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How to do Doppler Probe EUS for Bleeding

Richard C.K. Wong

Case Western Reserve University and University Hospitals Case Medical Center, Cleveland, OH, USA

Background and equipment

Doppler ultrasound, particularly use of the endoscopic Doppler ultrasound (DopUS) probe, is quite different from traditional endoscopic ultrasound (EUS) and miniature EUS probes inasmuch that the currently available DopUS probe is non‐imaging, the equipment is portable and significantly less expensive than EUS systems, and advanced endoscopic training in traditional EUS is not required. In addition, because the DopUS probe makes direct physical contact with the gastrointestinal (GI) tract lesion of interest, acoustic coupling with instilled water or with a water‐filled balloon are not required. Signal output from the non‐imaging DopUS probe system is in the form of an audible Doppler ultrasound signal with or without graphic display of the acoustic Doppler ultrasound waveform.

Within the last decade, two DopUS systems have been utilized in published studies: Endo‐Dop (DWL GmbH, Singen, Germany) and VTI Endoscopic Doppler System (Vascular Technology Inc., Nashua, NH) (Figures 39.1 and 39.2). However, only the VTI system has received US Food and Drug Administration (FDA) clearance for use in GI endoscopy in the United States. Both systems are AC powered.

Practical application of DopUS probe

Advanced endoscopic training, detailed knowledge of EUS, or specific training in EUS is not required to use DopUS. The technique of DopUS can be readily acquired by most GI endoscopists in a relatively short time.

Modern DopUS probe systems utilize pulsed‐wave ultrasound technology, which allows the endoscopist to vary scanning depth, to select the most appropriate depth for the specific bleeding lesion of interest, and to exclude deep serosal vessels (“innocent bystanders”) that are not involved in the bleeding process. Available DopUS systems are small and portable, and can be easily placed on an emergency endoscopy cart for patients located in intensive care units or in operating rooms.

With current DopUS probe technology, a 16‐ or 20‐MHz pulsed‐wave ultrasound beam is emitted in a linear fashion from the distal tip of a small flexible probe that is passed down the accessory channel of a standard diagnostic (or therapeutic) forward‐viewing (or side‐viewing) endoscope to make direct physical contact with the GI tract lesion of interest. It is important to select the scanning depth based on the lesion of interest: shallow (0–1.5 mm) for peptic ulcers versus mid (0–4 mm) for varices. Depending on the manufacturer, DopUS probes are marketed either as disposable, single‐use only, or reusable after gas sterilization or high‐level liquid disinfection.

Preprocedure system check

Before each use, it is important to perform a preprocedure check to ensure that the DopUS system is functioning appropriately. This is done by first connecting the DopUS probe to the base unit, turning the power on, and tapping the distal probe tip gently with an ungloved finger. In an appropriately functioning system, a corresponding tapping sound should be heard. In units that allow for adjustment of sound volume, this should be kept at maximum. The preprocedure system check is then completed. Note that the system should be turned off before passing the probe through the accessory channel of the endoscope.

Doppler ultrasound signals

Positive versus negative versus artifact:
- Positive signal: a repetitive and similar audible and/or visual signal of at least three consecutive cycles duration.
- Negative signal: absence of a positive signal.
  
  Figure 39.1 VTI endoscopic Doppler system. (a) A 20‐MHz pulsed‐wave Doppler ultrasound system. Doppler ultrasound output signal: audible only. Weight: 1.18 kg. United States Food and Drug Administration (FDA) clearance: yes. (b) Doppler ultrasound probe: single‐use, probe diameter 2.5 mm, lengths 165 cm and 245 cm.
  
  Source: reproduced by permission of Vascular Technology, Inc., Nashua, NH.
  
  Figure 39.2 Endo‐Dop, 16‐MHz pulsed‐wave, multigated Doppler ultrasound (DopUS) system with reusable DopUS probe and optional foot pedal. Doppler US output signal: visual and audible. Weight: 6.76 kg. United States Food and Drug Administration (FDA) clearance: no.
  
