What it is (overview)

CT Guided Nephrostomy (also called CT-guided percutaneous nephrostomy) is a minimally invasive kidney procedure that uses CT imaging (computed tomography) to guide a doctor in placing a thin tube (nephrostomy catheter) through the skin of your back directly into the kidney’s urine-collecting system. The goal is to drain urine (and sometimes pus or blood) when normal urine flow is blocked.

Although people sometimes refer to it as a “test,” it is primarily an image-guided procedure that can be both diagnostic and therapeutic. It helps your care team: confirm the location and severity of a urinary obstruction, evaluate kidney drainage, and immediately relieve pressure on the kidney by allowing urine to flow out through the catheter into a drainage bag.

What it measures / shows: CT (renal imaging) helps map your kidney anatomy and pinpoint the safest path for catheter placement. During and after placement, the doctor assesses whether urine is draining well and whether the blockage is above the bladder (for example, in the ureter). Sometimes contrast dye may be used to outline the collecting system and identify where the obstruction is.

What the “results” mean in plain language: Instead of a single lab value, the outcome is based on whether the nephrostomy provides effective kidney drainage and what the imaging shows. A “successful” result typically means the catheter is in the correct position and urine (or infected fluid) drains freely, which can improve pain, fever, and kidney function. If drainage is poor, it may suggest a tight blockage, catheter kinking, clots/debris, or a complex kidney/urinary tract problem that needs further treatment by urology or interventional radiology.

When & why it's usually done

A CT Guided Nephrostomy is usually ordered when your doctor needs urgent or precise relief of a blockage or infection affecting the kidney, especially when ultrasound guidance is difficult or when detailed CT scan mapping is helpful. It may be recommended by urology, emergency, oncology, or interventional radiology teams.

Common reasons include:

1) Suspected or confirmed urinary obstruction that is preventing urine from draining normally (often seen as hydronephrosis—swelling of the kidney). Obstruction may be caused by a kidney stone, ureteral narrowing, scar tissue, or an external mass pressing on the ureter.

2) Infection behind a blockage (urgent), such as obstructed pyelonephritis or kidney infection where urine can’t drain. This can be a medical emergency because pressure and bacteria can damage the kidney and spread into the bloodstream.

3) Kidney drainage when a stent is not possible or has failed. If a ureteral stent cannot be placed from the bladder side (or stops working), a nephrostomy offers another route to drain urine.

4) Pre- or post-surgical planning and support. A nephrostomy may be used to protect kidney function before surgery, after urinary tract surgery, or to help manage complications such as leaks or strictures.

5) Evaluation of the urinary collecting system. In some cases, CT-guided access supports additional procedures (for example, to remove stones or to perform targeted imaging).

Symptoms or findings that may prompt this procedure include: flank or back pain, fever/chills with suspected kidney infection, nausea/vomiting with urinary blockage, reduced urine output, blood in urine, rising creatinine or worsening kidney function on blood tests, or imaging that shows hydronephrosis/blocked ureter.

Common diseases related to it

• Kidney stones (nephrolithiasis) and ureteral stones causing urinary obstruction
• Hydronephrosis (swelling of the kidney due to blocked urine flow)
• Obstructive pyelonephritis (kidney infection with obstruction)
• Pyonephrosis (infected, pus-filled obstructed kidney)
• Ureteral stricture (narrowing from scarring, inflammation, or prior surgery)
• Urinary tract obstruction from tumors or masses (e.g., bladder, prostate, cervical, uterine, colorectal, or retroperitoneal cancers)
• Benign prostatic hyperplasia (BPH) with upper-tract obstruction in severe cases
• Blood clots or debris blocking the urinary tract (e.g., after trauma or procedures)
• Congenital or structural urinary tract abnormalities (selected cases)
• Urinary leak or fistula requiring diversion/drainage (post-operative or post-injury)

Health goals where it may help

• Relieving urinary obstruction to protect kidney health and prevent permanent kidney damage
• Rapid drainage of infected urine to help control kidney infection and reduce sepsis risk
• Improving or stabilizing kidney function (supporting recovery of renal function when blockage is removed)
• Managing symptoms such as flank pain, fever, nausea, and pressure from hydronephrosis
• Supporting urology care plans, including preparation for stone removal, stent placement, or surgery
• Helping guide cancer-related urinary drainage when a tumor compresses the ureter (maintaining urine flow during treatment)
• Monitoring drainage effectiveness over time (ensuring the catheter remains patent and urine drains properly)