Retrospective analysis of computed tomography examinations in patients with lower abdominal pain: A single-center experience

Abstract

BACKGROUND

Lower abdominal pain presents as a common complaint with diverse etiologies ranging from benign conditions to surgical emergencies. Computed tomography (CT) imaging has become instrumental in accurate diagnosis and management planning, though clinicians must carefully balance its benefits against radiation exposure concerns and resource allocation constraints.

AIM

To comprehensively evaluate the diagnostic accuracy, utility and clinical implications of CT in patients with acute lower abdominal pain, emphasizing rare anatomical variations, pregnancy-related issues, and practical limitations of other imaging modalities in emergency settings in Japan.

METHODS

This retrospective review included 230 patients who underwent CT scans for acute lower abdominal pain at Juntendo University Shizuoka Hospital throughout 2014. CT findings were systematically correlated with the final clinical diagnoses. Cases with diagnostic uncertain underwent independent reviewed by two experienced radiologists. The CT protocols included portal venous-phase imaging with selective arterial-phase acquisition when clinically indicated.

RESULTS

Idiopathic pain was the most common diagnosis (104 cases, 45.2%), followed by appendicitis (46 cases, 20.0%) and diverticulitis (27 cases, 11.7%). Right lower quadrant pain predominantly revealed appendicitis (20.2%), whereas left lower quadrant pain frequently indicated diverticulitis (12.1%). Nonspecific pain cases have diverse etiologies. Rare conditions included situs inversus (one case) and intestinal malrotation (one case). Pregnancy-related diagnoses included acute appendicitis and uterine fibroid degeneration.

CONCLUSION

CT significantly aids in the diagnosis of lower abdominal pain, especially given limited access to ultrasonography and MRI during emergency hours in Japan. Awareness of the anatomical variations and pregnancy-related constraints is crucial. Diagnosis-specific protocols for CT based on pain location can optimize clinical management and resource utilization.

Key Words: Acute abdomen; Computed tomography; Lower abdominal pain; Pregnancy; Situs inversus; Point-of-care ultrasound

Core Tip: This study highlights computed tomography (CT) as the primary imaging modality for diagnosing acute lower abdominal pain, especially in emergency settings with limited availability of ultrasonography and magnetic resonance imaging. The results emphasize the diagnostic importance of recognizing rare anatomical variations (situs inversus and intestinal malrotation) and pregnancy-related conditions, underlining the necessity of tailored CT protocols based on pain localization. Given Japan’s practical constraints, including limited after-hours ultrasonography and magnetic resonance imaging access, our findings advocate for optimized, evidence-based CT imaging protocols to enhance diagnostic accuracy, patient safety, and efficient resource utilization.

INTRODUCTION

Acute lower abdominal pain is a frequent emergency presentation, with diagnoses ranging from benign gastrointestinal issues to surgical emergencies. Accurate diagnosis is essential to minimize complications[1]. Computed tomography (CT) remains preferred for acute abdominal pain owing to its high sensitivity and specificity, yet concerns about radiation exposure persist[2,3]. Japanese emergency settings face challenges in utilizing ultrasonography (US) due to a shortage of trained personnel and limited access after-hours[4]. Although point-of-care US is promising, its adoption is limited to Japanese hospitals[5]. Magnetic resonance imaging (MRI) is rarely practical for urgent abdominal imaging because of its lengthy examination times, limited availability, and technical constraints during emergencies[6]. This study assessed the performance of CT in diagnosing acute lower abdominal pain, focusing on rare anatomical variations, pregnancy-related conditions, and practical imaging strategies.

MATERIALS AND METHODS

This retrospective study reviewed 230 patients who underwent CT for lower abdominal pain at the Juntendo University Shizuoka Hospital during 2014. Clinical records and CT reports were analyzed. CT was performed using a GE Discovery CT750 HD with standardized contrast protocols tailored to renal function. The decision to perform contrast-enhanced CT and arterial-phase imaging was made by the attending emergency physician. Contrast-enhanced scans were typically acquired in the portal venous phase (90-120 seconds post injection). Arterial phase imaging (30-45 seconds post-injection or the SmartPrep technique) was performed in selected cases. The contrast media included Iopamiron 300/370 (Bayer), Omnipaque 300 (Daiichi Sankyo), and Optiray 320 (Mallinckrodt), with standard doses of 520-600 mg I/kg, adjusted according to body weight and renal function. Equilibrium-phase images were captured approximately 100 seconds post-injection. Additional imaging was performed in hemodynamically unstable patients. The diagnostic accuracy was verified through clinical follow-up, with uncertain cases reviewed independently by two senior radiologists. Statistical comparisons were performed to assess the diagnostic patterns according to pain location.

RESULTS

Pain distribution and CT usage

Pain distribution and CT usage: (1) Right lower quadrant: 94 patients (40.9%); contrast-enhanced CT: 79 (84.0%); (2) Left lower quadrant: 58 patients (25.2%); contrast-enhanced CT: 40 (69.0%); and (3) Nonspecific lower abdomen: 78 cases (33.9%); contrast-enhanced CT: 51 cases (65.4%).

