A Comparative Ultrasound and Plain Abdominal X-Ray: Evaluation of Non-Classical Clinical Cases of Appendicitis

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1 A Comparative Ultrasound and Plain Abdominal X-Ray: Evaluation of Non-Classical Clinical Cases of Appendicitis Dorothy Makanjuola, FRCR; Qasim Al-Qasabi, FRCS; Tajuddin Malabarey, FRCR From the Departments of Radiology (Drs. Makanjuola and Malabarey), and Surgery (Dr. Al-Qasabi), King Khalid University Hospital, Riyadh. Address reprint requests and correspondence to Dr. Makanjuola: King Khalid University Hospital, Department of Radiology (40), P.O. Box 7805, Riyadh 11472, Saudi Arabia. Accepted for publication 11 April A prospective study of 109 patients with non-classical symptoms of appendicitis using the standard ultrasound (US) machine and plain abdominal x-rays demonstrated that US was superior to plain x-ray with a sensitivity, specificity and overall accuracy of 89%, 96% and 91%, respectively as compared with plain x-ray with 48%, 93% and 67% respectively. The negative appendectomy rate was 7%. In the alternative diagnosis, plain x-ray was superior to US due to the prevalence of intestinal diseases, ureteric calculi and basal pneumonia which were best shown in plain x- rays. US was, however, most useful in detecting female pelvic pathology. It is hoped that with improved imaging expertise and the application of high resolution US machine a higher sensitivity and accuracy can be achieved. US is therefore recommended as the first line in the imaging of non-classical cases of appendicitis. However, in areas where enteric diseases and urinary calculus are endemic, it is prudent to perform both ultrasound and plain abdominal x-rays while the patient is in the radiodiagnostic department. D Makanjuola, Q Al-Qasabi, T Malabarey, A Comparative Ultrasound and Plain Abdominal X-Ray: Evaluation of Non-Classical Clinical Cases of Appendicitis. 1993; 13(1): Appendicitis is a common surgical emergency worldwide and in children it constitutes the most common cause of acute abdomen requiring surgery. In about 80% of cases the diagnosis is purely clinical [1]. However, after over a century of its first description [2] the diagnosis remains an illusion in a significant percentage. Normal appendectomy of 25% is regarded as the surgical norm in suspected appendicitis [3,4] and even the best results describe removal of normal appendices in 10 15% of suspected cases [5]. In women of childbearing age, pelvic problems simulate appendicitis, leading to an unnecessary appendectomy in 35 46% of cases [4,6,7]. With the advent of good imaging devices, the radiological attitude has changed to a more committed approach. Several parameters are now suggested and used in various centers. These include plain abdominal x-rays, ultrasonography (US), barium enema, radioisotope scan and computed tomography (CT) scan. With the advent of high resolution real time ultrasound scanners which allow direct visualization of the inflamed appendix or periappendiceal abscess, sonographic evaluation now has a sensitivity of 75 90%, specificity of % and an overall accuracy of 87 96% [8,9]. While CT, radioisotope imaging and high resolution US machines are not available in most peripheral hospitals, the standard ultrasound machines and radiographic facilities are readily available. Also, where enteric diseases like

