We searched the institutional database from July 2018 to March 2019 for patients who had undergone US-guided paracentesis with available records in a case form (discussed later). Among the 234 eligible patients, 97 were excluded because of minimum-to-mild ascites (depth of peritoneal fluid less than 3 cm on US). Finally, 137 patients (95 men, 42 women; median age, 62 years; range, 31–84 years) were included. Among them, 82 patients, classified as group A (57 men, 25 women; median age, 62 years) underwent US-guided paracentesis with a newly developed puncture needle, and other 55 patients, classified as group B (38 men, 17 women; median age, 60 years) underwent US-guided paracentesis with a routinely used puncture needle, with a general sheath, and without plastic wings. The puncture needle type was randomly selected.

We retrospectively analyzed reporting templates for US-guided therapeutic paracentesis. At our institution, the clinical and periprocedural data for all patients who underwent US-guided paracentesis were recorded. The reporting template contained the following items: sex, age, platelet count, prothrombin time (PT), PT-international normalized ratio (INR), type of puncture needle (newly developed vs. routinely used), amount of ascites, the thickness of the abdominal wall, duration of the procedure from puncture to fixation, degree of pain, puncture site, and presence of repuncture. For the amount of ascites and thickness of the abdominal wall, the depth of peritoneal fluid and the distance between the skin and ascites were measured in cm on US before puncture. The degree of pain was assessed on the Likert scale (1–10; 1, no pain; 10, intolerable pain) using a questionnaire following paracentesis. The puncture site was selected based on the location of ascites, depending on the operator’s comfort. If the drainage was not smooth after the puncture, repuncture was performed immediately using the same puncture needle. We also reviewed the medical records for complications associated with US-guided paracentesis and classified them as major and minor based on the Society of Interventional Radiology guidelines [14].

Compared to the routinely used puncture needle (BD Angiocath Plus; Becton Dickinson Medical, Franklin Lakes, NJ, USA), the newly developed puncture needle (3S-A.D.Cath-16 gauge; Dukwoo Medical, Hwaseong, Korea) was longer (50 mm vs. 45 mm). The newly developed puncture needle had a hard plastic sheath and plastic wings. Both puncture needles had the same diameter (16 gauge) and the same method of application (Fig. 1).

All patients underwent US-guided therapeutic paracentesis in the supine position, performed by a single radiologist (SBH, 7 years of clinical experience). Punctures were made at the right lower quadrant and left lower quadrant of the abdomen, and the location targeting the Morrison’s pouch. Subsequently, the fluid was drained, and the metallic introducer needle was removed. Drainage of ascites was performed by fixing the remnant plastic sheath. When using the routinely used puncture needle, gauze packing was performed around the remnant plastic sheath. In the other case, plastic wings were attached to the skin by taping.

For periprocedural factors, categorical and continuous variables were expressed as counts (percentage) and median (range), respectively. We compared the periprocedural factors between the two groups using the Mann-Whitney U test and Fisher exact test and assessed the repuncture-associated factors using logistic regression analysis. For all tests, statistical significance was set at p<0.05. All statistical analyses were performed using the IBM SPSS version 22.0 (IBM Corp., Armonk, NY, USA).

Among the 137 patients, group A underwent US-guided paracentesis with the newly developed puncture needle, and group B underwent US-guided paracentesis with the routinely used puncture needle. The clinical causes of ascites were not significantly different between the two groups (Table 1). The rate of repuncture was significantly lower in group A (6.1%; 95% confidence interval [CI], 2.3–13.8) than in group B (21.8%; 95% CI, 12.8–34.5) (p=0.01). The duration of the procedure was significantly shorter in group A (median duration of 1 minute) than in group B (median duration of 2 minutes) (p=0.03) (Table 2). Other characteristics and periprocedural factors were not significantly different between the two groups.

There were no major or minor complications in either group. The thickness of the abdominal wall (p=0.04) and use of the newly developed puncture needle (p=0.01) were significantly associated with the rate of repuncture in the univariate analysis. In the multivariate analysis, only the use of the newly developed puncture needle was significantly associated with the rate of repuncture (p=0.02) (Table 3).

In the five cases of repuncture where US-guided paracentesis was done with the newly developed puncture needle, all repunctures were performed in patients with carcinomatosis peritonei. Among the 12 cases of repuncture with the routinely used puncture needle, most repunctures were performed in patients with liver cirrhosis (11 of 12). In the cases of US-guided paracentesis with the routinely used puncture needle, repuncture was performed because of kinking of the sheath (11 of 12) or lack of definite penetration of the parietal peritoneum (1 of 12).