Case Study: Infant with poor feeding

By Michelle Kelly, MD, and Erin Shaughnessy, MD

C.W. is an 8-month-old male who presented to a pediatrician's office with a two-month history of feeding difficulties. His mother first noticed a problem during transition from exclusive breastfeeding to formula and solids, when he began refusing food. On a good day, he would take only about 10 to 16 ounces of formula and minimal to no solids. He developed episodes of inconsolable irritability and at times appeared "out of it." During this time, gross motor development seemed to plateau.

On review of systems, C.W. had no vomiting, choking, gagging, diarrhea or seizures. He fed vigorously for the first five to six months of life and demonstrated normal growth and development. Birth history was full term, appropriate for gestational age, with no antepartum or peripartum complications. C.W. was noted to have hypoglycemia at birth that resolved with bottle feeding. No further workup was initiated. Newborn screen was normal.

In the office, on initial lab screening and subsequent repeat blood work, post-prandial blood glucoses were persistently below 45mg/dL. C.W. was directly admitted to the hospital for evaluation and treatment of hypoglycemia and feeding difficulties.

On admission, C.W. was noted to be awake, alert and interactive but irritable. His initial glucose was 19mg/dL, two hours after feeding 2 ounces of formula. The patient was rapidly treated with intravenous dextrose bolus with adequate rise in his blood glucose. A continuous dextrose infusion was then initiated. Two hours later, the patient's glucose dropped to 24 mg/dL, despite the infusion. Critical laboratory studies were drawn. Results included normal electrolytes without acidosis, normal cortisol, growth hormone, lactate, ammonia, insulin c-peptide and free fatty acids. Urine was negative for ketones. Insulin level was elevated. A subsequent glucagon challenge raised the patient's blood glucose from 39 mg/dL to over 130 mg/dL.

This patient was diagnosed with hyperinsulinism. After failed attempts with medication therapy, he was transferred to a tertiary care facility for definitive treatment. PET scan did not identify any discrete pancreatic lesions. Therefore, C.W. was scheduled for total pancreatectomy for suspected diffuse islet cell dysfunction. Intraoperatively, a small, discrete, insulin-secreting pancreatic mass was identified and resected. Postoperatively, C.W. had normalization of blood sugars. At his six-month follow-up, he was doing well with normal feeding and development.

Discussion

The initial management of a hypoglycemic patient always should include evaluation of airway, breathing and circulation followed by the rapid correction of blood glucose. Rapid treatment is vital to preventing brain injury. If the child is unable to take liquids by mouth, correction is typically done by an IV bolus of 0.5 to 1 g/kg or about 2 to 4 ml/kg of 10 percent dextrose (D10W). If IV placement is difficult, IM glucagon may be given, but should be followed immediately by intravenous dextrose infusion to prevent rebound hypoglycemia. 

Critical blood samples taken during hypoglycemic episodes will aid in the diagnosis. Blood is ideally obtained on initial IV placement prior to glucose correction; however, in an acutely ill hypoglycemic child, laboratory workup should never take priority over correction of glucose. When immediate correction of blood glucose is imperative, fasting laboratory studies always may be initiated later in a controlled hospital setting. 

Depending on the child's history and physical exam, the fasting sample may include: confirmatory glucose, electrolytes, insulin, insulin c-peptide, free fatty acids, ketones, cortisol, growth hormone, lactate, pyruvate, acylcarnitine profile, plasma amino acids, ammonia and toxicology screen. The child's first voided urine should be tested for ketones, glucose, reducing substance and organic acids. Figure 1 may be used as a guide in the interpretation of critical sample results. With negative urine ketones and high insulin levels, this patient demonstrated an inappropriate physiologic response to episodes of hypoglycemia. These findings, along with his negative insulin c-peptide and normal growth, made the diagnosis of hyperinsulinism apparent. From prior case studies, it is known that children with hyperinsulinism often develop feeding aversion that may be associated with persistently unrecognized hypoglycemia. Feeding aversion often resolves following normalization of blood glucose.

In a child, hyperinsulinism most often occurs transiently in the neonatal period, commonly in a small-for-gestational-age infant or infant of a diabetic mother. Persistent hyperinsulinism is rare. When present, it usually is due to a genetic mutation causing pancreatic beta cell dysfunction. In addition to continuous feedings and intravenous dextrose infusion, initial treatment for persistent hyperinsulism includes diazoxide, a medication that inhibits insulin release. Hyperinsulism is notoriously difficult to treat and often requires referral to a specialized center. If medications fail, a partial or full pancrea-tectomy often is necessary. Unfortunately, total pancreatectomy may lead to life-long insulin-dependent diabetes mellitus. Patients with focal lesions, such as the rare insulin-producing tumor found in C.W., may be cured with partial pancreatectomy.

References

Kapoor, RR et al, "Hyperinsulinaemic Hypoglycaemia," Archives of Disease in Childhood. 2009; 94:450-457.

Lteif AN, Schwenk WF, "Hypoglycemia in infants and children," Endocrinol Metab Clin North Am. 1999; 28:619-649.

Stanley C, Thornton P, Finegold D, Sperling M. "Hypoglycemia in infants," in Sperling M (ed): Pediatric Endocrinology, 2^nd ed. Philadelphia, WB Saunders, 2002: 135-139.

Verrotti A, Fusilli P, Pallotta R, et al, "Hypoglycemia in childhood: A clinical approach," J Pediatr Endocrinol Metab. 1998; 11(Suppl 1):147-152.

Zaoutis L, Chiang V, Comprehensive Pediatric Hospital Medicine. Philadelphia, Mosby, 2007: 173-175; 840-847.

Michelle Kelly, MD, is a critical care specialist at Children's Hospital of Wisconsin, an assistant professor of Pediatrics (Critical Care) at The Medical College of Wisconsin and a member of Children's Specialty Group.

Erin Shaughnessy, MD, is a pediatric hospitalist at Children's Hospital of Wisconsin,  an assistant professor of Pediatrics (Hospital Medicine) at The Medical College of Wisconsin and a member of Children's Specialty Group.

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