In the female the canal is occupied by the round ligament, along which a process of peritoneum, called the canal of Nuck, descends in the foetus for a short distance. A congenital form of inguinal hernia in the female may occur into this sac. It should be remembered that inguinal hernia is by no means uncommon in women, and that femoral hernia is frequently met with in men, although, as a rule, perhaps inguinal hernia is more common in men and femoral in women. Where a hernia is strangulated by some constricting band about the inner opening of the peritoneal sac, it is frequently necessary to make a slight cut in the band in order to relieve the constriction. In the case of inguinal hernia, the blade of the knife should generally be directed upwards and outwards so as to avoid the deep epigastric artery, while in femoral hernia it should be directed upwards and inwards so as to keep clear of the femoral vein, and in acquired umbilical hernia directly upwards.
A Richter's hernia is one in which only a portion of the circumference of the bowel is in the sac. Some apply the term Littres hernia to the same condition, or to a hernia of a small knuckle of bowel, or of a diverticulum.
With regard to the operative treatment of inguinal hernia, many methods of dealing with the sac and of closing the inguinal canal have been devised. In children simple ligature of the sac as far up as possible has been found to yield good results. In adults the sac is variously removed, drawn to some abnormal position, or placed as a pad on the inner surface of the abdominal wall, with the object of obliterating the funnel-shaped orifice of the canal, which may be said to ' tempt' the hernia (Macewen). With the object of further removing 'temptation,' redundant omentum is generally removed, as omentum frequently opens out the path for bowel to follow. In this connection also it may be said that abnormal length of mesentery is generally looked upon as a predisposing cause of hernia. The closure of the canal is generally accomplished by drawing the arching conjoined tendon down behind Poupart's ligament, and stitching up the external ring (Macewen), which latter in many operations is first slit up to give easier access to the conjoined tendon (Bassini). The cord is variously treated, being left at the inner side of the portion of conjoined tendon which has been pulled down (in which case it occupies a small natural channel, which cannot be obliterated owing to the vertical direction of the conjoined fibres at that point, and so is relieved from pressure) (Macewen), or brought out at the position of the internal ring, and then passed between the stitched conjoined, and external oblique (Bassini), or even taken out to the anterior superior spine by others (Halsted).
In femoral hernia there is less tendency to recurrence if care be taken to invaginate or otherwise treat the sac so as to remove its gaping mouth. Some have tried to obliterate the canal by turning up a flap of pectineus and its fascia over the mouth of the canal, and attaching it above to Poupart's ligament (Cheyne), while others seek to do so by suturing the tense ligament down to the subjacent bone.
Before leaving the subject of hernia some of the rarer forms may be mentioned. In pudendal hernia the bowel descends between the ascending ramus of the ischium and the vagina to the posterior portion of the labium. In perineal hernia it perforates the anterior fibres of the levator ani, and appears between the prostate and rectum, carrying the recto-vesical (and anal) fasciae before it. A sciatic hernia passes through the great sacro-sciatic notch, and appears under the gluteus maximus. A lumbar hernia presents through the triangle of Petit between the latissimus dorsi and external oblique, just above the highest point of the iliac crest, and in front of the quadratus lumborum, and either carries before it or perforates the fascia lumborum and internal oblique. Diaphragmatic hernia is most usually congenital, occurring through some developmental defect, and is more common on the left side owing to the presence of the liver on the right, passing through connective tissue intervals between sternal and costal origins of the diaphragm in front ; or vertebral and costal origins behind ; or the oesophageal foramen. It does not invade the aortic or vena caval foramina. The stomach, or transverse colon, forms the most common contents of the protrusion.