A 24-month-old boy is brought to the emergency department by his parents after they notice… — USMLE Step 2 CK

A $24$ -month-old boy is brought to the emergency department by his parents after they noticed a large amount of maroon-colored stool in his diaper. The parents state the child has not had any fever, vomiting, diarrhea, or crying episodes suggesting abdominal pain. He has been eating well and his activity level is at baseline. He was born at $39$ weeks gestation and has met all developmental milestones. His vital signs are temperature $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), heart rate $110/\text{min}$ , respiratory rate $22/\text{min}$ , and blood pressure $90/60\text{ mm Hg}$ . Physical examination reveals an alert, playful child with pale conjunctivae. The abdomen is soft, non-distended, and non-tender without palpable masses. Bowel sounds are normal. Examination of the perianal area shows no fissures or skin tags. Hemoglobin level is $9.2\text{ g/dL}$ . Which of the following is the most appropriate next step in management?

Perform a technetium- $99\text{m}$ pertechnetate scanCevap
B
Perform abdominal ultrasonography
C
Administer intravenous broad-spectrum antibiotics
D
Schedule upper and lower gastrointestinal endoscopy
E
Obtain a computed tomography (CT) scan of the abdomen

Cevap

The most appropriate next step is to perform a technetium-99m pertechnetate scan.

This patient's presentation of painless lower gastrointestinal bleeding (maroon-colored stool) in a toddler, accompanied by signs of mild anemia but normal vital signs, is highly characteristic of a Meckel diverticulum. It is the most common congenital anomaly of the gastrointestinal tract, resulting from incomplete obliteration of the vitelline (omphalomesenteric) duct. These diverticula frequently contain ectopic gastric mucosa, which secretes hydrochloric acid and causes ulceration of the adjacent normal small bowel mucosa, leading to painless bleeding. The best initial diagnostic test is a technetium-99m pertechnetate scan (Meckel scan), as the radiotracer has a high affinity for gastric mucosa and will accumulate in the ectopic tissue in the right lower quadrant.

Adım Adım Çözüm

Analyze the clinical presentation and vital signs.

The patient is a hemodynamically stable toddler with isolated, painless lower gastrointestinal bleeding (maroon stool) and signs of mild anemia (pale conjunctivae, low hemoglobin).

Establishing the acuity, nature of the bleeding, and associated symptoms is crucial for narrowing the differential diagnosis.

Formulate the most likely differential diagnosis based on the age group and symptoms.

Meckel diverticulum is the most likely cause. Other causes like intussusception or infectious colitis are less likely due to the absence of pain, fever, and diarrhea.

Meckel diverticulum is the most common cause of significant painless lower gastrointestinal bleeding in young children.

Select the appropriate diagnostic modality for the suspected condition.

A technetium-99m pertechnetate scan is chosen as the initial diagnostic test.

This specific scan detects the ectopic gastric mucosa that is characteristically found within a bleeding Meckel diverticulum.

Anahtar Kavram

Painless lower gastrointestinal bleeding in a young child is classically caused by a Meckel diverticulum, which is best diagnosed using a technetium-99m pertechnetate scan to detect ectopic gastric mucosa.

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