2 typhoid or urinary calculus disease are endemic, the value of plain radiographs of the abdomen cannot be overlooked. This study was designed to find the value of a combined study of ultrasonography and plain films in the evaluation of cases with subclassical features of appendicitis. The aim was to determine the efficacy of plain x-ray and/or US in detecting appendicitis or alternative diagnosis. Patients and Methods A total of 109 patients with subclassical clinical appendicitis reporting at the King Khalid University Teaching Hospital, Riyadh, over a period of 14 months provided the material for this study. Examined by surgeons of at least Senior Registrar status, these are patients with possible appendicitis, but in whom the total clinical features were not classical. However, abdominal pain, largely in the right lower quadrant, was present in all cases. Female patients with amenorrhea or other symptoms suggestive of pregnancy were excluded. There were 64 males and 45 females with an age range of years and a mean of 22.5 years. All patients had abdominal US and plain abdominal radiographs. The plain radiographs and ultrasound were interpreted independently by two radiologists. The reports were, however, relayed to the surgeons. The radiologists had no information regarding whether or not the patients were to have surgery. Surgical and pathological results were subsequently collected for analysis. Sonographic Equipment and Procedures The ultrasound examination was done using commercially available Siemen's equipment (Sonoline S1-2). A 5- MHz linear array was used for the right iliac fossa and a 3.5-MHz sector transducer for the pelvis with full bladder. Graded compression was applied to the area of interest through the transducer to improve sound transmission and to identify the area of maximum tenderness for thorough examination. Identification of the iliac crest, psoas muscle, iliac vessels and cecal tip provided the landmark for the location of the appendix. Scanning in both sagittal and transverse planes was done from the cecum to the liver area in order to include retrocecal appendix. In females, the pelvis was examined with a full bladder. When the right iliac fossa was normal, a general abdominal scan was performed. The examination was considered positive if any of the following occurred in isolation or in combination. Visualization of a non-compressible, aperistaltic appendix larger than 6 mm in diameter is noted in Figure 1 [9]. The "target" appearance in Figure 2 is a transverse view comprising a hypoechoic fluid-distended lumen, a hyperechoic inner ring representing the mucosa and submucosa and an outer hypoechoic ring representing the muscularis externa [9]. An appendiceal mass containing localized fluid collection around the appendix, an appendicolith, or free peritoneal fluid particularly in the pelvis and Morison's pouch, is noted in Figure 3. Normal cases had no masses at the right iliac fossa, minimal or no fluid collection and no localized tenderness. Plain Abdominal X-ray The standard erect and supine abdomen x-rays were obtained. The erect view was supplemented by the right side up decubitus view in patients who were unable to stand up. The following findings detected in isolation or in combination with others were recorded as positive: appendiceal fecalith (Figure 4) [11 13]; the colon cut-off sign [14 16] (Figures 5 and 6) comprising the absence of gas and feces in the right lower quadrant, reflex dilatation of the transverse colon and indentation of the colonic gas at the hepatic flexure; obliteration of pelvic fat planes [14]; right lower quadrant mass; extraluminal gas; acute small bowel obstruction [17,18] (defined as distention of more than three loops of small bowel out of proportion to the caliber of the ascending colon). Plain x-rays were considered negative when none of the above was found or indeterminate if intestinal gas pattern did not fit into any of the above patterns. Patients who had negative plain x-ray and US findings were investigated further with excretory urogram, barium enema or CT depending on the clinical state. These examinations were also used to confirm certain plain film and US findings such as urinary calculi and cecal mass. Results Table 1 shows an analysis of the final diagnosis as well as those detected by US or plain x-ray. Out of the total of 109 patients, 68 had surgery within 24 hours of the radiological findings. These were all positive on US or plain x-ray or both for appendicitis. Out of these 68 patients, 63 had appendicitis (44 unperforated while 19 were perforated) while five patients (7%) had a negative appendectomy.

3 Of the 46 patients (five surgical plus 41 nonsurgical) who did not have appendicitis, 24 had alternative diagnosis. Table 2 shows the analysis of the alternative diagnosis. In 22 patients, the cause of the pain was not found. These patients were discharged home asymptomatic after a few days of observation. These patients were labeled as cases with pain of unknown origin. Plain X-ray Result A total of 33 patients were positive for appendicitis while 76 were negative. Out of the positive cases, three had normal appendices at appendectomy. The radiographic sensitivity was therefore 48%, specificity 93%, positive predictive value of 91% and negative predictive value of 56%. The overall accuracy was 67%. The most common positive findings in plain x-ray were small bowel obstruction, appendicolith (Figure 4) and the "colon cut off" sign (Figures 5 and 6). US Result Ultrasound detected appendicitis in 59 cases and was negative in 50 cases. Out of the 59 cases, three had normal appendectomy. The sensitivity was therefore 89%, specificity of 96% positive predictive value of 95% and a negative predictive value of 86%. The overall accuracy was 91%. The most common US findings were free peritoneal fluid in the pelvis and Morison's pouch, an appendix mass or a thickened bowel loop simulating "target" sign in the appendix area. In the alternative diagnosis, US provided or suggested eight out of the 24 cases, i.e., 33%. Most of these cases were gynecological in origin. Figure 1. Longitudinal scan of the right iliac fossa showing a non-compressible, aperistaltic appendix of 12 mm in diameter. Plain x-ray was normal. Surgery confirmed unperforated appendix. Figure 2. Transverse scan of the right iliac fossa showing the "target" sign. The hypoechoic center is only faintly seen. The hyperechoic inner ring representing the mucosa and submucosa and the outer hypoechoic muscularis externa are well seen. Minimal features of small bowel obstruction were seen on plain x-ray. Surgery confirmed unperforated appendix.

