Percutaneous nephrostomy

interventional radiology

1. PERCUTANEOUS NEPHROSTOMY MODERATOR – DR. RAGHUNANDAN PRASAD PRESENTOR – DR SARFARAZ AHMAD 1

2. Percutaneous nephrostomy is placement of catheter into renal PCS. Percutaneous nephrostomy insertion is a commonly performed interventional procedure, most frequently for the relief of renal obstruction . 2

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4. IMPORTANT ANATOMICAL FACTORS Kidneys lies at the level of T12-L2/3 level vertebral bodies Upper pole is more medial and posterior than lower pole The important adjacent structures that may be inadvertently injured during renal access are the liver, spleen, diaphragm, pleura/lung and the colon. 4

5. 5 Source – Grainger and Allison textbook of radiology

6. The adult kidney has approximately 8–9 calyces. Calyces vary in orientation, facing either relatively anterior or posterior. The posterior calyx is ideal for access, being closer to the skin surface. Posterior calyces also allow better intrarenal navigation. 6

7. 7 Calyceal selection for renal access. (A) Axial CT image showing entry into a posterior facing calyx A allows easy navigation into the anterior calyx B as well as towards the infundibulum and the renal pelvis C. Entry into an anterior calyx B would be poor for intrarenal navigation. (B) Coronal fluoroscopic image demonstrating that upper pole A or interpolar entry B is better for ureteric access. Lower pole entry C is less favourable.

8. The main renal artery divides into a (larger) anterior division and smaller posterior division, and each division further separates into segmental and lobar divisions. Peripherally, the lobar and arcuate arteries skirt around the calyx. The safest place to puncture a calyx is its middle. Puncture into the infundibulum or renal pelvis may lacerate larger arterial branches. 8

9. Normally there is a single renal artery and vein, but up to 25% of kidneys have more than one renal artery and variant renal veins are seen in 3–17%. These do not influence access, but may explain the occasional vascular injury that occurs despite adherence to safe anatomical principles. 9

10. 10 The safest point for Calyceal puncture is the centre of the calyx, approached through the relatively avascular plane (Brödel’s line) between the branches of the anterior and posterior divisions of the renal artery. Puncturing the centre of the calyx avoids injury to the arcuate divisions that course around the infundibulum.

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12. GENERAL EQUIPMENT FOR - RENAL ACCESS Access Needle The two broad choices are a one-part 21G needle system (micropuncture access system) or a one-part 18G/4Fr sheath system. With micropuncture access system , the puncture is with a 21G needle, through which a 0.018- inch. platinum-tipped wire is inserted, followed by a 4Fr dilator and finally a 0.035-inch working guidewire. A one-part system is an 18G diamond point needle . The puncture size is smaller with the two-part system (21G vs 18G) and should be safer, but this has not been proven. 12

13. Guidewires To navigate out of the calyx, a soft flexible wire with good torque is important, whereas rigidity is less vital. A straight-tipped Bentson wire or an angled-tipped hydrophilic wire is sufficient. Once the guidewire has been manipulated out of the calyx rigidity becomes more important, and a stiffer Amplatz-type wire is useful, especially if the track is being dilated for PCNL or a stent is being inserted through a malignant stricture.. 13

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15. Catheters Used for either navigation or drainage. For the former, a short angled-tip (e.g. Kumpe) or Cobra shape, high torque catheter is best. Hydrophilic catheters are useful for bypassing tight ureteric strictures. For drainage, a pigtail catheter with large holes along the inner surface of the pigtail is chosen, as these are less likely to obstruct once the system decompresses. Any size > 6Fr should suffice. Drainage catheters less frequently used are straight catheters or those with a Malecot-type tip, both useful with the small renal pelvis. 15

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17. Indications for Insertion of PCN Urinary tract obstruction from internal or external causes: stones, malignancy, sloughed papillae, crossing vessels, retroperitoneal fibrosis, iatrogenic causes (operative damage to ureter producing oedema/ stricture) Pyonephrosis or infected hydronephrosis Urinary leakage or fistulas Access for interventional or endoscopic procedures:ureteric stenting, PCNL, delivery of chemotherapy/medication (stone dissolution, antibiotic therapy for fungal infection), foreign body retrieval. Urinary diversion for haemorrhagic cystitis 17

18. Ideally, a nephrostomy should be performed within working hours, on a stable, well-resuscitated and monitored patient. However, it is also important not to unnecessarily delay renal decompression, especially in those with suspected pyonephrosis or infected hydronephrosis or obstructed single or transplant kidneys. The technical success rate for PCN is quoted as 98–99% but success rate is reduced in patients with non-dilated collecting systems complex stone disease or staghorn calculi. There are no absolute contraindications to performing a PCN. Severe coagulopathy is a relative contraindication but this can be corrected. 18

