SONOGRAPHIC PREVALENCE OF GALLSTONE AMONG ADULT SUBJECTS IN NNEWI ANAMBRA STATE, NIGERIA

CHAPTER ONE INTRODUCTION

Background of the Study

Biliary diseases are the major cause of right upper quadrant pains. Other causes are diseases of the liver, porta hepatis, pancreas, right kidney, adrenal gland, and the right lung. The gallbladder is a pear-shaped fluid-filled structure located in a shallow fossa called gallbladder fossa, which lies at the junction between the right and left hepatic lobes. An average adult gallbladder is 7cm long and can hold up to 50 ml of bile (Keith et al., 2010). It has three different parts; the fundus, body and neck. The fundus is generally the most caudal and anterior in position, often projecting below the anterior margin of the liver. The gallbladder has a smooth thin wall which is about 2mm thick; with the thickest part in its neck region which measures about 3mm in thickness (Satish, 2007). The gallbladder wall is composed of an outer serosal layer, a middle fibromuscular layer and an innermost mucosa.

The sonographic appearance of the gallbladder is very distinct, especially after a long fasting period. Large accumulation of bile makes it well distended and appears clearly cystic thereby enabling easier location and identification of any pathology. Ruling out gallstone is perhaps the most common indications for a right upper quadrant scan (Roger, 1998). Gallstones are aggregated precipitates that form in the biliary tract, usually in the gallbladder (figures 2 and 3). Gallbladder stone is also called cholelithiasis. Gallstones develop insidiously and may remain asymptomatic for decades. Biliary colic is the most common presenting symptom of gallstone disease. The pain does not wax and wane, rather, it is felt as a steady, severe aching or pressure-type sensation. Usually the pain is felt in the epigastrium or right upper quadrant and often radiates to the right infrascapular area. Biliary colic is thought to be due to sudden obstruction of the cystic duct by a calculus which produces increased intraluminal pressure and distention of the gallbladder leading to a visceral-type pain. Discrete attack may be precipitated by a fatty meal, or may occur at any time of the day or night. The frequency of episode may vary from weeks to years.

Plain abdominal radiography is the simplest and oldest radiological procedure for gallbladder stone investigation and diagnosis. However, the concentration of calcium is only sufficient to make gallbladder radiopaque in about 10 to 15 % of the patients (Satish, 2007). Oral cholecystogram (Grahamcole test) later replaced the use of plain abdominal radiographs but this has long been replaced by ultrasound. Ultrasound is simple; safer, quicker and more accurate than x-ray in addition to providing the opportunity to examine more than just the gallbladder. Its characteristic positive findings typical of gallstone disease include stones, thickening of the gallbladder wall, pericholecystic fluid, and a positive Murphy sign on from pressure of the ultrasound probe. Although somewhat less accurate than computed tomography, ultrasonography provides quick, inexpensive and reproducible method of examining the biliary system. The safety of ultrasound has often been questioned but after four decades of use on over three generations it has been declared a low risk examination (Salvesen, 2002).The numerous studies of both functional and morphologic ultrasonic biological effects, seeking adverse effects on humans have failed to define any significant problems. This was declared by the Bioeffect Committee of American Institute of Ultrasound in Medicine (AIUM) in the year 1997. The committee stated that no confirmed biological effects on patients or instrument operator caused by exposure at intensities typical of present diagnostic ultrasound instruments have been reported. Although the possibility exists that such biological effects may be identified in the future, current data indicate that the benefits to the patients of prudent use of diagnostic ultrasound outweighs the risk, if any, that may be present. At present, the known risk of use of ultrasound in medicine is wrong or inaccurate diagnosis by poorly trained personnel manning the equipment.

Gallstone disease has far reaching consequences for the patient if undetected and treated appropriately. It is therefore important that its prevalence among adults in a densely populated and vibrant town like Nnewi is established. This is to give sonographers an indication of what level of suspicion they should have for patients presenting for abdominal ultrasound in the locality. There are no published data to rely on regarding the prevalence of the disease in this locality, as statistics relied upon here are derived from studies on Caucasian populations, and very few in the Western Nigeria. The aim of this study therefore is to establish the prevalence of the gallstones among adult subjects in Nnewi, Anambra State, Nigeria.

​​​​​​​Statement of Problem

Gallstone disease is often insidious and could at times present with life threatening conditions. Presence of stone in the gallbladder may lead to acute cholecystitis while presence of stones in other parts of the biliary tract can cause obstruction of the bile duct, which can lead to serious condition such as ascending cholangitis or pancreatitis. Either of these two conditions can be life threatening and therefore are considered medical emergencies.

Gallstone incidences vary from population to population as its occurrence is influenced by genetic characteristics of the population and prevailing environmental factors. Having reliable epidemiological statistics on gallstone about a population helps clinicians and sonographers with certain degrees of suspicion of gallstone in patients presenting with right upper quadrant pain. To the best of the researcher’s knowledge, there are no epidemiological data on gallstone disease on adult subjects in Nnewi, Anambra State. Clinicians and sonographers here, rely on data obtained from Caucasian population and other Negro population even when there are possibilities that this incidence may not be the same with our local population.

​​​​​​​Objectives of the Study

This study was aimed at determining the prevalence of gallstone among adult subjects in Nnewi, Anambra State, Nigeria.

Specific Objectives: The specific objectives are as follows:

1. To establish the prevalence of gallstone with respect to sex, age, parity and body mass index;

2. To determine the percentage of the total gallstone that is symptomatic and those associated with cholecystitis;

3. To establish the proportion of the solitary and multiple stones in the population; and,

4. To compare the established prevalence with that of the Caucasians.

​​​​​​​Significance of the Study

The result of the study will provide adequate statistical information on gallstone    incidence amongst adult subjects in Nnewi, Anambra State, Nigeria. The result will provide data on prevalence of gallstone in Nnewi and by extension its environs and Southeastern Nigeria in general.

​​​​​​​Scope of the Study

The study was confined to adult subjects from the four communities comprising Nnewi town, Anambra State. The subjects were volunteers recruited at various locations within the communities and who expressed willingness to be part of the study. The study did not include subjects from towns other than Nnewi or subjects below 18 years of age. The study lasted for a period of 34 months; starting from June, 2011 and ending in April, 2014.

​​​​​​​Definition of Operational Terms

Cholelithiasis: A medical condition in which stones accumulate in the gallbladder.

Biliary: An adjective referring to anything that concerns the gallbladder and production of bile.

Biliary colic: Painful sensation originating from the biliary system due to inflammation or presence of stone in the biliary system.

Cholangitis: Inflammation of the bile ducts mainly due to bacterial invasion. Cholecystitis: An inflammatory condition characterized by retention of bile in the gallbladder and often secondary to infection by intestinal microorganisms.

Choledocholithiasis: A medical condition in which stone is found in the bile duct.

Murphy’s sign: Tenderness felt when an inflamed gallbladder is palpated clinically, usually in deep inspiration.

Ultrasonography: Diagnostic procedure in medicine that involves the use of devices that produces very high frequency sound waves to examine the internal body organs (Sanders, 1998).

Transducer: A device in ultrasound equipment that is capable of transmitting and receiving high frequency sound waves (Sanders, 1998).

Sonographic appearance: Characteristic appearance of normal and diseased tissues, organs, and systems at sonography.

Cyst: A term used to describe fluid filled structure that appears dark in ultrasound image.

Asymptomatic: A medical condition showing no symptoms.

Oral cholecystogram: The radiological procedure in which the gallbladder is demonstrated on a radiograph following oral intake of a contrast medium.