4 Figure 3. Transverse scan of the right iliac fossa showing an appendiceal mass. A mixed density mass with poorly defined boundaries. The hyperechoic area possibly represents gas or mucus. Plain x-ray showed the "colon cut off" sign Figure 6 (same patient). Surgery confirmed perforated appendix. Figure 4. A large appendicolith is shown at the RIF. Gas-filled large and small bowel loops are also present. Gallstone ileus was also considered. A perforated appendix with abscess and appendicolith were found at surgery. A total of 32 patients were positive for appendicitis in both US and x-ray examinations. All of these were positive for appendicitis at surgery except one who had ileocecal tuberculosis. Out of the five patients who had negative appendectomy, two were falsely positive in US alone, two in plain x- ray alone and one in both, as earlier mentioned. In the false positive cases, free peritoneal fluid in the pelvis and Morison's pouch were the findings on US while features of small bowel obstruction were the findings on plain x-ray. Three of these cases had urinary tract infection while one had radiolucent ureteric stone, all confirmed by excretory urogram. The false negative cases of appendicitis occurred in largely obese patients with unperforated appendices on the US imaging while those undetected by plain x-ray were both perforated and unperforated.

5 Figures 5 and 6. Two separate patients with plain supine abdominal x-raysshowing the "colon cut off" sign. The three components are: relative absence of gas at the right lower quadrant, reflex dilatation of the transverse colon and amputation of the colonic gas at the hepatic flexure. Note associated feature of distended small bowel loops. A total of 22 patients were negative in all forms of investigation and were therefore labeled as pain of unknown origin. Discussion The negative appendectomy rate in this study group of patients with non-classical symptoms of appendicitis was 7%. US was superior to plain x-rays in the detection of appendicitis with a sensitivity, specificity and overall accuracy of 89%, 96% and 91%, respectively as opposed to plain x-ray with 48%, 93% and 67%, respectively.

6 However, in the group with alternative diagnosis, plain x-ray detected more abnormalities, largely due to the nature of the abnormalities such as basal pneumonia, calcified ureteric stones, intestinal diseases with perforation or bowel obstruction. Although US could indirectly suggest the presence of these pathologies, plain x-rays are currently considered superior to US with the exception of pelvic pathologies. Campbell and Gunn [19] emphasized the limited contribution made by plain abdominal x-rays in assessing patients with suspected appendicitis, urinary tract infection and non-specific abdominal pain. On the other hand, the literature is replete with reports of increasingly accurate results using US in the evaluation of cases of appendicitis and various abdominal pathologies. However, US has its limitations, especially as efficiency is dependent on the resolution of the ultrasound machine, the imaging expertise of the operator, as well as obesity and the amount of intestinal gas in the patient. Table 1. The main final diagnosis and a comparison of numbers detected by US and plain x-ray. Final diagnosis Total Number Number detected by US Number detected by x-ray Appendicitis Alternative diagnosis Pain of unknown origin 22 Total Table 2. Analysis of the alternative diagnosis including US and plain x-ray findings. Alternative diagnosis Total number US detection X-ray detection Urinary calculus 6 1 (renal) 4(1 renal, 3 ureteric) Enteritis 5 1 (mesenteric lymph node) 3 (2 with bowel perforation) Urinary infection 3 Small bowel obstruction 2 2 Mesenteric infarction 2 1 (bowel wall thickening) 2 (1 sickle cell and 1 cardiac pathology) Ruptured ectopic pregnancy (pelvic fluid collection) Twisted ovarian cyst 1 1 Pelvic inflammatory disease 1 1 Cecal malignancy 1 1 Right basal pneumonia 1 1 Total In appendicitis, the most commonly found abnormalities in plain x-ray were small bowel obstruction followed by appendicolith and the "colon cut off" sign. On US, free peritoneal fluid and a loop of thickened bowel loop simulating the "target" sign in the appendix area and appendiceal mass were the most common findings. Free peritoneal fluid occurred in both perforated and unperforated appendicitis and was also the finding in two of the false positive cases of appendicitis on US. Therefore, as common and useful as this sign may be, it should be interpreted with caution since it can occur in various other abdominal conditions as well as in normally ovulating females. Ileocecal tuberculosis was the cause of the false positive cases on both US and plain x-ray. This is not surprising since bowel wall thickening below the cecum and features of small bowel obstruction can occur in various conditions including enteric tuberculosis, Yersinia enterocolitis and Crohn disease. Urinary tract infection was subsequently found in three (all females) of those who had negative appendectomy. The false negative cases in US were largely due to poor imaging in the initial stage of the study and problems with obesity. Also, these patients had unperforated appendicitis. There is no doubt that a high resolution US machine would give better details. However, two-thirds of the cases of appendicitis were unperforated. Also significant is the fact that when both US and plain film were positive or negative, the positive and negative predictive values were higher than either US alone or plain film alone. This is because each modality is capable of detecting certain parameters suggestive of appendicitis where the other could not. For example, while x-rays are

