What Is a Pyeloplasty?

Start with the repair itself, in the order it happens. A pyeloplasty rebuilds the one short stretch of plumbing where urine leaves the kidney — the ureteropelvic junction, where the kidney's collecting funnel (the pelvis) narrows into the ureter, the tube running down to the bladder. When that junction is too tight, urine drains slowly, the kidney swells with backed-up fluid, and the operation fixes it by cutting the narrowed section away and sewing a wider join. The video at the top of this page, "Bilateral Laparoscopic Pyeloplasty in Children" (seven minutes), shows the keyhole version of that repair done on both kidneys in a child — both sides in one sitting, through small incisions, with a camera guiding the work. Most pyeloplasties treat one side only, but the steps are the same, and they run like this.

Step one: proving the junction is really the blockage

Nobody operates on a suspicion. A swollen kidney on a scan — doctors call the swelling hydronephrosis — has more than one possible cause, so the first step is pinning the blockage to the junction itself. Ultrasound usually shows the swelling first. A renal scan, in which a tracer is followed as it drains from the kidney, then shows whether urine is genuinely held up at the outlet and how much work each kidney is doing; blood tests add the overall picture of kidney function, the same function our eGFR calculator helps estimate. A blockage further down has different answers entirely — a kidney can also swell when a stone jams the ureter below the junction, which is a different problem with different treatment, covered in our kidney stones hub. Junction blockages are often present from birth and picked up on scans in childhood, which is why so many pyeloplasties, including the one in the video above, are children's operations; they also turn up in adults, sometimes after years of intermittent flank ache that comes and goes with fluid intake.

Step two: reaching the kidney and removing the tight section

You'll be asleep under a general anaesthetic for this part. The surgeon reaches the junction either through a single larger incision (the open approach, still common in small children) or through several small ones with a camera and long instruments — the laparoscopic approach the video above follows; some centres use robotic assistance for the same keyhole route. Once there, the surgeon cuts away the narrowed segment of junction altogether rather than trying to stretch it open, trims the swollen funnel of the kidney if it has ballooned, and shapes the top of the ureter so it can be joined widely. Removing the bad section instead of persuading it wider is the whole point of the operation: scarred, badly formed tissue that never drained properly isn't asked to start now.

Step three: sewing the new join, usually over a stent

The healthy ureter is then stitched to the kidney's funnel with fine sutures, creating a wide, funnel-shaped join that urine can fall through freely. In many cases a thin, soft tube called a stent is left running through the new join while it heals — one end coiled in the kidney, the other in the bladder — so any early swelling can't close the repair from inside. Some children instead have a temporary drain arrangement suited to their age and the surgeon's preference. Either way, the join gets protected time to heal watertight before it has to carry the full flow on its own. Working from the other direction is possible for some urinary-tract problems — our article on ureteroscopy shows scopes travelling up the ureter from inside — but a junction that needs rebuilding is repaired from outside, which is what you're watching in the anchor video.

Step four: recovery, stent removal, and proving it worked

Most people — and most children — are up, drinking, and moving around surprisingly soon, with a hospital stay measured in days rather than weeks. Expect soreness around the incisions and, if a stent is in place, some bladder irritation or pink-tinged urine at times; both are common while it is there. The stent comes out a few weeks later in a short second procedure, usually a brief anaesthetic for a child. After that, follow-up scans do the proving: an ultrasound to watch the swelling settle, and sometimes a repeat renal scan to confirm the kidney now drains freely. That checking matters, because a repaired junction occasionally narrows again as it heals, and catching that early keeps the options simple. At any point after the operation, get assessed promptly for fever, worsening flank or tummy pain, vomiting, or a child who stops passing urine normally — those aren't symptoms to wait out at home.

References & further reading

• MedlinePlus — Hydronephrosis of one kidney (Medical Encyclopedia): https://medlineplus.gov/ency/article/000506.htm
• Great Ormond Street Hospital — Pyeloplasty: https://www.gosh.nhs.uk/conditions-and-treatments/procedures-and-treatments/pyeloplasty/
• NHS — Hydronephrosis: https://www.nhs.uk/conditions/hydronephrosis/
• MedlinePlus — Renal scan (Medical Encyclopedia): https://medlineplus.gov/ency/article/003790.htm

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Frequently Asked Questions

What does pyeloplasty fix?

It fixes a blockage at the ureteropelvic junction — the point where urine leaves the kidney and enters the ureter. The surgeon removes the narrowed section and sews a wider join, so urine drains freely again and the swollen kidney (hydronephrosis) can settle.

Is pyeloplasty always keyhole surgery?

No. It can be done through one larger incision (open surgery) or through small incisions with a camera (laparoscopic surgery, sometimes robot-assisted), as in the video on this page. The repair inside is the same; your surgeon will recommend the approach that suits the patient's age, size, and anatomy.

Why did the video show both kidneys being repaired?

Because that child's blockage affected both sides, so both junctions were rebuilt in one operation. That's the less common situation — most pyeloplasties repair one kidney only — but the steps for each side are the same.

Will there be a stent after pyeloplasty?

Often, yes. A thin internal stent is commonly left through the new join for a few weeks while it heals, then removed in a short second procedure. Some surgeons use a different temporary drain arrangement instead, particularly in small children.

How do you know the operation worked?

By follow-up imaging. Ultrasound checks that the kidney's swelling is settling, and a renal scan can confirm urine now drains freely. Follow-up also watches for the uncommon problem of the join narrowing again as it heals.

This article is for general education only and is not medical advice. It does not replace consultation with a qualified clinician. Fever, worsening pain, vomiting, or a marked drop in urine output after kidney surgery should be assessed promptly.

Dr. Mohamed Ibrahim, MD, PhD

Physician-scientist · Founder, MedicalVideos.com

Dr. Ibrahim founded MedicalVideos.com in 2007 to make medical and surgical education freely accessible to students, clinicians, and patients.

Last reviewed: 11/09/26