Idiopathic pain was the most common diagnosis, with 40 cases (43%) of right lower limb pain, 29 cases (50%) of left lower quadrant pain, and 35 cases (45%) of nonspecific lower abdominal pain. Appendicitis was prominent in the right lower quadrant (19 patients, 20%), whereas diverticulitis was prevalent in the left lower extremity (3 patients, 5%). Other diagnoses included ileocecal inflammation, ischemic colitis, ileus, colonic malignancies, mesenteric lymphadenitis, enteritis, chronic constipation, urological conditions, gynecological emergencies, intraperitoneal abscesses, abdominal wall hernia, ascites of unknown origin, and advanced gastric cancer (Table 1).

Table 1 Distribution of diagnoses by pain location among 230 patients undergoing computed tomography for lower abdominal pain, n (%).

Diagnosis	Right lower pain (n = 94)	Left lower pain (n = 58)	Lower abdominal pain (n = 78)
Idiopathic pain	40 (43)	29 (50)	35 (45)
Appendicitis	19 (20)	2 (3)	2 (3)
Diverticulitis	11 (12)	3 (5)	3 (5)
Ileocecal inflammation	6 (6)	-	2 (3)
Ischemic colitis	-	2 (4)	1 (1)
Ileus	2 (2)	1 (2)	4 (2)
Colonic malignancies	2 (2)	1 (2)	1 (2)
Mesenteric lymphadenitis	-	1 (2)	2 (3)
Enteritis	-	-	4 (5)
Chronic constipation	-	-	2 (3)
Urological conditions	10 (11)	10 (17)	10 (17)
Gynecological emergencies	2 (2)	6 (10)	5 (6)
Intraperitoneal abscess	-	-	2 (4)
Abdominal wall hernia	-	1 (2)	1 (1)
Ascites of unknown origin	-	-	1 (1)
Advanced gastric cancer	-	-	1 (1)

Rare anatomical variations identified

Rare anatomical variations identified: (1) Appendicitis in pregnancy (1 case): Mild inflammation in a pregnant patient (19 weeks) (Figure 1); (2) Situs inversus (1 case): Complete visceral inversion with appendicitis (Figure 2); and (3) Intestinal malrotation (1 case): Abnormal vascular positioning with appendicitis and abscess (Figure 3).

Figure 1 Contrast-enhanced coronal computed tomography images of a 34-year-old woman at 19 weeks gestation presenting with right lower quadrant abdominal pain. Images demonstrate an enlarged appendix (approximately 7 mm in diameter) with fecal stones located adjacent to the gravid uterus (orange arrow), consistent with acute appendicitis in pregnancy (blue arrow).

Figure 2 Contrast-enhanced coronal computed tomography images of a 57-year-old male with left lower quadrant abdominal pain demonstrating situs inversus totalis. The liver and appendix are visualized in the left abdomen. The appendix is swollen at its root (approximately 1 cm in diameter) with high-density fecal material, indicative of acute appendicitis associated with complete visceral inversion. Orange arrow: Inflamed appendix arising from the cecum in the left lower quadrant. The appendix is filled with contrast and shows distal swelling up to 9 mm in diameter; Blue arrow: Inverted position of the liver on the left side of the abdomen, indicating complete visceral inversion.

Figure 3 Contrast-enhanced coronal computed tomography images of a 44-year-old woman presenting with lower abdominal pain and fever, showing evidence of intestinal malrotation with abnormal positioning of the superior mesenteric artery (white triangle) and superior mesenteric vein (white arrow). Perforated acute appendicitis (orange arrow) is identified within an abnormally positioned cecum, resulting in the formation of a midline pelvic abscess (blue arrow).

DISCUSSION

CT consistently demonstrated high diagnostic for acute lower abdominal pain evaluation, strongly corroborating previous multi-center investigations[7,8]. Our findings highlighted the strategic value of contrast-enhanced CT protocols for suspected appendicitis and diverticulitis, reflecting its diagnostic reliability[9,10]. Comprehensive comparison between ultrasonography, MRI and CT modalities reveals the technical the superiority CT regarding diagnostic accuracy, and efficiency, despite recognized radiation exposure concerns[11]. Given the limitations of MRI and US in emergency scenarios, especially at night, CT remains indispensable in the Japanese setting[12]. Consensus guidelines justify CT use in pregnancy if the clinical benefits outweigh potential radiation risks, emphasizing dose optimization[13]. Awareness of rare anatomical variations is critical because of their clinical implications and potential for misdiagnosis[14].

Limitations

This single-center retrospective study has limited generalizability. The high prevalence of idiopathic pain suggests the potential overuse of CT; however, practical constraints on US and MRI justify this usage pattern in Japan.

CONCLUSION

CT is essential for evaluating acute lower abdominal pain, particularly considering the limitations of alternative modalities during emergencies. Clinicians should adopt pain location-specific protocols to balance diagnostic efficacy, radiation exposure, and resource utilization in order to enhance patient management.