A 22-year-old patient, G ₂ P₁ had the following images during a 21 week ultrasound examination:

Figure 1: Anhydrammnios

Figure 2-3: A large fluid filled collection with septation

Figure 4: Umbilical arteries color dopler

Figure 5: Umbilical vein doppler.

These images demonstrate anhydramnios and a large cystic multilocular abdominal mass.

Many probably noticed the anhydramnios but did not included it in their differential diagnosis process. It is important though, since other masses like lymphangiomas could look like the one in this case, but the anhydramnios is highly suggestive of a obstructive urinary process.

This mass is fairly typical for massively distended ureters. The wispy septation seen in the cystic mass represent the folding of the ureters. The diagnosis is then simply that of urethral agenesis. Compare to Case of the week #110   where the cystic mass represented the distended bladder. Here the bladder is barely seen, but the most visible sign is that of the bunched up ureters.

After delivery of the fetus, the massively distended abdomen is evident

Figure 6: Newborn appearance after delivery.

As you can also see the urethral agenesis is seen (no penile urethra) and there is a concomitant anal atresia. The anal atresia is rarely seen prenatally since the symptomatology is so overwhelmingly due to the urinary obstruction.

Note also that this is a male fetus and they are less commonly affected with urethral agenesis them female fetuses.

Figures 7-8: Anal and urethral atresia