Application Of Contrast-Enhanced Ultrasound (CEUS) In The Evaluation Of Kidney Wound Healing After Partial Nephrectomy

Objectives To explore the feasibility,repeatability and usefulness of CEUS in the assessment of kidney wound healing after minimally invasive partial nephrectomy(MIPN),and preliminarily analyze the clinical factors associated with the extravasation of ultrasound contrast agent on the first day after surgery and the length of extravasation(LOE).Subjects and MethodsFrom April 2019 to January 2020,130 patients underwent RPN or LPN in our center were included,90 patients(90/130)were examined by CEUS each one day from the postoperative day 1(POD1)and were divided into two groups according to the extravasation or not of contrast agent from the kidney wound on POD1.The primary endpoint was the discovery of no extravasation of contrast medium from the renal wound named "ultrasonic healing",which was regarded as the criterion for the preliminary wound healing.We recorded the R.E.N.A.L.nephrometry scores,perioperative parameters and LOE.Factors associated with the extravasation of contrast agent on POD1 and LOE were determined by single and multiple factor analysis.ResultsCEUS represented the continuous extravasation of the contrast agent as a drip or a band-like spot with a low velocity from kidney wound to the free fluid outside the sutured capsule.Significant differences existed in R component and A component of R.E.N.A.L.nephrometry score between no extravasation group(49/90)and extravasation group(41/90).The incidence of extravasation in patients with R scores of two points and anterior location was higher than those with R scores of one point and posterior location(68.4% and 39.4%,62.1% and 30.3%,p(27)0.05).No extravasation group represented lower complication rate(49% and 75.6%,p=0.016).Multiple-factor analysis presented R scores of two points and other than posterior location were risk factors for the extravasation of contrast agent on POD1.The average postoperative LOE was 1.76 days(standard deviation,1.115;95%confidence interval: 1.52-1.99).The median(interquartile range)LOE was 1(1–2)days.95.6% patients(86/90)achieved "ultrasonic healing" within three days after surgery,LOE longer than three days was observed in only four patients(4.4%).The univariable results showed only R and A component in R.E.N.A.L.nephrometry score were associated with LOE.We noted a significant increase of mean LOE in patients with R scores of two points and anterior masses compared to those with R scores of one point and posterior masses(2.26 vs 1.62 days,2.14 vs 1.42 days,P(27)0.05).Multivariable linear regression analysis showed R scores of two points and other than posterior location contributed to the longer LOE than R scores of one point and posterior location.The prediction formula for LOE was: LOE=0.640+0.647×R scores+0.717× "A" +0.324× "X"(reference=posterior,A=0,X=0;anterior,A=1,X=0;unknown A or P,A=0,X=1).ConclusionsCEUS was feasible,repeatable and useful in the evaluation of kidney wound healing after MIPN.R and A component of R.E.N.A.L nephrometry score were found associated with the extravasation of contrast agent on POD1 and LOE.Tumor diameter(29)4cm and other than posterior location were risk factors for the extravasation of contrast agent on POD1 and prolonged LOE.Postoperative length of bedrest of patients should be individually managed combined with clinical comprehensive factors.Postoperative length of bedrest of patients after MIPN within three days might be relatively safe.