Answer:USMLE step 2 Mcq 175:A woman in the third month of her first pregnancy develps assymptomatic pyuria

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Correct Answer: A

Explanation:
The well-known dilatation of the ureters and renal pelves begins by the second month of pregnancy and becomes maximal by the middle of the second trimester, when ureteric diameter may be as much as 2 cm, and the volume of urine in each ureter 20 to 50 ml. The right ureter is almost invariably more dilated than the left, and the dilatation usually cannot be demonstrated below the pelvic brim. These findings have led some to argue that the dilatation is entirely due to mechanical compression of the ureters by the enlarging uterus and the ovarian venous plexus. It would seem that mechanical factors are the most important cause of this dilatation, but the early onset of ureteral enlargement supports the hypothesis that smooth muscle relaxation caused by progesterone plays a role as well. The consequences of ureterocalyceal dilatation include an ncreased incidence of pyelonephritis among gravidas with asymptomatic bacteriuria.


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