Master the board step 3

Master the Boards: USMLE Step 3
Fundus
Antrum cardiacum
curvature
BODY
Pyloroduodenal
opening
Pyloric antrum
Sulcus intermedius
Incisura angularis
Lesser
Greater
curvature
Pyloric part
Anatomy of the Stomach
Hypertrophy: enlarged
cells, but the same number
of cells
Hyperplasia: normal cell
size, but more cells
Pyloric stenosis is caused by a hypertrophied pylorus. The hypertrophied pylorus
obstructs the outlet, so nothing passes to the duodenum and projectile
vomiting ensues. The vomitus does not contain bile. (Food must be able to get
to the duodenum in order to come in contact with bile.)
The absence or presence of bile in vomitus is the key difference between duodenal
atresia (no bile) and pyloric stenosis (bile). Hypochloremic metabolic alkalosis
is pathognomonic of pyloric stenosis. Vomiting causes loss of the gastric
acid (i.e., hydrochloric acid). The low chloride level prevents the kidneys from
excreting bicarbonate, leading to alkalosis.
Malrotation and Volvulus
Look for an infant with bilious emesis and recurrent abdominal pain with
vomiting. Always suspect volvulus when the patient has an acute small-bowel
obstruction without a history of bowel surgery.
Diagnostic Testing
··
Best initial test: Ultrasound (inversion of superior mesenteric artery and
vein and duodenal obstruction) or barium enema (cecum is not in the right
lower quadrant)
··
Abdominal x-ray is not helpful (only helpful in duodenal destruction; shows
“double-bubble” sign).
Treatment
Treatment is with surgery.
396