  Source: reproduced by permission of Elsevier.
- Artifact signal: simple movement of the probe tip against mucosa will produce a false, artifact signal. This can be readily differentiated from a positive signal by the fact that physical movement is required. In addition, artifact signals can occur if the probe tip is placed in an area where there are naturally transmitted pulsations, e.g. transmitted cardiac pulsations in the fundus of the stomach.
Arterial versus venous blood flow:
- Arterial blood flow: spiking, high‐pitch sound and/or waveform.
- Venous blood flow: continuous, low‐pitch sound and/or waveform.

Peptic ulcer (Figures 39.3–39.7)

Irrigate the base of the ulcer with water to clear away any fibrinopurulent exudate.
Position the DopUS probe in direct physical contact with the ulcer base using moderate pressure, at multiple points, including immediately adjacent to any stigmata of recent hemorrhage (SRH).
The endoscopist should vary the angle of the probe with the ulcer base so as to minimize the chance of a false‐negative Doppler signal. Note that a false‐negative Doppler signal can occur if the ultrasound beam is directed at a right angle (90 degrees) to the subsurface blood vessel.
Scanning depth: in peptic ulcer hemorrhage, the selection of scanning depth depends on whether there is increased physical distance between the ulcer base and the subsurface vessel of interest. For untreated ulcers, the scanning depth should be kept shallow (0–1.5 mm). For treated ulcers, selection of scanning depth depends on whether injection therapy has been performed and whether a subsurface cushion (or bleb) of injectate (fluid) is still present at the time of the DopUS examination. Thus, if injection therapy is performed alone (monotherapy), scanning depth should be increased to mid‐range (0–4 mm) because of the existence of the subsurface fluid bleb. On the other hand, if dual combination therapy is performed (injection therapy first followed by thermal‐contact therapy with a heat probe or bipolar probe), then the subsurface fluid bleb has been eliminated by the cratering effect of the thermal‐contact treatment and scanning depth can be kept shallow (0–1.5 mm).
- Shallow (0–1.5 mm):
  1. Untreated peptic ulcer
  2. Injection followed by thermal‐contact therapy
  3. Thermal‐contact therapy alone
  4. Endoclip therapy alone.
- Mid (0–4 mm):
  1. Firmly adherent clot
  2. Injection therapy alone
  3. Injection followed by endoclip.
- Deep (0–7 mm):
  1. Usually not needed.

Published studies

Published studies using the DopUS probe in acute peptic ulcer bleeding have demonstrated the following.

Schematic illustration of a bleeding peptic ulcer with a non-bleeding visible vessel (NBVV) undergoing Doppler ultrasound (DopUS) examination using an endoscopic DopUS probe that was passed via the accessory channel of a standard endoscope. — **Figure 39.3** Illustration of a bleeding peptic ulcer with a non‐bleeding visible vessel (NBVV) undergoing Doppler ultrasound (DopUS) examination using an endoscopic DopUS probe that was passed via the accessory channel of a standard endoscope.

Source: Wong RCK. Risk stratification of nonvariceal UGI hemorrhage for the practicing endoscopist. *Tech Gastrointest Endosc* 2005;7(3):118–123. © 2005, Elsevier.

Photo depicts doppler ultrasound (DopUS) in acute peptic ulcer bleeding. — **Figure 39.4** Doppler ultrasound (DopUS) in acute peptic ulcer bleeding. (a) Endoscopic image of a DopUS probe on a bleeding duodenal ulcer with a non‐bleeding visible vessel: Doppler positive. (b) Visual graphic display of the corresponding positive DopUS signal: y‐axis, frequency shift (kHz); x‐axis, time (s). (c) Endoscopic image of the same ulcer after combination endoscopic therapy with epinephrine injection and heat probe: Doppler negative. (d) Visual graphic display of the corresponding negative DopUS signal.

Source: (b, d) Wong RCK. Endoscopic Doppler US probe for acute peptic ulcer hemorrhage. *Gastrointest Endosc* 2004;60(5):804–812. © 2004, Elsevier.

Photos depict doppler ultrasound-guided hemostasis in acute peptic ulcer bleeding. — **Figure 39.5** Doppler ultrasound‐guided hemostasis in acute peptic ulcer bleeding. (a) Gastric ulcer with a non‐bleeding visible vessel: Doppler positive. (b) Immediately following dual combination endoscopic therapy with epinephrine injection and heat probe: Doppler positive. (c) Targeted, additional heat probe application to location of positive Doppler signal: Doppler negative. No recurrent bleeding at 30 days.