19. Patient Preparation Prior to renal drainage, cross-sectional imaging is important to evaluate the presence of hydronephrosis, anatomic variants (duplication, malposition, horseshoe kidney), cysts, tumors, stones, and/or perinephric urinoma. Patient education should include a description of the procedure, consent for risks and complications, alternative therapies, catheter maintenance, and long-term plan. Relevant labs include hematocrit (Hct), white blood cell (WBC), platelet count, international normalized ratio (INR), and creatinine (Cr). 19

20. Coagulopathy should be corrected to local guidelines. Typical goals include an INR of <1.5 and a platelet count >50,000 per μL. Oral anticoagulation should be withheld, utilizing a bridging strategy if anticoagulation cannot be stopped entirely. Nil per os (NPO) according to hospital guidelines to allow safe sedation. Patients can have clear liquids 2 to 6 hours prior to the procedure and are strict NPO for the 2 hours prior. Establish intravenous (IV) access for sedation and preprocedure antibiotic prophylaxis should be given. 20

21. Procedure Prone or prone-oblique. During pregnancy, the patient may only be comfortable lying on her side. Fluoroscopy and/or ultrasound are used to determine an appropriate access site which is then prepped and draped. The skin entry site is along the ipsilateral posterior axillary line, preferably below the 11th rib to avoid entering the thorax. A subcostal approach is most comfortable for patients. To avoid bleeding complications, the needle path to the kidney should be along “Brodel bloodless line” . This path, typically 30 to 45 degrees with respect to the table. Ideally, a posterior lower zone calyx should be targeted. 21

22. A direct posterior entry is only useful for opacifying the collecting system; this approach should not be used to place a catheter as it is uncomfortable for the patient and leads to catheter kinking and poor function. Administer local anesthesia at the chosen skin entry site. Make a small skin incision through the dermis to facilitate catheter passage. 22

23. During gentle respiration, advance the skinny needle toward the intended calyx using either fluoroscopic or ultrasound guidance Ultrasound guidance is preferred when there is hydronephrosis. Fluoroscopic guidance is more appropriate when radiopaque landmarks (e.g., calcified stones, surgical clips, indwelling ureteral stent) are present. When the needle enters the renal parenchyma, the tip will move synchronously with the kidney. When the collecting system is entered, there is an abrupt decrease in resistance to forward movement of the needle. Remove the stylet from the needle. In cases of hydronephrosis, urine will drain freely. Otherwise, slowly retract the needle while aspirating with a plastic syringe half filled with contrast on a connecting tube until urine emerges. 23

24. Inject a small amount of dilute contrast to confirm needle position and, only if there is no suspicion of infection, to opacify the collecting system. In cases of suspected infection, the system should be partially decompressed prior to contrast injection to minimize bacterial translocation due to further distension of the collecting system. Complete decompression should be avoided as it will make subsequent entry difficult if access is inadvertently lost. If a central puncture is made, the collecting system may be gently opacified to visualize an appropriate peripheral calyx for puncture with a second needle. Urine is aspirated for culture and/or cytology. Once access into the target calyx is achieved, the needle is exchanged over a 0.018/0.035-in guide wire for the coaxial introducer. Widen the skin nick with a hemostat to a depth of about 0.5 cm prior to introducing the catheter. 24

25. The coaxial introducer is exchanged over a 0.035-in. or 0.038-in. guidewire for a PCN . Introduction of an 8 Fr. or larger PCN catheter may be facilitated by the passage of Teflon dilators. Once the catheter tip is well within the renal pelvis or proximal ureter, reform the pigtail tip within the renal pelvis . Remove the guidewire completely and inject contrast to confirm catheter position. Open the catheter to external drainage and obtain an image to document decompression of the collecting system, confirming good function of the catheter. Anchor the catheter to the skin with a retention disk and/or suture. Attach a drainage bag to the external hub. 25

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28. Tube fixation – Roman scandal or reverse roman scandal technique 28

29. CT-Guided Nephrostomy This technique is useful and safer when variant renal anatomy is suspected: e.g. horseshoe kidney, pelvic kidney or suspected retrorenal colon. A planning pyelographic phase CT is performed in the prone or supine/oblique position. The procedure can be performed under sole CT guidance or as a combined CT/fluoroscopy method. Needle access is gained under CT guidance and a guidewire inserted. Subsequent tract dilatation and catheter insertion is done under fluoroscopic control. For the latter, care should be taken to ensure the access is secure before transferring the patient to the fluoroscopy suite. 29

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31. Difficult/Complicated Nephrostomy Non-dilated Kidneys Non-dilated calyces are not usually visualized on ultrasound examination and, being small, they are difficult to puncture. Also the space is too restricted for wire/catheter manipulation. The double contrast technique can be used in these cases. If the renal pelvis can be seen on US then this can be punctured with a 22G needle and a double contrast pyelogram performed to identify and distend the posterior calyces. If no part of the collecting system can be seen on US, then intravenous contrast medium is used to opacify the system and a posterior calyx selected and punctured. Using this technique, a success rate of up to 96% can be achieved in the non-dilated system. 31

