Non-vascular interventional procedures refer to various percutaneous procedures performed under imaging guidance. Representative procedures include percutaneous drainage of abscesses, hematomas, or cysts; percutaneous nephrostomy for urinary diversion in cases of urinary tract obstruction or to create a conduit for urinary tract treatment; and suprapubic cystostomy. When planning percutaneous procedures, it is important to select the method that provides the most direct and shortest path to the target [7]. This means avoiding the colon, liver, spleen, pleura, and vascular structures. Generally, the procedure requires particular caution in patients with an international normalized ratio > 1.5 or a platelet count < 50,000 /cm3 [13].

Percutaneous catheter drainage (PCD)

PCD is the gold standard for treating abscesses, hematomas, lymphoceles, and pseudocysts. After reviewing images captured before the procedure, the puncture site and percutaneous route are selected under ultrasound or computed tomography guidance to place the catheter in the lesion site (Fig. 5a) [14].

Fig. 5

Percutaneous catheter drainage (PCD). a Pre-procedure coronal computed tomography (left) image reveals a renal abscess in the left kidney (black arrows). The renal abscess cavity is punctured with a 21-gauge needle (middle, white arrow), and contrast is injected to confirm proper access (middle, black arrowhead). An 8.5 Fr pigtail catheter (right, black dashed arrow) is successfully placed for drainage. b PCD for renal cyst and subsequent sclerotherapy with absolute alcohol. Pre-procedure coronal CT image (left) reveals an 8.5-cm-sized left renal cyst (white arrows). Sclerotherapy with absolute alcohol is performed through the catheter inserted into the cyst (middle). Follow-up CT (right) shows marked cyst size reduction (white dashed arrows)

Renal cysts, including cortical and parapelvic cysts, are common and usually asymptomatic. However, large, infected, or bleeding cysts can be accompanied by symptoms such as flank pain. PCD and sclerotherapy (Fig. 5b) have a success rate of 75–100% as the primary treatment for renal cysts. Various sclerosants are available, but absolute alcohol is the most commonly used. Sclerotherapy is performed by completely draining the fluid in the cyst and injecting absolute alcohol, not exceeding 100 mL. Complications of sclerotherapy using absolute alcohol include bleeding, drug reactions, inflammation, fat necrosis, and retroperitoneal fibrosis [14].

Percutaneous urinary diversionPercutaneous nephrostomy (PCN)

PCN is used for urinary tract obstruction, urinary extravasation, and diversion purposes. It is also used to provide a conduit for other treatments, such as percutaneous nephrolithotomy and ureteral stent placement (Fig. 6a, b) [15].

Fig. 6

Percutaneous urinary diversion. a, b Percutaneous nephrostomy (PCN) for hydronephrosis. a Pre-procedure coronal computed tomography image reveals the right hydronephrosis. b A 21-gauge needle (left, black arrow) is inserted into the lower polar calyx of the right kidney under imaging guidance. A guidewire (middle, black dashed arrows) is introduced into the right renal pelvis. A pigtail catheter (right, black arrowhead) is placed in the right renal pelvis over the guidewire. c Suprapubic cystostomy. A 50-year-old woman presented with acute urinary retention and voiding difficulty after concurrent chemoradiotherapy for recurrent endometrial cancer The sagittal CT image (left) reveals a distended bladder (black asterisk) due to obstruction caused by the mass (white arrows) between the bladder and vagina. The fluoroscopic image (middle) shows the access needle (black arrow), which is percutaneously inserted above the symphysis pubis. After a guidewire is introduced through the access needle, an 8.5 Fr pigtail catheter (right, black dashed arrow) is subsequently inserted over the wire. d Antegrade ureteral double-J stent placement via a percutaneous nephrostomy tract. Antegrade pyelography shows proximal ureter opacification only (left, black arrows). A double-J stent is successfully placed over the guidewire. The proximal tip of the double-J stent is positioned in the renal pelvis, and the distal tip (right, black dashed arrow) is located in the bladder. e Tandem double-J stent placement for ureteral stenosis after renal transplantation. Antegrade pyelography (left) shows a focal stenosis in the anastomosed ureter (left, black arrow). Two guidewires (middle, black dashed arrows) are introduced into the bladder, and then two double-J stents are sequentially inserted over the guidewires (right)

