Gastric Emptying Scintigraphy: Solid and Liquid

Gastric Emptying Scintigraphy: Solid and Liquid

Historical Context

  • 1966: First gastric emptying scintigraphy (GES) study utilized Cr-51 labeled food.

  • Early Methods: Used radioactive chicken liver in stew.

    • Problem: Lack of standardization across institutions.

  • 2008: SNMMI (Society of Nuclear Medicine and Molecular Imaging) and ANMS (American Neurogastroenterology and Motility Society) published consensus guidelines.

Why Standardization Matters

  • Variable meals: Affect test reliability leading to inconsistent results.

  • Complicates treatment decisions: Without standardized values, comparisons across studies are difficult.

  • Questioning test validity: Gastroenterologists express concerns regarding test reliability due to lack of standardization.

2008 Consensus Statement

  • Focused on standardized methods for measuring gastric emptying (GE) via scintigraphy.

  • Recommended a low-fat, egg-white meal with imaging performed at 0, 1, 2, and 4 hours post-meal ingestion.

    • Pub-licized through a multicenter protocol.

    • Aims to resolve uniformity issues related to liquid meals.

  • Gastric counts from scintigraphy correlate directly with meal volume remaining, minimizing geometric assumption needs about stomach shape.

  • Ultrasound: Noted to be dependent on operator expertise, primarily measures liquid emptying.

    • Traditional indirect tests for GE include breath testing and acetaminophen absorption tests.

  • Clinical Utility: Improved credibility and reliability of GE tests.

Introduction to Gastric Emptying Scintigraphy (GES)

  • Definition: A noninvasive technique to assess gastric motility utilizing radio-labeled meals.

  • History: First publication in 1966; GES became the clinical standard for measuring gastric motility.

  • Functionality: Provides physiological, quantitative measures of GE while assuming normal small bowel absorption and pulmonary function.

  • Medication Tests: Acetaminophen absorption tests liquids and regular blood sampling.

  • Issues of Standardization: Differences occur in meals, imaging duration, patient positioning, and quantitative data reporting.

    • Lack of normal values hampers clinical utility and complicates interpretations across institutions.

GES Procedure Guidelines

Purpose

  • Assist nuclear medicine practitioners with recommendations for gastric emptying and motility studies in adults.

Background Information and Definitions

  • GES studies are among the most comprehensive for assessing gastric motor functions.

  • These tests are noninvasive and quantitative, using physiological meals.

  • Need for a standard meal and imaging protocol to allow easier comparison across institutions.

Patient Preparation

  1. Minimum Fasting: Nothing by mouth for at least 4 hours before the study. Ideal is a midnight fast.

  2. Logistics of Procedure: Explain meal usage, consumption time, number of images required, and activities allowed between images.

  3. Diabetic Patient Instructions:

    • Bring glucose monitors and insulin; record serum glucose at meal ingestion.

    • Optimal blood sugar should be <200 mg/dL.

  4. Timing for Premenopausal Women: Ideal to conduct tests on days 1-10 of the menstrual cycle to sidestep hormonal variations.

  5. Medication Management:

    • Stop prokinetic agents (e.g., metoclopramide) 2 days before testing unless evaluating drug efficacy.

    • Caution with medications that delay gastric emptying.

Relevant Medical History

  • Include previous conditions, surgeries, medication history, and any existing GI disorders.

Photographic and Image Acquisition Guidelines

  • Use a large field-of-view camera with correct matrix settings and energy windows.

Gastric Anatomy and Function

  • Proximal Fundus: Functions as a reservoir to accommodate food.

  • Body: Engages in mixing processes with enzymes and churning.

  • Distal Antrum: Breaks down food into 1-2 mm particles.

  • Pyloric Sphincter: Regulates entry to the duodenum.

Gastric Emptying Scintigraphy (GES) Rationale

  • Radiolabeled meals allow assessment of the physiological function of the stomach, tracking normal, delayed, or rapid emptying.

Clinical Indications for GES

  • Confirming or excluding conditions like:

    • Gastroparesis

    • Diabetes with post-prandial symptoms

    • Unexplained nausea/vomiting/weight loss

    • Early satiety and post-prandial bloating

    • Assessment of response to therapies, evaluate dumping syndrome post-surgery.

Gastroparesis: Symptoms & Causes

  • Symptoms: Nausea (92%), Vomiting (84%), Bloating (75%), Early Satiety (60%).

  • Common Causes: Diabetes mellitus, surgical complications, infections, neuromuscular disorders, medications, idiopathic reasons (30%).

Contraindications for GES

  • Allergy to egg components or gluten, hypoglycemia (<40mg/dL), severe hyperglycemia (>275mg/dL).

Patient Preparation Requirements

  • Fasting status (NPO for 4-6 hours minimum)

  • No smoking permitted

Medications to Withhold

  • Withhold medications based on half-lives relevant to their effects on gastric motility.

  • Important to maintain a patient-specific approach for adjusting insulin or diabetic medications in case of fasting.

Meal Composition Effects on Gastric Emptying

  • Variations in solids versus liquids, meal sizes, caloric content impact emptying rates significantly.

Standardized Meal Definition

  • Composition: 120 grams (4 oz) solid meal with specified nutritional values intended for GES.

Radiopharmaceutical Handling

  • Preparation: Utilizing Tc-99m sulfur colloid (18.5-37 MBq), ensuring accurate binding and proper cooking methods.

Image Acquisition Protocol

  • Image Timing Expectations: Follow specified time intervals for image capture (0 hours, 1 hour, etc.) to assess gastric retention accurately.

Percent Retention Calculations

  • Detailed methodology for calculating percent retention, ensuring decay corrections for accuracy.

Normal and Abnormal Results Interpretation in GES

  • Normal results defined by specified retention percentages based on time intervals.

  • Abnormal Result Indicators: Established retention percentages signal issues like dumping syndrome.

Dual Isotope GES Testing

  • Addresses weaknesses of single meal studies by combining solid and liquid assessments for enhanced diagnostic value.

Quality Control Checklist for GES Studies

  • Comprehensive assessment points outlined covering pre-study checks to post-study operational quality control processes.

GES Key Takeaways

  • GES is the gold standard for evaluating motility disorders, necessitating a standardized protocol for validity and reliability.

  • Understanding the physiological implications of preparation and imaging duration enhances clinical outcomes.

Gastroesophageal Reflux Study Overview

  • Identifies reflux conditions in pediatric patients and employs dynamic imaging for sensitivity in outcome assessments.

  • Guidelines for calculating reflux indices and interpreting results are delineated for ensuring effective diagnosis.