Acute appendicitis is the most common cause of acute surgical abdomen, with an estimated lifelong risk of 8.6% in men and 6.7% in women [1]. It is often regarded as a disease of the young population with a peak incidence in the second and third decades of life [1, 2]. Appendicectomy is generally accepted as a first-line treatment for non-complicated acute appendicitis. Reports have shown that preoperative radiographic evaluation has helped to decrease negative appendicectomy rates from 20% to as low as 5% [3]. Computed tomography (CT) has been frequently used as an imaging modality in the evaluation of acute appendicitis and has improved the diagnostic ability leading to a significant reduction in the number of negative appendectomies [4]. With a reported sensitivity of up to 96.5% and specificity of about 98%, CT plays a major role in the clinical decision-making process in acute appendicitis and is considered as a first-line imaging modality in the diagnostic work-up for suspected acute appendicitis [5-8]. In 1986, Alvarado presented a clinical scoring system on the basis of eight predictive clinical factors to improve the accuracy of physicians’ clinical assessments in diagnosing acute appendicitis. This scoring system produces a maximum total score of 10 points and includes clinical symptoms (nausea and anorexia), signs (fever, shifting pain, right lower quadrant pain, and rebound tenderness), and laboratory findings (leukocytosis and neutrophilia). Right lower quadrant pain and leukocytosis contribute 2 points each while the rest contributes 1 point [9]. The goal of the study was to analyze the CT criteria and clinical Alvarado scoring system and to find out the best cut-off value for appendiceal diameter in the diagnosis of acute appendicitis.

This study adopts an observational, cross-sectional design to evaluate the diagnostic accuracy of computed tomography (CT) in acute appendicitis and its complications. Among patients admitted with right lower quadrants pain in surgical wards of BRIMS, Teaching Hospital, Bidar. The study was conducted for the duration of 1 year (Jan 2023-Dec 2023) in the department of Radiology BRIMS Teaching Hospital, Bidar, and a tertiary care facility. Inclusion and Exclusion Criteria Category Criteria Inclusion Criteria • Adults (≥18 years) with right lower quadrant pain. • Clinically suspected appendicitis (Alvarado score ≥4). • CT performed due to indeterminate ultrasound or high-risk presentation. Exclusion Criteria • Confirmed diagnosis via ultrasound prior to CT. • Pregnancy (due to radiation risks). -Prior appendectomy. • Unwillingness to participate. Ethical approval: the ethical approval was obtained from the institutional ethics committee of BRIMS, Bidar. Sample Size Calculation Fixed Sample Size: 50 patients, based on the study duration (1 Year) and average monthly case load of suspected appendicitis at BRIMS, Bidar. Procedure for Data Collection 1. Patient Recruitment: Consecutive sampling of eligible patients referred for CT. 2. Imaging Protocol a) CT Technique: Non-contrast or IV contrast-enhanced MDCT (based on clinical urgency). b) Parameters: Slice thickness ≤3 mm; reviewed by two radiologists blinded to clinical scores. 3. Variables Recorded: a) Primary CT Findings: Appendiceal diameter (>6 mm = positive), wall thickening, periappendiceal fat stranding, mass, or perforation. b) Alvarado Score Components: Pain migration, leukocytosis, fever, etc. 4. Reference Standard a) Surgical pathology (for operated cases). b) Clinical follow-up (for non-operated cases). Statistical Analysis SPSS version 22. Descriptive statistics, Sensitivity/specificity of CT vs. Alvarado score. ROC curve analysis for optimal appendiceal diameter cut-off.

