A study of resistive indices in the arcuate arteries of the kidney over the course of gestation.

OBJECTIVE: Our purpose was to assess whether there was a variation in the resistive index (RI) of the arcuate artery in the kidneys of patients with hydronephrosis in pregnancy. STUDY DESIGN: Forty-seven patients were studied to establish norms for the RI of the arcuate arteries in pregnancy, and these measurements were correlated with the development of hydronephrosis over the course of gestation. RESULTS AND CONCLUSIONS: The RIs were noted to remain unchanged from the nonpregnant state throughout gestation. They were also unchanged by the presence of the physiologic hydronephrosis of pregnancy.

The hyponatremia of neonatal urinary ascites: clinical observations, experimental confirmation and proposed mechanism.

A case of neonatal urinary ascites with severe hyponatremia is reported. Critical review of the literature on neonatal urinary ascites, which included determination of serum electrolytes, revealed a 70% incidence of hyponatremia. In an attempt to explain the mechanism of the hyponatremia, urinary ascites was produced in rats by creation of either a unilateral (uretero-peritoneal) or bilateral (vesicoperitoneal) shunt. Hyponatremia did not occur in the unilateral group but it was profound in the bilateral group. At 48 hours postoperatively renin was unchanged in the unilateral group but it was significantly elevated in the bilateral group. Aldosterone was elevated in the unilateral group and markedly elevated in the bilateral group. Urine entering the peritoneal cavity equilibrates with plasma. The proposed mechanism of hyponatremia in the bilateral group is autodialysis with intraperitoneal urine containing progressively lower sodium concentration secondary to increased renin and aldosterone.

Urodynamic evaluation of the continence mechanism following urethral lengthening--reimplantation and enterocystoplasty.

In an attempt to create continence in myelomeningocele children we performed urethral lengthening/submucosal reimplantation, a form of bladder neck reconstruction, to create a valve allowing catheterizable access to the bladder. We present the urodynamic findings of 23 patients 4 to 89 months (mean 43.1 months) after bladder neck reconstruction and enterocytoplasty to determine the continence mechanism of this 1-way valve and characteristics of the augmented bladder. Standard cystometrograms with simultaneous pressure recording of the submucosal portion of the neourethra were undertaken with a 10F, triple lumen, urethral pressure profile catheter. Baseline pressures in the submucosal neourethra were higher than in the bladder (mean 25.3 versus 13.4 cm, water, p less than 0.001). Submucosal tunnel and bladder pressures paralleled throughout filling, with mean tunnel pressures remaining greater at the time of first (53.6 versus 45.5 cm. water, p less than 0.01) and peak (62.9 versus 55.8 cm. water, p greater than 0.05) cystoplasty contractions. Bladders augmented with detubularized ileum had fewer significant contractions (greater than 40 cm. water) than other types of cystoplasties (36% versus 92%) and over-all they had first and peak contractions at greater volumes and lesser magnitude. We conclude that continence following urethral lengthening/reimplantation results from an anatomical arrangement allowing transmission of dynamic bladder pressure changes to the submucosal neourethra and that urethral pressure exceeds bladder pressure throughout filling. Additionally, our data suggest that detubularized ileum provides a large capacity, low pressure reservoir suitable for augmentation.