Keto-Bezoar: Adverse Event Related to Initiation of Ketogenic Diet in an Infant

**Background:** The ketogenic diet (KD) is an established dietary therapy for refractory epilepsy in children and adolescents. With the increasing availability of ketogenic formulas, KD use in infants has grown, yet data on adverse effects in this very young population remain limited. This case report presents a previously undocumented severe adverse event—bezoar formation with bowel obstruction—in an infant initiated on KD.

**Methods:** This is a single-patient case report from an unspecified institution. The patient was a 6-week-old term infant with drug-resistant epilepsy beginning hours after birth, refractory to escalating antiepileptic medications. Due to high clinical suspicion for a BRAT1 gene mutation (the patient's sibling with the same mutation had responded well to KD), the patient was started on KD on day of life 27. Under dietician guidance, ketosis was achieved on day of life 31 using a ketogenic ratio of 4.5 g of fat to 1 g of protein and carbohydrates. Two weeks later, the patient developed feed intolerance with abdominal distention and nonbilious emesis. Diagnostic workup included abdominal radiography, ultrasound, sepsis evaluation, and ultimately exploratory laparotomy. Pathologic evaluation of resected colon tissue was performed.

**Key Results:** Two weeks after achieving ketosis, the patient developed abdominal distention, nonbilious emesis, and abnormal stools described as a combination of diarrhea and 'rock hard pebbles.' Abdominal radiograph showed right-sided bubbly lucencies concerning for pneumatosis intestinalis. Despite bowel rest and a negative sepsis evaluation, abdominal distention persisted with passage of blood-streaked mucus per rectum. The patient progressed to abdominal compartment syndrome and acute kidney injury, prompting exploratory laparotomy. Operative findings included copious clear ascites, normal bowel anatomy, and a severely impacted, immobile bezoar at the hepatic flexure. The bezoar had devascularized and circumferentially eroded the colonic wall, necessitating a right hemicolectomy. Due to clinical instability, an end ileostomy was created with the distal left colon left diverted in situ. Gross pathologic evaluation confirmed a large stool bezoar; histology demonstrated normal ganglion cells, ruling out Hirschsprung disease. The bezoar was not analyzed for chemical composition. A postoperative contrasted enema of the diverted left hemicolon showed no obstructive pathology. The patient improved after surgery, tolerated advancement to maternal breast milk, and KD was not resumed. Genetic testing confirmed a BRAT1 gene mutation. Seizures were controlled on seven antiepileptic medications. Ileostomy takedown was performed two months later, and the patient was discharged home on term formula and maternal breast milk.

**Clinical Implications:** This case documents a novel and severe adverse event—stool bezoar causing colonic erosion, abdominal compartment syndrome, and acute kidney injury—associated with KD initiation in a very young infant. Several factors may have contributed: the patient's age (6 weeks, younger than most reported KD initiations), the high ketogenic ratio of 4.5:1 required to achieve ketosis (above the 3:1 ratio typically used in infants), and the immature lipid metabolism in neonates leading to decreased fat absorption and potential gut inflammation. While international guidelines support KD use in infants under 23 months and a systematic review found it generally safe, this case highlights that KD—particularly at high ratios in neonates—carries risk of life-threatening gastrointestinal complications. The authors recommend initiating KD with caution in very young patients, weighing individual benefits and risks, and suggest that clinicians maintain a high index of suspicion for severe fecal impaction when abdominal symptoms arise in this population.