Table 1: Demographic and Clinical Characteristics of Study Population (n=50) Characteristic Category Number (%) / Mean ± SD Age (years) 18-30 22 (44%) 31-50 18 (36%) >50 10 (20%) Gender Male 28 (56%) Female 22 (44%) Alvarado Score 4-6 (Equivocal) 15 (30%) 7-10 (Positive) 35 (70%) Presenting Symptom RLQ pain 50 (100%) Fever 32 (64%) Nausea/vomiting 38 (76%) This table presents the demographic and clinical characteristics of the study population (n=50). The majority were aged 18-30 (44%), with 56% males and 44% females. All patients presented with right lower quadrant (RLQ) pain, while 64% had fever and 76% reported nausea/vomiting. Based on the Alvarado score, 70% had a positive score (7-10), while 30% fell into the equivocal range (4-6). Table 2: CT Findings in Diagnosed Appendicitis Cases (n=42) CT Finding Number (%) 95% CI Appendiceal diameter >6mm 42 (100%) 91.6-100% Wall thickening (>2mm) 39 (92.9%) 80.5-98.5% Peri appendiceal fat stranding 42 (100%) 91.6-100% Appendicolith 18 (42.9%) 28.0-58.9% Perforation signs 8 (19.0%) 8.6-34.1% Mass formation 5 (11.9%) 4.0-25.6% This summarizes CT findings in confirmed appendicitis cases (n=42). All cases showed appendiceal diameter >6mm and peri-appendiceal fat stranding. Wall thickening was present in 92.9%, while appendicoliths were seen in 42.9%. Perforation signs and Mass formation were detected in 19% and 11.9% of cases, respectively. Table 3: Diagnostic Performance of CT vs Alvarado Score Parameter CT (%) Alvarado ≥7 (%) p-value Sensitivity 97.6 81.0 0.016 Specificity 87.5 62.5 0.031 PPV 95.3 85.7 0.042 NPV 92.3 55.6 0.008 Accuracy 94.0 76.0 0.003 Compares the diagnostic performance of CT and the Alvarado score (≥7). CT demonstrated significantly higher sensitivity (97.6% vs. 81%), specificity (87.5% vs. 62.5%), PPV (95.3% vs. 85.7%), NPV (92.3% vs. 55.6%), and accuracy (94% vs. 76%) (p<0.05 for all). Table 4: Appendiceal Diameter Cut-off Analysis Diameter (mm) Sensitivity Specificity Youden's Index >5 100% 37.5% 0.375 >6 97.6% 87.5% 0.851 >7 83.3% 100% 0.833 This table analyzes appendiceal diameter cut-offs for diagnosing appendicitis. A >6mm threshold provided the best balance (Youden’s index=0.851) with 97.6% sensitivity and 87.5% specificity, while >7mm achieved 100% specificity but lower sensitivity (83.3%). Table 5: Complications Identified by CT (n=50) Complication Number (%) Management Changed Perforation 8 (16%) 8/8 (100%) Mass 5 (10%) 5/5 (100%) Gangrenous changes 6 (12%) 6/6 (100%) No complication 31 (62%) - The complications identified by CT (n=50). Perforation (16%), Mass (10%), and gangrenous changes (12%) were detected, with management altered in all such cases. No complications were seen in 62% of patients.

The present study evaluated the diagnostic performance of CT imaging compared to the Alvarado score in suspected appendicitis cases, while also analyzing key CT findings and their clinical implications. Our results demonstrate that CT offers superior diagnostic accuracy, with a sensitivity of 97.6% and specificity of 87.5%, significantly outperforming the Alvarado score (sensitivity 81%, specificity 62.5%). These findings align with existing literature, reinforcing the role of CT as the gold standard in appendicitis diagnosis. One of the most consistent CT findings in our study was appendiceal diameter >6 mm and peri-appendiceal fat stranding (both 100%), followed by wall thickening (92.9%). These results are comparable to a study by Raja et al. [10], which reported a sensitivity of 98% and specificity of 98% for CT, with appendiceal dilatation and fat stranding being the most reliable indicators. Similarly, Poletti et al. [11] found that a diameter >6 mm had a sensitivity of 94% and specificity of 91%, closely matching our observations (97.6% sensitivity, 87.5% specificity). The Alvarado score, while useful as an initial screening tool, showed limited diagnostic accuracy in our cohort, particularly in specificity (62.5%) and NPV (55.6%). This is consistent with Ohle et al. [12], who reported that the Alvarado score had a pooled sensitivity of 82% but a highly variable specificity (50-81%). Additionally, CT played a crucial role in detecting complications, with perforation (16%), Mass formation (10%), and gangrenous changes (12%) leading to altered management in all affected cases. This is in line with Kim et al. [13], who found that preoperative CT changed surgical planning in 22% of cases by identifying perforations or Masses. While CT demonstrates superior diagnostic performance, ultrasound (USG) remains an alternative modality for acute appendicitis diagnosis, particularly in specific populations. However, USG has several limitations: • Patient characteristics: Body habitus and bowel gas patterns (identity envelope gap) can limit visualization. • Atypical locations: Retrocecal or deep pelvic appendices (Retrocecal or deep) are often challenging to visualize. • Patient cooperation: The technique is particularly limited in young children or uncooperative patients. • Operator dependence: Diagnostic accuracy heavily relies on the sonographer's expertise. These limitations reinforce CT's role as the primary imaging modality, especially in equivocal cases or when complications are suspected.

Our findings reinforce that CT is significantly more accurate than the Alvarado score in diagnosing acute appendicitis, with high sensitivity and specificity. Key CT markers such as appendiceal diameter >6 mm, fat stranding, and wall thickening are highly reliable indicators. Moreover, CT’s ability to identify complications directly influences clinical management, reducing the risk of missed diagnoses or delayed interventions. While the Alvarado score may serve as an initial screening tool, CT remains indispensable for definitive diagnosis and optimal patient care. Future studies could explore cost-effectiveness and radiation exposure concerns in low-risk populations to further refine diagnostic pathways.

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