Low serum vitamin B12 is common in spina bifida, including patients without ileal urologic reconstruction: A case for...

Vitamin B12 deficiency is a recognized complication of bowel-based urinary reconstruction, but its prevalence among individuals with spina bifida without or before urologic reconstruction is unknown. We evaluated the prevalence of low serum vitamin B12 in patients with spina bifida and compared it with population-based estimates from the National Health and Nutrition Examination Survey (NHANES).

Retrospective cross-sectional study of patients with spina bifida tested for serum vitamin B12 at a single institution between November 2004 and August 2023. Patients with no small-bowel reconstruction, and those reconstructed ≤5 years before measurement, were included. Low serum vitamin B12 was defined a priori as <200 pg/mL. Prevalence was compared with NHANES 1999-2002, the most recent cycles measuring serum vitamin B12, using indirectly standardized morbidity ratios (SMR).

Of 317 patients (159 children, 158 adults), 29 (9.1%) had low serum vitamin B12, more often adults than children (13.3% vs 5.0%, p = 0.012). No associations were seen with sex, race, ethnicity, or Distressed Communities Index quintile. Weighted NHANES prevalence was 1.84% (95% CI 1.61-2.10), giving an SMR of 7.72 (95% CI 5.17-11.09). SMRs were elevated both in patients without small-bowel reconstruction (7.27, 95% CI 4.55-11.01) and in those reconstructed within 5 years (9.61, 95% CI 3.85-19.80), and reconstruction was not associated with the outcome after adjustment for age and sex (odds ratio 0.73, 95% CI 0.25-2.08). Twenty-two of the 29 affected patients (76%) had no small-bowel reconstruction. The excess persisted at a stricter threshold of <150 pg/mL (SMR 16.14, 95% CI 8.05-28.89). Hemoglobin and mean corpuscular volume did not differ by vitamin B12 status.

Low serum vitamin B12 was substantially more common among patients with spina bifida than expected for their age and was not confined to those with prior small-bowel reconstruction. Because reconstruction-triggered screening would have missed three quarters of affected patients, these findings support consideration of routine screening across the spina bifida population.