European Journal of Cardiovascular Medicine

Acute appendicitis (AA) is the most common surgical emergency responsible for acute abdominal pain necessitating emergency laparotomy or laparoscopy across all age groups, with a lifetime risk of approximately 7-8% in the general population.[1] In the Indian emergency department setting, right iliac fossa pain constitutes one of the commonest presenting complaints, and appendicitis must be differentiated from a wide range of medical and surgical mimics, including mesenteric lymphadenitis, ovarian and tubal pathology, right-sided ureteric colic, and terminal ileitis.[2]

The diagnosis of acute appendicitis is traditionally clinical, based on history, examination, and supportive laboratory investigations such as total leucocyte count and C-reactive protein.[2,3] However, the classical presentation of periumbilical pain migrating to the right iliac fossa, associated with anorexia, nausea, vomiting, and localized tenderness at McBurney's point, is seen in only 50-60% of patients, and atypical presentations are particularly common in young children, elderly patients, and women of reproductive age.[3] This diagnostic uncertainty has historically resulted in a negative appendicectomy rate ranging from 15% to 30% in various series, exposing a substantial proportion of patients to the morbidity of an unnecessary operation, while delayed diagnosis in the remainder increases the risk of perforation, peritonitis, and post-operative complications.[4]

Clinical scoring systems such as the Alvarado score, described in 1986, and its several modifications have been widely validated as bedside tools to risk-stratify patients with suspected appendicitis.[5,6] The Alvarado score, built on the mnemonic MANTRELS (Migration of pain, Anorexia, Nausea/vomiting, Tenderness in right iliac fossa, Rebound tenderness, Elevated temperature, Leucocytosis, and Shift of leucocytes to the left), assigns a maximum of ten points and stratifies patients into low (≤4), intermediate (5-6), and high (≥7) probability groups.[5,6] The RIPASA score, developed for Asian populations including India, has also been shown in several Indian series to have higher sensitivity than the Alvarado score in the local population.[7] Nonetheless, clinical scores alone are imperfect, particularly in the intermediate-risk group, necessitating adjunctive imaging.[7]

Graded compression ultrasonography, first described by Puylaert in 1986, has since become the imaging modality of first choice for suspected appendicitis in most Indian tertiary care teaching hospitals because of its ready availability in the emergency department, absence of ionising radiation, low cost, and short acquisition time.[8] A normal appendix is often difficult to visualise, but an inflamed appendix typically appears as a non-compressible, blind-ending tubular structure measuring more than 6 mm in outer diameter, with a target or cockade sign on cross-section, peri-appendiceal fat stranding, loss of the submucosal layer, and, in advanced cases, an appendicolith or peri-appendiceal collection.[8,9] Several Indian studies, including those from north-eastern India and from the All India Institute of Medical Sciences (AIIMS), New Delhi, have reported sensitivities of graded compression USG ranging from 76% to 94% and specificities from 78% to 96% for the diagnosis of acute appendicitis, though considerable operator-dependence has been documented.[9,10]

Computed tomography (CT) offers higher sensitivity than USG in several Western series, but its use is limited in the Indian ED setting by concerns regarding ionising radiation, especially in children and women of reproductive age, cost, and limited around-the-clock availability in smaller centres.[11,12] Magnetic resonance imaging, while radiation-free and useful in pregnancy, is similarly constrained by cost, availability, and acquisition time in the acute setting.[12] Consequently, ultrasonography continues to occupy a pivotal position in the Indian diagnostic algorithm for suspected appendicitis, frequently used as the sole imaging test or as a triage tool before selective use of CT in equivocal cases.[13]

Despite its widespread use, there remains considerable variation in the reported diagnostic accuracy of USG for appendicitis across different Indian centres, related to operator experience, patient body habitus, time of presentation, and stage of disease at the time of scanning.[9,13,14] With this background, the present prospective study was undertaken in the emergency department of a tertiary care teaching hospital to systematically evaluate the diagnostic accuracy of graded compression ultrasonography against the gold standard of histopathological examination, and to determine its correlation with clinical scoring, with the aim of defining its appropriate role in the local diagnostic pathway for acute appendicitis.

Aims and Objectives.

1. To determine the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of graded compression ultrasonography in the diagnosis of acute appendicitis, keeping histopathological examination as the gold standard.
2. To correlate ultrasonographic findings with the modified Alvarado score.

Study Design and Setting

This was a hospital-based, prospective, observational, cross-sectional study conducted jointly in the Department of Emergency Medicine and Department of Radiodiagnosis of a tertiary care teaching hospital, over a period of 18 months, after obtaining clearance from the Institutional Ethics Committee. Written informed consent was obtained from all participants, or from their legal guardians in the case of minors, prior to enrolment.

Sample Size

Taking the expected sensitivity of ultrasonography in the diagnosis of acute appendicitis as 88%, based on previously published Indian data, with an absolute precision of 6% and a 95% confidence interval, the minimum calculated sample size was 113. Allowing for a non-response and dropout rate of approximately 15%, a total of 150 patients were enrolled in the study.

