Principles of Operations on the Testis
The scrotum has two layers, a richly vascularized rugous skin and a thin nonstriated dartos muscle (dartos tunic). The three layers of fascia that form the testicular coats and covering of the cord are the external spermatic fascia, the cremasteric fascia and muscle, and the internal spermatic fascia, the last related to the transversalis fascia. The testis rests within the tunica vaginalis, the distal extension of the processus vaginalis. The spermatic cord starts at the internal inguinal ring and ends at the testis and epididymis. The external spermatic fascia is accompanied by the cremasteric nerves and vessels. The internal spermatic fascia covers the vas deferens surrounded by its vessels and lymphatics, the testicular and epididymal arteries, the pampiniform plexus, and the autonomic nerves to the testis.
The circulation approaches the testis on a stalk, permitting venous occlusion by torsion. In the parenchyma, the vessels run under the capsule both centrally and peripherally, making most of the surface unsuitable for biopsy or the placement of fixation stitches.
Related to orchiopexy, the arterial vessel to each testis arises from the anterolateral surface of the aorta just below the renal artery. As the testicular artery approaches the upper end of the testis, it divides into two tortuous main branches—an outer branch, the internal testicular artery, and an inner branch, the inferior testicular artery.
The tail of the epididymis is vascularized by a complex arrangement of vessels involving the epididymal, vasal, and testicular arteries, with supplementation from the cremasteric artery. This system provides an extensive anastomotic loop among these vessels that is important when the testicular artery must be divided to achieve scrotal placement of the testis.
The vasal artery branches to join the posterior epididymal arteries to form an epididymal-deferential loop. After ligation of the testicular artery during orchiopexy, the testis becomes dependent on the anastomosis of this loop with the terminal part or distal branches of the testicular artery, a connection that may or may not be adequate to support the testis.
Testis biopsy can be done as an outpatient procedure. Local anesthesia is adequate for adolescents and adults if supplemented with analgesics such as midazolam or diazepam. The drawback of local infiltration is possible injury to the spermatic vessels. An alternative is to introduce a Biopty gun with a 17-mm sampling notch percutaneously to obtain one or two cores. In this technique, one must stabilize the testis and secure the epididymis posteriorly. The potential disadvantage of this technique is inadvertent and unrecognized injury to a testicular blood vessel or epididymis. Other limitations include the small sample volume and distortion of seminiferous tubule histology.
Because of the intragonadal distribution of the arteries in the tunica vasculosa, the biopsy should be taken from either the medial or the lateral aspect of the superior pole where the vascularity is sparse, not from the well-vascularized anterior surface ( Fig. 106.1 ).
Stand to the left. Block the spermatic cord by pulling the testis down to relax the cremaster muscle. Grasp the cord with the left hand and place the thumb in front and the index finger behind the cord at the top of the scrotum ( Fig. 106.2 ). With the needle approaching the index finger, infiltrate both the anterolateral and anteromedial sides of the cord as it emerges from the external ring near the pubic tubercle with 2% lidocaine solution without epinephrine through a 2.5-inch, 25-gauge needle. Avoid injecting near the vas for fear of puncturing it. Grasp the testis in the left hand and squeeze it against the scrotal skin, being certain that the epididymis is held posteriorly out of the way. Infiltrate the skin and dartos layer with 2% lidocaine. Do not inject the tunica albuginea. Do not relax your grip on the testis.
Incise transversely through the skin, dartos, and tunica vaginalis to follow the vasculature of the scrotum; these layers retract as the scrotum is squeezed around the testis ( Fig. 106.3 ). Place a hemostat on each side of the tunica vaginalis for exposure but maintain a firm grip on the scrotum to hold the site in position. Manipulate the testis so that the least vascular area, either the upper medial or lateral aspect of the upper pole, is exposed. Drip 2 to 3 mL of lidocaine on the tunica albuginea and wait 30 seconds.