Knowledge of renal vascular anatomy, calyceal orientation, and the perirenal environment on imaging is crucial for achieving safe access while minimizing complications. The optimal approach for safe PCN is via the lateral margin of the paraspinal muscle, traversing the watershed zone (Brodel’s avascular zone) toward the posterior calyx. This method can mitigate bleeding risk. For urinary tract diversion, puncturing the lower calyx is the best approach. Conversely, puncturing the middle calyx facilitates subsequent procedures by providing a conduit for ureteral stent placement or nephrolithotomy. Upper calyx puncture should be avoided because of the risk of intercostal artery or nerve injury, pneumothorax, and catheter displacement. However, for transplanted kidneys, a lateral and upper-pole approach is required to avoid peritoneal puncture [13].

Pigtail catheters are predominantly used for PCN; however, straight, Malecot, double pigtail, and Foley catheters may also be used, depending on the specific circumstances. If a Kumpe catheter is inserted before a percutaneous nephrolithotomy, it can secure a path from the stone location to the distal ureter, greatly facilitating large-bore tract dilatation, sheath insertion, and intrarenal navigation (Supplementary Fig. 3) [7, 16]. Generally, PCN catheters should be changed every 2–3 months [15].

Suprapubic cystostomy

Suprapubic cystotomy is performed in patients who require long-term catheterization. Access should be obtained through the midline of the rectus sheath, approximately 2–3 cm above the pubic symphysis, and directed toward the bladder. Before the puncture, a bladder capacity of at least 300 mL should be maintained (Fig. 6c). The first catheter change after cystotomy should be performed after at least 4 weeks, followed by every 2–3 months [13].

Antegrade ureteric stent placement via the PCN tract

Antegrade ureteric stents are used to alleviate urine leakage or stricture by providing ureteral splinting or a conduit for urinary flow. Regarding the selection of stents, various designs and materials are utilized depending on the clinical contexts. The most widely used internal drainage device is a double-J plastic stent, which covers the full ureteral length and has multiple holes in the shaft and at either end (Fig. 6d) [15]. The appropriate stent length is selected based on the patient’s height, but a length of 22–24 cm is typically used [17]. While double-J stents typically require exchange every 3–6 months [15], conventional metal stents (e.g., Wallstent) or specialized covered metallic stents (e.g., Allium or Uventa) are available as durable alternatives in selected cases [18]. In contrast, a nephroureteral stent—which features locking loops in both the renal pelvis and bladder—serves as an internal-external device, incorporating an external drainage apparatus for versatile access [15].

Additionally, to treat ureteral stricture in transplanted kidneys, a tandem ureteral stent procedure can be performed by placing two 12 cm-long double-J stents side-by-side (Fig. 6e) [19].

Antegrade retrieval of a foreign body

Percutaneous antegrade retrieval of a foreign body via the PCN tract can be performed under fluoroscopic guidance without nephroscopy. It is conducted to remove an entrapped or fractured double-J stent (Fig. 7a) or a fractured catheter (Fig. 7b); however, it can also be used to remove a ureteral stone (Fig. 7c) or a fungus ball. Various instruments can be used to remove foreign bodies from the urinary tract, including loop snares, baskets, and forceps [14, 15].

Fig. 7

Antegrade retrieval of urinary foreign bodies. Various foreign bodies, including an entrapped double-J stent (a, black arrow), a fractured catheter fragment (b, black arrows), and ureteral stones (c, black arrow), are successfully retrieved via a percutaneous nephrostomy tract using a basket (a, black arrowhead) and snare catheter (b, black dashed arrow), with the basket capturing the stone (c, black arrowhead)