 - 35)
Adjusted calcium: 2.59 mmol/L (2.10 - 2.55)
Phosphate: 0.77 mmol/L (0.81 - 1.45)
Uric acid: 192 umol/L (149 - 446)
Bilirubin: 14 umol/L (3 - 22)
Alkaline phosphatase: 135 IU/L (<126)
ALT: 10 IU/L (<56)
CRP: 37 mg/L (<8)
Free T4: 8.3 pmol/L (10 - 26)
TSH 41.1 mU/L (0.25 - 5.5)
The lady had been seen in Renal Outpatients three months earlier, when
fewer tests had been requested, but urea, creatinine, and albumin were very
similar to these values.
This curious set of abnormalities attracted 30 participants, and there was
some consensus on the interpretation. However, everyone (including myself)
got it wrong, bar one (well done, Avril).
6 participants felt it vital to talk to the Registrar to find out more,
[0.8]
particularly with regard to drug therapy.
1 participant would check to see if the sample were lipaemic. [0.0]
20 participants mentioned primary hypothyroidism; [1.8]
1 adding 'with myopathy'; [-0.3]
Participants were concerned about the discrepancy between urea and
creatinine:
8 mentioning that the high creatinine could be due to (drug) interference;
[0.5]
5 mentioning that the low urea could be due to low protein intake; [1.0]
3 suggesting end stage renal failure with severe protein restriction; [0.0]
3 queried an immediate post-dialysis sample; [-1.0]
1 said typical of a CAPD patient; [0.0]
1 suggested overhydration. [-1.0]
8 queried nephrotic syndrome/ glomerulonephritis; [0.8]
3 mentioned renal disease; [-0.8, one assessor stating 'insulting to a
Renal specialist']
3 mentioned liver disease; [0.0]
3 queried inflammation/ autoimmunity; [-1.0]
3 queried infection; [-1.0]
2 queried hyperparathyroidism. [0.0]
1 said the low albumin invalidates calcium adjustment. [0.8]
13 would suggest a 24 hour urine protein; [1.0]
3 would add creatinine clearance; [-1.0]
5 would suggest serum protein electrophoresis; [0.8]
3 would measure glucose; [0.8]
1 each would suggest
ionized calcium; [0.5]
serum CK; [-0.5]
abdominal ultrasound. [-0.5]
I was frankly puzzled by these results, and concerned about the possibility
of a neoplasm. I thought an immediate post-dialysis sample was most
unlikely since the patient had not been seen for three months. I also
thought it most unlikely that renal protein loss was the cause of the low
albumin since surely this would have been detected by dipstick in a Renal
Outpatient Clinic. The Renal Outpatient Clinic had been held on the
previous day, and was closed on the day I saw these results, the Registrar
who had seen the patient was off duty, and the Duty Registrar knew nothing
about this patient. The Consultant Renal Physician was unavailable. So much
for the ease of modern medical communication. I asked for the Patient Notes
to be sent to me, and should probably have put the report on hold till I
received them. However being naturally impatient and perhaps influenced by
the previous Case for Comment, I didn't and commented
'Disproportionately low urea through increased anabolism?
Hyperparathyroidism secondary to renal disease? - PTH to follow. Also
primary hypothyroidism. Worth checking serum protein electrophoresis?'
When the Case Notes arrived, they showed that the patient had been treated
for hyperthyroidism two years previously, and presumably the current
hypothyroidism had resulted from that. More important, they showed that the
patient was on CAPD (continuous ambulatory peritoneal dialysis) - something
which was not indicated on the request card, and I guess that the low urea,
low phosphate and relatively low urate were the result of this. This Case
only goes to show that we can (almost all) get it wrong when faced with
incomplete information, and makes me wonder how we can define an Expert!
Stand by for an important announcement about Cases for Comment.
With best wishes for Christmas and the New Year to all participants
Gordon Challand
I'm still puzzled that we haven't seen any 24 hour urine sample arrive for
protein (perhaps it would have been worth stating the obvious in this
case).
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