Background: Appendicitis remains the most common indication for surgical intervention in acute abdomen. The negative appendicectomy rate is 25% at KNH according to a recent study. This study seeks to investigate the diagnostic accuracy of a protocol based on modified Alvarado score and ultrasonography in equivocal cases in appendicitis at KNH.

Objective: To determine the diagnostic accuracy of a protocol based on modified Alvarado score and ultrasonography in equivocal cases in appendicitis at Kenyatta National Hospital.

Design: A prospective observational study

Setting: KNH accident and emergency and general surgery departments

Patients and methods: Patients presenting with suspected appendicitis will be scored using the modified Alvarado score. Patients who score 7 and above will proceed to surgery while those who score the equivocal range of 4 to 6 will undergo ultrasound scanning for suspected appendicitis as described by Puylaert. Confirmation of appendicitis will be based on histology.

Main outcome measures: the main outcome measure will be the negative appendicectomy rate.

Data analysis: The sensitivity, specificity, positive predictive value and negative predictive value of the modified Alvarado score, Ultrasonography in equivocal cases and their combined use will be calculated.

INTRODUCTION

Appendicitis was first described in 1886 by Reginald Fitz. It remains the most common cause of acute abdomen requiring surgical intervention both in Kenya and elsewhere.1,2,3,4,5,6 Accurate diagnosis of acute appendicitis remains a major challenge the world over and is perhaps more pronounced in constrained resource setups.7,8 Accuracy in diagnosis of acute appendicitis by clinical acumen has been found to be largely dependent on experience.7 Aids to assist in diagnosis of acute appendicitis exist but many are complex, expensive and unavailable especially in poor settings. Numerous scoring systems have been devised to aid the clinician.9 Perhaps the best well known is the modified Alvarado score. Various imaging modalities are available but their use is largely dependent on levels of resource. Ultrasonography has been used and studied widely in diagnosis of appendicitis.10 The aim of this study is to determine the diagnostic accuracy of a protocol based on the use of modified Alvarado score and ultrasonography in the equivocal cases in diagnosis of acute appendicitis with the main outcome measure being the negative appendicectomy rate.

LITERATURE REVIEW

Reginald Fitz first described the entity appendicitis in 1886. Diagnosis of acute appendicitis has remained a challenge despite great advances in technology. Jones concluded that a negative appendicectomy rate of 20% has been generally accepted in a review of trends in management over thirty years.11 It is known that negative appendicectomy rates vary widely principally due to differences in experience. John et al found the sensitivity of clinical acumen in diagnosis of acute appendicitis to range between 71% and 97% depending on the experience of the clinician .7 Various studies have demonstrated that clinical acumen remains the mainstay in the diagnosis of acute appendicitis. Appendicitis in the young offers unique challenges with higher rates of perforation being observed with decreasing age.8 A study by Macklin et al showed that clinical diagnosis was superior to the modified Alvarado score in children.12

Pruekprasert found that in the hands of an experienced surgeon clinical acumen was superior to either modified Alvarado or CRP measurements. CRP measurements and the Alvarado score were quoted to be of value to the inexperienced surgeon.13 Disparities in clinical acumen will continue to exist since the apprentice nature of surgical training is both time and training dependent.

Various scoring systems have been devised to assist in improving accuracy in diagnosis of appendicitis. They include Alvarado, Teicher, Christian, Fenyo and Lindberg. 9

The Alvarado score puts a score to the common symptoms, signs and laboratory typically found in appendicitis. It was first described by Alvarado in 1986. 14

The modified Alvarado scoring system was found by the Abdominal Pain Study Group to meet the set criteria in terms of reduction in morbidity and mortality in reevaluation of published data. 9

This scoring system gives points for symptoms (migration of pain, anorexia, and nausea), physical signs (right lower quadrant tenderness, rebound tenderness, and pyrexia), and laboratory values (leukocytosis). Whether to include a right to left shift is dependent on the laboratory in use. The modified Alvarado score does not include the shift.

Modified Alvarado score

MANIFESTATION

VALUE

Symptoms

Migration of pain

1

Anorexia

1

Nausea/vomiting

1

Signs

RLQ tenderness

2

Rebound tenderness

1

Elevated temperature (≥ 37.3ºC)

1

Laboratory value

Leukocytosis (≥10,000/µL)

2

Total points

9

A prospective study of 116 patients by Ongaro at Kenyatta National Hospital in 2005 found that use of modified Alvarado score would have reduced negative appendicectomy rates from 25% to 11.2%. The sensitivity of the scoring system was found to have a sensitivity of 91 %. 15

The modified Alvarado score has been found a useful tool for admission criteria with one study giving a negative appendicectomy rate of 12.5%.In this study by Al Qahtani in Saudi Arabia, no patients with a score less than 4 had appendicitis.16

Kalan et al found that high Alvarado score was an easy and satisfactory aid in diagnosis of acute appendicitis in children and men. There was however an unacceptably high false positive among women of 33% versus 22% in the others. 17

Alvarado scoring in children is a useful tool in taking the decision for admission in suspected acute appendicitis. 18

Khan and Rehman found a negative appendicectomy rate of 15.6% and a positive predictive value of 84.3% in a study of 100 patients. They recommended Alvarado score as an easy, simple and complementary tool for the diagnosis of acute appendicitis especially for the junior surgeons.19

Ahmed et al reported that the score had a positive predictive value of 98.1% in their study of 100 patients with acute appendicitis. 20

McKay and Shepherd did a study on 150 patients. Alvarado score below 3 was found to have a sensitivity of 96.2%. The sensitivity and specificity of the score above 7 was 77% and 100% respectively. 21

A study by Denizbasi et al showed there was no statistical difference between the use of Alvarado score by the emergency medicine residents and the general surgery residents in terms of suspecting the diagnosis of appendicitis. Overall sensitivity was 95.4% and a spe