Disseminated septic arthritis caused by Ureaplasma urealyticum in an immunocompromised patient with hypogammaglobulinemia after rituximab therapy.

PURPOSE: Ureaplasma urealyticum is a rare pathogen associated with septic arthritis that predominantly affects patients with hypogammaglobulinemia. Bacterial identification of fastidious organisms is challenging because they are undetectable by routine culture testing. To the best of our knowledge, this is the first report of septic arthritis induced by U. urealyticum infection in Japan. CASE DESCRIPTION: We describe the case of a 23-year-old Japanese female with secondary hypogammaglobulinemia (serum immunoglobulin level < 500 mg/dL), identified 8 years after treatment with rituximab. The patient presented with persistent fever and polyarthritis that were unresponsive to ceftriaxone and prednisolone. Contrast-enhanced computed tomography and gallium-67 scintigraphy revealed effusion and inflammation in the left sternoclavicular, hip, wrist, knee, and ankle joints. Although Gram staining and bacterial culture of the drainage fluid from the left hip joint were negative, the condition exhibited characteristics of purulent bacterial infection. The patient underwent empirical treatment with doxycycline, and her symptoms promptly resolved. Subsequent 16S ribosomal RNA (rRNA) gene sequencing of the joint fluid confirmed the presence of U. urealyticum, leading to the diagnosis of septic arthritis. Combination therapy with doxycycline and azithromycin yielded a favorable recovery from the inflammatory status and severe arthritic pain. CONCLUSION: This case highlights U. urealyticum as a potential causative agent of disseminated septic arthritis, particularly in patients with hypogammaglobulinaemia. The 16S rRNA gene analysis proved beneficial for identifying pathogens in culture-negative specimens, such as synovial fluid, in suspected bacterial infections.

Ablation of Kidney Tumors in Patients with Substantial Kidney Impairment: Current Status.

PURPOSE OF REVIEW: To review the current status of kidney tumor ablation in patients with substantial kidney impairment. RECENT FINDINGS: Few reports of kidney tumor ablation in such patients have recently been published. The reported prevalence of patients with stage 4 or 5 chronic kidney disease (CKD) among patients undergoing ablation is 2.0%-10%. In patients with stage 4 or 5 CKD, local tumor control rates were 88%-100%. The effect of ablation on CKD stage is unclear, and the observed deteriorations in kidney function are consistent with both the effect of cryoablation and the natural course of advanced CKD. According to guidelines, active surveillance may be selected. The goals of treatment are complete tumor removal and maintenance of kidney function, both of which can be met by ablation. Given the limited treatment options, ablation may play a pivotal role in the management of patients with advanced CKD.

Robotic systems in interventional oncology: a narrative review of the current status.

Interventional oncology offers minimally invasive treatments for malignant tumors for curative and palliative purposes based on the percutaneous insertion of needles or catheters into the target location under image guidance. Robotic systems have been gaining increasing attention as tools that provide potential advantages for image-guided interventions. Among the robotic systems developed for intervention, those relevant to the oncology field are mainly those for guiding or driving the needles in non-vascular interventional procedures such as biopsy and tumor ablation. Needle-guiding robots support planning the needle path and align the needle robotically according to the planned trajectory, which is combined with subsequent manual needle insertion by the physician through the needle guide. Needle-driving robots can advance the needle robotically after determining its orientation. Although a wide variety of robotic systems have been developed, only a limited number of these systems have reached the clinical phase or commercialization thus far. The results of previous studies suggest that such interventional robots have the potential to increase the accuracy of needle placement, facilitate out-of-plane needle insertion, decrease the learning curve, and reduce radiation exposure. On the other hand, increased complexity and costs may be a concern when using robotic systems compared with conventional manual procedures. Further data should be collected to comprehensively assess the value of robotic systems in interventional oncology.

Arterial embolization via retrograde approach using steerable microcatheter and triaxial system.

