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A 24-year-old woman has a marked increase in the size of her uterus between 26 and 30 weeks' gestation. Ultrasonography shows a marked increase in the amount of amniotic fluid; the fetus is normal in size for gestational age. Which of the following is the most likely diagnosis?

(A) Congenital heart disease
(B) Duodenal atresia
(C) Erythroblastosis fetalis
(D) Horseshoe kidney
(E) Neural tube defect
 

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The fetus produces urine through its primitive urinary system, passes it to the amniotic fluid, and then swallows it through its mouth. An amount is absorbed and re-excrited as water through the urine, while another amount is excreted through the fetus' feces, know as meconium. Finally, a third portion of this fluid fills up the primitive lungs, which do not function until the first breath during labor, but it is necessary to be filled by this fluid in order for the alveoli to develop properly.

If there is a defect in the urinary tract (i.e. Potter sequence), the fetus cannot produce urine, thus the amount of amniotic fluid is decreased (oligohydramnios). This has an impact on the development of the respiratory system, which manifests clinically as ARDS of the newborn (that's the most usual cause of perinatal death in pt's with Potter sequence).

If there is abnormal development of the fetus' GI tract (i.e. abnormal formation of the GI lumen), the fluid produced by the urinary system cannot be reabsorbed sufficiently, thus it accumulates in the amniotic fluid and causes polyhydramnios (which is the case here). So, the correct answer is B.
 

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yes the answer is B.

I thought it was horseshoe kidney at first. thank u dr.ath.pantelis for the explanation. now i understand. i understood it as if the kidneys are blocked as well, the fluid accumulates in the amnion. but i was wrong. kidney blockage causes Potter's sequence or hypoplastic lungs ryte?
 
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