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What are the 3 main elements of diagnostic information that a GI bleed study can provide?
1. Establish the presence or absence of a bleeding site
2. Identify patients best suited for diagnostic and interventional angiography
3. Triage patents for medical or surgical intervention
What is the anatomical dividing point differentiating between upper and lower gastrointestinal bleeds?
The suspensory muscle or sometimes called ligament of the duodenum, also known as the ligament of Treitz
List the 4 common causes for upper GI bleeding
1. gastric ulcers
2. duodenal ulcers
3. gastritis
4. esophageal varices
List the 4 common causes for lower GI bleeding
1. diverticular disease
2. angiodysplasia
3. inflammatory bowel disease
4. cancer
The rate of GI hemmorrhage determines what imaging modality will be used. List the study that goes with:
1. Low grade
2. Intermediate
3. Severe
1. Low grade - Barium contrast study
- endoscopy
2. Intermediate - GI bleeding scan
3. Severe - angiography
- surgical laparotomy
What are the 2 radiotracers used in GI bleed study?
1. 99mTc RBC labeled
2. 99mTc SC
List the 3 advantages of using SC
1. shows slower bleeding rates, greater than or equal to .05 ml/min
2. Can image immediately
3. higher target to background ratio
list the 5 disadvantages of using SC
1. Rapidly cleared from intervascular space
2. must see bleeding within a few min post inj
3. can't visualize bleeds near liver/spleen
4. poor for intermittent bleeds
5. short vascular half life, 2.5-3.5 min
List the 5 advantages of using 99mTc RBC tracer
1. faster bleeding rates greater than or equal to .1 ml/min
2. stays in intravascular space for 48 hrs
3. Can visualize bleeds near liver/spleen
4. good for intermittent bleeds
5. long vascular half life, 29 hrs
what is the one disadvantage?
lower target to background ratio
Imaging protocol for GI bleed with SC
7-10 mCi SC
pt supine, image anteriorly every 1-2 min to obtain 500-750k count for 20-30 minutes
at 30 min if no bleed is visualized do 1 mil count image of abdomen, may extend imaging for 15-20 min
if initial study is negative pt must be reinjected with SC since tracer is extraced from circulation
When is the best time to see a bleed using SC?
when background clears activity at bleeding site is seen
Imaging protocol for GI bleed with tagged RBC 99Tc
20-30mCi 99mTc tagged RBC
pt prep: no barium contrast in system
60 min imaging using sequential sets of 15 min dynamic with 15 sec framing or frequent images every 10-60 sec for 60-90 min
imaging is complete when bleed is visualized
delayed at 2-6 hrs and 18-24 hrs if acute onset of bleeding occurs
due to overlapping of bladder and rectal activity ant obl and post images are helpful
What is important to monitor on pt upon arrival and throughout imaging procedure?
BP for treatment of hypotension if present
What are the 3 general criteria for diagnosing a positive GI bleed?
hint: SIP
1. spontaneous appearance
2. Increasing intensity
3. Peristalsis through bowel
What are the most common sites for GI bleeding?
1. rectosigmoid
2. cecum
3. descending colon
what is the most common?
sigmoid colon
List 3 pitfalls in imaging GI bleeding with SC
1. due to increased activity in liver/spleen upper GI bleeding can be difficult to detect
2. very low lying rectal hemorrhages may be missed from attenuation from pelvic structures
3. any esotopic splenic activity(accessory spleen, splenosis) may be confused with with GI bleeding site
What are 5 possible pitfalls when imaging a GI bleed with tagged RBC?
1. Inadequate rbc labeling can result in free tech as evidenced by hot stomach and thyroid
2. Penile activity can be confused as a bleed and can be differentiated by lateral and oblique views
3. Bladder activity can be confused with rectosigmoid bleeding, other views
4. Renal activity can also cause confusion, should be cleared up by end or study or on delayed image
5. Uterine activity in female pts during menstrating