We report a case of postoperative pseudoaneurysm, successfully treated with selective arterial embolization, using a steerable microcatheter and triaxial system via retrograde approach. A pseudoaneurysm was detected in the dorsal pancreatic artery, a severely narrow and steeply inverted branch of the superior mesenteric artery, making microcatheter insertion via the antegrade approach challenging. However, a steerable microcatheter was advanced beyond the orifice and the tip was reversed, changing the route to retrograde allowing for easy insertion of the microguidewire. Subsequently, a small microcatheter was advanced beyond the pseudoaneurysm into the dorsal pancreatic artery, and arterial embolization was successfully completed without complications.

Is cryoablation a valid option for renal cell carcinomas in direct contact with critical organs?

PURPOSE: This study aimed to assess the outcomes of percutaneous cryoablation (PCA) for renal cell carcinomas (RCCs) contacting critical organs without intervening fat tissue. MATERIAL AND METHODS: Twenty-three patients with 24 RCCs (mean size, 28.8 mm) contacting critical organs on preprocedural images were included. The organ displacement techniques, technical success, efficacy, and adverse events per Clavien-Dindo classification were retrospectively reviewed. RESULTS: The organs contacting the RCCs included the colon (n = 16), pancreas (n = 3), duodenum (n = 3), small intestine (n = 1), and stomach (n = 1). In all procedures, hydrodissection was conducted, and probe traction was additionally utilized in one to displace organs. Two procedures were terminated with an insufficient ice-ball margin (<6 mm) due to recurring proximity of the colon or thermal sink effect by renal hilar vessels, yielding a technical success rate of 91.6% (22/24). No severe adverse events were noted. All patients were alive without any metastases during a median follow-up of 34.4 months. The primary and secondary technical efficacy rates were 91.6% (22/24) and 95.8% (23/24) of tumors, respectively. CONCLUSION: PCA can be a valid option for RCCs contacting critical organs with a good safety profile and sufficient technical efficacy.

Complications of Percutaneous Cryoablation for Renal Tumors and Methods for Avoiding Them.

Percutaneous cryoablation of renal tumors is widely used because of its high efficacy and safety. This high safety can be attributed, at least in part, to the visibility of the ablated area as an "ice ball". This therapy has fewer complications (incidence, 0-7.2%) and is less invasive than surgery. Minor bleeding is inevitable in most kidney-related procedures, and indeed the most common complication of this therapy is bleeding (hematoma and hematuria). However, patients require treatment such as transfusion or transarterial embolization in only 0-4% of bleeding cases. Various other complications such as ureteral or collecting system injury, bowel injury, nerve injury, skin injury, infection, pneumothorax, and tract seeding also occur, but they are usually minor and asymptomatic. However, operators should know and avoid the various complications associated with this therapy. This study aimed to summarize the complications of percutaneous cryoablation for renal tumors and provide some techniques for achieving safe procedures.

Percutaneous cryoablation combined with prior transcatheter arterial embolization for renal cell carcinomas of 3 cm or larger: a prospective study.

BACKGROUND: We prospectively evaluated the safety and efficacy of percutaneous cryoablation combined with transcatheter renal arterial embolization for the treatment of tumors ≥ 3 cm in diameter. METHODS: We included patients aged ≥ 20 years with histologically proven renal cell carcinoma with a tumor diameter ≥ 3 cm who were inoperable or refused surgery. Prior to ablation, transcatheter arterial embolization was performed using a mixture of absolute ethanol and iodized oil. All cryoablation procedures were performed percutaneously under computed tomography fluoroscopy guidance. The primary endpoint was safety, which was evaluated for adverse events using CTCAE version 4.0. The secondary endpoint was survival; overall survival, progression-free survival, and cancer-specific survival were calculated. RESULTS: From October 2013 to March 2016, 19 patients (mean age, 75 ± 13 years; 5 women, 14 men) were prospectively enrolled. The mean tumor diameter was 3.9 ± 0.7 (range 3.1-5.3) cm. Four grade 3 hematologic adverse events occurred, while no symptomatic grade ≥ 3 events occurred. The median follow-up period was 68 (range 52-84) months. During the follow-up period, two patients developed local tumor progression at 3 and 42 months after the initial ablative procedure; no patient showed distant metastasis. Two patients died from causes other than RCC. Overall survival, progression-free survival, and cause-specific survival were 100%, 95%, and 100% at 3 years, and 95%, 84%, and 100% at 5 years, respectively. CONCLUSION: Percutaneous cryoablation combined with prior TAE for the treatment of tumors ≥ 3 cm in diameter was safe and achieved favorable survival.

