hiatal hernia : INTRODUCTION

Background: A hiatal hernia occurs when a portion of the stomach prolapses through the diaphragmatic esophageal hiatus. Although the existence of hiatal hernia has been described in earlier medical literature, it has come under scrutiny only in the last century or so because of its association with gastroesophageal reflux disease (GERD) and its complications. By far, most hiatal hernias are asymptomatic and are discovered incidentally. On rare occasion, a life-threatening complication, such as gastric volvulus or strangulation, may present acutely.


Pathophysiology: The esophagus passes through the diaphragmatic hiatus in the crural part of the diaphragm to reach the stomach. The diaphragmatic hiatus itself is approximately 2 cm in length and chiefly consists of musculotendinous slips of the right and left diaphragmatic crura arising from either side of the spine and passing around the esophagus before inserting into the central tendon of the diaphragm. The size of the hiatus is not fixed, but narrows whenever intra-abdominal pressure rises, such as when lifting weights or coughing.

The lower esophageal sphincter (LES) is an area of smooth muscle approximately 2.5-4.5 cm in length. The upper part of the sphincter normally lies within the diaphragmatic hiatus, while the lower section normally is intra-abdominal. At this level, the visceral peritoneum and the phrenoesophageal ligament cover the esophagus. The phrenoesophageal ligament is a fibrous layer of connective tissue arising from the crura, and it maintains the LES within the abdominal cavity. The A-ring is an indentation sometimes seen on barium studies, and it marks the upper part of the LES. Just below this is a slightly dilated part of the esophagus, forming the vestibule. A second ring, the B-ring, may be seen just distal to the vestibule, and it approximates the Z-line or squamocolumnar junction. The presence of a B-ring confirms the diagnosis of a hiatal hernia. Occasionally, the B-ring also is called the Schatzki ring.

Any sudden increase in intra-abdominal pressure also acts on the portion of the LES below the diaphragm to increase the sphincter pressure. An acute angle, the angle of His, is formed between the cardia of the stomach and the distal esophagus and functions as a flap at the gastroesophageal junction and helps prevent reflux of gastric contents into the esophagus (see Image 1). The gastroesophageal junction acts as a barrier to prevent reflux of contents from the stomach into the esophagus by a combination of mechanisms forming the antireflux barrier. The components of this barrier include the diaphragmatic crura, the LES baseline pressure and intra-abdominal segment, and the angle of His.


Frequency:


In the US: Hiatal hernias are more common in Western countries. The frequency of hiatus hernia increases with age, from 10% in patients younger than 40 years to 70% in patients older than 70 years.
Internationally: Burkitt et al suggest that the Western, fiber-depleted diet leads to a state of chronic constipation and straining during bowel movement, which could explain the higher incidence of this condition in Western countries.
Mortality/Morbidity: Paraesophageal hernias generally tend to enlarge with time, and sometimes the entire stomach is found within the chest. The risk of these hernias becoming incarcerated, leading to strangulation or perforation, is approximately 5%. This complication is potentially lethal, and surgical intervention is necessary. Because of the high mortality associated with this condition, elective repair often is advised wherever a paraesophageal hernia is found.

Sex: Hiatal hernias are more common in women than in men. This might relate to the intra-abdominal forces exerted in pregnancy.

Age: Muscle weakening and loss of elasticity as people age is thought to predispose to hiatus hernia, based on the increasing prevalence in older people. With decreasing tissue elasticity, the gastric cardia may not return to its normal position below the diaphragmatic hiatus following a normal swallow. Loss of muscle tone around the diaphragmatic opening also may make it more patulous.


by Waqar A Qureshi, MD,