What is the protocol for performing an ultrasound on an ileal conduit and what are the normal findings?

Ultrasound Protocol for Ileal Conduit Assessment

While the provided evidence focuses primarily on intestinal ultrasound for inflammatory bowel disease rather than ileal conduit evaluation specifically, the fundamental ultrasound techniques for bowel assessment can be adapted to examine an ileal conduit, though this is not a standard or well-established imaging protocol.

Equipment Requirements

• Use a high-frequency linear array transducer (5-17 MHz) to achieve adequate spatial resolution for assessing the conduit wall structure 1
• A low-frequency convex transducer (2-5 MHz) may be needed for deeper structures or in patients with larger body habitus 1
• Activate harmonic imaging when available to improve delineation of the bowel wall 1

Patient Preparation

• Recommend a fasting period of at least 4-6 hours before examination to reduce bowel gas that may interfere with visualization 1, 2
• No laxative or non-flatulent preparations are required for routine examination 1
• Avoid administering spasmolytic agents as they may interfere with real-time assessment of conduit peristalsis 2

Scanning Technique

• Perform systematic real-time scanning of the ileal conduit from the stoma site tracking proximally toward the ureteroileal anastomoses 1
• Use graded compression technique to displace overlying bowel gas and improve visualization 2
• Scan in at least two orthogonal planes (longitudinal and transverse) to fully characterize the conduit 1
• The conduit should be examined from multiple acoustic windows, adjusting patient position (including left lateral decubitus) as needed 1

Normal Ultrasound Findings in Ileal Conduit

Wall Thickness

• Normal bowel wall thickness should not exceed 2-3 mm when properly measured 3
• The recognizable 5-layer wall pattern should be visible with high-frequency transducers 1

Luminal Characteristics

• The conduit lumen should appear patent without significant narrowing or obstruction 4
• Some fluid content within the conduit is expected and normal given its urinary diversion function
• Normal peristalsis may be reduced or absent compared to native ileum, as the conduit functions primarily as a passive conduit 2

Anastomotic Sites

• The ureteroileal anastomoses should appear smooth without focal wall thickening or fluid collections 5
• No evidence of hydronephrosis in the upper urinary tracts on extended examination

Surrounding Structures

• No peristomal fluid collections or abscesses 1
• No abnormal vascularity on Doppler examination (Color or Power Doppler can assess wall vascularity) 1

Important Clinical Caveats

This examination has significant limitations:

• Ultrasound is operator-dependent and requires significant experience 1
• Patient body habitus and overlying bowel gas are major limiting factors 1, 2
• The deep pelvic location of ureteroileal anastomoses may be difficult to visualize with transabdominal ultrasound 1
• CT or MRI are superior modalities for comprehensive evaluation of ileal conduit complications including stenosis, stones, and upper tract changes 1, 5

When to Use Alternative Imaging

Given the high complication rate in ileal conduits (66% in long-term survivors), with 27% having kidney function/morphology issues and 14% having conduit/ureteral anastomosis problems 5, ultrasound should be considered a screening tool only. CT enterography or MRI should be obtained when:

• Complications such as obstruction, stricture, or abscess are suspected 1
• Upper urinary tract assessment is needed 5
• Detailed evaluation of the ureteroileal anastomoses is required 1
• Ultrasound findings are equivocal or technically limited 1

Contrast-enhanced ultrasound (CEUS) may improve diagnostic accuracy for differentiating phlegmon from abscess if available 1, though this is not standard practice for ileal conduit evaluation.