In Vivo Microwave Ablation of Normal Swine Lung at High-power, Short-duration Settings.

To evaluate the volume and heat-sink effects of microwave ablation (MWA) in the ablation zone of the normal swine lung. MWA at 100 W was performed for 1, 2, and 3 min in 7, 5, and 5 lung zones, respectively. We assessed the histopathology in the ablation zones and other outcome measures: namely, length of the longest long and short axes, sphericity, ellipsoid area, and ellipsoid volume. The mean long- and short-axis diameters were 22.0 and 14.1 mm in the 1-min ablation zone, 27.6 and 20.2 mm in the 2-min ablation zone; and 29.2 and 21.2 mm in the 3-min ablation zone, respectively. All measures, except sphericity, were significantly less with 1-min ablation than with either 2- or 3-min ablation. There were no significant differences between the 2- and 3-min ablation zones, but all measures except sphericity were larger with 3-min ablation. Although there were no blood vessels that resulted in a heat-sink effect within the ablation zones, the presence of bronchi nearby in 5 lung ablation zones resulted in reduced ablation size. In high-power, short-duration MWA, the lung ablation volume was affected by ablation time. Some ablations showed that a heat-sink effect by a neighboring bronchus might occur.

Transhepatic Placement of Metallic Biliary Stent for Internal Drainage of Persistent Liver Abscesses.

Transhepatic placement of a metallic biliary stent for internal drainage of persistent liver abscesses was performed in 9 patients (males; median age, 65 years; range, 57-82 years) with refractory liver abscess. The median follow-up period was 2.8 months (range, 0.4-50.3 months). Technical success was achieved in all cases without any major complications. Clinical success, defined as the removal of the drainage tube without recurrent symptoms of infection, was achieved in 8 cases. Median duration until removal of the drainage tube from stent placement was 7 days (range, 0-36).

Automated Feeder-Detection Software for Renal Cell Carcinoma Embolization: A Retrospective Evaluation of Detection Rate Using Transarterial Time-Resolved Computed Tomography Angiography.

PURPOSE: To evaluate the detection rate of feeding arteries in renal cell carcinoma with automated feeder-detection software and determine the optimal imaging phase for accurate feeder detection with transarterial time-resolved computed tomography angiography. MATERIALS AND METHODS: The performance of automated feeder-detection software was retrospectively evaluated using transarterial renal time-resolved computed tomography angiography images of 15 renal cell carcinomas (mean size, 22.1 mm); the images were obtained via the renal artery using a hybrid angio-CT system with 320-row computed tomography, across nine phases with 0.5-s intervals over a contrast delay time of 1.0-5.0 s. Automated feeder-detection software was applied to each phase in all tumors (135 image series in total). The feeder-detection rate (i.e., sensitivity) in each phase was evaluated, and the number of false feeders demonstrated by the software was counted for each tumor. RESULTS: A total of 22 feeders were identified. The feeder-detection rate was the highest (95.5% [21/22]) at delay times of 1.5 s and 2.0 s and lower in later phases. At delay times of 1.0 s and 1.5 s, the software demonstrated no or only a few (≤ 3) false feeders in 93.3% (14/15) of the tumors. In later phases, however, many (≥ 4) false feeders were observed in > 50% of tumors. CONCLUSION: The automated feeder-detection software showed a favorable feeder-detection rate and may be useful in transarterial embolization for renal cell carcinoma. The optimal delay time to avoid the demonstration of false feeders and achieve a high detection accuracy was 1.5 s. LEVEL OF EVIDENCE IV: Case Series.

