THE EFFECTIVENESS OF ULTRASOUND IMAGING IN THE DIAGNOSIS OF ACUTE APPENDICITIS

Acute appendicitis is still one of the most common surgical abdominal emergencies. Ultrasound could increase the diagnostic accuracy in those patients presented with unclear symptoms and signs of acute appendicitis. The aim of this study is to evaluate the effectiveness of U/S in the diagnosis of acute appendicitis. This prospective study was conducted at the department of general surgery in ALSader Teaching Hospital from June 2008 to October 2011. It included 129 patients suspected to have acute appendicitis. Ultrasound (U/S) was done for all these patients. There were (66) males represent (51%) and (63) females represent (49%). These patients are grouped according to gender, age, signs & symptoms, laboratory tests, operative finding, the result of U/S examination and histopathological result. Ultrasound was positive in (111) patients (86 %) and negative in (18) patients (14%). Six patients out of (18) had true negative results while (12) patients were false negative. Ultrasound sensitivity was (90 %) in diagnosing acute appendicitis, specificity was (66.6%), accuracy rate was (88.3%), positive predictive value (97.2%) and negative predictive value (33.3%). It is concluded that U/S is a useful tool in providing valuable information for the diagnosis of suspected cases of acute appendicitis. Introduction cute appendicitis is still one of the most common surgical abdominal emergency 1 . Because of overlap with other clinical conditions, and associated significant morbidity, which increase with diagnostic delay, no single sign, symptom or diagnostic test accurately confirms the diagnosis of appendiceal inflammation in all cases 2 . Over the 10-year period from 1987 to 1997, the overall appendectomy rate decreased in parallel with a decrease in incidental appendectomy 3 . This fact due to the use of the Alvarado score and the facility of modern investigations, tools like U/S, CT, and MRI. Several investigators have created diagnostic scoring systems in which a definite number of clinical variables is elicited from the patient and each is given a numerical value, the sum of these values is used to predict the likelihood of acute appendicitis. The best known of these is the Alvarado score, which tabulate migration of pain, anorexia, nausea and/or vomiting, tenderness in the RIF, rebound tenderness, elevated temperature, leukocytosis, and shift of WBC to the left 4 . (table I): Table I: Alvarado score 1 Migratory RIF pain symptoms


Introduction
cute appendicitis is still one of the most common surgical abdominal emergency 1 .Because of overlap with other clinical conditions, and associated significant morbidity, which increase with diagnostic delay, no single sign, symptom or diagnostic test accurately confirms the diagnosis of appendiceal inflammation in all cases 2 .Over the 10-year period from 1987 to 1997, the overall appendectomy rate decreased in parallel with a decrease in incidental appendectomy 3 .This fact due to the use of the Alvarado score and the facility of modern investigations, tools like U/S, CT, and MRI.Several investigators have created diagnostic scoring systems in which a definite number of clinical variables is elicited from the patient and each is given a numerical value, the sum of these values is used to predict the likelihood of acute appendicitis.The best known of these is the Alvarado score, which tabulate migration of pain, anorexia, nausea and/or vomiting, tenderness in the RIF, rebound tenderness, elevated temperature, leukocytosis, and shift of WBC to the left 4

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In Alvarado score all the patients with score between 7-10 were regarded as probable acute appendicitis, all patients with score <7 were submitted to a period of active observation, during which, if patient clinical condition changed significantly, the score was reassessed [4][5][6][7][8][9][10][11] .An ultrasound test is a radiology technique, which uses high frequency sound wave to produce images of the organs and structures of the body, the sound waves are sent through body tissues with a device called a transducer 11 .The appendix on sonography is an ovoid or round blind-ending tubular structure, which shows no peristalsis.Often air can be found intraluminally.The anteroposterior diameter of a normal appendix is less than 6 mm, if the appendix is compressible an inflammation is unlikely 11 .Recommended criteria for the diagnosis of appendicitis are summarized 12 as demonstrated in table II.The most common error in the diagnosis of appendicitis with U/S includes misinterpretation of the terminal ileum as the appendix and misinterpretation of the normal appendix as an inflamed appendix 12 .Adherence to the diagnostic criteria is of importance.Poor quality examination undoubtedly account for some diagnostic errors, if the inflammation is localized to only the tip of the appendix, it can be missed.Therefore you must visualize the entire length of the appendix to avoid a false negative diagnosis.Other problem is related to the position of the appendix that makes it more difficult to appreciate, particularly when it is in the pelvis or retrocecal.Perforation of the appendix may lead to decompression of the appendix, and this will removes the specificity of the U/S study and also lead to diagnostic errors 13,14 .

