**3. Anatomical considerations**

Following assessment of the primary diagnosis and indication for percutaneous nephrostomy for each particular case, the procedure should not be performed without adequate review of all relevant imaging performed prior to the procedure. Percutaneous nephrostomy is usually performed using ultrasound or fluoroscopic guidance, although in many cases, CT may have been performed to arrive at the diagnosis prior to the procedure and correlation with these images may prove to be beneficial.

The primary diagnosis should be reviewed thoroughly, and this should include the cause and level of obstruction, degree of pelvicalyceal dilatation, as well as the most accessible renal calyx for catheter placement. If urinary calculi are present within the renal pelvis, their exact nature and location must be elucidated. The success rate for percutaneous nephrostomy has been reported to be lower in patients with a non-dilated collecting system, complex calculus disease and staghorn calculus (Ramchandani, Cardella et al. 2003). The kidney itself must also be assessed for the presence of anatomical variants or congenital anomalies such as horseshoe kidney.

Equally important to note is the vascular anatomy of the target kidney. Its precise delineation, as well as the presence of abnormal vascular malformations or aneurysmal dilatation should be noted. Injury to the first order segmental renal arteries may occur in the region of the renal pelvis, particularly if the puncture is made too medially. To prevent vascular injury and bleeding complications, the safest approach has been described by approaching the cusp of the papilla as far peripherally as possible, and by entering the kidney via the Brodel's line (Dyer, Regan et al. 2002). Brodel's line is a zone of relative avascularity and watershed territory, which is located just posterior to the lateral convex margin of the kidney, between the major anterior and posterior divisions of the renal artery. Care should be taken to avoid a through-and-through two-wall puncture of the renal pelvis as this runs the risk of injury to the anterior segmental renal artery.

The position of the affected kidney relative to the surrounding abdominal viscera should be thoroughly assessed as this has a bearing in determining the safest and most effective approach for renal puncture. Under normal circumstances, the posterolateral margins of the kidneys are immediately adjacent to the posterolateral aspects of the abdominal wall with no organs to interpose in between. Hence, a posterior approach is advantageous in avoiding the surrounding organs (Hruby 1990). Although the spleen, liver, pancreas and the adrenal glands are in close proximity to the kidneys, they are usually not shown to interpose

Percutaneous Nephrostomy 301

perforation. Occasionally, a retrorenal colon may also be encountered, and approach should therefore be negotiated accordingly. Although uncommon, cases of colonic perforation has

As described, a patient who is about to undergo percutaneous nephrostomy should be thoroughly assessed for current physical status and presence of comorbidities that may affect the risk of developing complications following the procedure. Hyperkalaemia, should be corrected appropriately. Patients who are coagulopathic will have to be managed with plasma or platelet transfusion. Acceptable platelet and INR (International Normalised Ratio) levels vary between institutions, but INR values of less than 1.3 or platelet levels of more than 80,000/dL have been considered acceptable (Ramchandani, Cardella et al. 2003).

Prophylactic antibiotics have been widely used in preparing patients for percutaneous nephrostomy, although no clinical trial has published reports of its benefits to date. A prospective controlled study of patients undergoing percutaneous nephrolithotomy (Mariappan, Smith et al. 2006) reported significant reduction in the risk of upper tract infection and urosepsis following 1 week of prophylactic ciprofloxacin. However this may not be extrapolated in cases of percutaneous nephrostomy not related to underlying calculus or nephrolithotomy, as the presence of calculus is known to be associated with increased risk of infection. On a similar note, McDermott et al regarded the genitourinary tract as being contaminated in the presence of advanced age, diabetes, bladder dysfunction, indwelling urinary catheter, prior manipulation, ureterointestinal anastomosis, bacteriuria and calculi particularly of the struvite variety (McDermott, Schuster et al. 1997). This is particularly so in the presence of clinical signs of infection. It has been recommended that patients with low risk of infection receive a single dose of 1g of intravenous cefazolin or ceftriaxone prior to the procedure (Ramchandani, Cardella et al. 2003). If these patients do not develop continuing signs of infection following the procedure, no further antibiotic treatment is necessary. Patients who are septic or with the above risk factors and at risk of developing infections, are recommended to prophylactically receive 1g of intravenous ceftriaxone 8-hourly or 1g of IV sulbactame 6-hourly, along with 80mg of IV gentamycin 8 hourly (Ramchandani, Cardella et al. 2003). Antibiotics are given for 5-7 days in the periprocedure period, and should be adjusted according to the results of urine culture obtained

Other aspects of patient preparation are common to most other interventional procedures performed in a hospital setting, and this entail obtaining informed consent regarding the procedure as well as adequate fasting if conscious sedation is considered. Certain groups of patients such as young children may have to undergo general anaesthesia, in which case

The patient is traditionally positioned in the prone or prone-oblique position, with the target puncture side elevated by approximately 20-30 degrees. The prone technique was originally adopted by Goodwin probably to avoid the colon and has since gained acceptance. The

been reported and this will be discussed further later in this chapter.

