Ultrasonic evaluation of patients with clinical suspicion of acute appendicitis

 

 

Abstract              Background: Acute appendicitis is a highly prevalent disease that needs timely and accurate diagnosis. USG has been suggested as the first imaging modality for its diagnosis. The present hospital-based study describes the experience with ultrasound evaluation of patients with clinical suspicion of acute appendicitis at a rural tertiary care centre in Kerala state in India. Methods: This study included 215 patients attending the tertiary care centre during the one and half year study duration with suspected acute appendicitis on clinical evaluation. The sonographic examination was based on the graded compression technique proposed by Puylaer. A detailed histological analysis was performed on all surgically removed appendices, which formed the basis of definitive judgement. Final discharge records were reviewed for the patients who did not have appendicitis. In the group that did not undergo surgery, the final diagnosis was substantiated by combining clinical findings and radiological follow-up. Sensitivity, specificity, positive and negative predictive value, and overall accuracy parameters for USG in acute appendicitis diagnosis were described. Results and Conclusions: The maximum number of cases, i.e. 72 (33.5%), belonged to the age group in the third decade of life. The mean age was 25.4 years. Out of 215 total suspected cases, 150 (69.8%) were males, and 65 (30.2%) were females with a male: female ratio of 2.3:1. In 68% of cases, ultrasound suggested a diagnosis, whereas, in 32% of cases, no diagnosis was suggested by USG. The sensitivity of USG was found to be 90.3%, sensitivity was 92.3%, positive predictive value was 92.1%, and the negative predictive value was 91.2%. Overall accuracy was found to be 91.6%. The study results reflect a reasonable degree of sensitivity, specificity, and accuracy of the ultrasound evaluation for suspected acute appendicitis patients.

Keywords: Appendicitis, ultrasonography.

 

INTRODUCTION

Acute appendicitis is a highly prevalent disease that needs timely and accurate diagnosis. The lifetime probability of suffering from this commonest abdominal emergency is about 7%. The disease's presentation, often atypical, makes it difficult to diagnose as the symptoms are not very specific and similar to various other conditions.^1-4 In this scenario, the imaging modalities play an essential role in the diagnosis of acute appendicitis. The imaging options include ultrasonography (USG), computed tomography (CT) and magnetic resonance imaging (MRI). Although the sensitivity and specificity of CT and MRI are more, there is a need to balance the exposure to ionising radiation and the financial aspect. So, USG has been suggested as the first imaging modality.^2-4 The present hospital-based study describes the experience with ultrasound evaluation of patients with clinical suspicion of acute appendicitis at a rural tertiary care centre in Kerala state in India.

 

METHODS

This study included 215 patients attending the tertiary care centre during the two years of study duration with suspected acute appendicitis on clinical evaluation. The sonographic examination was done using state of the art real-time greyscale ultrasound equipment GE Logic 400 Pro with a 7.5 MHz mechanical transducer. The method of assessment was based on the graded compression technique proposed by Puylaert⁵. If an abnormal appendix was not identified on the initial examination, the transducer was removed, and the patient was asked to indicate the point of maximum tenderness. Scanning was then resumed at the new location. In addition to the right lower quadrant, the entire abdomen and pelvis were examined to look for alternative diagnoses, especially in those patients without evidence of acute appendicitis. This examination of the abdomen and pelvis was carried out with a 3.5 MHz sector probe. The USG findings were recorded at the time of examination. Appendicitis was diagnosed if the appendix was visualised and not compressible, sausage-shaped, and blind-ended; if maximal cross-sectional diameter with compression exceeded 6mm or if an appendicolith or complex mass was noted.^6,7 Non-visualization of the appendix was recorded as a negative result. The decision for operative versus nonoperative management was based solely on the clinical judgement of the surgeon responsible for the patient. However, the findings at ultrasonography were known to the surgeon. A detailed histological examination was performed on all surgically removed appendices, which formed the basis of definitive judgement. Final discharge records were reviewed for the patients who did not have appendicitis. In the group that did not undergo surgery, the final diagnosis was substantiated by a combination of clinical findings and radiological follow-up. In those cases, where no definitive diagnosis could be confirmed, the diagnosis was abdominal pain of unknown origin.

To determine diagnostic accuracy of sonography in acute appendicitis, the following criteria were considered.

Sensitivity = True positive/(True positive + false negative)*100%

Specificity = True negative/(True negative+false positive)*100%

Predictive value of positive result = True positive/(True positive + false positive)*100%

Predictive value of negative result = True negative/(True negative + false negative)*100%.

Overall accuracy = (True positive+True negative)/(True positive + True negative + false positive + false negative)*100%

Observations

Table 1 shows the age and sex-wise distribution of suspected cases of acute appendicitis. The maximum number of cases, i.e. 72 (33.5%), belonged to the age group in the third decade of life. The youngest patient was four years old, and the most geriatric patient examined was 70 years old. The mean age was 25.4 years. Out of 215 total suspected cases, 150 (69.8%) were males, and 65 (30.2%) were females with a male: female ratio of 2.3:1. Table 2 shows the final and ultrasonic diagnoses in the 215 patients of suspected cases of acute appendicitis. Out of 215 suspected patients, 103 (47.9%) had been finally diagnosed with acute appendicitis. The mean outer diameter of the inflamed appendix was 9 +/- 2.2 mm. Table 3 shows the parameters for sensitivity, specificity and accuracy analysis of USG in acute appendicitis. In 68% of cases, ultrasound suggested a diagnosis, whereas, in 32% of cases, no diagnosis was suggested by USG. The sensitivity of USG was found to be 90.3%, sensitivity was 92.3%, positive predictive value was 92.1%, and the negative predictive value was 91.2%. Overall accuracy was found to be 91.6%.

 

 

 

 

 

 

 

 

 

Height, IVDL-Intervertebral Disc Length