GI: Meckel's Diverticulum

What is the treatment of Meckel's Diverticulum?

bowel/diverticulum resection

What other tests are associated with the diagnosis of Barrett's?

endoscopy and biopsy

How does Barrett's esophagus appear on NM imaging?

increased focal areas in the lower esophagus. hiatal hernia or reflux may also be present

How can you prevent excess gastric secretions in a Meckel's scan?

may require NG suction

What is the purpose of ensuring that the patient is NPO?

reduces stomach secretions and movement in the bowel

How do you position the patient?

supine, stomach in the upper FOV and bladder in the lower FOV (xiphoid to pubis symphysis)

What symptoms are associated with Barrett's esophagus?

ulcers, strictures and esophageal adenocarcinoma

What is the dosage/administration for Ranitidine?

- 1 mg/kg IV up to a maximum of 50 mg (min 2 mg dose): slow infusion over 20 min - 150-300 mg orally 2-3 hours prior to the test (adults)

What is the dosage/administration of Cimetidine?

- 300 mg po, q.i.d for two days prior to study in adults - 10-20 mg/kg/day for two days prior to the study in infants and children

What is the dosage/administration of glucagon?

- 50 ug/kg to 1 mg/kg IV

How can you prevent vascular abnormalities in a Meckel's scan?

- AVM, hemangioma, aneurysm - should diminish with time

Indications for Meckel's Diverticulum

- Detection of Meckel's diverticulum - Localize ectopic (heterotopic) gastric mucosa - Painless hematochezia - Presentation of GI bleed in child

What is the difference between a gastrointestinal duplication and a Meckel's on a NM scan?

- Duplication will appear in any part of the GI tract but usually the ileum ~20% occur in the mediastinum. - Meckel's occurs proximally within 2 feet of the ileocecal valve - Duplication may be cystic or tubular - Meckel's is tubular, ~ 2 inches long (80%)

How does assessment of Barrett's esophagus compare with Meckel's diverticulum assessment?

- Patient preparation, radiopharmaceutical and imaging parameters are the same - patient positioning is altered to include the mid and distal esophagus

What is the etiology of Meckel's Diverticulum?

- Remnant of the fetal omphalomesenteric duct (vitaline duct) that produces a congenital out-pouching or diverticulum. - Located in the RLQ in the distal ileum. - More common in males than females - contain, gastric (50% of the time), pancreatic, colonic or duodenal mucosa.

What is the mechanism of action for Ranitidine?

- antagonist to histamine in the gastric H2-receptor sites - Inhibits gastric secretions, enhancing pertechnetate accumulation

What is the mechanism of action for Cimetidine?

- antagonist to histamine in the gastric H2-receptor sites - inhibits gastric secretions, enhancing pertechnetate accumulation

What is the normal presentation of a Meckel's Diverticulum scan?

- cardiac blood pool - large vessels (decreasing over time) - hepatic and splenic pool (transiently) - uptake in stomach (increasing over 10-20 minutes then gradually decreases over time) - may see early renal activity - collecting system - scrotal/testicle activity

What are the signs of a positive Meckel's Diverticulum scan?

- focal area of increased uptake in the abdomen (usually anterior RLQ) - uptake increases over time - same timing and intensity as stomach - appears prior to bladder activity

Gastrointestinal Duplications

- found by surgery, barium radiography or sonography, NM imaging unlikely - symptoms like Meckel's, often symptomatic prior to 2 years of age - will accumulate pertechnetate if gastric mucosa is present

Upon reviewing a 90 minute dynamic GI bleed study you notic an area of increased uptake in the mid/LUQ that does not move over time. What is the next appropriate step?

Acquire an image over the head/neck (possible free pert)

What technical steps can be taken to limit the effects of renal or bladder activity on a Meckel's scan?

- lateral/oblique views to localize (urinary activity more posterior) - upright image empties renal pelvis - visualization not be the same time as the stomach - voiding

What is the most common symptom of Meckel's Diverticulum?

- many (~40%) are asymptomatic - bleeding due to peptic ulceration of the bowel by acid secreted from the gastric mucosa in the diverticulum (rare >40 years)

What are false negatives of Mechel's Diverticulum?

- minimal gastric mucosa, small diverticula - rapid washout - competing meds

What is the rule of 2's?

- occurs in 2% of the population - congenital anomaly in which only 1/2 contain gastric mucin-secreting mucosa - occurs within 2 feet of the ileocecal valve - 2 inches long (80%) - 2:1 male:female - 1/2 are symptomatic by 2 years

What are the symptoms of Meckel's Diverticulum?

- often asymptomatic, but may present with painless lower GI bleed (hematochezia) - potential for abdominal pain - bloating and nausea (if obstruction present) - pain and tenderness at level of umbilicus

What is the purpose of a flow study for a Meckel's?

- screen for vascular lesion that may be causing the bleeding - Meckel's has a negative flow study

How do you image for Barrett's Esophagus?

- since the abnormality will accumulate pertechnetate, imaging over the esophagus will demonstrate the lesion. - before imaging, get the patient to drink some water to flush any swallowed saliva which can contain pertechnetate - anterior - 370-555 MBq of pert - image 30 minutes post injection

What might cause a false positive result on a Barrett's esophageal study?

- swallowed oral activity - reflux from the stomach - hiatal hernia

What is Barrett's Esophagus?

- this occurs when a section of the lining of the esophagus is made up of gastric-like epithelium leading to esophagitis and ulceration - cells can secrete acid/pepsinogen and may cause ulcers (heartburn) in the distal esophagus

What is the patient preparation needed?

- thoroughly explain procedure - NPO 2-4+ hours - good hydration, void - Pharmacological pre-treatment - No barium studies, no invasive GI studies - No competing pharmaceuticals administered in advance of the procedure - no recent Tc-99m RBC procedure

What are false positives of Meckel's Diverticulum?

- urinary tract activity (most common) - aneurysms, AVM, hemangioma - bowel inflammation - neoplasms - ulcers, Crohn disease, colitis, peptic ulcer - intussusception - Barium enema - irritation

Retained Gastric Antrum

- will accumulate pertechnetate if gastric mucosa si present - appears as a collar of activity in the duodenal stump of the afferent loop

Administration to imaging time for Glucagon

10 minutes prior to and 10 minutes post pertechnetate administration

Administration to Imaging time for Pentegastrin

5-20 minutes prior to pert administration

What is the dosage/administration of Pentegastrin?

6 ug/kg SQ

What radiographic studies might be relevant to diagnosing a Meckel's?

Barium, angiography, and colonoscopy

What are the causes of heterotrophic gastric mucosa?

Barrett's esophagus, Meckel's diverticulum, Gastrointestinal duplication, and retained stomach antrum

Administration to imaging time for Ranitidine

Begin imaging 30-60 minutes following IV infusion (or 2-3 hours after oral administration

Administration to imaging time for Cimetidine?

Can begin imaging immediately because the patient has been pre-treated over 2 days

What is the mechanism of action for Glucagon?

Decreases peristalsis in the bowel, thereby causing stasis of the secreted pertechnetate (usually coupled with pentagastrin)

What is another name for Pentegastrin?

Peptavalon

What is the mechanism of action for pentagastrin?

Stimulates gastric secretions (gastrin/acids) and therefore increases the rate of pert uptake from the blood

What is another name for Cimetidine?

Tagamet

What is another name for Ranitidine?

Zantac