Inclusion Criteria

All patients of either sex, aged above 5 years, presenting to the emergency department with clinical features suggestive of acute appendicitis (right iliac fossa pain, with or without migration, fever, anorexia, nausea, or vomiting), who consented to participate, were included.

Exclusion Criteria

Patients with a clinically obvious alternative diagnosis, those with a palpable right iliac fossa lump suggestive of an appendicular mass or abscess of more than five days' duration, pregnant women, patients with generalized peritonitis requiring emergency laparotomy without prior imaging, and those unwilling to give consent were excluded from the study.

Methodology

Every enrolled patient underwent a detailed history and clinical examination in the emergency department, and a modified Alvarado score was calculated for each patient by the attending emergency physician prior to imaging. Baseline haematological investigations, including total and differential leucocyte count and C-reactive protein, were sent for all patients. Graded compression ultrasonography of the abdomen and pelvis was performed within six hours of presentation by a radiologist with more than five years of experience in abdominal sonography, using a high-frequency (7.5-10 MHz) linear array transducer for evaluation of the right iliac fossa, supplemented by a 3.5-5 MHz curvilinear probe for a general abdomino-pelvic survey, on a high-resolution colour Doppler ultrasound machine. The radiologist performing the scan was blinded to the modified Alvarado score of the patient.

Ultrasonography was considered positive for acute appendicitis if one or more of the following criteria were fulfilled: a non-compressible, blind-ending tubular structure with an outer antero-posterior diameter exceeding 6 mm; a target (cockade) appearance on the transverse section; presence of an appendicolith; peri-appendiceal fat stranding or free fluid; loss of the normal submucosal echogenic layer; or a peri-appendiceal collection or phlegmon. The scan was labelled equivocal when the appendix could not be visualised and no secondary signs were present, and negative when a normal compressible appendix was demonstrated or an alternative diagnosis was identified.

All patients with a positive or strongly suggestive ultrasonographic and clinical diagnosis underwent emergency appendicectomy (open or laparoscopic, as per the operating surgeon's preference), and the resected specimen was sent for histopathological examination, which served as the gold standard for confirmation of the diagnosis. Patients with an equivocal or negative scan but a high clinical suspicion were observed with serial clinical examination and, where necessary, referred for contrast-enhanced computed tomography; those managed conservatively were followed up telephonically and in the outpatient department at two weeks to confirm resolution of symptoms or need for subsequent intervention.

Statistical Analysis

Data were entered in Microsoft Excel and analysed using SPSS software (version 25.0). Categorical variables were expressed as frequencies and percentages, and continuous variables as mean ± standard deviation. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of USG were calculated against the histopathological/final clinical diagnosis using a standard 2×2 contingency table. The Chi-square test was used to assess the association between categorical variables, and a p-value of less than 0.05 was considered statistically significant.

Table 1: Age and Sex Distribution of Study Population (n=150)

The mean age of the study population was 28.6 ± 13.2 years (range 6-72 years), with maximum patients (41.3%) belonging to the 16-30 year age group. There was a slight male preponderance, with a male-to-female ratio of 1.2:1.

Table 2: Clinical Presentation of Study Population (n=150)

Table 3: Distribution of Modified Alvarado Score and Correlation with Final Diagnosis

A statistically significant association was observed between a higher modified Alvarado score and confirmed acute appendicitis on final diagnosis (χ2 = 62.4, p<0.001).

Table 4: Ultrasonographic Findings in Study Population (n=150)

Table 5: Diagnostic Accuracy of Ultrasonography vs. Histopathological/Final Diagnosis (2×2 Table)

Table 6: Diagnostic Accuracy Parameters of Ultrasonography

The overall negative appendicectomy rate (patients who underwent appendicectomy but had a histopathologically normal appendix) in this study was 7.4% (9 out of 122 patients operated), which compares favourably with historically reported rates of 15-30% in series that did not employ pre-operative imaging.

Table 7: Comparison of Diagnostic Accuracy of USG with Other Published Indian Studies

On analysis, patients with a high Alvarado score (≥7) combined with a positive USG had a very high probability of confirmed appendicitis (97.9%, Table 3), suggesting that combined clinico-sonographic assessment improves diagnostic confidence beyond either modality alone. The mean time interval between presentation to the emergency department and completion of ultrasonography was 1.8 ± 0.9 hours, and the mean time to definitive surgical intervention in operated patients was 6.4 ± 2.1 hours from presentation, reflecting the practical feasibility of incorporating USG into the acute emergency department workflow without significant delay.

Acute appendicitis continues to be a diagnostic challenge in the emergency department despite advances in imaging, largely because of its variable clinical presentation and the overlap of its symptomatology with several other causes of acute abdomen.[1,2] In the present study, the mean age of patients was 28.6 ± 13.2 years with a peak incidence in the second and third decades of life and a mild male preponderance (M:F = 1.2:1), findings that are consistent with several other Indian series, including the study by Das et al. from north-eastern India and the Rajasthan-based ultrasonographic study, both of which reported a similar young adult predominance with a comparable male-to-female ratio.[9,15].