Time course of complications after small renal mass biopsy: evaluation of initial follow-up images.

PURPOSE: To retrospectively assess the time course of complications after image-guided small renal mass biopsy using initial follow-up imaging. MATERIALS AND METHODS: A total of 190 masses (mean, 2.1 ± 0.70 cm; range, 0.6-3.8 cm) were assessed using initial computed tomography (43 non-enhanced and 141 enhanced) or magnetic resonance imaging (five non-enhanced and one enhanced) after biopsy. Initial follow-up imaging was classified into two groups (i.e., with or without hematoma) and various factors were compared. RESULTS: The masses were histologically diagnosed in all patients except one. Post-procedural complications included 129 Grade I hematomas, 1 Grade I hemothorax, 9 Grade II hematomas, and 1 Grade IIIa pneumothorax. Residual 28 Grade I and 6 Grade II hematomas and 8 new complications (6 small hematomas, 1 pseudoaneurysm, and 1 arteriovenous fistula) were observed on the initial follow-up imaging obtained at a median of 21 days (3-90 days) after the biopsy. On the initial follow-up imaging, the groups with and without hematoma differed significantly in the following factors: age (P = 0.04), size (P = 0.02), guided images (P < 0.01), hematoma at the end of the procedure (P < 0.01), and days after biopsy (P < 0.01). Although three masses exhibited > 25% shrinkage, no significant change was observed in mass diameter on initial follow-up imaging (mean, 2.1 ± 0.71 cm; P = 0.90). CONCLUSION: Initial follow-up imaging after a biopsy revealed improvements in most of the complications, a few new complications, and an unchanged mass diameter.

Prospective evaluation of core number of biopsy for renal tumor: are multiple cores preferable?

PURPOSE: This single-center, single-arm, prospective, open-label study was conducted to evaluate the optimal number of cores (single or multiple) in renal tumor biopsy. MATERIALS AND METHODS: Forty-four biopsies of 44 tumors (mean diameter, 2.7 ± 1.0 cm; range, 1.6-5.0 cm) were included. Biopsy was performed under ultrasound or computed tomography fluoroscopy guidance using an 18-gauge cutting needle and the co-axial method. Two or more specimens were obtained, which were divided into first and subsequent specimens. "First specimen" and "all specimens" were histologically evaluated (i.e., appropriateness of specimen, histological diagnosis, subtype, and Fuhrman grade of renal cell carcinoma [RCC]) blindly and independently by two board-certified pathologists. RESULTS: Multiple specimens were successfully and safely obtained in all the biopsies. All tumors were histologically diagnosed; 40 malignancies included 39 RCCs and 1 solitary fibrous tumor, and 4 benign lesions included 2 angiomyolipomas, 1 oncocytoma, and 1 capillary hemangioma. In all RCCs, the subtype could be determined (32 clear cell RCCs, 4 chromophobe RCCs, and 3 papillary RCCs), and the Furman grade was determined in 38 RCCs. When only the first specimen was evaluated, 22.7% of the specimens were inappropriate for diagnosis, and 34 (77.3%) were histologically diagnosed. The diagnostic yield was significantly lower than that of all specimens (P = 0.0044). Univariate analysis revealed that smaller lesions were a significant predictor of diagnostic failure (P = 0.020). CONCLUSION: Biopsy with multiple cores significantly improved diagnostic yield. Thus, operators should obtain multiple cores during renal tumor biopsy.

Depiction rate of feeding arteries of renal cell carcinoma on four-dimensional computed tomography angiography.

