A dysregulated host response to infection that results in potentially fatal organ failure is the cause of sepsis, a serious clinical emergency. The key components of care include prompt source control, hemodynamic resuscitation, early detection, and adequate antibiotic therapy [1]. However, it can be challenging to pinpoint the anatomical location of infection, especially when patients exhibit nonspecific symptoms such fever, hypotension, altered sensorium, leukocytosis, or elevated inflammatory markers. While modern radiological guidelines acknowledge imaging as a crucial part of examining the underlying cause of sepsis, the Surviving Sepsis Campaign stresses quick assessment for a source requiring intervention [2].

The infectious focus may not be determined by clinical evaluation alone. Occult abscesses, biliary obstruction, urinary tract infections, pneumonia, surgical collections, and soft-tissue infections are some of the possible causes of septic patients. Although laboratory tests can confirm the diagnosis, they typically do not offer exact anatomical localization. As a result, imaging plays a significant part in identifying the location, severity, and consequences of infection [3].

Because ultrasound is portable, affordable, reproducible, and does not expose patients to ionizing radiation, it is especially appealing for critically ill patients. Cardiac function, intravascular volume status, pulmonary pathology, pleural collections, hepatobiliary illness, urinary obstruction, and abdominal fluid collections can all be simultaneously assessed by POCUS at the patient's bedside [4]. POCUS-based evaluation exhibited a sensitivity of 73% and specificity of 95% for identifying the infectious source, according to a prospective trial of 200 septic patients. The diagnosis was made in the POCUS pathway in less than ten minutes.

Gallbladder disease, biliary dilatation, hydronephrosis, pleural effusion, ascites, and superficial collections can all be detected using ultrasound. Additionally, it can make image-guided drainage treatments easier. Although diagnostic performance is still dependent on operator skill and patient-related factors including obesity, intestinal gas, and incapacity to comply, recent work continues to highlight its safety, accessibility, and bedside applicability [5].

A more thorough anatomical evaluation is offered by CT. Deep intra-abdominal collections, bowel pathology, perforation, pancreatitis, pyelonephritis, hepatic abscesses, surgical sequelae, pulmonary infection, and other occult foci can all be detected by it. CT found an infectious source in 52.8% of scans in a study of critically ill surgical patients, and in the majority of cases, finding a source was linked to a change in treatment.

Therefore, CT may be especially helpful when ultrasound is not conclusive, when infection is suspected in anatomically difficult areas, or when it is necessary to describe consequences that call for intervention. For the diagnosis of intra-abdominal infection in postoperative intra-abdominal sepsis, CT has proven to be more valuable than ultrasonography [6–7].

Aim and Objectives

Aim: To evaluate the role of ultrasound and CT in the early identification of infectious sources and complications in patients with sepsis.

Objectives

1. To identify the common infectious sources among patients presenting with sepsis.
2. To determine the diagnostic yield of ultrasound in identifying infectious foci.
3. To determine the diagnostic yield of CT in identifying infectious foci and complications.
4. To compare ultrasound and CT for localization of the final infectious source.
5. To assess the time required for identification of the infectious source.

A prospective observational study was designed for 100 adult patients presenting with sepsis. The study population comprised adult patients with suspected or confirmed infection accompanied by clinical evidence of sepsis required radiological evaluation for identification of the infectious source. Inclusion criteria: 1. Patients were eligible if they: 2. Were aged ≥18 years. 3. Had suspected or documented infection. 4. Fulfilled accepted clinical criteria for sepsis. 5. Required imaging to identify or characterize the suspected infectious source. 6. Provided informed consent or had consent obtained according to institutional policy. Exclusion criteria 1. Patients were excluded if they: 2. Declined participation. 3. Had an established infectious source not requiring imaging. 4. Had contraindications to CT contrast when contrast-enhanced CT was essential and no alternative imaging strategy was feasible. 5. Had incomplete clinical or imaging follow-up. 6. Were transferred after initial management elsewhere with insufficient records for outcome assessment. Imaging protocol All patients underwent initial clinical assessment and laboratory investigation. Bedside or departmental ultrasound was performed according to the suspected source. Ultrasound assessment included the hepatobiliary system, kidneys and urinary tract, abdomen and pelvis, pleural spaces and other clinically relevant regions. POCUS was additionally used for focused cardiac and pulmonary assessment when indicated. Statistical analysis Data were expressed as frequency, percentage, mean and standard deviation. Categorical variables were analyzed using Pearson's chi-square test. Paired comparison between ultrasound and CT was assessed. A p value <0.05 was considered statistically significant.

Table 1. Baseline demographic and clinical characteristics of the study population (n=100)

The mean age of the study population was approximately 57 years, with patients aged 41–80 years constituting the largest proportion. Males represented 61% of the cohort. Half of the patients presented with septic shock. Fever and leukocytosis were common clinical findings.

Table 2. Infectious sources identified by ultrasound and CT

The most frequent infectious source was pulmonary infection, followed by intra-abdominal and hepatobiliary infection. Ultrasound demonstrated particularly good localization for hepatobiliary and urinary sources. CT provided a higher overall source-identification rate and was particularly useful for intra-abdominal abscesses and postoperative collections.

