Correlation of ultrasound, clinical and Surgical findings of suspected acute Appendicitis in Kenyatta national hospital

Abstract

Acute appendicitis is the most common surgical abdominal emergency with a life time prevalence of one in seven (I) The incidence rate of acute appendicitis is approximately 1 III 400 (0.25%) and the prevalence of7% to 8% in United States of America (USA) (2) Acute appendicitis continues to provide a diagnostic challenge to clinicians today resulting in an increased demand for ultrasonographic evaluation of patients suspected of having acute appendicitis. Misdiagnosis is not uncommon. The lack of statistically tested results of the accuracy of ultrasound in the evaluation of acute I appendicitis in Kenyatta National Hospital prompted this study. OBJECTIVE The main objective of the study was to investigate the role of ultrasonography in establishing diagnosis in patients with clinical suspicion of acute appendicitis. METHODOLOGY A prospective study was carried out at Kenyatta National Hospital (KNH) within a period of six months at Radiology department. Patients suspected to have acute appendicitis on the basis of history and clinical examination underwent abdominal ultrasonography using high frequency linear probes. The patients were then followed up at the surgical department and the theatre findings determined. Data collection sheets were used to record the demographic information, the clinical information, ultrasound findings and surgical findings. This data was analyzed using computer software and the results presented in form of tables, charts and graphs. Results: A total of 112 patients operated between March to November 2010 were studied, 73 patients were males and 39 females, giving a male to female ratio of 1.9: 1. The age of patients -7 - ranged from 8years to 70years. All patients presented with abdominal pain (100%) which was localized at right iliac fossa in 96(86%) patients and in 16 (14%) patients the pain was generalized. The abdominal pain was associated with vomiting and fever in 75 (67%) and 66 (57%) patients respectively. Majority 111(99%) of the patients had abdominal tenderness with 78% of them had rebound tenderness at right iliac fossa region. Ultrasound examination of abdomen showed that, 97 out of 112 patients had findings suggestive of appendicitis in which 76 had RIF maximum tenderness, 64 had blinded ending tubular structure of diameter of 6mm or larger, 39 had fluid at RIF and echogenic peri-appendiceal fat in 25 patients. The rest (15) patients had normal sonographic features. All patients underwent appendicectomy and 61(54.5%) had inflamed appendices, 32(28.6%) perforated appendices, 27(24.l %) abscess and 5(4.5%) were gangrenous. The histology of the excised appendices resulted in accuracy, sensitivity, specificity, PPV and NPV of sonographic diagnosis of acute appendicitis to be 88.4%, 92%, 58.3%, 95% and 47% respectively. Only 12 patients out of the total 112 had normal appendices on histology giving an overall negative appendicectomy rate of 10.7%. This finding is similar to what was reported by Mohammed Akbar Mardan and Stefan Puig (\2, \9) in which 9.8% of patients who underwent preoperative US resulted in negative appendicectomy. Conclusions: Ultrasound by graded compression technique is a useful adjuvant to the clinical diagnosis of acute appendicitis. It can reduce the negative appendicectomy rate without adversely affecting the perforation rate particularly in equivocal cases. However US findings should be correlated carefully with clinical findings since its negative predictive value is quite low (47%). A high clinical suspicion is still of paramount important in the management of acute appendicitis