Eliminating the Residual Negative Pressure in the Endoscopic Ultrasound Aspirating Needle Enhances Cytology Yield of Pancreas Masses

Abstract

Background: Prior to withdrawing the EUS-FNA needle from the lesion, the stopcock of the suction syringe is closed to reduce contamination. Residual negative pressure (RNP) may persist in the needle despite closing the stopcock.

Aims: To determine whether neutralizing RNP before withdrawing the needle will improve the cytology yield.

Methods: Bench-top testing was done to confirm the presence of RNP followed by a prospective, randomized, cross-over study on patients with pancreas mass. Ten milliliters of suction was applied to the FNA needle. Before withdrawing the needle from the lesion, the stopcock was closed. Based on randomization, the first pass was done with the stopcock either attached to the needle (S+) or disconnected (S-) to allow air to enter and neutralize RNP and accordingly the second pass was crossed over to S+ or S-. On-site cytopathologist was blinded to S+/S-.

Results: Bench tests confirmed the presence of RNP which was successfully neutralized by disconnecting the syringe (S-) from the needle. Sixty patients were enrolled, 120 samples analyzed. S+ samples showed significantly greater GI tract contamination compared to S- samples (16.7 vs. 6.7%, p = 0.03). Of the 53 patients confirmed to have pancreas adenocarcinoma, FNA using S- approach was positive in 49 (93%) compared to 40 using the S+ approach (76%, p = 0.02).

Conclusions: Despite closing the stopcock of the suction syringe, RNP is present in the FNA needle. Neutralizing RNP prior to withdrawing the needle from the target lesion significantly decreased GI tract contamination of the sample thereby improving the FNA cytology yield.

Clinical trials registration number: NCT01995474.

Keywords: Endoscopic ultrasound (EUS); Fine needle aspiration (FNA); Pancreas adenocarcinoma; Pancreas mass; Tissue acquisition.

Figures

Figure 1. Fine needle aspiration: Suction On and Suction Off

The EUS needle was inserted into an ex-vivo chicken thigh (simulating a target lesion). Suction was applied by opening the stopcock (A) and the recorded pressure was over minus (−) 20” Hg. Before withdrawing the needle-tip from the simulated target lesion, pressure measurements were also obtained with the suction stopcock closed but syringe still attached to the needle (Syringe-on: S+). Despite closing the stopcock the recorded pressure remained over minus (−) 20” Hg (B).

Figure 2. Fine needle aspiration with suction off and syringe (A): attached to and (B): detached from the needle

With the stopcock closed and the needle-tip still within the simulated target lesion: A: The residual negative pressure (RNP) recorded was over minus (−) 20” Hg with the suction-syringe and the stopcock still attached to the needle (Syringe On, S+). B: Disconnecting syringe with the stopcock from the needle handle (Syringe Off: S−) neutralized the RNP by allowing air to enter the needle form its handle-end and the pressure reverted to 0” Hg.

Figure 3. Fine needle aspiration with suction off and needle tip within the chicken and withdrawn from the chicken

This figure demonstrates that the RNP exists up to the tip of the needle rather than limited to the needle space proximal to the aspirated material in a simulated lesion. Suction was applied and needle passes were made in standard fashion. The stopcock was then closed and the negative pressure recorded was over minus (−) 20” Hg (A; Syringe On, S+ scenario). With the syringe still attached to the needle handle and the stopcock closed, the needle-tip was withdrawn from the chicken piece (B). The pressure reverted to 0” Hg as air entered the needle from its tip-end thereby suggesting that RNP effect exists up to the needle-tip.

Figure 4. A: Suction On, B: Suction Off syringe still attached (S+), and C: Syringe detached from the needle (S−)

Figure 5. Flow diagram of the patients studied and randomization with cross-over