Percutaneous Nephrostomy

Percutaneous nephrostomy (PCN) is the placement of a catheter through the skin and renal parenchyma into the collecting system of the kidney, to drain urine and relieve obstruction.

The procedure uses ultrasound (to find the kidney and the dilated collecting system) and fluoroscopy (to confirm needle position with contrast). The patient lies prone or prone oblique. A posterior lower pole calyx is punctured through the avascular plane of Brodel (the posterolateral border, between the anterior and posterior segmental arteries).

A wire is coiled in the pelvis, the tract is dilated, and a pigtail drainage catheter (8 to 12 French) is placed and fixed.

The catheter drains externally to a bag. Antegrade pyelography (contrast injection through the catheter) shows the level and cause of obstruction. The same access is used for ureteric stent placement, dilatation of strictures, stone removal (percutaneous nephrolithotomy, with larger tracts of 24 to 30 French), foreign body retrieval, biopsy, and ureteric embolisation.

Urinary tract obstruction is the commonest indication, especially infected obstruction (pyonephrosis), which is a urological emergency with high mortality if not drained (sepsis in 25 to 75% of untreated cases). Obstruction from stones is the commonest cause in young adults, and malignancy (cervical, bladder, prostate, colorectal, ovarian, retroperitoneal disease) in older patients.

Retrograde ureteric stenting is an alternative, and percutaneous nephrostomy is chosen when the stent cannot be passed (tumour, distorted anatomy, impacted stone) or when the patient is unstable and sedation or lithotomy is unsafe. Technical success is 98 to 99% in dilated systems and 80 to 90% in non-dilated ones.

Indications.

• Infected obstructed kidney (pyonephrosis, obstructive pyelonephritis, urosepsis) for urgent decompression.
• Obstruction with renal failure or a solitary kidney (stone, tumour, retroperitoneal fibrosis, post-operative stricture, ureteric injury, pelvic malignancy), when retrograde stenting fails or is not possible.
• Ureteric leak or fistula (urinoma, vesicovaginal or ureterovaginal fistula after surgery or radiotherapy): urinary diversion.
• Access for stone treatment (percutaneous nephrolithotomy), stricture dilatation, ureteric stent placement (antegrade), and removal of foreign bodies.
• Pelviureteric junction obstruction when other treatments are unsuitable, and haemorrhagic cystitis or fistula requiring diversion.
• Renal transplant obstruction or leak.
• Diagnostic: antegrade pyelography when retrograde study is not possible, and the Whitaker pressure flow test for chronic obstruction (rarely).
• Not when the collecting system is undilated and not accessible (relative), or when the kidney is non-functioning without infection.

Contraindications. Uncorrectable coagulopathy (international normalised ratio over about 1.5 to 1.8, platelets under 50 000 in each microlitre, as the local rule sets), though in life threatening pyonephrosis the procedure is done after correction attempts.

Further contraindications: no safe window (interposed colon, spleen, liver, or pleura); and uncontrolled hypertension.

Relative: contrast allergy, bleeding diathesis, anticoagulation that cannot be paused (high risk bleeding procedure), solitary kidney with risk of damage (care is needed), and ascites or a very mobile transplant kidney.

Preparation.

• Informed consent, with benefits, alternatives (retrograde stent) and risks explained.
• Review of imaging (ultrasound, CT or MR) for the anatomy, the level of obstruction, the position of the colon and other organs, and hydronephrosis.
• Blood tests: full blood count, clotting, renal function, electrolytes (check potassium in renal failure, with correction of hyperkalaemia), and group and screen; urine culture.
• Intravenous broad spectrum antibiotics before the procedure (gentamicin or a cephalosporin or a piperacillin type drug as local microbiology directs), continued if infected, and fluid resuscitation in sepsis.
• Local anaesthetic with analgesia and sedation, monitoring, and fasting for 4 to 6 hours in elective cases (not required for emergencies).

Technique. The patient lies prone (or prone oblique with the side raised by 30 degrees). Ultrasound identifies the kidney, the collecting system, and the safest approach.

