When investigating infertility one regularly encounters azoospermia, the condition where no sperm cells at all are present in the ejaculate.

The number of new cases per year in the Netherlands is estimated at 300 to 400, of which two-thirds are caused by abnormalities in the production of sperm cells and about a third by a ‘kink’ in the duct system, or an obstruction.

The firm diagnosis of ‘obstructive azoospermia’ is made by micro­scopic examination of a section the size of a grain of rice from the larger of the two testicles. A Johnsen score is given, which is obtained by assessing the sperm-cell forming tubules for the degree of maturation from stem cell to ‘mature’ sperm cells. The presence of fully grown sperm cells gives a score of ten, nine or eight, the presence of spermatids, sperm cells that are not quite mature, gives a score of seven or six, spermatocytes five or four and only spermatogonia, sperm cells that are far from mature, a score of three. The Johnsen score has a strong correlation with the quality of the spermatogenesis. With a normal spermatogenesis the average score is 9.4.

The Sertoli cell-only syndrome is one of the commonest causes of non-obstructive azoospermia. ‘Sertoli cell-only’ refers to what the pathologists see on microscopic examination of a section of testicular tissue, that is sperm-cell forming tubules that are too small, have a thickened wall and are coated only with Sertoli cells. No germinating sperm cells are found, let alone fully mature ones. Patients with Sertoli cell-only have a normal male body, but often rather small testicles. With them the level of fsh, the hormone that from the hypophysis prompts the testicles to produce sperm cells, is too high. The cause of the syndrome is unknown. Very exceptionally in the testicular biopsy small areas of normal sperm cell production are found alongside the Sertoli cell-only picture.

Nowadays sperm cells can be obtained directly from the testicle or the epididymis, so that no spermatozoa need be present in the ejaculate. Because of these new options it is necessary for the pathologist to make a careful distinction between a ‘complete’ and an ‘incomplete’ Sertoli cell-only syndrome. For this reason several biopsies are done in differ­ent directions. In Belgium by doing several ‘open’ testicular biopsies doctors succeeded in obtaining sperm cells from a third of these patients, which means that even with a serious disruption of sperm cell production, icsi (see below) is sometimes possible.