CHAPTER ONE

INTRODUCTION

1.1 DEFINITION OF PEPTIC ULCER DISEASE

Peptic ulcer disease refers to ulcerative disorders in the lower oesophagus, upper duodenum, and lower portion of the stomach. Approximately 4 to 5 million people in the United States have peptic ulcers. The types of peptic ulcers are gastric and duodenal, both of which are chronic diseases. The ulcer represents the development of a circumscribed defect in the gastric or duodenal mucosa that is exposed to acid and pepsin secretion. The ulcer may extend through the tissue layers of the muscle and serosa into the abdominal cavity. Stress ulcers, which are caused by a physiological response to major trauma, are clinically distinct from chronic peptic ulcers (Silverthorn and Dee, 2016).

Gastric ulcers are less common than duodenal ulcers and usually occur in the lesser curvature of the stomach within 1 inch of the pylorus. The ulcer formation is caused by an inability of the mucosa to protect itself from damage by acid/pepsin in the lumen (which is caused by a breakdown of the defensive factors). Duodenal ulcers occur in the proximal part of the duodenum (95%), are less than 1 cm in diameter, and are round or oval. A higher number of parietal cells in the stomach causes hypersecretion, or rapid emptying of the stomach; this may lead to a larger amount of acid being delivered to the first part of the duodenum and may result in the formation of an ulcer. Haemorrhage and peritonitis can occur if the peptic ulcer erodes through the intestinal wall. Other complications include abdominal or intestinal infarction or erosion of the ulcer into the liver, pancreas, or biliary tract (Trowers et al., 2014).

1.2 Classification

Peptic ulcer can be classified under the following headings;

1.2.1 By area

• Duodenum (called duodenal ulcer)
• Oesophagus (called esophageal ulcer)
• Stomach (called gastric ulcer)
• Meckel’s diverticulum (called Meckel’s diverticulum ulcer; is very tender with palpation)

1.2.2 Modified Johnson

• Type I: Ulcer along the body of the stomach, most often along the lesser curve at incisura angularis along the locus minoris resistantiae. Not associated with acid hypersecretion.
• Type II: Ulcer in the body in combination with duodenal ulcers. Associated with acid oversecretion.
• Type III: In the pyloric channel within 3 cm of pylorus. Associated with acid oversecretion.
• Type IV: Proximal gastroesophageal ulcer.
• Type V: Can occur throughout the stomach. Associated with chronic use of NSAIDs (such as ibuprofen) (Trowers et al., 2014).

1.3 GASTROINTESTINAL PHYSIOLOGY

The function of the gastrointestinal tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products. The gastrointestinal tract is composed of the alimentary canal, which runs from the mouth to the anus, as well as the associated glands, chemicals, hormones, and enzymes that assist in digestion. The major processes that occur in the gastrointstinal tract are: motility, secretion, regulation, digestion and circulation. The proper function and coordination of these processes are vital for maintaining good health by providing for the effective digestion and uptake of nutrients (Trowers et al., 2014; Silverthorn and Dee, 2016).

1.3.1 Motility

The gastrointestinal tract generates motility using smooth muscle subunits linked by gap junctions. These subunits fire spontaneously in either a tonic or a phasic fashion. Tonic contractions are those contractions that are maintained from several minutes up to hours at a time. These occur in the sphincters of the tract, as well as in the anterior stomach. The other type of contractions, called phasic contractions, consist of brief periods of both relaxation and contraction, occurring in the posterior stomach and the small intestine, and are carried out by the muscularis externa (Silverthorn and Dee, 2016).

1.3.2 Stimulation

The stimulation for these contractions likely originates in modified smooth muscle cells called interstitial cells of Cajal. These cells cause spontaneous cycles of slow wave potentials that can cause action potentials in smooth muscle cells. They are associated with the contractile smooth muscle via gap junctions. These slow wave potentials must reach a threshold level for the action potential to occur, whereupon Ca²⁺ channels on the smooth muscle open and an action potential occurs. As the contraction is graded based upon how much Ca²⁺ enters the cell, the longer the duration of slow wave, the more action potentials occur. This, in turn, results in greater contraction force from the smooth muscle. Both amplitude and duration of the slow waves can be modified based upon the presence of neurotransmitters, hormones or other paracrine signaling. The number of slow wave potentials per minute varies based upon the location in the digestive tract. This number ranges from 3 waves/min in the stomach to 12 waves/min in the intestines (Silverthorn and Dee, 2016).

1.3.3 Contraction patterns

The patterns of GI contraction as a whole can be divided into two distinct patterns, peristalsis and segmentation. Occurring between meals, the migrating motor complex is a series of peristaltic wave cycles in distinct phases starting with relaxation, followed by an increasing level of activity to a peak level of peristaltic activity lasting for 5–15 minutes (Bowen, 2006). This cycle repeats every 1.5–2 hours but is interrupted by food ingestion. The role of this process is likely to clean excess bacteria and food from the digestive system (Nosek, 2008).