Indirect inguinal hernia
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An indirect inguinal hernia is an inguinal hernia that results from the failure of embryonic closure of the deep inguinal ring after the testicle has passed through it. Like other inguinal hernias, it protrudes through the superficial inguinal ring. It is the most common cause of groin hernia.
In the male fetus, the peritoneum gives a coat to the testicle as it passes through this ring, forming a temporary connection called the processus vaginalis. In normal development, the processus is obliterated once the testicle is completely descended. The permanent coat of peritoneum that remains around the testicle is called the tunica vaginalis. The testicle remains connected to its blood vessels and the vas deferens, which make up the spermatic cord and descend through the inguinal canal to the scrotum.
The deep inguinal ring, which is the beginning of the inguinal canal, remains as an opening in the fascia transversalis, which forms the muscular outer wall for the spermatic cord. When the opening is larger than necessary for passage of the spermatic cord, the stage is set for an indirect inguinal hernia. The protrusion of peritoneum through the internal inguinal ring can be considered an incomplete obliteration of the processus.
In an indirect inguinal hernia, the protrusion passes through the deep inguinal ring and is located lateral to the inferior epigastric artery. Hence, the conjoint tendon is not weakened.
- Bubonocele: in this case the hernia is limited in inguinal canal.
- Funicular: here the processus vaginalis is closed at its lower end just above the epididymis. The content of the hernial sac can be felt separately from the testis which lies below the hernia.
- Complete (or vaginal): here the processus vaginalis is patent throughout. The hernial sac is continuous with the tunia vaginalis of the testis. The hernia descends down to the bottom of the scrotum and it is difficult to differentiate the testis from hernia.
A hernia occurs when intra-abdominal contents, commonly including preperitoneal fatty tissues, the peritoneum itself, and eventually omentum and intestines, traverse the ring to enter the inguinal canal. As time passes, the hernia contents may enlarge, extend the length of the canal, and even exit the canal through the external inguinal ring, an opening in the external oblique fascia, into the scrotum.
Failure of the processus vaginalis to close properly is very common in infants and will usually leave only a small hole through which abdominal fluid can pass from the abdomen into the scrotum. This is termed a communicating hydrocele and must be differentiated from a non-communicating hydrocele.
In a communicating hydrocele, the fluid collection will change in size from time to time as fluid may drain back and forth between abdominal cavity and scrotum and on examination there will be no way to "get over" the hydrocele when palpating. This is in contrast to a non-communicating hydrocele, which is a distinct entity that occurs when there is excess fluid formation within the scrotum for any number of reasons.
In the female, groin hernias are only 4% as common as in males. Indirect inguinal hernia is still the most common groin hernia for females. If a woman has an indirect inguinal hernia, her internal inguinal ring is patent, which is abnormal for females. The protrusion of peritoneum is not called "processus vaginalis" in women, as this structure is related to the migration of the testicle to the scrotum. It is simply a hernia sac. The eventual destination of the hernia contents for a woman is the labium majus on the same side, and hernias can enlarge one labium dramatically if they are allowed to progress.
Watchful waiting is the common management of minimally symptomatic inguinal hernias. In few instances, surgery can be required. In this case, the surgeon recognizes the "indirect" hernia by noting that the hernia sac begins lateral to the inferior epigastric artery and vein, indicating that it arose at the top of the inguinal canal.