PURPOSE: To retrospectively evaluate the depiction rate of feeding arteries in biopsy-proven clear cell renal cell carcinoma (CCRCC) on four-dimensional computed tomography angiography (4D-CTA) images. MATERIALS AND METHODS: This study included 22 patients with 22 CCRCC and 30 feeding arteries treated with transcatheter renal artery embolization. The depiction rate of the feeding arteries on preprocedural 4D-CTA was evaluated. Images were acquired by 320-row multi-detector computed tomography (CT) 15‒36 s after starting to inject a contrast agent (600 mg/kg iodine) intravenously into patients at 2.1 s intervals (11 phases). Two board-certified radiologists retrospectively assessed the feeder depiction rate in all 11 phases with reference to the procedural images as the gold standard. Discrepancies were resolved by consultation with a third radiologist. RESULTS: Among the feeders, 11 (36.7%) were segmental or lobar, and 19 (63.3%) were interlobar or arcuate arteries. The feeder depiction rate was the highest (25 [83.3%] of 30) in the 5th phase (delay, 23.4 s) where the gap in contrast enhancement between the renal artery and cortex was the largest. This was followed by the 6th (23 [76.7%] of 30), 4th (22 [73.3%] of 30]), and 7th (21 [70.0%] of 30) phases. The overall rate of depicting feeding arteries in the 11 phases of 4D-CTA was 28 (93.3%) of 30. CONCLUSIONS: The depiction rate of CCRCC feeding arteries including lobar or smaller artery branches by 4D-CTA was favorable. The feeding arteries were optimally visualized during the phase with the largest contrast gap between the renal artery and cortex.

Image-Guided Ablation Therapies for Extrahepatic Metastases from Hepatocellular Carcinoma: A Review.

The most common sites of extrahepatic metastases from hepatocellular carcinoma (HCC) are the lungs, intra-abdominal lymph nodes, bones, and adrenal glands, in that order. Although systemic therapies are a common treatment for patients with extrahepatic metastases, local ablative therapies for the extrahepatic metastatic lesions can be performed in selected patients. In this article, the literature on image-guided thermal ablation for metastasis to each organ was reviewed to summarize the current evidence. Radiofrequency ablation was the most commonly evaluated technique, and microwave ablation, cryoablation, and percutaneous ethanol injection were also utilized. The local control rate of thermal ablation therapy was relatively favorable, at approximately 70-90% in various organs. The survival outcomes varied among the studies, and several studies reported that the absence of viable intrahepatic lesions was associated with improved survival rates. Since only retrospective data from relatively small studies has been available thus far, more robust studies with prospective designs and larger cohorts are desired to prove the usefulness of thermal ablation for extrahepatic metastases from HCC.

Clinical outcomes of image-guided percutaneous drainage of pericardial effusion in cancer patients: A single-center retrospective analysis.

AIM: Catheter removal, survival, and recurrence rates after percutaneous pericardial effusion drainage in cancer patients are not fully understood. We evaluated the clinical outcomes of image-guided percutaneous pericardial effusion drainage in cancer patients. METHODS: From January 2014 to September 2017, 113 percutaneous drainages for symptomatic pericardial effusion were performed in 100 cancer patients (median 60 years; range, 7-84 years) using ultrasound or angio-computed tomography. An 8-Fr drainage catheter was placed using the Seldinger technique via the subxiphoid (n = 73), apical (n = 23), or left parasternal (n = 17) routes. Success rates, complications, and postprocedural clinical outcomes of drainages were retrospectively assessed. RESULTS: The technical and clinical success rates were 100% and 99%, respectively, without major complications. The median duration of catheterization and evacuated pericardial effusion volume were 6 days (range, 1-72 days) and 970 ml (range, 140-7635 ml), respectively. Catheters were removed after the first drainage in 86 cases (86%). Symptomatic pericardial effusion recurred in nine patients after catheter removal, in whom redrainages were performed 13 times with a median duration to redrainage time of 48 days (range, 13-529 days). During the follow-up period (median 106 days [range, 1-1396 days]), 61 patients died. The median survival was 140 days (95% confidence interval [CI], 95-276 days), and the median catheter-free survival was 111 days (95% CI, 60-152 days). CONCLUSIONS: Image-guided percutaneous pericardial effusion drainage for cancer patients is safe and helps alleviate symptoms. Additionally, catheter removal is possible in most patients, allowing a catheter-free period for patients.

