on 10-Aug-2021 (Tue)

A hernia is the bulging of part of the contents of the abdomi- nal cavity through a weakness in the abdominal wa

Many structures pass into and out of the abdominal cavity creating weakness which can lead to hernia formation. The most common example is the inguinal canal in males, along which the testis descends from abdomen to scrotum at the time of birth. The testicular artery, veins and vas pass though this canal (the round ligament in females). The resultant weakness leads to an indirect or lateral-type inguinal hernia. In adult surgery, 80% of all hernia repairs are for inguinal her- nia. The evolutionary advantage of testicular descent must outweigh the disadvantage of a high risk of herniation.

An inguinal hernia (indirect) also occurs through the developmental failure of the processus vaginalis to close. As the testis descends, it pulls a tube of peritoneum along with it. This tube should naturally fibrose and become obliterated but often it fails to fibrose and allows a hernia to form. Recent studies have shown that calcitonin gene-related peptide and hepatocyte growth factor influence the closure of the pro- cessus, raising the possibility of a hormonal cause of hernia development.

Failure of normal development may lead to weakness of the abdominal wall. Examples are diaphragmatic, umbilical and epigastric hernias. Muscles which should unite during development fail to form strong unions with hernia develop- ment at birth or in later life. Herniation at the umbilicus has both components, i.e. weakness due to structures passing through the abdominal wall in fetal life and developmental failure of closure.

The risk of inguinal hernia is related to the anatomical shape of the pelvis and is higher in patients having a wider and shorter pelvi

it has been shown that hernia is no more common in Olympic weight lifters than the general population, suggesting that high pressure is not a major factor in causing a hernia. Many patients will first notice a hernia after excessive straining.

There is good evidence that hernia is a ‘collagen disease’ and due to an inherited imbalance in the types of collagen. This is supported by histological evidence and relationships between hernia and other diseases related to collagen, such as aortic aneurysm

Hernia development is more common in pregnancy due to hormonally induced laxity of pelvic ligaments. It is also more common in elderly people due to degenerative weak- ness of muscles and fibrous tissue. A recent Swedish report has shown that inguinal hernia is less common in obese patients, with hernia risk being negatively related to body mass index (BMI), contrary to widespread belief. Hernia is more common in smokers.

The narrowest part of the sac, at the abdominal wall defect, is called the ‘neck of the sac’.

An interstitial hernia occurs when the hernia extends between the layers of muscle and not directly through them. This is typical of a spigelian hernia (see below under Spigelian hernia).

An internal hernia is a term used when adhesions form within the peritoneal cavity. leading to abnormal pockets into which bowel can enter and become trapped. As there is no defect within the abdominal wall, the term ‘hernia’ is confusing.

Patients are usually aware of a lump on the abdominal wall under the skin. Self-diagnosis is common. The hernia is usu- ally painless but patients may complain of an aching or heavy feeling. Sharp, intermittent pains suggest pinching of tissue. Severe pain should alert the surgeon to a high risk of stran- gulation. One should determine whether the hernia reduces spontaneously or needs to be helped. The patient should be asked about symptoms that might suggest bowel obstruction. It is important to know if this is a primary hernia or whether it is a recurrence after previous surgery. Recurrent hernia is more difficult to treat and may require a different surgical approach. General questions about the cardiac and respiratory sys- tems are necessary to assess a patient’s anaesthetic risk. In a man with a groin hernia, history of prostatic symp- toms indicates a high risk of postoperative urinary retention. Intake of anticoagulants such as warfarin is important because this impacts on future surgery. Many hernia opera- tions can be performed as a day case or single overnight stay, so that suitability for such treatment needs to be assessed, including home support, distance from the hospital, mobility levels, etc