In our study, ultrasonography demonstrated a sensitivity of 90.6%, specificity of 81.8%, and an overall diagnostic accuracy of 89.3% for the diagnosis of acute appendicitis, which is comparable to the results reported by Gamanagatti et al. from the All India Institute of Medical Sciences, New Delhi, who documented a sensitivity of 84.6% and specificity of 89.9% for graded compression ultrasonography compared with unenhanced spiral CT in the diagnosis of acute appendicitis.[11] Our sensitivity was somewhat higher than that reported by Das et al. from a tertiary centre in north-eastern India (76.5%), possibly reflecting differences in operator experience, patient body habitus, and the proportion of early-presenting patients in the respective cohorts.[9] The wide range of sensitivity (57-94%) reported across various Indian and international studies underscores the well-recognised operator dependence of ultrasonography in the diagnosis of appendicitis, a limitation also highlighted in the review by Hubail from a tertiary Gulf hospital.[16,17].

The relatively lower negative predictive value observed in our study (60.0%) is consistent with the inherent limitation of ultrasonography in reliably excluding appendicitis when the appendix is not visualised, a scenario reported in 12% of our patients, comparable to non-visualisation rates of 10-15% described in other Indian series.[9,14] This finding reinforces existing recommendations that a negative or equivocal ultrasonogram in a patient with high clinical suspicion should not be taken as conclusive evidence against appendicitis, and such patients merit close observation, a repeat scan, or selective use of computed tomography, as also emphasised in the Pondicherry-based study evaluating CT in patients with negative USG findings.[18].

A significant positive correlation was observed in our cohort between a high modified Alvarado score (≥7) and both a positive ultrasonogram and confirmed histopathological diagnosis (p<0.001), a finding mirrored in the comparative study of Alvarado and RIPASA scoring systems conducted at a general hospital in Andhra Pradesh, which similarly demonstrated that higher clinical scores correlated strongly with a confirmed histopathological diagnosis of appendicitis.[7] This supports the widely advocated strategy, also followed in our institution, of using clinical scoring systems as an initial triage step, reserving ultrasonography for patients in the low-to-intermediate risk category or those in whom imaging confirmation is desired before proceeding to surgery, thereby optimising resource utilisation in a busy emergency department.[6,7].

The negative appendicectomy rate in our study was 7.4%, considerably lower than the historically quoted rates of 15-30% in the pre-imaging era, and comparable to rates reported from other Indian centres that have incorporated routine pre-operative ultrasonography into their diagnostic algorithm.[4,14] This finding is of particular relevance in the Indian context, where a reduction in unnecessary appendicectomies translates directly into reduced hospital stay, reduced healthcare cost, and reduced operative morbidity in a resource-constrained public healthcare setting.[19] Our results are also in broad agreement with the international meta-analysis by Doria et al., which reported a pooled sensitivity of 88% and specificity of 94% for ultrasonography in children, and somewhat lower figures in adults, reaffirming that the diagnostic yield of ultrasonography, while excellent, is generally inferior to computed tomography, a difference that must be weighed against the radiation risk of CT, especially in younger patients and women of reproductive age who form a large proportion of the Indian ED population presenting with right iliac fossa pain.[13,20].

The findings of the present study must be interpreted in light of certain limitations. First, ultrasonography was performed by a single experienced radiologist, which, while ensuring consistency, may not reflect the diagnostic performance achievable across less experienced operators, particularly in peripheral and non-teaching hospital settings where round-the-clock availability of a dedicated sonologist cannot always be guaranteed.[9,17] Second, the sample size, though adequately powered for the primary objective, was relatively modest for robust subgroup analysis by age and sex. Third, the relatively small number of true negative and false negative cases in our cohort widens the confidence intervals around specificity and negative predictive value, and larger multicentric Indian studies would help refine these estimates further.[11,18] Despite these limitations, the present study reinforces the continued relevance of graded compression ultrasonography as a first-line, feasible, and safe imaging investigation for suspected acute appendicitis in the Indian emergency department, particularly when used in conjunction with validated clinical scoring systems.[6,7,19].

Graded compression ultrasonography is a highly sensitive, reasonably specific, safe, and cost-effective first-line imaging investigation for the evaluation of clinically suspected acute appendicitis in the emergency department of a tertiary care teaching hospital. In the present study, USG demonstrated a sensitivity of 90.6%, specificity of 81.8%, and an overall diagnostic accuracy of 89.3%, and its use, especially in combination with the modified Alvarado score, was associated with a marked reduction in the negative appendicectomy rate. Given its wide availability, absence of ionising radiation, low cost, and short turnaround time, ultrasonography should continue to be employed as the initial imaging modality of choice for suspected acute appendicitis in Indian emergency departments, with selective use of computed tomography reserved for patients with an equivocal or negative scan in the presence of persistent high clinical suspicion. Larger multicentric prospective studies are recommended to further validate these findings and to standardise imaging protocols across Indian tertiary care institutions.

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