After local anaesthesia, an 18 to 22 gauge needle is advanced into a posterior calyx under ultrasound and fluoroscopy. Urine is aspirated for culture (a sample of infected urine is sent, and pus is drained with minimal contrast to avoid overdistension and bacteraemia). A small volume of contrast confirms the position, and a wire is advanced into the pelvis or the ureter.

The tract is dilated, and a self-retaining pigtail catheter is placed and secured with a suture or fixation device. Antegrade pyelography is performed after the sepsis settles or when safe. The catheter is connected to a drainage bag.

Findings.

• Aspirated urine: clear urine, cloudy urine (infection), frank pus (pyonephrosis), blood, chyle, or urinoma fluid.
• Antegrade pyelogram: a dilated pelvicalyceal system, the level and shape of obstruction (smooth tapered narrowing in benign stricture, irregular narrowing or a filling defect in tumour, a rounded filling defect for a calculus, extrinsic compression in retroperitoneal fibrosis with medial deviation of the ureter).
• Antegrade pyelogram also shows the length of stricture, ureteric leak (extravasation of contrast), and fistula.
• Renal findings: cortical thinning, calyceal clubbing, and a poorly functioning kidney.
• Response: free flow of urine, fall in creatinine (recovery over days to weeks, depending on the duration of obstruction), resolution of fever, and relief of hydronephrosis on ultrasound.
• Post-obstructive diuresis: large urine volumes (over 200 mL each hour) after relief of bilateral obstruction.

Critical findings needing immediate action. Pyonephrosis with septic shock (drain urgently, give antibiotics, fluids and vasopressors; minimal contrast), haemorrhage (blood in the drain, hypotension, flank haematoma: clamp the catheter, resuscitate, CT, embolisation of an arterial injury or arteriovenous fistula), pneumothorax or hydrothorax from a high puncture,

bowel or colonic perforation, urinary leak, post-obstructive diuresis with dehydration and electrolyte loss (fluid and electrolyte replacement), hyperkalaemia in renal failure, catheter dislodgement in a septic patient, and anaphylaxis.

Complications. Sepsis and septic shock (1 to 3% in elective procedures, up to 7 to 9% in infected systems), major haemorrhage requiring transfusion (1 to 4%) or embolisation (under 1 to 3%), minor haematuria (common, settles in 2 to 3 days).

Pneumothorax or pleural effusion (under 1 to 2%, higher with upper pole punctures), injury to the colon, spleen, liver or bowel (under 1%).

Other complications: catheter blockage or dislodgement (common: needs exchange every 2 to 3 months), urine leak, renal pelvis perforation, arteriovenous fistula and pseudoaneurysm, pain, and infection of the tract.

Procedure related mortality is about 0.05 to 0.3%.

Aftercare.

• Bed rest for several hours, with observation of vital signs, urine output, pain, and haematuria; analgesia.
• Monitor creatinine, potassium and fluid balance daily after relief of bilateral obstruction, and watch for post-obstructive diuresis.
• Flush the catheter with 5 to 10 mL of sterile saline once or twice a day if blocked; keep the bag lower than the kidney, and keep the site dry and clean.
• Exchange the catheter every 2 to 3 months (or sooner if blocked, leaking or infected) or convert to an internal ureteric stent once the cause is treated.
• Continue antibiotics as the culture results direct.
• Definitive treatment of the cause (stone removal, tumour treatment, stenting or surgery).
• Return for fever, rigors, flank pain, blood clots, the catheter falling out, stopped drainage, or leaking.

Special groups.

• Children: congenital obstruction (pelviureteric junction, ureterovesical junction, valves) with general anaesthesia and small catheters.
• Pregnancy: obstruction from stones or compression; ultrasound control with minimal fluoroscopy.
• Renal transplant: anterior approach to the graft kidney, with specialist advice.
• Patients with coagulopathy or anticoagulation: temporary correction and a careful risk assessment.
• Malignant obstruction: nephrostomy decisions weigh prognosis and quality of life, as tubes carry long term burden.
• Regions: urinary schistosomiasis, stones, tuberculosis of the urinary tract, obstetric fistula, and advanced cervical cancer cause obstruction; nephrostomy with a basic ultrasound machine is a life saving treatment where urological services are limited.