Normal Abdominal & Pelvic CT Anatomy: Algorithm – Radiology | Lecturio

Summary

This lecture provides a comprehensive overview of normal abdominal and pelvic CT anatomy, emphasizing a systematic approach to evaluating CT scans. The speaker outlines a methodical process, starting with lung and bone windows, followed by a detailed assessment of organs like the liver, spleen, pancreas, and kidneys. Key distinctions between intraperitoneal and retroperitoneal structures are highlighted, along with the importance of proper bowel distension. A case study on renal calculi illustrates the significance of imaging phases, cautioning against the use of contrast in certain situations. This foundational knowledge sets the stage for further exploration of pathology.

Takeaways

• 😀 Use multiple window levels and scroll through CT scans multiple times to ensure thorough evaluation.
• 🗂️ Focus on one organ at a time during analysis to reduce the risk of missing abnormalities.
• 🌬️ Begin the assessment with lung windows to identify any free or abnormal air collections.
• 🔍 Utilize bone windows to check for occult fractures or abnormalities in bony structures.
• 🍖 Examine the liver's anatomy, noting its lobes and segments defined by blood vessels.
• 🩸 The spleen should appear homogeneous on imaging and is best measured via ultrasound.
• 🔄 The pancreas may not be visible on single slices and requires scrolling through multiple images.
• 🏥 Assess the gallbladder, which should not exceed 3 mm in wall thickness, best evaluated via ultrasound.
• 🔬 Understand the distinction between intraperitoneal and retroperitoneal organs, using the mnemonic 'sad pucker' for recall.
• 📊 Analyze vascular structures in the abdominal area during arterial and venous phase imaging to evaluate blood supply.

Q & A

What is the standard approach to reviewing abdominal and pelvic CT scans?

The standard approach involves evaluating one organ at a time and using multiple window levels to scroll through the CT scan several times for thorough evaluation.

Why is it important to focus on one organ at a time during a CT scan evaluation?

Focusing on one organ reduces the likelihood of missing findings, as the abdominal CT scan contains many different organs.

What organs are typically evaluated first in a CT scan?

The evaluation typically starts with the lung bases, followed by the liver, spleen, gallbladder, pancreas, kidneys, adrenal glands, pelvic organs, mesentery, blood vessels, and bowel.

How should free air be identified on a CT scan?

Free air can be identified using lung windows, where abnormal collections of air appear outside any structure, differentiating it from air within the bowel wall.

What anatomical structures comprise the liver?

The liver is divided into right, left, and caudate lobes, which are further subdivided into segments by vessels such as the middle hepatic vein and the portal vein.

What is the significance of the pancreas's visibility on a CT scan?

The pancreas is not normally seen on a single slice and requires scrolling through multiple slices. If the pancreatic duct is visualized, it may indicate abnormality.

What is the normal measurement for the gallbladder wall, and how is it best evaluated?

The gallbladder wall should not measure more than about three millimeters in thickness and is best evaluated using ultrasound.

What mnemonic can help remember retroperitoneal organs?

The mnemonic 'SAD PUCKER' can be used to remember retroperitoneal organs, which include the suprarenal glands, aorta and inferior vena cava, duodenum, pancreas, ureters, colon, kidneys, esophagus, and rectum.

Why is proper distension of the bowel important for assessment?

Proper distension allows for accurate assessment of bowel wall thickness and helps differentiate normal findings from potential pathologies.

What are the potential pitfalls of using contrast in imaging when suspecting renal calculi?

Using contrast may obscure renal calculi, as the contrast can hide the stone's visibility, particularly in delayed phase imaging.