32. Horseshoe Kidney Because of its anatomical disposition, the horseshoe kidney is prone to impaired drainage, infection and stone formation. The orientation of the calyces and vessels are such that percutaneous access is relatively safe. As horseshoe kidneys are located more inferiorly, the upper poles are usually well below the ribs. The lower pole and pelvis are usually more anterior facing and a lower pole lateral entry may damage large anterior division arteries or accessory branches from the iliac artery. Thus a medial lying, upper pole calyx entry should be chosen for PCN. 32

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34. Transplant Kidney Ultrasound-guided PCN is usually relatively straightforward in a transplant kidney as it is superficial and good views can be obtained. The procedure is performed with the patient supine. A lateral, upper pole entry is preferred to avoid puncturing the peritoneum. An upper pole or interpolar anterior-facing calyx is ideal as this allows more favourable access to the PUJ and ureter for subsequent ureteric stenting. Careful ultrasound technique helps reduce the risk of bowel injury or puncture of the inferior epigastric artery. Often , there is marked capsular fibrosis around the transplant and this can make dilation and catheter insertion difficult. Over-dilatation of the tract by 2Fr will facilitate catheter passage. 34

35. Paediatric Nephrostomy Percutaneous nephrostomy in children should be performed under general anaesthesia. Ultrasound-guided PCN is technically straightforward as the collecting system is well seen, as it is superficial and usually generously dilated. However, in children the collecting system can rapidly decompress on needle entry and access may be lost. Decompression may occur because the system is under high pressure or because it is non-compliant. Therefore , the catheter must be inserted as swiftly as feasible. Special neonatal nephrostomy catheters (5Fr) are available; however, a standard 6Fr pigtail system works well. Care should be taken to minimize radiation dose to the patient by using low-dose techniques, good collimation and fluoroscopic image capture with minimal screening. 35

36. Pregnancy Urolithiasis is the common cause of true ureteric obstruction in pregnancy and will usually resolve with conservative measures. If this fails, nephrostomy may be required and an ultrasound-guided procedure should be performed. Fluoroscopy should be used sparingly and only if necessary. A lateral or supine/oblique approach may be used. When fluoroscopy is used, radiation exposure should be minimized by lead shielding of the mother’s abdomen and by using similar safeguards as those recommended for pediatric cases. 36

37. Postprocedure Management For new catheter placement or catheter exchanges with sedation, bed rest and every 15- to 30-minute vital sign monitoring for 2 to 4 hours. If drainage was performed to relieve obstruction, there may be a profuse postobstructive diuresis. Monitoring urine output permits IV replacement of volume. If PCN is for decompression, continue external drainage until antegrade flow is restored. If PCN is to provide a tract for later stone removal and there is no obstruction, the catheter may be capped until the stone removal procedure. Resume preprocedure diet. Continue antibiotics only if signs of infection are present. Treat pain and fever symptomatically. If blood clot(s) obstruct the catheter and prevent good drainage, forward-flush 5 to 10 mL of bacteriostatic normal saline every 4 to 8 hours. 37

38. Blood-tinged urine may be seen for up to 48 hours. If gross hematuria persists, a tract study may be performed. If Hct falls without gross hematuria, check for retroperitoneal hemorrhage. PCN catheters and nephroureterostomy catheters are routinely changed every 3 months (or more commonly as needed) to prevent occlusion from encrustation and debris . Patients with frequent catheter occlusions may benefit from routine forward flushing with normal saline (10 mL twice daily). The use of antibiotic prophylaxis for routine catheter exchange is debatable. 38

39. Complications of PCN and Management 39 Major: 4.0% Massive hemorrhage requiring surgery or transcatheter embolization: 1% to 3.6% a. Angiography and embolization may, on rare occasion, be necessary. b. If a culprit vessel is not seen, the PCN should be retracted over a wire and repeat renal arteriogram performed to allow visualization of any bleeding or abnormal vessels that are obscured or tamponaded by the catheter. Immediately after the angiogram, the PCN is quickly reinserted to tamponade the bleed. Sepsis: 1% to 2% Pneumothorax: <1% Death due to hemorrhage: <0.2% Peritonitis: rare

40. 40 Minor Macroscopic hematuria: very common, clears within 12 to 48 hours Pain: - usually treated with acetaminophen but occasionally requires short-term opioids Urine extravasation: <2.0% Perirenal bleeding: rare Urinary infection: 1.4% to 21% (45% of patients with struvite stones) will develop signs of infection . Postprocedure rigors may respond to meperidine (Demerol): 25 to 50 mg IV. Dislodgment: 1% in early postprocedural period; 2% by end of the first month. Catheter occlusion occurs in 1% of patients; these tubes require replacement.

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