Basics of KUB interpretation Flashcards
Main views for AXR
Upright
Supine
Lateral decubitus
Air in different orientations of AXR
- Upright: subdiaphragmatic
- Supine: ~belly button area
- Decubitus: Lateral
Rigler’s sign
Air on both sides of the bowel wall, resulting in a very defined bowel wall
Indicates pneumoperitoneum
However, highly overcalled by beginners, often in the setting of superimposed bowel loops.
Falciform ligament sign
If you can see the falciform ligament, there is pneumoperitoneum
Imporant SBO signs in AXR
Systematic approach to AXR interpretation
-
Dark things
- Free air
- Bowel gas pattern
- Other aberrant air
-
Bright things
- Lines
- Foreign bodies
- Calcifications
-
Organ outlines
- Liver, kidneys, spleen, psoas muscles
- If poorly defined, think ascites vs cachexia
- Everything else
Approach to reading a KUB
- Look at the overall gas pattern
- Look for any extraluminal gas
- Look for abnormal abdominal calcifications or stones (gall, kidney, appendiceal)
- Assess for any soft tissue masses
Rule of thumb for appropriate distension of bowel compartments
Small intestine: 3 cm
Colon: 6 cm
Cecum: 9 cm
Where should you basically always see gas on a KUB?
The rectosigmoid region (black arrow on this diagram)
How do you tell apart large and small bowel on a KUB?
By how close the septations are together
Large bowel’s valvulae are further apart
Phleboliths
Calcifications found in the pelvis in women as age increases. They often have a central clearing, though it may be too small to see.
They are almost always totally benign, but they can make it more challenging to diagnose nephrolithiasis at the ureterovesicular junction.
The laws of bowel obstruction
- The area proximal to the obsturction dilates
- The area distal to the obstruction is decompressed/airless, including the rectosigmoid colon
- The loops that become most dilated are those with the largest resting diameter (the cecum, if it is involved)
Ileus and obstruction table
Pathophysiology of focal ileus
- Etiology: Focal irritaiton (infection or inflammation of adjacent structure) leads to loss of peristalsis in an isolated segment of bowel
- Almost always occurs in small bowel “(sentinel loops”)
- Most common cause by location is listed in the attached table
If a patient presents to the ED with apparent generalized ileus, it is probably on of these three things:
- Ogilvie syndrome
- Recent (~ few days) post-OP after abdominal/pelvic surgery
- Severe electrolyte imbalance (often hypokalemia)
Most sensitive test to determine the etiology and point of bowel obstruction
CT scan
Three main radiographic signs of air in the abdomen
Air under the diaphragm on upright film
Visualizing air on both sides of the bowel wall (Rigler sign)
Visualization of the falciform ligament (shown in image)
What is shown in this image?
Pneumatosis intestinalis
Bad news.
This is a premature newborn with necrotizing enterocolitis.
Urinary bladder calcifications
Occurs in schistosomiasis, bladder cancer, TB
Ureters may also be calcified in schistosomiasis
Pattern of calcification concerning for malignancy
Amorphous, cloud-like calcificaitons
The image shown is calcified ovarian cancer metastases
___ is the test you order if you aren’t sure if someone has bowel obstruction.
___ is the test you order if you are pretty sure that the patient has bowel obstruction and want to know more.
KUB is the test you order if you aren’t sure if someone has bowel obstruction.
CT abdomen/pelvis with IV contrast is the test you order if you are pretty sure that the patient has bowel obstruction and want to know more.
