An external abdominal hernia is the protrusion of the contents of a patient's abdomen (some abdominal organ, part of his omentum, or his abdominal fat) through an abnormal opening in his abdominal wall. The swelling varies in size from time to time, but tends to become larger. He may learn to reduce it himself. The only way to repair it is to excise the sac, and usually to repair his abdominal wall also; so you will need to operate on most hernias.
If you or he can easily return the contents of his hernia to his abdomen, it is reducible, and you can operate at your convenience. A reducible hernia expands as he coughs, the gut in it may gurgle as you reduce it, and if it contains omentum, it feels doughy.
Several things can happen to a hernia:
(1) It may become irreducible. Coughing or straining may push the omentum, or a loop of gut, through the neck of the sac, after which oedema may prevent them slipping back. Sometimes, you may be able to reduce an otherwise irreducible inguinal hernia manually by taxis (14.6). This is dangerous in all other hernias. If you attempt it for an inguinal hernia, be sure to observe him carefully, and operate urgently if it fails, or if he develops signs of obstruction or strangulation.
(2) The gut in a hernia can obstruct, so that food and faeces cannot pass along it. Hernias are one of the commonest causes of intestinal obstruction (10.4). His symptoms depend on the level of the obstruction. If his upper small gut is obstructed, he has colicky central abdominal pain and vomits early. If his distal small gut is involved (common), he vomits late. If his large gut is obstructed (very uncommon in a hernia), he also vomits late.
(3) Blood may be unable to enter or leave the organs in a hernia, so that they strangulate. This is more likely to happen in a hernia with a narrow neck. Most strangulated hernias are therefore either inguinal or femoral, because these hernias have narrow necks.
(4) If strangulation persists for more than a few hours, the organs in a hernial sac become gangrenous. If this happpens to the omentum or Fallopian tube, the risk to a patient's life is small. But if his gut becomes gangrenous, the bacteria inside it can escape, so that peritonitis, cellulitis, or a fistula follow. If more than a little of the gut strangulates, it cannot propel its contents onwards normally, so it obstructs. Most strangulated gut is therefore obstructed also. The important exception is a Richter's hernia (see below).
The term ''incarceration' is a bad one and is not used here. The terms reducible, and irreducible, obstructed, and strangulated describe everything that can happen to a hernia.
When a hernia strangulates, it suddenly becomes painful, tense, and tender, and loses its cough impulse. Even so, you will often find it difficult to know if a hernia is merely irreducible and obstructed, or whether it is strangulated, because pain and constipation are present in both. Pain usually remains colicky until ileus and peritonitis develop, so the change from colicky to continuous pain is a bad sign. Occasionally, a strangulated hernia causes so little pain that a patient does not call your attention to it. Usually, however, his pain, his general condition, and the signs at the hernial site are reliable indicators.
Unfortunately, you have no way of being certain what has been caught in a hernial sac, and you can never be sure that whatever has caught has not strangulated. Obstruction is ultimately as dangerous as strangulation, because, if you leave it, strangulation usually follows. So, be safe, and treat all painful, tense hernias as if they were strangulated.
If only part of the wall of a patient's gut is involved, he has a Richter's hernia (not very common). This is particularly dangerous because: (1) His gut may strangulate without being obstructed, so that he may not vomit, or be constipated. Instead, he may have diarrhoea until he finally develops peritonitis. (2) Occasionally, the local signs of strangulation may not be obvious.
If only his omentum strangulates, he has local abdominal pain, but his attacks of general abdominal pain may stop, and he may not vomit or be constipated. Gangrene is delayed, but after days or weeks his necrotic omentum may become infected, so that a local abscess or general peritonitis follows.
If the peritoneal lining of his hernial sac is incomplete, an abdominal organ (commonly his caecum), may slide into it, partly behind his peritoneum. When this happens he has a sliding hernia.
The common mistakes are: (1) To forget to examine the hernial sites of anyone with an abdominal pain or vomiting. (2) To forget the possibility of a Richter's hernia, which may confuse the diagnosis by causing diarrhoea instead of constipation. (3) To persist in using taxis (14.6) when an inguinal hernia should be operated on.
Here we only describe the more common hernias[md]indirect and direct inguinal hernias (14.2), femoral hernias (14.7), umbilicial hernias in children (14.10) and adults (14.11), and epigastric (14.12) and incisional hernias (14.13). You will have many inguinal hernias to repair, so let them provide you with an unhurried opportunity to increase your surgical skills. If they are very common, it may be worth teaching an assistant to do them. This chapter partly follows from the sections on the acute abdomen (10.1), and on intestinal obstruction (10.3).
TREAT ALL PAINFUL HERNIAS AS IF THEY WERE STRANGULATED Fig. 14-1 THE PATHOLOGY OF SOME HERNIAS. A, a loop of gut has been caught in a hernial sac. The contents of the gut cannot enter or leave it, so it is obstructed. Blood cannot enter or leave it, so it is also strangulated. Note the afferent and the efferent loops, and the constriction ring. B, Richter's hernia. C, a sliding hernia. D, a sliding hernia opened. E, and F, invaginating a Richter's hernia is safe, if the gangrenous segment does not extend across more than half the circumference of the gut, and its margins are clearly healthy. G, an incomplete inguinal hernia; the sac of the hernia and the tunica vaginalis remain separate. H, a complete inguinal hernia; the sac and the tunica vaginalis are in continuity. E, and F, kindly contributed by Brian Hancock.