Gobet R, Bleakley J, Peters C A
Department of Urology, Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
J Urol. 1998 Oct;160(4):1463-7.
Congenital hydronephrosis is more common in male individuals. We investigate whether an alteration in fetal bladder function induced by premature urachal closure contributes to fetal hydronephrosis, consequently explaining this male predominance.
The urachus was clipped in 8 male and 4 female ovine fetuses at 95 days of gestation (term 140 days). Subjects were sacrificed, and the urinary tract was assessed at 109 and 116 days of gestation in 3 and 1 male fetuses, respectively, and at term in 4 male and 4 female lambs.
At 109 and 116 days of gestation 3 of the 4 male fetuses had upper tract dilatation. At term no female but 4 male lambs had hydroureteronephrosis, including some with marked pelvic dilatation and parenchymal thinning. At term mean bladder weight in the male animals with urachal clipping was 5.28 gm. (range 3.5 to 8.2), which was significantly greater than normal (p = 0.02). Bladder weight at term in the female lambs with urachal clipping was not different from normal values. Histological evaluation of the kidneys in the male lambs revealed cortical thinning and loss of medullary tissue, while the overall renal architecture was well preserved.
Our observations indicate that normal ovine fetal urinary tract function and drainage depend on urachal function and the timing of urachal closure. Therefore, fetal hydronephrosis is associated with this alteration in bladder function but it may also be associated with other factors, such as bladder sphincter maturation or prostate development. Our experiment shows that hydroureteronephrosis develops in ovine fetuses when all bladder drainage occurs via the urethra. This condition may be an amplification of the differences in bladder outlet resistance in human fetuses, which may explain the male predominance in the various forms of hydroureteronephrosis.
先天性肾积水在男性个体中更为常见。我们研究过早的脐尿管闭合所诱导的胎儿膀胱功能改变是否会导致胎儿肾积水，从而解释这种男性优势现象。
在妊娠95天（足月为140天）时，对8只雄性和4只雌性绵羊胎儿进行脐尿管夹闭。分别在妊娠109天和116天时，对3只雄性胎儿和1只雄性胎儿进行处死并评估其泌尿道情况，在足月时对4只雄性和4只雌性羔羊进行评估。
在妊娠109天和116天时，4只雄性胎儿中有3只出现上尿路扩张。足月时，雌性羔羊未出现肾积水，但4只雄性羔羊出现了肾盂积水，包括一些伴有明显肾盂扩张和实质变薄的情况。足月时，接受脐尿管夹闭的雄性动物的膀胱平均重量为5.28克（范围为3.5至8.2克），显著高于正常水平（p = 0.02）。接受脐尿管夹闭的雌性羔羊足月时的膀胱重量与正常值无差异。对雄性羔羊肾脏的组织学评估显示皮质变薄和髓质组织丢失，而整体肾脏结构保存良好。
我们的观察结果表明，正常的绵羊胎儿泌尿道功能和引流依赖于脐尿管功能及脐尿管闭合的时间。因此，胎儿肾积水与膀胱功能的这种改变有关，但也可能与其他因素有关，如膀胱括约肌成熟或前列腺发育。我们的实验表明，当所有膀胱引流都通过尿道进行时，绵羊胎儿会发生肾盂积水。这种情况可能是人类胎儿膀胱出口阻力差异的放大，这可能解释了各种形式的肾盂积水中男性占优势的现象。