Photo depicts atypical peptic ulcer bleeding: recurrent major bleeding from a gastric ulcer, clean base, without stigmata of recent hemorrhage. — **Figure 39.6** Atypical peptic ulcer bleeding: recurrent major bleeding from a gastric ulcer, clean base, without stigmata of recent hemorrhage (requiring a 7‐unit blood transfusion in a healthy 23‐year‐old man). Doppler ultrasound (DopUS) localized a strongly positive arterial Doppler at the 11 o’clock position, targeted DopUS‐guided hemostatic therapy was performed with no recurrent bleeding at 30 days.

Photo depicts doppler-negative non-bleeding visible vessel. — **Figure 39.7** Doppler‐negative non‐bleeding visible vessel. Endoscopic image of a Doppler ultrasound probe being placed on an untreated bleeding duodenal ulcer.

Table 39.1 Correlation of endoscopic appearance of peptic or anastomotic ulcers with endoscopic Doppler ultrasound signal.

Endoscopic appearance	Doppler (+) (%)
Active bleeding (spurting)	100
Active bleeding (oozing)	60
Non‐bleeding visible vessel	44
Adherent clot	14
Flat pigmented spot	9
Clean base	11

Recurrent bleeding is significantly more likely to occur in ulcers that are Doppler positive than in those that are Doppler negative.
Ulcers that remain Doppler positive immediately after endoscopic therapy are at significantly increased risk of recurrent bleeding than those where the Doppler signal is abolished.
Positive correlation exists between endoscopic SRH and Doppler signal (Table 39.1).

Clinical scenarios

Clinical scenarios where use of the endoscopic DopUS probe could be useful include the evaluation of uncertain visual SRH, in the assessment of adequacy of endoscopic hemostatic therapy, and in the evaluation of bleeding ulcers that behave functionally as high risk but which appear to be low risk by visual stigmata alone (e.g. recurrent bleeding from a clean‐based ulcer or ulcer with flat pigmented spot).

Gastric varices versus thickened gastric folds versus gastrointestinal stromal tumor (Figures 39.8 and 39.9)

Place probe tip on lesion of interest using light pressure.
Scanning depth: mid (0–4 mm).
Vary incident angle.
- Gastric varices: continuous, low‐pitch sound and/or waveform. Consistency: soft.
- Thickened gastric folds: no Doppler signal. Consistency: soft.
- Gastrointestinal stromal tumor: ± Doppler signal, but only at base of lesion. Consistency: firm.
DopUS probe‐guided glue injection of bleeding gastric varices. Although there are reports of this technique being used, further studies are required to evaluate its clinical utility.

Miscellaneous disorders

DopUS probe has been used in the following disorders but further studies are required to evaluate clinical utility.

Dieulafoy’s lesion (Figures 39.10 and 39.11).
Diverticular bleeding.
Colonic polyps.
Esophageal varices.

Figure 39.8 Atypical appearance of a bleeding gastric varix. Mild active oozing of blood from a single, small, yellowish submucosal lesion in the gastric fundus, Doppler positive.

Source: reproduced by permission of Elsevier.

Figure 39.9 Doppler ultrasound examination of a gastrointestinal stromal tumor in the gastric fundus, Doppler negative. Source: reproduced by permission of Elsevier.

Figure 39.10 Dieulafoy lesion in gastric cardia. (a) Active bleeding. (b) Doppler ultrasound probe examination immediately following dual combination hemostatic therapy.

Figure 39.11 Dieulafoy lesion in rectum, Doppler with strong arterial signal.
Major papilla before endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy.
Post‐endoscopic submucosal dissection (ESD) ulcer.

Conclusions

The endoscopic DopUS probe allows the endoscopist to determine the presence or absence of subsurface blood flow in bleeding lesions, to differentiate between arterial and venous blood flow, to estimate depth of the subsurface blood vessel, and to estimate location of the subsurface blood vessel. Being able to generate such a subsurface map of blood flow could potentially allow for precise targeting and titration of endoscopic hemostatic therapy based not on visual surface stigmata alone, but with additional knowledge of subsurface blood flow.