High-Anion-Gap Metabolic Acidosis During a Prolonged Hospitalization Following Perforated Diverticulitis: An Educational Case Report

RATIONALE: The metabolic acidoses are generally separated into 2 categories on the basis of an anion gap calculation: high-anion-gap and normal anion-gap metabolic acidosis. When a high-anion-gap metabolic acidosis (HAGMA) is not clearly explained by common etiologies and routine confirmatory testing, specialized testing can definitively establish rare diagnoses such as 5-oxoproline, d-lactate accumulation, or diethylene glycol toxicity. PRESENTING CONCERNS OF THE PATIENT: A 56-year-old woman had a prolonged hospital admission following perforated diverticulitis requiring sigmoid resection. Her hospitalization was complicated by feculent peritonitis and surgical wound dehiscence needing prolonged broad-spectrum antibiotics and wound debridements. She developed acute kidney injury and HAGMA in the hospital. DIAGNOSES: Chart review showed that she received a large cumulative dose of acetaminophen during her hospital stay. Laboratory studies showed markedly increased serum 5-oxoproline causing HAGMA. INTERVENTIONS (INCLUDING PREVENTION AND LIFESTYLE): Patient was admitted to the intensive care unit and treated with N-acetylcysteine and renal replacement therapy. OUTCOMES: After admission to the intensive care unit, the patient continued to require vasopressor and ventilatory support for septic shock and a ventilator-associated pneumonia. After an initial recovery and resolution of her HAGMA, she subsequently suffered recurrent aspirations which were fatal. TEACHING POINTS: 1. The acronym GOLD MARK is useful when assessing patients with HAGMA and most causes of HAGMA can be established with routine testing. 2. When the etiology of HAGMA remains unclear, additional testing can be required to diagnose rare causes of HAGMA. 3. Rare causes of HAGMA are diethylene glycol, 5-oxoproline, and d-lactate accumulation. 4. Acidosis secondary to 5-oxoproline accumulation can occur even with “therapeutic” doses of acetaminophen in patients receiving it regularly for a prolonged period and who have depleted glutathione stores. 5. Risk factors for glutathione depletion include malnutrition, older age, sepsis, pregnancy, multiple chronic illnesses, and chronic kidney disease.