A simple surgical procedure can treat what some regard as a leading cause of male infertility, scientists report.
Some believe varicoceles can reduce a man's sperm count
A team found using a minimally invasive technique to correct blocked vessels in the testicle enabled some previously infertile men to have children.
The German study was presented at the annual meeting of the Radiological Society of North America.
But other experts said the results were not conclusive because the team had not carried out a control study.
Some researchers believe varicose veins in the testicle, varicoceles, are a leading cause of male infertility.
Varicoceles, which are a tangled network of blood vessels, are caused by blood circulation problems. They are relatively common: about 10-15% of men are estimated to have them.
Although in many cases they are harmless, some believe they can lead to fertility problems because they cause warm blood to pool, increasing the scrotum temperature and reducing sperm count.
Previous reviews of research have found that using open surgery to remove the varicoceles in sub-fertile men have not made any difference to their ability to conceive, but the researchers in Germany used a different technique called embolisation.
This involves inserting a small catheter into the groin and steering it into the varicocele. A tiny platinum coil and a special fluid are then injected, via the catheter, to block off the faulty vein, diverting the blood flow through an alternative route.
Because the operation is minimally invasive, patients can typically return to work the next day.
The scientists carried out the operation on 173 infertile men, and on average, found the men's sperm motility and count had improved within three months.
Six month after the operation 45 couples - 26% - had reported a pregnancy.
Sebastian Flacke, assistant professor of radiology at the University of Bonn in Germany, said: "This study confirms that varicocele repair can significantly improve sperm count and motility."
But Dr Allan Pacey, a male fertility expert from Sheffield University was more cautious.
He said: "Varicoceles are very common in men, but whether or not they actually cause fertility problems has been quite controversial. Even more controversial has been the suggestion that male fertility could be improved by correcting the varicocele by surgery.
"A recent systematic review of seven randomised controlled trials concluded that there was no improvement to fertility by correcting the varicocele by surgery, although most of the studies considered used the older technique rather than embolisation."
He added it appeared that the authors had not compared their sperm data and fertility rates with those of infertile men with varicoceles who did not have the embolisation procedure.
"That makes it very difficult to conclude how successful the embolisation technique has really been at restoring fertility."