Ivanesa Pardo, MD, FACS, Eugene Wang, MD, Matthew Sharbaugh, DO, Anyea Lovette, MS, RD, LD, Timothy Koch, MD, FACG, Timothy Shope, MD, FACS, FASMBS. Medstar Washington Hospital Center
INTRODUCTION: Hyperammonemia secondary to Ornithine Transcarbamylase (OTC) deficiency is a rare and potentially lethal disorder. The prevalence of OTC deficiency is reported to be 1:14,000 to 1:70,000 in the general population. OTC deficiency has been reported in patients presenting with neurological symptoms after Roux-en-Y gastric bypass (RYGB), and less than 30 cases have been reported in the literature. The aims of this study are to examine the apparent incidence of this uncommon disorder in patients after bariatric surgery and to examine potential predictors of mortality.
METHODS AND PROCEDURES: This is a single center, retrospective study in a large, urban teaching hospital of post-bariatric surgery patients who developed hyperammonemia from January 2012 to August 2017. Elevated plasma ammonia with an elevated urinary orotic acid level is accepted as consistent with a diagnosis of OTC deficiency. All patients in our program are instructed on a post-operative diet containing 60 grams/day of protein. Descriptive and correlative statistics are calculated for all variables.
RESULTS: Between January 2012 and August 2017, 1597 bariatric surgical procedures were performed at this single medical center. Seven women with neurological symptoms had plasma ammonia levels above the upper limit of normal range. Their average BMI is 45 kg/m2. Two patients underwent vertical sleeve gastrectomy (VSG), 1 underwent VSG with duodenal switch, and 4 underwent RYGB. All patients were hospitalized. The mean peak plasma ammonia level is 142 umol/L (range: 57-235). The mean urinary orotic acid level is 3.3 mmol/mol creatinine (range: 1.6-7.9). There were 2 patients with no orotic acid level checked, secondary to demise. No patient had clinical features or findings of progressive hepatic failure. There are four mortalities (57.1%). Serum folate and peak lactic acid levels are predictors of mortality with p-values of 0.048 and 0.006 respectively. The apparent incidence of OTC deficiency is 1:319 in post-operative patients.
CONCLUSIONS: In our post-operative population, hyperammonemia results in a high mortality. Its apparent incidence, secondary to OTC deficiency, amongst bariatric surgery patients is higher than that reported in the general population. Since OTC deficiency is identified after multiple bariatric surgical procedures, further investigation will be important to examine potential mechanisms for its development which may include a genetic predisposition (possibly triggered by nutritional deficiencies), upper gut bacterial overgrowth (supported by elevated serum folate levels), or preexisting, subclinical hepatic dysfunction.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 87972
Program Number: P632
Presentation Session: iPoster Session (Non CME)
Presentation Type: Poster