Spotlight Case March 2006

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Spotlight Case March 2006

• The Wet Read

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Source and Credits

• This presentation is based on the March 2006
  AHRQ WebMM Spotlight Case
• See the full article at 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 WebMM Robert Wachter, MD
• Spotlight Editor Tracy Minichiello, MD
• Managing Editor Erin Hartman, MS

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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

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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.

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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.

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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.

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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.

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Case The Wet Read

• The next morning, the patients 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.

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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

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CT Findings that may Simulate PE
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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.
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Example CT Improper Bolus Timing
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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

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Off-Hours Radiographic Interpretationin a
Teaching Hospital
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
Hunter TB, et al. Acad Radiol. 20007165-170.
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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. 2001671175-1177.
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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.
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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. 1998208125-128.Erl
y WK, et al. AJNR Am J Neuroradiol.
200223103-107.Kangarloo H, et al. Acad Radiol.
20007149-155.
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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.
2003181367-373.
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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.

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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

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Radiology Resident Oversight Solutions

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

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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

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Oversight Teleradiology
Kangarloo H, et al. Acad Radiol. 20007149-155.
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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. 20007165-170.
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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

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Documentation of InterpretationsWet 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 physicians initial impression
• Interpretation immediately communicated to
  referring physicians via PACS workstation,
  pagers, hand-held devices

Tellis WM, Andriole KP. J Digit Imaging.
200518316-325.
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ED Form for Entering Impressions
UCSF Department of Radiology
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Radiologist Form for Entering Wet-read
UCSF Department of Radiology
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View from PACS Display
UCSF Department of Radiology
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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.
200518316-325
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Form for Entering Attending Q/A Review
UCSF Department of Radiology
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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

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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