What is the significance of extending 4 imaging (Four Imaging) in medical diagnostics?

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Last updated: April 5, 2025View editorial policy

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From the Guidelines

To extend 4 imaging, I recommend using CT of the abdomen and pelvis with IV contrast as the primary imaging modality for diagnosing acute pyelonephritis (APN) in complicated patients without a prior history of stone disease. This approach is supported by the most recent and highest quality study, which found that contrast-enhanced CT detected parenchymal involvement in 62.5% of patients, whereas unenhanced CT detected parenchymal involvement in only 1.4% of cases 1. The use of CT imaging with IV contrast allows for the detection of signs of APN, including focal or multifocal decreased parenchymal enhancement, complications of APN, and underlying problems such as hydronephrosis, obstructing stones, or congenital abnormalities.

Some key points to consider when extending 4 imaging include:

  • The importance of including the pelvis in CT imaging to detect unsuspected urolithiasis, congenital abnormalities, and abnormalities of the urinary bladder 1
  • The superiority of contrast-enhanced CT over unenhanced CT in detecting parenchymal involvement and complications of APN 1
  • The potential for CT imaging to detect acute extrarenal conditions such as cholecystitis, liver abscess, and appendicitis 1
  • The limited value of unenhanced CT in combination with contrast-enhanced CT in the absence of a history of renal stones 1

In terms of other imaging modalities, ultrasound (US) and magnetic resonance imaging (MRI) may also be used to diagnose APN, but they have some limitations. For example, US may not detect renal abscesses as well as CT imaging, and MRI may not be as readily available or as sensitive as CT imaging for detecting urolithiasis 1.

Overall, the use of CT imaging with IV contrast is the most effective way to extend 4 imaging for the diagnosis of APN in complicated patients, due to its high sensitivity and ability to detect a wide range of abnormalities.

From the Research

Extending 4 Imaging

  • The use of contrast media in medical imaging can provide better differentiation of tissue enhancement and improve soft tissue contrast resolution, but it may also cause complications, especially in patients with renal failure 2.
  • Contrast-enhanced ultrasound (CEUS) is considered an effective first-line imaging modality for post-operative early and long-term follow-up in renal transplantation, reducing the need for biopsies and providing adequate guidance for drainage procedures 3.
  • Imaging of the kidney relies on three main imaging modalities: ultrasound, CT scan, and MRI, each with its pros and cons and specific indications 4.
  • Ionizing radiation from diagnostic imaging procedures has contributed to improvements in medical care, but it also carries potential risks, including cancer, and efforts should be made to reduce radiation exposure while still providing effective imaging 5, 6.
  • The benefits of medical imaging, including reduced mortality and morbidity, should be weighed against the potential risks, and strategies should be implemented to minimize radiation exposure and optimize imaging procedures 5, 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

What you need to know about: imaging in patients with renal failure.

British journal of hospital medicine (London, England : 2005), 2023

Research

[Imaging of the kidney].

Bulletin du cancer, 2012

Research

Benefits and Risks in Medical Imaging.

Health physics, 2019

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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