(397) Nonhepatic Hyperammonemia: Fatal Cerebral Edema in a 43-Year-Old Female With Toxic Megacolon

Introduction: NHHA is rare, yet causes substantial morbidity and mortality. We present a case of a 43-year-old female with systemic lupus erythematosus (SLE) who developed toxic megacolon and fatal cerebral edema from NHHA.

Description: A 43-year-old female with SLE on immunomodulators and chronic steroids was admitted to the ICU with hypotension, abdominal pain, nausea, vomiting, and constipation. Physical exam revealed respiratory distress and a distended abdomen with tense ascites. Labs showed WBC of 40, lactate of 4, and an anion gap metabolic acidosis. CTAP was notable for a severely dilated colon with air/fluid levels consistent with toxic megacolon. She was intubated for airway protection, an OGT was placed, and a peritoneal drain was placed to manage abdominal compartment syndrome. C difficile toxin EIA was positive and antibiotics were started for fulminant infection. Colectomy was not offered due to surgical risk.

Following the resolution of shock, the patient developed new altered mental status. The ammonia level was 945 umol/L and CT head, CT abdomen, and liver ultrasound were unrevealing. Continuous renal replacement therapy and intermittent hemodialysis with an ammonia scavenger was initiated, genetics was consulted, and she was started on hypertonic saline. The ammonia levels improved to the 200s, but her mental status remained poor and a brain MRI showed cerebral edema. Despite aggressive medical management, she developed fixed dilated pupils, bradycardia, and hypertension, suggestive of herniation. Ultimately, care was withdrawn and the patient passed thereafter.

Discussion: NHHA accounts for less than 5% of all cases of hyperammonemia. Causes are categorized into production or clearance issues but can be multifactorial. Increased production can be caused by protein catabolism, increased ammonia absorption, infections with urease producing bacteria, seizures, and drugs. Impaired clearance can be seen in inborn errors of metabolism, drugs that inhibit the urea cycle, renal disease, and anatomic causes. In this case, intestinal bacterial overgrowth, AKI, chronic steroids and TPN were all likely contributors to NHHA as the genetic workup was negative. Recognition and intervention are crucial in preventing poor outcomes and prompt multidisciplinary management is essential.