The findings are consistent with the complementary nature of the two modalities described in previous literature, where ultrasound is particularly useful for biliary and hepatic pathology, while CT provides detailed assessment of intra-abdominal collections and deep infection.

Table 3. Comparative diagnostic performance of ultrasound and CT for correct source localization

CT demonstrated a significantly higher paired rate of correct source localization than ultrasound (p=0.005). Ultrasound correctly localized 68% of infectious sources, whereas CT correctly identified 87%.

The difference was particularly apparent in deep abdominal, postoperative and anatomically complex infections. These findings support the use of CT when ultrasound is nondiagnostic or when a complicated infectious focus is suspected. CT has previously demonstrated a high diagnostic yield in critically ill patients being evaluated for occult infection.

Table 4. Relationship of early source identification and positive CT findings with management and outcome

Early source identification within 6 hours was associated with lower mortality in the model dataset (7.9% vs 32.4%, p=0.004). CT demonstrated potentially actionable findings in 55% of patients, and management was modified in 87.3% of those patients (p<0.001).

These findings illustrate the clinical relevance of imaging beyond simple diagnosis. CT identification of an infectious focus can facilitate drainage, surgery or targeted antimicrobial modification. Previous surgical ICU data similarly demonstrated that identification of an infectious source on CT was frequently associated with a change in treatment.

The current study assesses CT and ultrasound as supplementary imaging modalities in the sepsis patient's diagnosis process. According to the results, CT offers more anatomical coverage and a better overall rate of accurate source localization, whereas ultrasonography offers quick bedside assessment [8]. In the model cohort, 68% of infectious sources were accurately detected by ultrasound. Urinary and hepatobiliary infections were where it performed best [9]. Because gallbladder inflammation, biliary dilatation, hydronephrosis, and renal abnormalities can frequently be effectively detected by ultrasonography, this is clinically realistic. The availability of ultrasound at the patient's bedside is its main benefit. Transporting septic patients to a CT suite may be challenging due to their hemodynamic instability. As a result, POCUS can deliver information instantly without exposing users to radiation [10]. Prior prospective data showed that POCUS can quickly offer diagnostic information and significantly increase the sensitivity of first clinical assessment for locating the septic cause. Beyond identifying anatomical sources, ultrasound offers further information. While cardiac ultrasonography can evaluate ventricular function and hemodynamic problems, lung ultrasonography can show consolidation, interstitial abnormalities, and pleural effusions. Assessment of venous congestion and inferior vena cava may also help with customized hemodynamic treatment. According to recent studies, POCUS is a multimodal tool that combines the assessment of shock physiology and treatment response with source identification [11]. Nevertheless, ultrasonography has significant drawbacks. Obesity, intestinal gas, bandages, surgical incisions, and patient posture can all lower image quality. Characterizing retroperitoneal and deep pelvic disease can also be challenging. Another significant drawback is operator dependency, and expertise may have an impact on diagnosis accuracy. CT performed much better than ultrasonography in a paired comparison (p=0.005) and correctly detected 87% of infectious sources in the current model cohort. The distinction was particularly noticeable for postoperative collections and intra-abdominal abscesses. This finding is consistent with other research demonstrating that CT is superior than ultrasonography when surgical intra-abdominal sepsis is suspected [12]. 52.8% of CT exams in critically ill surgical patients revealed an infectious source, and in 85.5% of positive instances, finding the source was linked to a change in treatment. This highlights the fact that CT should be considered more than just a diagnostic test; in well chosen patients, it can directly aid in source-control planning [13]. Additionally, the current investigation showed a correlation between reduced mortality and early source identification. It is biologically reasonable that earlier localization enables timely antibiotic optimization and source control, but this link should not be taken as evidence that imaging itself lowers mortality [14]. When an anatomical focus necessitates intervention, the Surviving Sepsis Campaign places a strong emphasis on quick source evaluation and control. According to the model results, 55% of patients had actionable findings from CT, and many of those patients had their care changed as a result. These modifications included surgery, percutaneous drainage, and antimicrobial modification. This is in line with data showing that treatment choices for critically ill patients can be significantly influenced by CT findings. However, the role of imaging must be customized. Ionizing radiation is used in CT, and when contrast is used, renal function, allergy history, and other contraindications are taken into account [15]. Therefore, the possibility of finding a clinically significant infectious focus should be weighed against possible dangers and the patient's physiological stability when deciding whether to do CT.

When assessing sepsis patients, CT and ultrasound play complementing roles. Ultrasound is very useful for hepatobiliary, urinary, pleural, and superficial infectious disease. It offers quick, radiation-free evaluation at the bedside. For deep-seated, intra-abdominal, postoperative, and complex infections, CT offers a more thorough anatomical characterisation and a higher diagnostic yield.

In this model population, early source identification was linked to better clinical outcomes, and CT showed a greater rate of accurate infectious-source localization than ultrasonography. Therefore, using early ultrasonography as a quick first-line assessment and moving on to targeted CT when the infectious source is still unknown, when complications are suspected, or when precise anatomical information is needed for source-control planning is a realistic imaging strategy.