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Excessive urinary oxalate excretion occurs in long-term TPN patients both with and without ileostomies
A L Buchman1, A A Moukarzel, M E Ament
1Section of Gastroenterology, Baylor College of Medicine, Houston, TX, USA.
Objective:
To determine if excessive oxalate and deficient citrate excretion were associated with TPN-associated nephropathy.
Design:
Crossectional cohort.
Setting:
Outpatient clinic.
Subjects:
Twenty-five patients (15 males, 10 females) aged 51 +/- 17 (mean +/- SD) years who had received home total parenteral nutrition (TPN) for 10 +/- 4 years. Fifteen subjects had ileostomies (Group A) and 10 had functional colons (Group B).
Outcome Measures:
Glomerular filtration rate (GFR), tubular reabsorption of phosphate (TRP), urinary oxalate and citrate excretion.
Results:
The mean GFR was 68.1 +/- 34.5 ml/minute/1.73 m2 and did not differ between Groups A and B. The mean TRP was 65.0 +/- 32.2% for Group A and 80.5 +/- 16.0% for Group B. The difference was not statistically significant. Urinary oxalate and citrate excretion were 40.2 +/- 30.2 and 324.4 +/- 239.0 mg/day respectively for Group A, and 63.2 +/- 34.2 and 474.8 +/- 936.3 respectively for Group B. The differences were not statistically significant. Thirty-eight percent (38%) of patients with ileostomies and 78% of patients without ileostomies had excessive urinary oxalate excretion (> 40 mg/day). Fifteen percent (15%) of patients with ileostomies and 50% of patients without ileostomies had decreased urinary citrate excretion (< 140 mg/day).
Conclusions:
Increased endogenous oxalate production may occur in patients receiving long-term TPN.