A 3-year-old boy is brought to the office by his parents due to constipation. The boy previously had soft stools 1-2 times daily. However, over the past 3 months, his bowel movements have decreased to 1 stool every 3-4 days with significant straining and production of hard stool balls. The boy has intermittent diffuse abdominal pain and increased irritability, but these symptoms have not affected his overall appetite. Family history is notable for a maternal aunt with celiac disease and a paternal grandmother with "thyroid problems." Four months ago, the boy and his parents moved into a house owned by their family for generations, and the parents are worried that the stress of the move might be contributing to his symptoms. Height and weight have been tracking appropriately. Physical examination shows a pale, tired boy with palpable stool in his abdomen but no abdominal tenderness. Which of the following is the most appropriate diagnostic test for this patient?

Question

A 3-year-old boy is brought to the office by his parents due to constipation.  The boy previously had soft stools 1-2 times daily.  However, over the past 3 months, his bowel movements have decreased to 1 stool every 3-4 days with significant straining and production of hard stool balls.  The boy has intermittent diffuse abdominal pain and increased irritability, but these symptoms have not affected his overall appetite.  Family history is notable for a maternal aunt with celiac disease and a paternal grandmother with "thyroid problems."  Four months ago, the boy and his parents moved into a house owned by their family for generations, and the parents are worried that the stress of the move might be contributing to his symptoms.  Height and weight have been tracking appropriately.  Physical examination shows a pale, tired boy with palpable stool in his abdomen but no abdominal tenderness.  Which of the following is the most appropriate diagnostic test for this patient?

Quizplus · Accepted Answer

11ec160b_39fd_fa4c_9249_331ec5cfb3df_MD0001_00 This patient's constipation, abdominal pain, irritability, and pallor (suggesting anemia) are most likely due to lead poisoning. Policy efforts resulted in the elimination of lead, a toxic metal, in gasoline (1985) and paint (1977). Current lead exposure occurs through contact with dust/paint in homes built before 1978; this is the most likely cause of this patient's condition given the onset of symptoms after moving. Lead binds to sulfhydryl groups on proteins, replaces calcium in calcium-dependent cellular functions, and directly inhibits enzymes in heme synthesis. Symptoms of lead poisoning are neurologic (cognitive impairment, irritability), gastrointestinal (constipation, abdominal pain), renal (interstitial nephritis), and hematologic (anemia). Risk factors include having a sibling with prior elevated lead levels and living in older homes with recent renovation/construction. Because irreversible neurodevelopmental effects occur during exposure to low lead levels, screening is recommended for young children at high risk. Diagnosis is made by measuring the blood lead level. Urine δ-aminolevulinic acid (heme synthesis substrate) is also elevated. (Choice A) Hirschsprung disease typically presents in the newborn period with bilious vomiting and failure to pass meconium. Anorectal manometry measures rectal pressure via rectal catheter and shows absent relaxation of the internal anal sphincter. The diagnosis of Hirschsprung disease is confirmed by rectal biopsy. (Choice C) Hypokalemia and hypercalcemia can present with constipation. However, patients with hypokalemia exhibit muscle weakness or arrhythmias, whereas hypercalcemia is accompanied by muscle weakness, confusion, and renal insufficiency. (Choice D) Hypothyroidism can cause constipation, and primary hypothyroidism is associated with elevated TSH. However, constipation due to hypothyroidism is usually accompanied by other symptoms, such as decreased growth velocity and short stature in children. (Choice E) Tissue transglutaminase is a screening test for celiac disease, which typically presents with diarrhea, weight loss, and abdominal pain. Some patients present with constipation instead of diarrhea. However, given this patient's appropriate growth and symptom onset after the recent move, lead poisoning is the more likely diagnosis. Educational objective: Lead poisoning can cause neurologic, gastrointestinal, renal, and hematologic complications. Although symptoms can be vague, lead poisoning should be suspected if these symptoms arise while residing in a home built before 1978. Diagnosis is made by measuring the patient's blood lead level. __________ References: Lead poisoning in children. (http://www.ncbi.nlm.nih.gov/pubmed/25037135) A review of a preventable poison: pediatric lead poisoning. (http://www.ncbi.nlm.nih.gov/pubmed/16223376)

A 3-Year-Old Boy Is Brought to the Office by His