7 largely dependent on intestinal bowel gas pattern, the presence of gas is a deterent to adequate US imaging. Therefore, a dual positive result has a maximum probability of appendicitis and a dual negative result is more reassuring. Hence, the 22 patients who were discharged home symptomfree had negative findings on US and plain x-ray as well as on other investigations that were carried out. Although computed tomography (CT) evaluation is not mentioned in our study, Balthazer et al [20] have used CT successfully to diagnose appendicitis in patients with ambiguous clinical findings. However, CT is particularly useful in characterizing inflammatory masses around the appendix [21]. The distinction between periappendiceal phlegmon and abscesses is important since the former is often managed conservatively with antibiotics while the latter can be drained percutaneously with CT guidance when it is well defined [8]. The authors also used CT to show the extent of periappendiceal masses or collections whenever the patients presented with palpable masses. High risk patients such as hemophiliacs and patients with heart failure have also been investigated with CT following negative US and plain x-ray studies. In these instances the CT was normal. In conclusion, an accurate surgical evaluation remains the mainstay of diagnosis of appendicitis. However, when the presentation is atypical, radiological evaluation using US is suggested as the first line of evaluation. If ultrasound is inconclusive or negative, plain radiographs should be obtained for evaluation before the patient leaves the department. In areas where the quality of US imaging is sub-optimal and where enteric diseases such as typhoid and urinary calculi are endemic, it is prudent to use both US and plain abdominal x-ray as a preliminary assessment. References 1. Marguilis AR, Burhenne HJ. Alimentary tract radiology, 4th ed St. Louis: Mosby Company 1989;1: Berry J Jr, Mart RA. Appendicitis near its centenary. Ann Surg 1984;200: Silen W. Acute appendicitis. In: Harisson's principles of internal medicine, 10th ed. Petersdorf RG, Adams RD, Brauwald E, et al, eds. New York: McGraw Hill 1983; Lewis FR. Holcroft JW, Boerg J, et al. Appendicitis: a critical review of diagnosis and treatment in 1000 cases. Arch Surg 1975;110: Siblberman V. The incidence of appendectomy in a large metropolitan hospital: an update. Surg Rounds G 1983; Dunn EL, Moore EE, Elerding SC, et al. The unnecessary laparotomy for appendicitis: can it be decreased? Am Surg 1982;48: Baeley LE, Finley RK Jr, Miller SF, et al. Acute appendicitis during pregnancy. Am Surg 1986;52: Brown JJ. Acute appendicitis: the radiologist's role. Radiology 1991;180: Schwerk WB, Wichtrup B, Rothmund M, et al. Ultrasonography in the diagnosis of acute appendicitis: a prospective study. Gastoenterology 1989;97: Monzer M, Abu-Yousef MM, Edmund A, et al. An overview of graded compression in sonography. In: diagnosis of acute appendicitis. Seminars in Ultrasound, CT, and MR 1989;4: Vaudagner JS, McCort JJ. Plain film diagnosis references of retrocecal appendicitis. Radiology 1975;117: Faegenburg D. Fecaliths of the appendix: incidence and significance. AJR 1963;89: Shimkir PM. Radiology of acute appendicitis (commentary). AJR 1978;130: Holgersen NO, Stanley-Brown GG. Acute appendicitis with perforation. Am J Dis Child 1971;122: Swischuk LE, Hayder CC. Appendicitis with perforation: the dilated transverse colon sign. AJR 1980;135: Johnson JF, Pickett WJ, Enzenauer RW. Contrast demonstration of a colon cut-off sign in a baby with perforated appendicitis. Pediatric Radiol 1982;12: Riggs W, Parvey LS. Perforated appendix presenting with disproportionate jejunal distention. Pediatric Radiol 1976;5: Leonidas JC, Harris DJ, Armoury RA. How accurate is the roentgen diagnosis of acute appendicitis in children. Ann Radiol 1975;18: Campbell JPM, Gunn AA. Plain abdominal radiographs and acute abdominal pain. Br J Surg 1988;75: Balthazar EJ, Megibono AJ, Siegel SE, Birnbaum BA. Appendicitis: prospective evaluation with highresolution CT. Radiology 1991;180: Jeffrey RB Jr, Federle MP, Tolertio CS. Periappendiceal inflammatory mass: CT directed management and clinical outcome

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