# Presentation: 554199

## Spotlight Case March 2006

**The Wet Read**

## Source and Credits

- This presentation is based on the March 2006 AHRQ WebM&M Spotlight Case
- See the full article at _[http://webmm.ahrq.gov](http://webmm.ahrq.gov/)_
- CME credit is available through the Web site
- Commentary by: **Ronald Arenson, MD**
- Sidebar by:** Michael B. Gotway, MD**
- Editor, AHRQ WebM&M: Robert Wachter, MD
- Spotlight Editor: Tracy Minichiello, MD
- Managing Editor: Erin Hartman, MS

## Objectives

*	**At the conclusion of this educational activity, participants should be able to:*
- Appreciate the limitations of radiology resident emergency coverage
- Understand alternative approaches to emergency radiology coverage, including teleradiology
- Appreciate the diagnostic pitfalls of CT angiography for PE
- Realize the limitations on subspecialists’ or general radiologists’ emergency coverage

## Case: The Wet Read

*	**A 66-year-old man with prostate cancer and known bone metastases presented to the emergency department (ED) with a gradual increase in back pain and difficulty ambulating. Initial radiographic evaluation demonstrated stable metastatic bone lesions in the lumbar spine without evidence of cord compression.*

## Case: The Wet Read

*	**The patient was admitted for pain control with intravenous morphine and started on patient-controlled analgesia (PCA). Admitting laboratory studies were notable for mild anemia. Renal function, LFTs, and coags were within normal limits. CXR and urinalysis were unremarkable.*

## Case: The Wet Read

*	**On the night of hospital day #2, the patient developed acute shortness of breath and was tachycardic and slightly less responsive. His oxygenation was 78% on room air and 92% when placed on a non-rebreather mask. ECG showed evidence of right heart strain and a room air blood gas revealed a pH of 7.33, a CO2 of 50, and a paO2 of 55.*

## Case: The Wet Read

*	**Given suspicion for pulmonary embolism, the resident ordered a CT angiogram of the lungs. The on-call radiology resident read it and reported that his findings were consistent with a large pulmonary embolism in the right main pulmonary artery. As the patient was mildly hypotensive and had hypoxemic respiratory failure requiring intubation and mechanical ventilation, thrombolytic therapy was started.*

## Case: The Wet Read

*	**The next morning, the patient’s blood pressure, oxygenation, and level of consciousness had improved. While the team was rounding and discussing plans for extubation, the radiology attending contacted the ICU and reported that the final reading of the CT angiogram showed *_*no*_* evidence of pulmonary embolism. He explained that what was initially read that way was in fact a large artifact on the image cut reviewed by the overnight resident.*

## Pitfalls in Diagnosing PE with Helical CT 

- Proper scan interpretation depends on awareness of several diagnostic entities that may simulate PE
- Normal bronchovascular structures
- Improper bolus timing
- Streak artifacts
- Patient motion artifacts
- Pulmonary arterial catheters
- Vascular shunts

**Notes:**
Normal bronchovascular structures: such as pulmonary veins, bronchi, lymph nodes

## CT Findings that may Simulate PE 

| Anatomic | Lymph nodes, impacted bronchi, pulmonary artery catheters, pulmonary veins, pulmonary artery sarcoma, intracardiac shunts |
| --- | --- |
| Technical | Streak artifact from dense contrast in the superior vena cava, respiratory motion, cardiac motion, improper bolus timing (may obscure PE or, occasionally, simulate PE), mottle |
| Artifact | Flow artifact (related to timing of bolus), motion, tip of a pulmonary catheter |

## Example CT: Streak Artifact

**Example CT: Streak Artifact**

- Axial CT image shows decreased attenuation affecting right upper lobe pulmonary artery (arrow), potentially simulating PE. Decreased attenuation is caused by streak artifact emanating from dense contrast column in superior vena cava.

**Notes:**
Example of CT Showing Streak Artifact. Axial CT image shows decreased attenuation affecting right upper lobe pulmonary artery (arrow), potentially simulating PE. Decreased attenuation is caused by streak artifact emanating from dense contrast column in superior vena cava. 

## Example CT: Improper Bolus Timing

**Example CT: Improper Bolus Timing**

**Notes:**
Example of CT Showing Improper Bolus Timing. Image on left shows poor enhancement of pulmonary vasculature due to early contrast bolus. Note that contrast is primarily within right ventricular outflow tract, and has not yet reached aorta. Poor enhancement of right interlobar pulmonary artery (arrow) causes difficulty in PE diagnosis. 
Image on right obtained with correct contrast bolus timing shows excellent pulmonary artery enhancement, allowing diagnosis of PE (arrow). 