**4. Patient preparations, procedure and technique** 

**4.1 Patient preparations** 

from the procedure.

**4.2 Technique** 

collaboration with an anaesthetist may be necessary.

between the posterior aspect of the kidney and the adjacent abdominal wall. Hruby described no injury to these organs in their retrospective review of 3100 patients who underwent percutaneous nephrostomy. However trans-splenic puncture has been reported in a series of patients who underwent percutaneous nephrostomy for nephrolithotomy (Carey, Siddiq et al. 2006).

Fig. 1. Axial diagram of a kidney as seen in a prone patient illustrating the relations of the relatively avascular zone of Brodel (shaded) with the posterior (p) and anterior (a) branches of the main renal artery as well as the posterior calyx (#).

Fig. 2. The shaded wedge represents an ideal approach through Brodel's avascular zone. This approach of approximately 20°– 30° from the sagittal plane (dotted line) into the posterior calyx (#) minimizes the risk of bleeding. A CT pyelogram is used to better illustrate the pelvicalyceal system.

There are exceptions to the above, as parts of the pleura lie in the posterior costodiaphragmatic recess that may overlap with the anterior pole of the kidney. Under normal circumstances, the lower line of the pleura usually crosses the 12th rib at the lateral border of the erector spinae muscle, and part of the 12th rib posterior to this point lies above the pleural line. This is important to note as a transpleural puncture may result in pneumothorax or hydrothorax, and for this reason, a subcostal approach should be used. Hruby described the best subcostal approach to be below the 12th rib, approximately 2 fingerbreadth lateral to the lateral border of the paraspinal musclature, which is approximately along the posterior axillary line.

It is important to note however that the position of the kidneys in relation to the pleura varies according to respiration and individual anatomical variations, and this may be best assessed by using fluoroscopy just prior to puncture. The lower pole calyx is therefore the most likely to lie below the pleural line, and may in this way provide the safest approach. This is even more so in the right kidney, which is normally lower in position as compared to the left. However the upper pole calyx may have to be punctured in such cases where there is limited access to the lower pole calyx, for example due to presence of a large calculus. In such cases, a supracostal approach may have to be used with care.

In addition to the pleura, the colon is frequently found in close contact with the anteromedial aspect of the kidney, and too medial an approach may run the risk of colonic

between the posterior aspect of the kidney and the adjacent abdominal wall. Hruby described no injury to these organs in their retrospective review of 3100 patients who underwent percutaneous nephrostomy. However trans-splenic puncture has been reported in a series of patients who underwent percutaneous nephrostomy for nephrolithotomy

There are exceptions to the above, as parts of the pleura lie in the posterior costodiaphragmatic recess that may overlap with the anterior pole of the kidney. Under normal circumstances, the lower line of the pleura usually crosses the 12th rib at the lateral border of the erector spinae muscle, and part of the 12th rib posterior to this point lies above the pleural line. This is important to note as a transpleural puncture may result in pneumothorax or hydrothorax, and for this reason, a subcostal approach should be used. Hruby described the best subcostal approach to be below the 12th rib, approximately 2 fingerbreadth lateral to the lateral border of the paraspinal musclature, which is

It is important to note however that the position of the kidneys in relation to the pleura varies according to respiration and individual anatomical variations, and this may be best assessed by using fluoroscopy just prior to puncture. The lower pole calyx is therefore the most likely to lie below the pleural line, and may in this way provide the safest approach. This is even more so in the right kidney, which is normally lower in position as compared to the left. However the upper pole calyx may have to be punctured in such cases where there is limited access to the lower pole calyx, for example due to presence of a large calculus. In

In addition to the pleura, the colon is frequently found in close contact with the anteromedial aspect of the kidney, and too medial an approach may run the risk of colonic

Fig. 2. The shaded wedge represents an ideal approach through Brodel's avascular zone. This approach of approximately 20°– 30° from the sagittal plane (dotted line) into the posterior calyx (#) minimizes the risk of bleeding. A CT pyelogram is used to better

illustrate the pelvicalyceal system.

(Carey, Siddiq et al. 2006).

the posterior calyx (#).

Fig. 1. Axial diagram of a kidney as seen in a prone patient illustrating the relations of the relatively avascular zone of Brodel (shaded) with the posterior (p) and anterior (a) branches of the main renal artery as well as

approximately along the posterior axillary line.

such cases, a supracostal approach may have to be used with care.

perforation. Occasionally, a retrorenal colon may also be encountered, and approach should therefore be negotiated accordingly. Although uncommon, cases of colonic perforation has been reported and this will be discussed further later in this chapter.