Picture (I):-(Ultrasound examination of the right lower quadrant demonstrates a hyporeflective, non compressible structure with diameter of 8 mm .hyporeflective aspect of adjacent fatty tissue is due to inflammatory oedema).
Bas J Surg, March, 18, 2012

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As for the U/S technique to detect the vermiform appendix graded compression technique described by Puylaert was used 15 .This technique based on the fact that compression should be always applied in graded manner to avoid pain.Pain during the U/S examination should not exceed the pain experienced by the patients during the careful physical examination.
Compressions useful in order: To displace and compress bowel loop.To decrease the distance between the transducer and the bowel.To asses if a lesion is rigid or not by judging it's reaction upon compression 15 .Visible appendix is not enough for diagnosis of acute appendicitis because the normal appendix is frequently visualized.So other criteria are needed for confirmation of the diagnosis 16 .
In 70% of patients with acute appendicitis, the diagnosis is made clinically based on classic sign and symptoms.In the remaining 30% of patients with uncertain clinical finding radiological imaging is needed to establish the diagnosis 16 .
Either graded compression sonography or CT scan can be utilized to evaluate patients with suspected appendicitis 16 .This prospective study aims to evaluate the effectiveness of U/S in the diagnosis of acute appendicitis and to determine the usefulness of its use to increase the diagnostic accuracy in those patients presented with unclear symptoms and signs of acute appendicitis.

Patients and methods
A prospective study conducted from June 2008 to October 2011, during these three years there were too many patients admitted to the surgical unit suspected to have acute appendicitis and it was possible to have an ultrasound result for only 129 patients, there were no selection criteria.All patients were admitted to the surgical ward in AL-Sader Teaching Hospital in Basrah.
Initially, patients suspected to have acute appendicitis were admitted to the emergency ward and a preformed data sheet included the name, gender, age, complete history, and physical examination was recorded, laboratory tests like WBC, and GUE were done to all patients while chest X-ray and plain abdomen X-ray was done to certain patients according to their presentation.Ultrasound examination was obtained to all patients.Twenty nine patients had their U/S were already done in private clinics, for 60 patients U/S were done in our hospital during the working hours, while 40 patients had their U/S done outside the working hours.All patients suspected to have acute appendicitis, regardless their U/S report, were admitted to the hospital.All the operations were done by the same surgeon.The appendix was removed by classical appendectomy through Grid iron or Lanz incisions and all the specimens were send for histopathological examination.For statistical analysis, we calculated the estimated U/S results.These probabilities include sensitivity, specificity, positive and negative predictive values and accuracy.Sensitivity: is the conditional probability that a diseased person has a positive result: Sensitivity =(TP/TP+FN)×100% Specificity: is the conditional probability that a diseased free person has a negative result: Specificity=(TN/TN+FP)×100% Positive predictive value (PPV): is the conditional probability that a person with a positive test result is truly diseased: PPV=(TP/TP+FP)× 100% Negative predictive value (NPV):is the conditional probability that a person with a negative test result is truly free of disease: NPV= (TN/TN+FN)×100% Accuracy = TP+TN × 100% TP+TN+FP+FN TP:True positive.FP:False positive TN:True negitive FN:False negative.

