Published on 11/04/2015 by admin
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Last modified 11/04/2015
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15 Hernia
A hernia is a protrusion of a viscus or other structure beyond the normal coverings of the cavity in which it is contained, or between two adjacent cavities, e.g. abdomen and thorax. Hernias most frequently occur in the inguinal, femoral and umbilical regions and are classified into congenital or acquired. The commonest congenital hernia is found in infants where a patent processus vaginalis occurs, giving rise to an inguinal hernia. Acquired hernias may be primary, occurring at natural weak points, e.g. femoral hernias or umbilical hernias, or secondary at sites of surgical incisions (incisional hernias).
Predisposing factors include increased intra-cavity pressure due to heavy lifting, chronic cough, straining to pass urine or faeces, abdominal distension or the presence of ascites or tumour. A weakened abdominal wall occurs with abnormal collagen, metabolism, age, malnutrition, or damage or paralysis of motor nerves.
A hernia consists of a sac, its coverings and contents. The sac is composed of a mouth, neck, body and fundus. The coverings of hernia refer to the layers which are attenuated as the hernia emerges, consisting of skin, subcutaneous fat, aponeurosis, muscle, fascia and endothelial lining. The contents of the hernia may vary, but are most usually the small bowel or greater omentum.
Any abdominal hernia regardless of site may be reducible, irreducible, incarcerated, strangulated or obstructed.
The contents can be returned to the abdomen but the sac persists.
The contents cannot be returned due to a narrow neck with or without adhesions forming between the contents and the sac.
This describes a hernia that is irreducible but not strangulated.
The contents of a hernia become stuck in the sac, impeding the blood supply. Initially the venous return is occluded causing further engorgement of the contents until eventually the arterial flow is also compromised. This leads to ischaemic necrosis of the contents of the sac. If the sac only contains omentum, the necrosis is sterile. If bowel is involved, gangrenous intestine occurs which may result in fatal peritonitis. A strangulated hernia is therefore a surgical emergency.
Bowel stuck in a hernia may obstruct, causing intestinal obstruction. Abdominal hernia is a common cause of small bowel obstruction (see pp. 85 and 87-88).
An extraperitoneal structure forms part of the wall of the sac (5% of all inguinal indirect hernias). The caecum and ascending colon are involved on the right side, and the sigmoid or descending colon on the left side. Occasionally a portion of the bladder may slide into a direct hernia.
A portion of the circumference of the small intestine is trapped, which may become ischaemic but without the development of intestinal obstruction (Fig. 15.1).
Figure 15.1 Richter’s hernia. Part of the bowel wall has strangulated in the hernia but the lumen of the bowel is not obstructed. This is most commonly seen in strangulated femoral hernias.
• A lump which varies in size which may disappear when lying down
• Pain – ache or symptoms of complication including intestinal obstruction or strangulation.
The patient should be examined in the supine and erect positions. The area of the swelling is palpated to determine its reducibility and whether an expansile cough impulse is present. A hernia is more likely to be reducible with the patient supine. Control of the hernia by direct pressure over the point at which reduction occurs locates the neck of the sac. Other hernial sites should be examined (bilateral groin hernias are common).
A strangulated hernia is painful, tender and irreducible. The surrounding tissues may be inflamed. Signs of small bowel obstruction may be present.
A general physical examination must be carried out to search for predisposing causes, e.g. benign prostatic hyperplasia or chronic cough.
Clinical examination is the gold standard but herniography, ultrasound, CT scan (especially if the patient is obese) and laparoscopy are occasionally used.
The natural history of a hernia is of progressive enlargement and the risks of complications, i.e. irreducibility and strangulation, increase with time. Most hernias should therefore be operated on. A hernia may be repaired under general anaesthetic, regional block or local anaesthetic. Surgical appliances (trusses) are not advised, due to the increased likelihood of incarceration or strangulation caused by irritation and scar tissue formation at the site of the truss. Most elective operations are now done as a day case or short stay. Groin hernias are now often repaired via the laparoscopic approach (usually bilateral or recurrent).
In the UK, the National Institute for Health and Clinical Excellence (NICE) has made recommendation that laparoscopic surgery is one of the treatment options for the repair of inguinal hernia, as long as the patient is fully informed of all the risks and benefits of open and laparoscopic surgery either by TAPP (trans-abdominal pre-peritoneal) or TEP (total extra-peritoneal) approaches, to enable them to choose between the procedures.
Herniotomy, the removal of the sac and closure of its neck, is all that is required for infant inguinal hernia and is the first step in nearly all hernia repairs.
Essentials of Clinical Surgery
