Does
anyone have thoughts on why this patient’s urinary sodium level would be
low?
76
year old man with widespread lymphoma
Serum
sodium levels have been low-normal for several months, but went down to 117
mmol/L on 16/7. The next day it was 121, with serum osmolality 259, urine
osmolality 495, but urine sodium <20.
The
last previous serum sodium was measured on 30/6, when it was 128.
He’d
had 2U blood on 19/6, Fludarabine for the first time on 20/6 and only returned
to the clinicians on 30/6 (day 10) despite having had a temperature of 37.9 one
evening.
He
was next seen on 16/7, when the sodium of 117 was measured, reporting that the
fludarabine had been “hard going”. He’d had abdominal
discomfort, a reduced appetite, some nausea, but no vomiting and regular
bowels.
On
17/7 a second course of Fludarabine was started and 2U blood were given.
The
follow-up serum sodium on 25/07 was 125, but the urine sodium was still <20.
Date |
Hb |
S-Na |
S-K |
S-urea |
S-creat |
S-alb |
S-osmo |
U-Na |
U-osmo |
18/6/08 |
9.5 |
132 |
3.7 |
6.3 |
94 |
27 |
|
|
|
30/6/08 |
10.2 |
128 |
3.7 |
4.6 |
95 |
25 |
|
|
|
16/7/08 |
8.7 |
117 |
4.3 |
3.4 |
93 |
27 |
|
|
|
17/7/08 |
|
121 |
4.3 |
3.6 |
93 |
|
259 |
<20 |
495 |
25/7/08 |
10.2 |
125 |
3.9 |
5.7 |
101 |
27 |
268 |
<20 |
543 |
His
other medications are Frusemide
40 mg od, Lanzoprazole 15 mg od, Allopurinol 300 mg od, Plavix 75 mg od
(Clopidogrel) and Co trimoxazole.
He
weighs 57 kg. PMH Hypertension and quadruple cardiac bypass in 1997.
The
most likely explanations for the hyponatraemia would each be expected to result
in a urine Na >20, and the urea and creatinine levels are not consistent
with either true or “effective” volume depletion.
Any
ideas gratefully received.
Thanks
Marieke
Dr
Marieke Jordaan
Consultant
Chemical Pathologist
Mid-Yorkshire
Trust
Pontefract
General Infirmary: (01977) 606238 or 606681