A 4-day-old baby boy has not defecated since coming home from the hospital even though feeding has been normal without any excessive vomiting. Rectal examination reveals a normal anus, anal canal and rectum. However, a large fecal mass is found in the colon and a large release of flatus and feces followsthe rectal examination. Which of the following conditions would be suspected?
**Core Concept**
A 4-day-old baby boy presents with failure to pass meconium, which is a critical sign of intestinal obstruction. The rectal examination reveals a normal anus, anal canal, and rectum, but a large fecal mass in the colon, indicating an obstruction at the level of the sigmoid colon or rectum. The release of flatus and feces following the rectal examination suggests a rectosigmoid impaction.
**Why the Correct Answer is Right**
Hirschsprung's disease is a congenital condition characterized by the absence of ganglion cells in the distal colon and rectum, leading to functional obstruction. The absence of ganglion cells results in an abnormal peristalsis, causing the colon to become dilated and the rectum to become narrow. The rectal examination in Hirschsprung's disease is often normal, but the passage of flatus and feces following the examination is a classic sign, as it indicates the presence of a fecal impaction in the rectosigmoid region. The condition is often diagnosed in infancy, with symptoms of failure to pass meconium within the first 48 hours of life.
**Why Each Wrong Option is Incorrect**
**Option A:** Meconium ileus is a condition associated with cystic fibrosis, where meconium is thick and sticky, causing an obstruction in the small intestine. However, the rectal examination in meconium ileus is often abnormal, with a characteristic "ground glass" appearance of the meconium.
**Option B:** Intussusception is a condition where a part of the intestine telescopes into another part, causing an obstruction. However, intussusception is more common in older children and is often associated with a palpable sausage-shaped mass on abdominal examination.
**Option C:** Imperforate anus is a congenital condition where the anal opening is absent or abnormal. However, the rectal examination in imperforate anus is often abnormal, with a blind-ending rectum.
**Option D:** Necrotizing enterocolitis is a condition where a portion of the intestine dies due to lack of blood supply. However, necrotizing enterocolitis is more common in premature infants and is often associated with abdominal distension and bloody stools.
**Clinical Pearl / High-Yield Fact**
Hirschsprung's disease is often diagnosed by rectal examination and the passage of flatus and feces following the examination. A rectal examination should always be performed in a baby who has not passed meconium within the first 48 hours of life.
**Correct Answer:** C. Hirschsprung's disease.