## Pitfalls in Diagnosing PE with CT Angiography

- Radiologists look for a filling defect within a blood vessel
- Contrast either stops abruptly or is seen around a central defect
- In this case, artifact mistaken for PE in right main pulmonary artery
- Only a few artifacts could be mistaken for centrally located PE
- A late-timed contrast bolus may create appearance of contrast at the periphery of vessel and unopacified blood in the center
- Streak artifacts, cardiac motion, the tip of a pulmonary artery catheter, and lymph nodes

## Off-Hours Radiographic Interpretationin a Teaching Hospital

*Hunter TB, et al. Acad Radiol. 2000;7:165-170.*

- Radiological study performed

- Resident provides preliminary interpretation “wet read”

- Referring physician receives report during off hours

- Attending physician provides formal report after review of resident interpretation in the morning

## Errors in Interpretation by Radiology Residents 

- One study found major and minor rates of discrepancy of 5% and 11%, respectively

*Velmahos GC, et al. Am Surg. 2001;67:1175-1177.*

## Errors in Interpretation by Radiology Residents 

- Other studies have shown that the frequency of significant errors by radiology resident is very low
- Major discrepancies: less than 1% - 2.3%
- Minor discrepancies: 3% - 7%

*See "Notes" for complete references.*

## Errors by Radiology Residents 

- More common among junior trainees
- Error rates are within reported interobserver differences among attending radiologist
- Error rates substantially below those recorded for ED staff

*Wyoski MG, et al. Radiology. 1998;208:125-128.**Erly WK, et al. **AJNR Am J Neuroradiol. 2002;23:103-107.**Kangarloo H, et al. Acad Radiol. 2000;7:149-155.*

## Errors by Radiology Residents

- Balance between learning and patient safety
- Off-hours experience important part of training experience
- Builds confidence
- Improves judgment
- Semi-independent environment

*Carney E, et al. **AJR Am J Roentgenol. 2003;181:367-373.** *

## Case (cont.): The Wet Read

*	**In light of the new reading, the team decided the clinical decompensation was likely due to aspiration and mucous plugging secondary to oversedation from narcotics. The right heart strain noted on ECG was an old finding from mild unexplained pulmonary hypertension. The patient had no bleeding complications from the thrombolytic therapy. He was extubated and discharged to a skilled nursing facility for rehabilitation.*

## Could Bronchial Mucoid Impaction be Mistaken for PE?

- For possible PE, radiologist is looking for a round structure with something dark in the middle
- Impacted bronchi may have this appearance
- Bronchial wall usually slightly denser than low attenuation mucus within lumen, especially if calcified
- Distinguishing plugged bronchus from PE can be difficult as pulmonary arteries and bronchi run together
- Right pulmonary artery is large, central structure
- Mucoid impaction not likely to be misinterpreted as PE in this vessel; this mistake usually occurs at the lobar, segmental, and subsegmental vessels

## Radiology Resident Oversight: Solutions

- 24-hour in-house attending radiologist coverage
- Teleradiology
- Web-based simultaneous review with out-of- hospital attending

## Oversight: In-House Attending Coverage

- Undesirable schedule with regular evening shifts
- Academic subspecialist may not feel comfortable covering cases outside their expertise
- Potential need for multiple in-house specialists

## Oversight: Teleradiology

*Kangarloo H, et al. Acad Radiol. 2000;7:149-155.*

| Pros | Cons |
| --- | --- |
| Can cover many hospitals at one time | Lack subspecialty training found in academic centers-additional read might be required by subspecialist |
|  | Only single interpretation would be reimbursed |

## Oversight: Web-based Options

- Attending back-up by Web-based access to Picture Archives and Communication System (PACS)
- Home review limited by speed of Internet access and fewer features than hospital-based workstation
- Concrete “rules” for contacting attending physician may help residents hesitant to do so, such as:
- When results of radiological study may lead to immediate surgery or invasive procedure
- When referring physician requests attending review

*Hunter TB, et al. Acad Radiol. 2000;7:165-170.*

## Interpretation Discrepancies

- Off-hours cases must be reviewed by attending early in the day
- If discrepancy exists, change in interpretation must be immediately communicated to referring physician
- A record of preliminary reports must continue to be accessible in the system, in the event the preliminary interpretation led to action such as procedure

## Documentation of Interpretations:“Wet Read” Computer System

- ED physician can enter initial impression
- Resident then reviews the film and enters preliminary findings into system; able to compare to ED physician’s initial impression
- Interpretation  immediately communicated to referring physicians via PACS workstation, pagers, hand-held devices

*Tellis WM, Andriole KP. J Digit Imaging. 2005;18:316-325.*

## ED Form for Entering Impressions

*UCSF Department of Radiology*

## Radiologist Form for Entering Wet-read

**Radiologist Form for Entering Wet-read**

*UCSF Department of Radiology*

## View from PACS Display

**View from PACS Display**

*UCSF Department of Radiology*

## Documentation of Interpretations

- Following morning, the attending radiologist reviews the resident report, indicates agreement or changes the read, indicates magnitude of the change and whether it might alter care for the patient

*Tellis WM, Andriole KP. J Digit Imaging. 2005;18:316-325*

## Form for Entering Attending Q/A Review

*UCSF Department of Radiology*

## Take-Home Points

- Radiology residents provide excellent emergency coverage off hours, but some significant errors do occur
- Junior residents make more mistakes than more senior residents, fellows, or faculty
- Without subspecialist review the next day, general radiologists who cover off-hours, often via teleradiology, appear to make more errors than residents

## Take-Home Points

- Attending radiologists need to provide back-up for the residents, and can do so by accessing the images remotely via PACS
- Computer systems can provide an excellent communication tool with referring physicians, including recording the frequency and significance of the discrepancies between the residents and attendings