Renal cryoablation combined with prior transcatheter arterial embolization in non-dialysis patients with stage 4 or 5 chronic kidney disease: a retrospective study.

PURPOSE: To retrospectively evaluate cryoablation combined with prior transcatheter arterial embolization (TAE) for renal cell carcinoma (RCC) in non-dialysis patients with stage 4 or 5 chronic kidney disease (CKD). MATERIALS AND METHODS: Patients with stage 4 or 5 CKD undergoing TAE and cryoablation for RCC between May 2012 and October 2021 were included. TAE was selectively performed using iodized oil with absolute ethanol or gelatin sponge 1-14 days before cryoablation. Local efficacy, safety, and changes in renal function were evaluated. RESULTS: Nine patients (seven men and two women; median age, 64 years; range 52-88 years) with nine RCCs (mean diameter, 3.0 ± 1.0 cm; range 1.7-4.7 cm) were included. The mean pre-treatment estimated glomerular filtration rate (eGFR) was 24.2 ± 5.6 ml/min/1.73 m2 (range 10.4-29.2 ml/min/1.73 m2). The mean amount of contrast medium used in TAE was 58 ± 29 ml (range 40-128 ml). Except in one patient (grade 3 pyelonephritis), no grade ≥ 3 complications occurred. During the follow-up period (median, 18 months; range 7-54 months), no local tumor progression occurred. In two patients with pre-treatment eGFR of < 20 ml/min/1.73 m2, hemodialysis was initiated at 3 and 19 months after cryoablation. At their last follow-up, the remaining seven patients showed a decrease of 6.2 ± 5.3 ml/min/1.73 m2 (range 0.7-17.2 ml/min/1.73 m2) in their eGFR. CONCLUSION: Cryoablation combined with TAE for RCC in non-dialysis patients with stage 4 or 5 CKD was effective and safe, with an acceptable impact on renal function.

CT fluoroscopy-guided biopsy of pulmonary lesions contacting the interlobar fissure: An analysis of 72 biopsies.

PURPOSE: The purpose of this study was to evaluate retrospectively the safety and diagnostic yield of computed tomography (CT) fluoroscopy-guided biopsy for pulmonary lesions with interlobar fissure contact. MATERIALS AND METHODS: Seventy-two lesions showing interlobar fissure contact (mean size, 15.2 ± 5.3 [SD] mm [range: 5.3-27.0 mm]; mean length of interlobar fissure contact, 8.9 ± 3.6 [SD] mm [range: 2.6-17.5 mm] in 72 patients (33 men, 39 women; mean age, 69.7 ± 10.3 [SD] years; age range: 37-91 years) were evaluated. Multiple variables were assessed to determine the risk factors for diagnostic failure and pneumothorax. Additionally, these variables were compared between these 72 lesions and randomly selected controls (i.e., non-contact lesions). RESULTS: All biopsies were technically successful using the transfissural (n = 14) or conventional routes (the route into the lung lobe with the target) with (n = 35) or without (n = 23) possible risk of needle insertion into the interlobar fissure after penetrating the target lesion. Sixty-eight (94.4%) procedures succeeded diagnostically and four (5.6%) failed. There were 27 grade I pneumothorax (37.5%), one (1.4%) grade II bleeding, and five (6.9%) grade IIIa pneumothorax requiring chest tube placement. Groups with and without pneumothorax did not differ significantly in patient-, lesion-, or procedure-related variables. Diagnostic yields and pneumothorax occurrence showed no significant differences between lesions with interlobar fissure contact and controls. CONCLUSION: CT fluoroscopy-guided biopsy of pulmonary lesions with interlobar fissure contact is a safe procedure with a high diagnostic yield. Furthermore, because of potential complications, the transfissural route should be used only when a safer route is not possible.

Correlation between renal ablation zone in contrast-enhanced CT and non-enhanced MRI during the early period following percutaneous cryoablation.

