Abnormal urine flow in boys with distal hypospadias before and after correction

We established the urine flow rate and the effect of surgical correction on that rate in patients with hypospadias.

The urine flow rate, voided volume and residual urine were measured using an ultrasound flow probe and bladder scan in boys with distal hypospadias before operative correction in 42 with a mean age of 16 months, 3 and 9 months after operative correction in 28 and 11, respectively, and in a control group of 51 boys 0 to 3 years old (mean age 11 months). Long-term flow data were obtained retrospectively from the records of 63 patients with hypospadias 1 to 10 years after operation.

Of the controls 37% had mainly intermittent and sometimes fractionated flows, 4% had a plateau phase flow and 59% had mainly bell-shaped flow curves. The average maximum flow rate +/- SD was 6.8 +/- 4.1 ml per second and maximum flow rate/voided volume was 0.26 +/- 0.11 l per second. Of the boys with distal hypospadias 76% produced intermittent flows (fractionated in the majority) before correction. After correction this percent decreased to 50%. The average maximum flow rate was 7.5 +/- 2.5 ml per second before correction, and 6.6 +/- 2.8 and 7.2 +/- 1.8 ml per second 3 and 9 months after operation, respectively. Average maximum flow rate/voided volume was 0.22 +/- 0.12 l per second before, and 0.16 +/- 0.09 and 0.16 +/- 0.09 l per second 3 and 9 months after operation, respectively. In the long-term group maximum flow rate/voided volume was 0.13 +/- 0.11 l per second. The number of patients voiding with a plateau phase increased from 6% before to 13% and 17% after correction, respectively. An obstructive pattern was also observed in 41% of the long-term followup group.

An intermittent flow pattern is common in 0 to 3-year-old boys. It appears to be more common and more pronounced or fractionated in boys with distal hypospadias at the same ages. In relation to voided volume patients with hypospadias already produce an abnormally low urine flow rate before correction and even more so thereafter in the short and intermediate term. The corrective procedure increases the occurrence of flows with an obstructive pattern.