Early recovery of urinary continence after robot-assisted radical prostatectomy is associated with membranous urethra and neurovascular bundle preservation.

OBJECTIVES: We investigated the correlation between surgical outcomes and postoperative urinary continence recovery in robot-assisted radical prostatectomy (RARP). METHODS: Patients who underwent RARP in our institution (n = 195) were included in this study. Preserved urethral length (PUL) was assessed during the procedure. Other outcomes of the surgical procedure were collected from operative records. Kaplan-Meier analysis with log-rank test was used to compare urinary continence recovery rate with the PUL, sparing of the neurovascular bundle (NVB), and other surgical procedures. Univariate and multivariate analyses were performed using Cox proportional hazards model, and p-values of <0.05 were considered significant. RESULTS: Patients with a PUL ≥26 mm had 10.0%, 24.7%, 36.6%, and 89.0% continence recovery rates at 30, 60, 90, and 365 days after surgery, respectively, while patients with a PUL <26 mm had 0%, 17.8%, 26.1%, and 80.9% recovery rates, respectively. Kaplan-Meier curves showed significantly better postoperative urinary continence recovery at 30 days after RARP in patients with a PUL ≥26 mm than those with a PUL <26 mm (p = 0.0028) and in patients with NVB preservation than those with no NVB preservation (p = 0.014). Urinary continence recovery within 30, 60, and 90 days after surgery was 90.6% for patients with a PUL of ≥26 mm and NVB preservation, while only 82.3% for patients with a PUL of <26 mm or no NVB preservation. CONCLUSION: Our results suggest that a PUL ≥26 mm and NVB preservation after RARP correlate with a significantly higher postoperative rate of recovery of urinary continence.

Urine output and resultant osmotic water shift are major determinants of plasma sodium level in syndrome of inappropriate antidiuretic hormone secretion.

Although various formulas predicting plasma sodium level ([Na]) are proposed for correction of hyponatremia, it seems that an anticipated [Na] frequently exceeds or falls below the measured [Na], especially in syndrome of inappropriate antidiuretic hormone secretion (SIADH). The causative factors of the fluctuation have never been investigated clearly. The aim of this study was to identify the determining factors for accurate prediction of [Na] by comparing data from previously proposed formulas and a novel osmotic compartment model (O-C model). The O-C model, which simulates the amounts of osmoles in extracellular and intracellular fluids, can estimate resultant osmotic water shift (OWS) and [Na]. The accuracy of representative formulas was verified in a point-to-point study using blood and urine samples obtained every 4 hours from 9 patients. Among 161 measurement points, a large fluctuation of urine volume and urine sodium level was observed. The gap between anticipated and measured [Na] in the widely used Adrogue-Madias formula was -0.5 ± 0.1 mEq/L/4 h (mean ± standard error), showing a marked tendency to underestimate [Na]. The gap in the O-C model including OWS was 0.1 ± 0.1 mEq/L/4 h, and that in the O-C model eliminating OWS was 1.9 ± 0.2 mEq/L/4 h, indicating that measurement of urine output and estimation of resulting OWS are essential for a superior prediction of [Na] in SIADH. A simulation study with the O-C model including OWS unveiled a distinctive correction pattern of [Na] dependent on the urine volume and urine sodium level, providing a useful choice for the proper type and rate of infusion.