The use of MASS in the diagnosis of acute appendicitis has been reported to improve the diagnostic accuracy and consequently reduces negative appendicectomy and complication rates [9, 10]. This study was conducted to evaluate the diagnostic value of Modified Alvarado Scoring System in patients with acute appendicitis in our setting.
The age distribution in our study was similar to other studies [9–11]. The female preponderance in this study is in agreement with other studies [11, 12]. Studies in Kenya, Nigeria and Ethiopia found a male dominance [13–15]. The reason for the difference in sex distribution in these studies may be attributed to the fact that female patients with right iliac fossa pain have a wide range of differential diagnoses as a result acute appendicitis may be over-diagnosed in this gender group. In this case, therefore, additional investigations may be required in female patients to confirm the diagnosis of acute appendicitis.
In this study, the duration of illness in majority of patients was four days and majority of patients reported to the hospital and seen by the admitting doctor in more than 24 hours after the onset of illness. This observation concurs with other reports [11, 12]. The reasons for delay in seeking medical consultation in this study may be attributed to delay in referral from peripheral hospitals, lack of money to pay for the medical services and for transport. Delayed presentation may also be due to misdiagnosis or fear of surgery as a result they are treated conservatively with analgesics and antibiotics to mask the symptoms. Delayed presentation is associated with increased morbidity and mortality due to appendiceal perforations and peritonitis.
The rate of perforation in our study was 9.4%, which is comparable to other reported rates [16, 17]. However, much higher perforation rates have been reported from other centres in Nigeria . In developing countries, rates of between 6-65% have been quoted . Delayed presentation, fulminate disease, misdiagnosis, or failure to accept surgical treatment, are contributory factors to high perforation rates. Perforation rates are much higher in the very young and the elderly, where diagnosis is often difficult leading to perforation rates as much as 80% in some reported series [20, 21]. In our study, the perforation of appendices occurred mostly in patients with MASS ≥ seven and in the children aged 0-15 years. Therefore, a more aggressive approach should be used in patients with high scores and in advanced age individuals and children.
The overall negative appendicectomy rate (33.1%) in our study was found to be higher than that reported in Nigeria [22, 23]. The reason for high negative appendicectomy rate in our series may be due to appendicectomies that were done to patients who presented with other conditions mimicking acute appendicitis. Our figures for negative appendicectomy rate in the present study were found to be slightly higher in females (38.3%) than in males (26.8%). This is because misdiagnosis may have occurred in females of reproductive age group where other pelvic diseases could make diagnosis difficult. In such cases, MASS should be complemented with diagnostic procedure like laparoscopy or imaging such as Ultrasound scan or CT scan to minimize the rate of negative appendectomy . However, a large population based study suggested that the rate of negative appendicectomy (15-20%) has not declined for 15 years despite the increasing use of such tests .
The histopathological findings in our study were not different from other reports in developing countries. However, the finding of appendiceal schistosomiasis due to Schistosoma haematobium, in contrast to Schistosoma mansoni as reported in some series is surprising. Similar histological finding was also reported by others [19, 25]. This could be explained by high endemicity of S. haematobium in Mwanza region which is along the shore of Lake Victoria and therefore the chance of S. haematobium infestation is high. S. haematobium usually affects the bladder, prostate, rectum, and the cervix but in endemic areas, it can be found in the appendix inducing chronic inflammation that could manifest as appendicitis .
The present study has shown that MASS provides high degree of sensitivity, specificity, PPV, NPV and accuracy in the diagnosis of acute appendicitis, which is in agreement with findings reported by others [7, 27], but in sharp contrast to what was observed in Kenya .
Our study also revealed that MASS is more helpful in male patients by showing lower negative appendicectomy rate and high positive predictive value for male patients as compared to females. In females, additional investigations may be required to confirm the diagnosis. Literatures also support this observation [28–30].
One limitation of our study is that HIV infection which has great effect on the WBC count was not tested in our patients, and this could have affected the results of the study.