PURPOSE: To retrospectively evaluate and correlate the contrast-enhanced computed tomography (CECT) and non-enhanced magnetic resonance imaging (MRI) during the early period following renal cryoablation. MATERIALS AND METHODS: Both dynamic CECT and non-enhanced MRI were performed within 4 days following cryoablation in 34 renal tumors in 33 patients. The renal volumes of the unenhanced regions on dynamic CECT (nephrogenic phase, 4 mm thickness) and the regions with signal intensity changes on non-enhanced MRI (fat-suppressed T2-weighted image, 4 mm thickness) were evaluated. Fusion images of the axial, coronal, and sagittal sections of CECT and MRI images were created from the maximum cross-section of the renal tumor, and the match score of each image was visually evaluated on a 5-point scale. RESULTS: The mean renal volume of the unenhanced regions on CECT and those with signal intensity changes on non-enhanced MRI following cryoablation were 29.5 ± 19.9 cm3 (range, 4.3-97.4 cm3) and 30.7 ± 19.8 cm3 (range, 6.7-94.0 cm3), respectively; the difference between them was -1.17 cm3 (95% confidence interval [CI] -2.74, 0.40, P = 0.139). The Pearson's product-moment correlation coefficient (r = 0.975; 95% CI, 0.951, 0.988; P < 0.0001) showed a strong correlation between the volumes. The average match score between CECT and non-enhanced MRI was as high as 4.5 ± 0.5 points (radiologist 1, 4.3 ± 0.5; radiologist 2, 4.7 ± 0.5). Local tumor control rate was 94.1% (32/34 tumors) and recurrence-free survival rate was 82.0% (95% CI: 64.2%, 91.5%) at 5 years. CONCLUSIONS: The region with signal intensity changes on non-enhanced MRI was strongly correlated with the unenhanced region on CECT during the early period following renal cryoablation.

Early enlarging cavitation after percutaneous radiofrequency ablation of lung tumors: Incidence, risk factors and outcome.

PURPOSE: The purpose of this study was to retrospectively determine the incidence of early enlarging cavitation after percutaneous radiofrequency ablation (RFA) of lung tumor and identify risk factors associated with their occurrence. PATIENTS AND METHODS: A total of 245 patients (140 men, 105 women; mean age, 62.7 ± 11.8 [SD] years; age range: 31-87 years) with 605 lung tumors who were treated using 401 RFA sessions from April 2010 to March 2020 were included. Of which, 31 patients with 38 early enlarging cavitation and control group (151 patients with 228 tumors) were analyzed. Early enlarging cavitation was defined as cavities with an enlarged size (>3 cm) occurring on ablated lesions within seven days after RFA. Incidence of cavitation, risk and post-procedural factors of occurrence, major adverse events (AEs) that occurred in RFA sessions with cavitation, and course of cavitation were evaluated. AEs were classified using the CIRSE classification system for complications. RESULTS: Thirty-eight cavities (6.3%, 38/605 tumors) in 31 patients occurred in an average of 3.1 ± 1.7 days (range, 1-7 days) after 32 RFA sessions. Distance from pleura ≥ 20 mm, contact with vessel ≥ 3 mm, multitined expandable electrode ≥ 3 cm, and bronchus ≥ 2 mm encompassed in the ablation zone were independent risk factors of occurrence. Fever ≥ 38.5 °C, white blood cell count ≥ 10,000/µl one day after RFA, and steroid therapy were independent post-procedural factors of occurrence. Twenty-four Grade 3 and two Grade 6 AEs occurred. Twenty-nine cavities disappeared within a mean duration of 111.9 ± 64.9 (SD) days (range: 44-274 days) and four remained with a mean follow-up of 279.2 ± 174 (SD) days; five patients were lost to follow-up. CONCLUSIONS: Early enlarging cavitation occurs in 6.3% of lung tumors treated with RFA and are associated with 26 major AEs in 32 sessions. Aforementioned procedural factors and post-procedural inflammation were significant risk factors of occurrence.