Discussion
Ultrasound has been shown to be an excellent diagnostic technique for patients with acute appendicitis and may have major influence on the way of the treatment of those patients 17 .The first case report of the sonographic detection of an inflamed appendix was published 1981 by Preusser R 17 .A lot of studies followed that article to improve the criteria of U/S diagnosis, Jeffery RB et.al.on April 1987 confirmed that non-compressible appendix was the primary criterion for diagnosis of acute appendicitis.Jeffery returned on 1988 and added the diameter of the appendix whenever it was greater than 6 mm as another criterion 14 .
Regarding the number of patients who were included in this study, there were 129 patients, and this number is small as compared to the number of patients in other studies, which was (250) 19 , (452) 20 and (669) 21 patients.This is because we had no facilities for U/S out of the normal working hours and most patients in our study had their U/S during the working hours or in private clinics.In this study, it was found that the peak incidence of acute appendicitis was between the age of 20-29 in both sexes, and this finding correlate with the finding of others 17,19,20,21 .The most common symptom was anorexia followed by abdominal pain and vomiting.
Maximum tenderness in RIF especially over Mcburney point was the most common sign followed by elevated temperature.As it is found in other studies mentioned below in table IX.We have used the Alvarado score for assessment of our patients who were suspected to have acute appendicitis and did not depend only on the results of U/S to make our final decision.In table VII, the histopathological result of the patients which were surgically managed.It was noticed that the majority of cases 120, (93%)) showed acute inflammation and it was catarrhal in 63 (51.2%), suppurative in 22 (17.8%),perforated in 12 (9.75%)and gangrenous in 9 (7.31%).Obstruction by fecolith was found in 14 (11.3%) while 3 patients (2.4%) had normal histopathology.In comparing the result of U/S with the operative finding and histopathological reports, table VIII, it revealed that in 111 patients (86%), the U/S results showed one or more of the criteria of acute appendicitis and depending on this result together with our clinical judgement, surgery was done.For those patients, 108 (83.7%), they have inflamed appendix on histopathological examination (true positive).Three out of (111) patients (2.4%), showed normal histopathological appearance of the appendix, one patient had rupture ovarian cyst and the other two were mesenteric lymph adenitis (false positive).When a normal appendix is affected by an adjacent lesion, reactive inflammation can cause secondary enlargement of the appendix giving a positive result of acute appendicitis 22,23 .This may be seen in women with a dilated fallopian tube or in inflammatory conditions such as tubo-overian abscess or Crohn's disease, which may secondarily affect the appendix.Eighteen patients (13.9%), in whom U/S did not show sign of acute appendicitis, 6 of them where kept on conservative treatment because of our clinical judgement was not infavour of surgery, and all of these 6 patients were free of symptoms in the next 24 hours and were discharge home (true negative), while the other 12 patients (9.3%) underwent operations because there clinical presentation mandate surgery and all of them have histopathological finding of acute appendicitis (false negative).False negative occur in retrocecal appendicitis, perforated appendicitis or in pregnant patients.In our study we believe it was due to the difference in the expert skills of the radiologist and the model of the instrument.According to our results the sensitivity was (90%) and specificity was (66.6%) and accuracy rate (88.3%) and this is compared with the work of the others as show in table IX.The usage of U/S in examination is very useful to detect unclear clinical diagnosis of acute appendicitis in some patients and especially in females.And in experienced hands graded compression sonography has more than 80% accuracy for diagnosing acute appendicitis 24 .
Recommendations: It is suggested that arranging a U/S examination for those patients who have atypical clinical signs and symptoms of acute appendicitis.We suggest that U/S should be available in the hospital during twenty four hours and the result should be reviewed and interpreted by experience radiologists.Advantages with sonography include lower cost and real time observation of bowel peristalsis.

Table III :The Gender distribution of the patients
Table (III).The age of patients range from 10 to 65 years with mean age was 37.5 years.Table IV.Table V, show the relation of WBC count in all patients suspected to have acute appendicitis.

Table VII : The data according to the histopathological results
patients as in table VI.